Life Processes
What Are Life Processes?
What is Life?
We can easily say that a dog, a cow, a human, or a plant is
alive. But how do we know that something is alive?
Many people think that movement is the sign of life.
For example:
- A
dog runs.
- A
cow chews food.
- A
human walks and talks.
But this idea is not completely correct.
Why is Movement Not a Perfect Sign of Life?
Example 1: Sleeping Person
A sleeping person may not show any visible movement.
Is he dead?
No.
He is still alive.
Example 2: Plants
Plants do not walk or run.
Still, they are living organisms because they grow and
perform many activities inside their cells.
Conclusion
Visible movement alone cannot be used to define life.
What is the Real Sign of Life?
The real sign of life is the presence of continuous
internal activities.
Even when we are sleeping:
- Our
heart keeps beating.
- Our
lungs keep breathing.
- Digestion
continues.
- Cells
keep working.
These activities never stop while we are alive.
Molecular Movements
Inside every living organism, millions of molecules are
continuously moving and reacting.
These movements are called molecular movements.
Examples:
- Movement
of oxygen into cells.
- Movement
of nutrients through blood.
- Formation
of proteins.
- Breakdown
of glucose for energy.
These movements are too small to be seen with naked eyes.
Why Are Molecular Movements Necessary?
Living organisms are highly organized structures made up of:
Organism → Organs → Tissues → Cells → Molecules
With time, body parts undergo wear and tear.
To stay alive, organisms must:
- Repair
damaged parts.
- Replace
old cells.
- Produce
new molecules.
- Maintain
body structure.
All these processes require continuous molecular movements.
Viruses – Living or Non-Living?
Viruses are special because they show characteristics of both
living and non-living things.
Outside a Host Cell
- No
growth
- No
reproduction
- No
molecular activity
They behave like non-living particles.
Inside a Host Cell
- Reproduce
rapidly
- Show
biological activity
They behave like living organisms.
Therefore, scientists still debate whether viruses are truly
living or non-living.
What Are Life Processes?
Living organisms must continuously maintain their bodies.
The processes that help in this maintenance are called life
processes.
Definition
Life processes are the processes that together perform the
maintenance functions necessary to keep an organism alive.
Why Are Life Processes Important?
Even when we are resting or sleeping:
- Cells
need energy.
- Tissues
need repair.
- Wastes
must be removed.
Therefore life processes continue throughout life.
If life processes stop, the organism dies.
Requirements for Life Processes
To perform life processes, organisms need:
1. Energy
Energy is required for:
- Growth
- Movement
- Repair
- Reproduction
- Cellular
activities
2. Raw Materials
Raw materials are needed to build and maintain the body.
Examples:
- Food
- Water
- Oxygen
- Minerals
These are obtained from the environment.
Major Life Processes
There are four major life processes discussed in this
chapter:
|
Life Process |
Function |
|
Nutrition |
Obtaining food |
|
Respiration |
Releasing energy from food |
|
Transportation |
Carrying materials throughout the body |
|
Excretion |
Removing waste materials |
Why Is Diffusion Not Enough in Humans?
In unicellular organisms like Amoeba, diffusion is enough
because every part of the cell is in contact with the surroundings.
However, humans are multicellular organisms.
Many cells are located deep inside the body.
Therefore, diffusion alone cannot supply oxygen and nutrients
to all cells.
Hence, specialized systems are needed:
- Respiratory
system
- Circulatory
system
- Excretory
system
Remember
Life is not defined by visible movement. Life is defined by
continuous internal activities that maintain the organism.
Nutrition
What is Nutrition?
All living organisms need:
- Energy
to perform life activities.
- Raw
materials for growth and repair.
These requirements are fulfilled by food.
Definition
Nutrition is the process by which organisms obtain food and
utilize it for energy, growth, repair and maintenance of the body.
Why Do Organisms Need Food?
Food performs three major functions:
1. Source of Energy
Energy is needed for:
- Walking
- Running
- Breathing
- Thinking
- Growth
- Cell
division
Without food, cells cannot produce energy.
2. Growth of the Body
Food provides materials needed for:
- Formation
of new cells
- Increase
in body size
- Development
of organs
3. Repair and Maintenance
Old and damaged cells are continuously replaced.
Food supplies raw materials for this repair work.
How Do Living Organisms Obtain Food?
Different organisms obtain food in different ways.
On the basis of nutrition, organisms are divided into:
1. Autotrophs
Organisms that prepare their own food.
Examples:
- Green
plants
- Algae
- Some
bacteria
2. Heterotrophs
Organisms that cannot prepare their own food and depend on
other organisms.
Examples:
- Human
beings
- Animals
- Fungi
Autotrophic Nutrition
Meaning
"Auto" = Self
"Troph" = Nourishment
Therefore,
Autotrophic nutrition is the mode of nutrition in which
organisms prepare their own food from simple inorganic substances.
Raw Materials Required for Photosynthesis
Green plants require:
1. Carbon Dioxide (CO₂)
Obtained from atmosphere.
2. Water (H₂O)
Absorbed by roots from soil.
3. Sunlight
Provides energy for food synthesis.
4. Chlorophyll
Green pigment present in chloroplasts.
Absorbs sunlight.
Photosynthesis
Definition
Photosynthesis is the process by which green plants prepare
food from carbon dioxide and water using sunlight in the presence of
chlorophyll.
Chemical Equation
6CO₂ + 12H₂O
──(Sunlight, Chlorophyll)──►
C₆H₁₂O₆ + 6O₂ + 6H₂O
Events of Photosynthesis
Photosynthesis occurs in three major steps.
Step 1: Absorption of Light Energy
Chlorophyll absorbs sunlight.
Step 2: Conversion of Light Energy into Chemical Energy
Light energy is converted into chemical energy.
Water molecules split into:
- Hydrogen
- Oxygen
This process is called photolysis of water.
Step 3: Reduction of Carbon Dioxide
Hydrogen combines with carbon dioxide.
Glucose is formed.
Where Does Photosynthesis Occur?
Photosynthesis occurs inside chloroplasts.
Chloroplasts contain chlorophyll.
They are found mainly in leaf cells.
Structure of Leaf Related to Photosynthesis
A leaf is specially designed for photosynthesis.
Important structures:
Lamina
Broad flat part of leaf.
Provides large surface area for sunlight absorption.
Veins
Transport water and food.
Chloroplasts
Contain chlorophyll.
Site of photosynthesis.
Air Spaces
Allow movement of gases.
How Do Plants Obtain Carbon Dioxide?
Plants obtain carbon dioxide through tiny pores called stomata.
Stomata
Definition
Tiny pores present mainly on the lower surface of leaves.
Structure of Stomata
Each stoma consists of:
- Stomatal
pore
- Two
guard cells
Functions of Stomata
1. Exchange of Gases
- CO₂
enters.
- O₂
exits.
2. Transpiration
Water vapour escapes through stomata.
Opening and Closing of Stomata
When Guard Cells Absorb Water
They become swollen.
Stomata open.
When Guard Cells Lose Water
They shrink.
Stomata close.
Other Raw Materials Needed by Plants
Apart from carbon dioxide and water, plants require minerals
such as:
- Nitrogen
- Phosphorus
- Iron
- Magnesium
These minerals are absorbed from soil.
Importance of Nitrogen
Nitrogen is required for:
- Protein
synthesis
- Growth
- Formation
of enzymes
Plants absorb nitrogen mainly as:
- Nitrates
- Nitrites
Storage of Food in Plants
Food produced during photosynthesis is stored as:
Starch
Examples:
- Potato
- Rice
- Wheat
Heterotrophic Nutrition
Meaning
"Hetero" = Different
"Troph" = Nourishment
Heterotrophs cannot prepare food.
They depend directly or indirectly on autotrophs.
Types of Heterotrophic Nutrition
1. Holozoic Nutrition
Organism ingests and digests food.
Examples:
- Human
beings
- Cow
- Lion
2. Saprophytic Nutrition
Organism feeds on dead and decaying matter.
Examples:
- Mushroom
- Bread
mould
3. Parasitic Nutrition
Organism obtains food from a living host.
Examples:
- Cuscuta
(Amarbel)
- Tapeworm
- Lice
4. Symbiotic Nutrition
Definition
A mode of nutrition in which two different organisms live
together and both benefit from each other.
This relationship is called symbiosis.
Examples
Lichen
A lichen consists of:
- Alga
- Fungus
How Both Benefit
Alga
- Performs
photosynthesis.
- Provides
food.
Fungus
- Provides
water.
- Provides
minerals.
- Provides
protection.
Both organisms benefit.
Another Example
Rhizobium and Leguminous Plants
Rhizobium bacteria live in root nodules of pea, gram and bean
plants.
- Bacteria
receive food and shelter.
- Plants
receive usable nitrogen.
Both benefit.
Comparison of the Four Types
|
Type |
Source of Food |
Example |
|
Holozoic |
Food taken inside body and digested |
Human, Cow, Amoeba |
|
Saprophytic |
Dead and decaying matter |
Mushroom, Bread mould |
|
Parasitic |
Living host organism |
Cuscuta, Tapeworm |
|
Symbiotic |
Mutual exchange of benefits |
Lichen, Rhizobium |
Nutrition in Amoeba
Amoeba uses temporary finger-like projections called pseudopodia.
Steps of Nutrition in Amoeba
1. Ingestion
Food is surrounded by pseudopodia.
2. Formation of Food Vacuole
Food gets enclosed.
3. Digestion
Enzymes break food into simple substances.
4. Absorption
Digested food enters cytoplasm.
5. Egestion
Undigested food is thrown out.
Key Terms
|
Term |
Meaning |
|
Nutrition |
Process of obtaining and utilizing food |
|
Autotroph |
Organism that prepares its own food |
|
Heterotroph |
Organism dependent on others for food |
|
Photosynthesis |
Food synthesis by green plants |
|
Chlorophyll |
Green pigment that traps sunlight |
|
Chloroplast |
Organelle where photosynthesis occurs |
|
Stomata |
Tiny pores for gaseous exchange |
|
Guard Cells |
Cells controlling stomatal opening |
|
Pseudopodia |
Temporary projections in Amoeba |
|
Food Vacuole |
Site of digestion in Amoeba |
NUTRITION IN HUMAN BEINGS
Introduction
Human beings follow holozoic nutrition.
In holozoic nutrition, food is:
1.
Ingested (taken in)
2.
Digested
3.
Absorbed
4.
Assimilated
5.
Egested
The human digestive system performs all these functions
through a long tube called the alimentary canal and several accessory digestive
glands.
Human Digestive System
The digestive system consists of:
A. Alimentary Canal
A long muscular tube extending from the mouth to the anus.
Parts of Alimentary Canal
1.
Mouth (Buccal Cavity)
2.
Pharynx
3.
Oesophagus
4.
Stomach
5.
Small Intestine
o Duodenum
o Jejunum
o Ileum
6.
Large Intestine
7.
Rectum
8.
Anus
B. Accessory Digestive Organs
These organs help digestion but food does not pass through
them.
1.
Salivary Glands
2.
Liver
3.
Gall Bladder
4.
Pancreas
Journey of Food Through Human Body
Food → Mouth (Buccal Cavity) → Pharynx → Oesophagus → Stomach
→ Small Intestine → Large Intestine → Rectum → Anus
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1. Mouth (Buccal Cavity)
Digestion begins in the mouth.
Functions
A. Ingestion
Food enters the body through the mouth.
B. Mechanical Digestion
Teeth break food into smaller pieces.
This increases the surface area available for enzyme action.
Types of Teeth
|
Type |
Function |
|
Incisors |
Cutting |
|
Canines |
Tearing |
|
Premolars |
Crushing |
|
Molars |
Grinding |
C. Role of Tongue
The tongue:
- Mixes
food with saliva
- Helps
in chewing
- Helps
in swallowing
- Helps
in tasting food
Salivary Glands
Three pairs of salivary glands secrete saliva.
Saliva contains:
- Water
- Mucus
- Salivary
Amylase enzyme
Salivary Amylase
Function
Breaks starch into simpler sugars.
Starch
↓
Salivary Amylase
↓
Simple Sugars
This is the first chemical digestion of food.
Why Is Saliva Important?
Saliva:
- Moistens
food
- Softens
food
- Helps
swallowing
- Starts
digestion of carbohydrates
2. Pharynx (Throat)
The pharynx is a common passage for:
- Food
- Air
Function
Transfers food from mouth to oesophagus.
Helps in swallowing.
3. Oesophagus (Food Pipe)
A long muscular tube connecting pharynx to stomach.
Peristalsis
Food does not fall into the stomach because of gravity.
Instead, muscles of oesophagus contract rhythmically.
This movement is called:
Peristaltic Movement
Definition
Wave-like muscular contractions that push food forward.
Function
Pushes food into the stomach.
Even if a person stands upside down, food can still reach the
stomach because of peristalsis.
4. Stomach
A J-shaped muscular sac.
Functions of Stomach
A. Temporary Storage
Food remains in the stomach for several hours.
B. Churning
Muscular walls mix food thoroughly.
Food becomes semi-liquid.
This semi-liquid mass is called:
Chyme
Gastric Glands
Present in stomach walls.
They secrete:
1.
Hydrochloric
Acid (HCl)
2.
Pepsin
3.
Mucus
Hydrochloric Acid (HCl)
Functions
1. Creates Acidic Medium
Pepsin works only in acidic conditions.
2. Kills Germs
Destroys harmful microorganisms present in food.
Pepsin
Protein-digesting enzyme.
Function
Protein
↓
Pepsin
↓
Peptides
Starts digestion of proteins.
Mucus
Function
Protects stomach lining from acid.
Without mucus, HCl would damage the stomach wall.
Acidity
Excess acid production may cause:
- Acidity
- Indigestion
- Burning
sensation
Sphincter Muscle
A muscular valve controls the exit of food from stomach.
Food enters the small intestine slowly through this
sphincter.
5. Small Intestine
The longest part of alimentary canal.
Length ≈ 6–7 metres.
Why Is It Long?
Provides enough time for:
- Digestion
- Absorption
Parts of Small Intestine
1. Duodenum
First part.
Receives:
- Bile
juice
- Pancreatic
juice
2. Jejunum
Middle part.
Continues digestion and absorption.
3. Ileum
Last part.
Major site of absorption.
Why Is Small Intestine the Main Site of Digestion?
Three digestive juices act here:
1. Bile Juice
2. Pancreatic Juice
3. Intestinal Juice
Liver
Largest gland in human body.
Functions of Liver
Produces:
Bile Juice
Stored in gall bladder.
Bile Juice
Important Fact
Bile contains NO digestive enzymes.
Functions of Bile
A. Neutralizes Acidic Chyme
Food from stomach is acidic.
Bile makes it alkaline.
B. Emulsification of Fats
Large fat globules are broken into smaller droplets.
This process is called:
Emulsification
Large Fat Globules
↓
Bile
↓
Small Fat Droplets
This increases surface area for enzyme action.
Gall Bladder
Stores bile produced by liver.
Releases bile into duodenum.
Pancreas
Produces pancreatic juice.
Pancreatic Enzymes
Trypsin
Digests proteins.
Protein → Amino Acids
Amylase
Digests carbohydrates.
Carbohydrates → Glucose
Lipase
Digests fats.
Fat → Fatty Acids + Glycerol
Sodium Bicarbonate (NaHCO₃)
Present in pancreatic juice.
Function
Neutralizes acidic chyme.
Maintains alkaline medium.
Intestinal Juice
Produced by intestinal glands.
Completes digestion.
End Products of Digestion
|
Nutrient |
End Product |
|
Carbohydrates |
Glucose |
|
Proteins |
Amino Acids |
|
Fats |
Fatty Acids + Glycerol |
Absorption in Small Intestine
The inner wall contains finger-like projections called: Villi
Structure of Villi
Each villus contains:
- Blood
capillaries
- Lymph
vessels
Functions of Villi
Increase Surface Area
Large surface area allows maximum absorption.
Absorb Digested Food
Nutrients enter blood through villi.
Blood transports nutrients to body cells.
Assimilation
After absorption:
Cells use nutrients for:
- Energy
production
- Growth
- Repair
This utilization is called:
Assimilation
6. Large Intestine
Undigested food enters large intestine.
Functions
Absorption of Water
Most water is reabsorbed.
Absorption of Salts
Minerals are reabsorbed.
Helpful Bacteria
Some bacteria produce vitamins such as Vitamin K.
Formation of Faeces
Remaining undigested matter forms faeces.
7. Rectum
Temporary storage chamber.
Stores faeces until removal.
8. Anus
Terminal opening of alimentary canal.
Function
Removal of faeces from body.
This process is called:
Egestion
Summary of Digestion
Mouth (Chewing + Salivary Amylase) → Oesophagus (Peristalsis)
→ Stomach (HCl + Pepsin + Churning) → Small Intestine (Bile + Pancreatic Juice
+ Intestinal Juice) → Digestion Completed → Villi Absorb Nutrients → Large
Intestine (Water Absorption) → Rectum → Anus
Important Terms
Ingestion – Taking food into the body
Digestion – Breakdown of complex food into simple substances
Absorption – Passage of digested food into blood
Assimilation – Utilization of absorbed food by cells
Egestion – Removal of undigested food
Peristalsis – Wave-like muscular movement pushing food
forward
Chyme – Semi-liquid food in stomach
Emulsification – Breaking fats into tiny droplets
Villi – Finger-like projections for absorption
Pepsin – Protein-digesting enzyme
Salivary Amylase – Starch-digesting enzyme
Trypsin – Protein-digesting enzyme from pancreas
Lipase – Fat-digesting enzyme from pancreas
Dental Caries (Tooth Decay)
Introduction
Dental caries, commonly known as tooth decay or cavities, is
the gradual destruction of teeth caused by acids produced by bacteria present
in the mouth.
It is one of the most common dental problems in children and
adults.
How Does Dental Caries Occur?
Our mouth naturally contains many bacteria.
When food particles, especially sugars and starches, remain
stuck on teeth, bacteria feed on them.
These bacteria produce acids.
Sugary Food Left on Teeth → Bacterial Growth → Acid
Production → Enamel Erosion → Cavity (Dental Caries)
Formation of Plaque
After eating, bacteria, food particles, and saliva form a
sticky layer on teeth called:
Plaque
Characteristics of Plaque
- Colorless
or pale yellow
- Sticky
in nature
- Forms
mainly between teeth and near gums
- Rich
in bacteria
If not removed, plaque accumulates and causes tooth decay.
Why Are Acids Harmful?
The outer covering of teeth is called:
Enamel
Enamel
- Hardest
substance in the human body
- Protects
inner parts of the tooth
When bacteria produce acids, these acids dissolve minerals
from enamel.
This process is called:
Demineralization
Gradually, holes develop in teeth.
These holes are called:
Cavities
Progression of Dental Caries
Stage 1: Enamel Damage
Only outer enamel is affected.
Usually painless.
Stage 2: Dentin Damage
Decay reaches dentin (layer below enamel).
Sensitivity begins.
Pain may occur while eating hot or cold foods.
Stage 3: Pulp Damage
Decay reaches the pulp containing nerves and blood vessels.
Severe toothache develops.
Infection may occur.
Symptoms of Dental Caries
- Toothache
- Sensitivity
to hot or cold foods
- Pain
while chewing
- Visible
holes in teeth
- Bad
breath
- Black
or brown spots on teeth
Why Are Children More Prone?
Children often:
- Eat
more chocolates and sweets
- Consume
soft drinks
- Do
not brush properly
- Neglect
oral hygiene
Therefore cavities are common among school-going children.
Prevention of Dental Caries
1. Brush Teeth Regularly
Brush at least twice a day.
Especially before sleeping.
2. Rinse Mouth After Meals
Removes food particles and reduces bacterial growth.
3. Limit Sugary Foods
Reduce:
- Chocolates
- Candies
- Cakes
- Soft
drinks
4. Use Fluoride Toothpaste
Fluoride strengthens enamel and prevents decay.
5. Visit Dentist Regularly
Regular dental checkups help detect cavities early.
Role of Toothpaste
Toothpaste is generally alkaline.
It helps neutralize acids produced by bacteria.
This reduces enamel damage.
Important Point
The pH of the mouth is normally around 7 (neutral).
When bacteria produce acids, the pH falls below 5.5.
At this level, enamel starts dissolving and tooth decay
begins.
Normal Mouth pH ≈ 7
↓
Acid Produced by Bacteria
↓
pH Falls Below 5.5
↓
Enamel Dissolves
↓
Dental Caries
Definition
Dental caries is the decay of teeth caused by acids produced
by bacteria acting on food particles left in the mouth, leading to the
formation of cavities.
Respiration
What is Respiration?
Respiration is the biological process by which living
organisms obtain energy from food.
The food we eat contains stored chemical energy. This energy
cannot be used directly by cells. Therefore, food is broken down inside cells
and energy is released.
Definition
Respiration is the process of breaking down food (especially
glucose) inside cells to release energy.
Why is Respiration Necessary?
Every activity of the body requires energy:
- Walking
- Running
- Studying
- Thinking
- Growth
- Repair
of tissues
- Heartbeat
- Breathing
itself
This energy comes from respiration.
Without respiration, life cannot exist.
Respiration vs Breathing
Many students think respiration and breathing are the same.
They are different.
|
Breathing |
Respiration |
|
Physical process |
Biochemical process |
|
Occurs in lungs |
Occurs inside cells |
|
Intake of O₂ and release of CO₂ |
Breakdown of food to release energy |
|
No energy released |
Energy released |
|
Visible process |
Microscopic process |
Example
When you inhale oxygen and exhale carbon dioxide, it is
breathing.
When glucose is broken down inside cells to release energy,
it is respiration.
Cellular Respiration
Respiration actually occurs inside cells.
The cell organelle responsible is:
Mitochondria
Mitochondria are called:
"Powerhouse of the Cell"
Because most cellular energy is produced here.
The Fuel of Respiration
The main food molecule used in respiration is:
Glucose
Glucose is obtained from digestion of carbohydrates.
Energy Currency of Cell
Energy released during respiration is stored in: ATP
Adenosine Triphosphate
ATP acts like an energy packet.
Whenever cells need energy, ATP is broken down.
ATP → ADP + Energy
Cells use this energy for all activities.
Types of Respiration
There are two types:
1. Aerobic Respiration
2. Anaerobic Respiration
1. Aerobic Respiration
Meaning
"Aero" means air.
Respiration that occurs in the presence of oxygen.
Equation
Glucose + Oxygen ──►
Carbon Dioxide + Water + Energy (ATP)
C₆H₁₂O₆ + 6O₂ ──►
6CO₂ + 6H₂O + 36–38 ATP Products
- Carbon
dioxide
- Water
- Large
amount of energy
Occurs In
- Humans
- Animals
- Plants
Characteristics
✔
Requires oxygen
✔
Complete breakdown of glucose
✔
Releases maximum energy
✔
Occurs mainly in mitochondria
2. Anaerobic Respiration
Meaning
"An" = without
Respiration that occurs without oxygen.
Equation in Yeast
C₆H₁₂O₆ ──►
2C₂H₅OH + 2CO₂ + Energy (ATP) Products
Glucose ──►
Ethanol + Carbon Dioxide + Energy (ATP)
- Ethanol
(Alcohol)
- Carbon
dioxide
- Small
amount of energy
Occurs In
- Yeast
- Some
bacteria
Anaerobic Respiration in Human Muscles
During heavy exercise:
- Running
- Boxing
- Cycling
- Sprinting
Muscles may not get enough oxygen.
Then muscles switch temporarily to anaerobic respiration.
Equation
C₆H₁₂O₆ ──►
2C₃H₆O₃ + Energy (ATP)Product
Glucose ──►
Lactic Acid + Energy (ATP)
Lactic Acid
Result
- Muscle
cramps
- Muscle
fatigue
- Burning
sensation
This is why intense exercise sometimes causes pain in
muscles.
Comparison of Aerobic and Anaerobic Respiration
|
Feature |
Aerobic |
Anaerobic |
|
Oxygen |
Required |
Not Required |
|
Breakdown of Glucose |
Complete |
Incomplete |
|
Energy Released |
High |
Low |
|
End Products |
CO₂ + H₂O |
Alcohol/ Lactic Acid |
|
Site |
Mitochondria |
Cytoplasm |
Respiration in Different Organisms
Humans
Use lungs for oxygen intake.
Respiration is mostly aerobic.
Plants
Plants also respire continuously.
They take oxygen and release carbon dioxide.
Photosynthesis and respiration are different processes.
Yeast
Performs anaerobic respiration.
Used in:
- Bread
making
- Wine
production
- Beer
production
Steps of Respiration in Human Body
Step 1: Breathing
Oxygen enters lungs.
Step 2: Transport
Blood carries oxygen to all body cells.
Step 3: Cellular Respiration
Glucose is broken down in cells.
Step 4: Energy Release
ATP is formed.
Step 5: Removal of Waste
Carbon dioxide returns to lungs and is exhaled.
Flow Chart
Food → Digestion
→ Glucose →
Cells → Respiration
→ ATP (Energy) →
Growth, Movement & Life Activities
Definition
Respiration is the biochemical process in which food
molecules such as glucose are broken down inside cells to release energy, which
is stored in the form of ATP.
Advanced Respiration: Krebs Cycle and Electron Transport
Chain (ETC)
Big Picture First
When you eat food, carbohydrates are digested into glucose.
The cell wants to extract every bit of energy stored inside
glucose.
This happens in three major stages:
Glucose → Glycolysis → Pyruvate → Krebs Cycle → ETC (Electron
Transport Chain) → ATP (Energy)
Most of the ATP is actually produced during the Electron
Transport Chain (ETC).
Stage 1: Glycolysis
Before Krebs Cycle starts, glucose must be broken down.
What is Glycolysis?
"Glyco" = Sugar
"Lysis" = Breaking
Therefore:
Glycolysis = Breakdown of glucose
Where does it occur?
In the:
Cytoplasm
(not mitochondria)
This is why your board mentions:
Glucose → Pyruvate
(Cytoplasm)
What happens?
One glucose molecule contains:
6 Carbon atoms
So:
Glucose (6C)
↓
Pyruvate (3C + 3C)
One glucose breaks into:
Two molecules of pyruvate
Each pyruvate contains:
3 Carbon atoms
Energy Produced
During glycolysis:
- 2
ATP produced
- 2
NADH produced
As shown on your board:
Net Gain:
2 ATP + 2 NADH
What is NADH?
This is extremely important.
Full Form
Nicotinamide Adenine Dinucleotide
When it gains hydrogen and electrons:
It becomes:
NADH
Think of NADH as:
An energy-carrying battery
It stores high-energy electrons.
Later these electrons will be used in ETC.
What Happens to Pyruvate?
Now pyruvate enters:
Mitochondria
But pyruvate cannot directly enter Krebs Cycle.
First it must be modified.
Formation of Acetyl CoA
Your board shows:
Pyruvate (3C)
↓
CO₂ removed
↓
Acetyl CoA (2C)
What is happening?
Pyruvate contains:
3 Carbon atoms
One carbon is removed as:
CO₂
Now only:
2 Carbon atoms remain
This 2-carbon molecule attaches to:
Coenzyme A
forming:
Acetyl CoA
Why is Acetyl CoA Important?
Acetyl CoA is the molecule that enters the Krebs Cycle.
Think of it as:
The entry ticket to Krebs Cycle
Stage 2: Krebs Cycle
Also called:
Citric Acid Cycle
Named after:
Hans Krebs
who discovered it.
Where Does Krebs Cycle Occur?
Inside:
Mitochondrial Matrix
(the fluid-filled interior of mitochondria)
Beginning of Krebs Cycle
Your board shows:
Acetyl CoA (2C)
+
Oxaloacetic Acid (4C)
Step 1
A 2-carbon Acetyl CoA joins a 4-carbon Oxaloacetic Acid.
2C + 4C = 6C
Result:
Citric Acid (6C)
This is why it is called:
Citric Acid Cycle
Step 2: Citric Acid Breakdown
Now Citric Acid undergoes a series of reactions.
During these reactions:
Carbon atoms are gradually removed.
CO₂ Released
Citric Acid
↓
CO₂
Carbon dioxide is released as waste.
Eventually the molecule returns to:
Oxaloacetic Acid (4C)
and the cycle starts again.
What is Produced in Krebs Cycle?
The major purpose is NOT ATP production.
Its main purpose is to produce:
NADH
and
FADH₂
These carry energy to ETC.
FADH₂
Full Form:
Flavin Adenine Dinucleotide
After accepting hydrogen:
FAD → FADH₂
Like NADH:
FADH₂ is also an energy carrier.
Think of Krebs Cycle Like This
Krebs Cycle
↓
Loads batteries
↓
NADH
FADH₂
↓
Sent to ETC
The cycle mainly charges these "energy batteries."
Stage 3: Electron Transport Chain (ETC)
This is where MOST ATP is produced.
Where Does ETC Occur?
In:
Inner Mitochondrial Membrane
(the folded membrane called cristae)
Why Is It Called Electron Transport Chain?
Because electrons are passed from one protein to another.
Like:
Person A
↓
Person B
↓
Person C
↓
Person D
Electrons move through a chain.
Hence:
Electron Transport Chain
Step 1: NADH and FADH₂ Arrive
Your board shows:
NADH
FADH₂
↓
ETC
These molecules donate their high-energy electrons.
Step 2: Energy Released
As electrons move through ETC proteins:
Energy is released.
This is shown on your board as:
High Energy
Step 3: Proton Pumping
Your board says:
Pumps H⁺
The released energy is used to pump hydrogen ions.
H⁺
H⁺
H⁺
H⁺
across the membrane.
What Is Created?
A huge concentration difference.
One side has:
Many H⁺ ions
Other side has:
Few H⁺ ions
This is called:
Proton Gradient
Your board mentions:
Creates proton gradient
Why Is Proton Gradient Important?
Nature always wants balance.
Therefore hydrogen ions try to flow back.
Step 4: Flow Back of H⁺
Your board shows:
Flow back of H⁺
Hydrogen ions rush back through a special protein.
ATP Synthase
The special protein is:
ATP Synthase
Think of it as a microscopic turbine.
Like water turning a dam turbine.
Hydrogen ions turn ATP Synthase.
ATP Production
Your board shows:
ATP Synthase
↓
ATP
As ATP Synthase spins:
ADP + Phosphate
↓
ATP
This produces huge amounts of ATP.
Why Is Oxygen Needed?
Many students misunderstand this.
Oxygen is not needed mainly for Krebs Cycle.
It is needed at the END of ETC.
Final Step
Oxygen
+
H⁺
+
e⁻
↓
Water
What Happens?
At the end of ETC:
Oxygen accepts:
- Electrons
- Hydrogen
ions
forming:
Water (H₂O)
O₂ + H⁺ + e⁻
↓
H₂O
Why Is Oxygen Called the Final Electron Acceptor?
Because oxygen receives the last electrons in ETC.
Without oxygen:
- ETC
stops
- ATP
production collapses
- Cells
die
This is why oxygen is essential for aerobic respiration.
ATP Yield (Simplified)
For one glucose molecule:
|
Stage |
ATP Produced |
|
Glycolysis |
2 ATP |
|
Krebs Cycle |
2 ATP |
|
ETC |
32–34 ATP |
|
Total |
About 36–38 ATP |
Most energy comes from:
ETC
Complete Flow Chart
Glucose (6C)
↓
Glycolysis
(Cytoplasm)
↓
2 Pyruvate (3C)
↓
Acetyl CoA (2C)
↓
Krebs Cycle
↓
NADH + FADH₂
↓
Electron Transport Chain
↓
Proton Gradient
↓
ATP Synthase
↓
ATP (Energy)
Oxygen + H⁺ + e⁻
↓
Water (H₂O)
One-Line Summary
Glycolysis breaks glucose into pyruvate, Krebs Cycle extracts
high-energy electrons and stores them in NADH and FADH₂, and the Electron
Transport Chain uses these electrons to create a proton gradient that powers
ATP Synthase to produce most of the cell's ATP.
Transportation
Introduction
Every cell in our body needs:
- Oxygen
- Nutrients
(food)
- Water
At the same time, every cell produces waste products such as:
- Carbon
dioxide (CO₂)
- Urea
- Other
metabolic wastes
Since these substances cannot move efficiently on their own
throughout a large body, organisms need a transportation system.
Definition
Transportation is the process of moving useful substances
(food, oxygen, hormones, water, minerals) to different parts of the body and
removing waste products from cells.
Why Do Organisms Need Transportation?
Imagine eating food.
Food enters the stomach and intestine, but:
- Brain
also needs food.
- Muscles
also need food.
- Skin
cells also need food.
Similarly:
Oxygen enters only the lungs, but every cell requires oxygen.
Therefore a transport system becomes necessary.
Transportation in Unicellular Organisms
Examples:
- Amoeba
- Paramecium
- Bacteria
These organisms are very small.
Their cells are directly exposed to the environment.
Therefore substances move through:
Diffusion
Diffusion
Movement of substances from higher concentration to lower
concentration.
Example:
Oxygen enters Amoeba directly through the cell membrane.
Why Diffusion Is Not Enough in Humans?
Humans contain trillions of cells.
Many cells are far away from the external environment.
Example:
Cells inside the liver or bones cannot obtain oxygen directly
by diffusion.
Therefore humans require a specialized transportation system.
Transportation in Humans
The transportation system consists of:
1.
Blood
2.
Blood
vessels
3.
Heart
4.
Lymph
Together these form:
Circulatory System
Human Circulatory System
Definition
The circulatory system is a network of heart, blood, blood
vessels and lymph that transports substances throughout the body.
Components of Human Circulatory System
Heart
↓
Pumps Blood
↓
Blood Vessels
↓
Carry Blood
↓
Body Cells
BLOOD
What is Blood?
Blood is a fluid connective tissue.
It flows throughout the body carrying:
- Oxygen
- Food
- Hormones
- Waste
materials
Functions of Blood
1. Transport of Oxygen
Carries oxygen from lungs to cells.
2. Transport of Food
Carries digested nutrients from intestine to body cells.
3. Transport of Hormones
Carries hormones from glands to target organs.
4. Removal of Waste
Carries carbon dioxide and urea to excretory organs.
5. Protection
Blood protects against diseases.
6. Clotting
Stops excessive bleeding after injury.
Components of Blood
Blood contains:
Blood
│
├── Plasma
├── RBCs
├── WBCs
└── Platelets
1. Plasma
Plasma is the liquid part of blood.
Approximately:
55% of blood is plasma.
Color:
Straw-yellow
Composition of Plasma
Contains:
- Water
(about 90%)
- Proteins
- Salts
- Nutrients
- Hormones
- Waste
products
Function of Plasma
Acts as a transport medium.
Carries:
- Digested
food
- Hormones
- Carbon
dioxide
- Waste
products
2. Red Blood Cells (RBCs)
Also called:
Erythrocytes
Characteristics
- Red
in color
- Most
numerous blood cells
- Produced
in bone marrow
- Lack
nucleus in mammals
Why Are They Red?
Due to:
Haemoglobin
A red pigment containing iron.
Function of RBCs
Transport oxygen.
Lungs
↓
Oxygen
↓
RBC
↓
Body Cells
Haemoglobin
Haemoglobin combines with oxygen.
Forms:
Oxyhaemoglobin
This carries oxygen throughout the body.
What Happens If Haemoglobin Is Low?
Condition:
Anaemia
Symptoms:
- Weakness
- Fatigue
- Dizziness
- Pale
skin
3. White Blood Cells (WBCs)
Also called:
Leukocytes
Characteristics
- Larger
than RBCs
- Have
nucleus
- Fewer
in number
Function
Protect the body from infection.
They destroy:
- Bacteria
- Viruses
- Harmful
microorganisms
Why Are WBCs Called Soldiers?
Because they defend the body against diseases.
4. Platelets
Also called:
Thrombocytes
Function
Help in blood clotting.
Blood Clotting
Suppose you cut your finger.
Without clotting:
Blood would continuously flow out.
Platelets form a clot.
This prevents excessive blood loss.
BLOOD VESSELS
Blood travels through special tubes called blood vessels.
There are three main types.
1. Arteries
Definition
Blood vessels that carry blood away from the heart.
Characteristics
- Thick
walls
- Elastic
walls
- High
pressure blood
- Usually
carry oxygenated blood
Exception
Pulmonary Artery
Carries deoxygenated blood.
Example
Heart
↓
Artery
↓
Body
2. Veins
Definition
Blood vessels that carry blood toward the heart.
Characteristics
- Thin
walls
- Wider
lumen
- Low
pressure
- Have
valves
Why Are Valves Needed?
To prevent backward flow of blood.
Exception
Pulmonary Vein
Carries oxygenated blood.
3. Capillaries
Definition
The smallest blood vessels in the body.
Characteristics
- Extremely
thin walls
- One-cell
thick
Function
Exchange of materials occurs here.
Such as:
- Oxygen
- Nutrients
- Carbon
dioxide
- Waste
products
Comparison of Arteries and Veins
|
Feature |
Arteries |
Veins |
|
Direction |
Away from heart |
Towards heart |
|
Wall |
Thick |
Thin |
|
Pressure |
High |
Low |
|
Valves |
Absent |
Present |
|
Blood |
Usually oxygenated |
Usually deoxygenated |
HEART
What is Heart?
Heart is a muscular pumping organ.
It pumps blood continuously throughout life.
Location
Between the lungs.
Slightly towards the left side of the chest.
Size
Approximately equal to a clenched fist.
Structure of Heart
Human heart contains:
Four Chambers
Right Atrium
Receives deoxygenated blood.
Right Ventricle
Pumps deoxygenated blood to lungs.
Left Atrium
Receives oxygenated blood from lungs.
Left Ventricle
Pumps oxygenated blood to the entire body.
Double Circulation
Humans have:
Double Circulation
Meaning blood passes through the heart twice during one
complete cycle.
Pulmonary Circulation
Heart
↓
Lungs
↓
Heart
Purpose:
Oxygenation of blood.
Systemic Circulation
Heart
↓
Body
↓
Heart
Purpose:
Supply oxygen and nutrients.
Path of Blood Flow
Body
↓
Right Atrium
↓
Right Ventricle
↓
Lungs
↓
Left Atrium
↓
Left Ventricle
↓
Body
Why Is Double Circulation Important?
It prevents mixing of:
- Oxygenated
blood
- Deoxygenated
blood
Result:
Efficient supply of oxygen.
This helps humans maintain a high metabolic rate.
Blood Pressure
Definition
Pressure exerted by blood on artery walls.
Normal value:
120 / 80 mm Hg
Meaning
120 = Systolic pressure
80 = Diastolic pressure
LYMPH
Besides blood, another fluid participates in transportation.
Lymph
A pale yellow fluid.
Functions of Lymph
1. Returns excess tissue fluid to blood.
2. Transports absorbed fats from intestine.
3. Provides immunity.
Transportation in Plants
Plants do not have a heart.
They use special vascular tissues.
Xylem
Function
Transports:
- Water
- Minerals
from roots to leaves.
Direction
Roots
↓
Stem
↓
Leaves
Mostly upward.
Phloem
Function
Transports food made during photosynthesis.
Direction
Food can move:
- Upward
- Downward
depending on need.
Translocation
Movement of food through phloem is called:
Translocation
One-Line Summary
Transportation is the life process by which blood in animals
and vascular tissues in plants distribute food, oxygen, water, hormones, and
other substances to all parts of the organism while removing waste products.
Haemostasis (Blood Clotting)
What is Haemostasis?
The word Haemostasis comes from:
- Haemo
= Blood
- Stasis
= Stopping
Definition
Haemostasis is the process by which the body stops bleeding
from a damaged blood vessel.
Whenever we get a cut or injury, blood starts flowing out. If
bleeding continues, a person may lose a dangerous amount of blood. Therefore
the body has a natural mechanism to stop blood loss.
Why is Haemostasis Necessary?
Imagine you accidentally cut your finger.
Without haemostasis:
- Blood
would continue flowing out.
- Blood
pressure would fall.
- Oxygen
supply to organs would decrease.
- Severe
blood loss could become life-threatening.
Therefore haemostasis is a protective mechanism.
Main Components Involved
1.
Platelets
2.
Prothrombin
3.
Calcium
ions (Ca²⁺)
4.
Thrombin
5.
Fibrinogen
6.
Fibrin
These work together to form a clot.
Step 1: Injury Occurs
When a blood vessel is damaged:
Blood Vessel Injury
↓
Bleeding Starts
The body immediately activates haemostasis.
Step 2: Platelet Activation
Your board starts with:
Platelets
Platelets are small cell fragments present in blood.
They are also called:
Thrombocytes
Function of Platelets
Platelets are the first responders to injury.
When a vessel is damaged:
- Platelets
stick to the injured area.
- Platelets
stick to each other.
- A
temporary plug is formed.
This is called:
Platelet Plug Formation
As shown on your board:
Platelets
↓
Plug Formation
This plug temporarily reduces blood loss.
Step 3: Activation of Prothrombin
Your board shows:
Inactive Prothrombin
↓
Calcium Ion
↓
Active Thrombin
What is Prothrombin?
Prothrombin is an inactive protein present in blood plasma.
By itself it cannot form a clot.
Therefore it must first become active.
Role of Calcium Ions (Ca²⁺)
Calcium ions act as essential clotting factors.
They help convert:
Prothrombin
↓
Thrombin
Without calcium ions, normal blood clotting cannot occur.
Step 4: Formation of Thrombin
After activation:
Prothrombin
↓
Thrombin
Thrombin
Thrombin is an enzyme.
Its main function is to convert fibrinogen into fibrin.
Think of thrombin as the "master switch" of blood
clotting.
Step 5: Conversion of Fibrinogen into Fibrin
Fibrinogen
↓
Fibrin
What is Fibrinogen?
Fibrinogen is:
A soluble plasma protein
"Soluble" means it remains dissolved in blood.
As long as fibrinogen remains soluble, clot formation does
not occur.
Action of Thrombin
Thrombin acts on fibrinogen.
It converts:
Fibrinogen
↓
Fibrin
What is Fibrin?
Long Sticky Threads
Fibrin forms long protein fibers.
These fibers behave like a net.
Function of Fibrin
The fibrin network traps:
- RBCs
- WBCs
- Platelets
forming a stable clot.
Imagine a fishing net trapping fish.
Similarly fibrin traps blood cells.
Step 6: Scab Formation
Your board shows:
Fibrin
↓
Scab Formation
What is a Scab?
The clot dries and hardens.
This hard protective covering is called:
Scab
Functions of Scab
- Stops
bleeding
- Protects
wound from infection
- Allows
tissue repair underneath
After healing, the scab falls off naturally.
Complete Clotting Pathway
Injury
↓
Platelets Activated
↓
Platelet Plug Formation
↓
Prothrombin (Inactive)
↓ Calcium ions
Thrombin (Active)
↓
Fibrinogen
↓
Fibrin
↓
Blood Clot
↓
Scab Formation
What is Haemophilia?
Definition
Haemophilia is a genetic disorder in which blood fails to
clot normally.
What Happens?
Due to deficiency of clotting factors:
- Even
small injuries may bleed for a long time.
- Clot
formation becomes difficult.
Symptoms
- Excessive
bleeding
- Easy
bruising
- Internal
bleeding
What is Thrombosis?
Definition
Formation of an unwanted blood clot inside a blood vessel.
Why is it Dangerous?
The clot may block blood flow.
Examples:
In Heart
May cause:
Heart Attack
In Brain
May cause:
Stroke
Anticoagulant Substances
These substances prevent unnecessary clotting.
Without them, blood would clot inside blood vessels all the
time.
1. Heparin
Function
Prevents formation of unwanted clots.
Doctors also use injectable heparin in hospitals.
2. Smooth Endothelial Lining
What is It?
The inner wall of blood vessels is lined by smooth
endothelial cells.
Function
Because the surface is smooth:
- Platelets
cannot easily stick.
- Clots
do not form unnecessarily.
Thus healthy blood vessels naturally resist clotting.
3. Antithrombin
Function
Antithrombin blocks thrombin activity.
Remember:
Too much thrombin
↓
Too much clotting
Antithrombin prevents this problem.
Heparin
Action
Immediate effect
Used when rapid anticoagulation is needed.
Warfarin
Warfarin → Long
Action
Acts slowly.
Used for long-term prevention of blood clots.
Aspirin
Aspirin reduces platelet aggregation.
Meaning:
Platelets become less likely to stick together.
Therefore clot formation decreases.
Sodium Citrate
Function
Sodium citrate binds calcium ions.
Remember:
Calcium is necessary for clotting.
If calcium is removed:
No Calcium
↓
No Clotting
Therefore sodium citrate is used in stored blood samples and
blood banks.
It prevents blood from clotting inside collection bags.
Difference Between Clotting and Anticoagulation
|
Clotting |
Anticoagulation |
|
Stops bleeding |
Prevents unnecessary clotting |
|
Needed after injury |
Needed inside healthy vessels |
|
Uses thrombin and fibrin |
Uses heparin, antithrombin etc. |
One-Line Summary
Haemostasis is the body's natural process of stopping
bleeding, where platelets form a plug and a series of clotting reactions
convert prothrombin → thrombin and fibrinogen → fibrin, ultimately producing a
stable clot and protective scab.
Excretion
Introduction
Every second, millions of chemical reactions occur inside our
cells.
These reactions are collectively called:
Metabolism
While metabolism is essential for life, it also produces
waste substances.
If these wastes accumulate in the body, they become poisonous
and can damage cells.
Therefore, organisms need a system to remove metabolic
wastes.
What is Excretion?
Definition
Excretion is the biological process of removing metabolic
waste products and toxic substances from the body.
Excretion vs Egestion
Students often confuse these terms.
|
Excretion |
Egestion |
|
Removal of metabolic waste |
Removal of undigested food |
|
Produced inside cells |
Never entered cells |
|
Example: Urea, CO₂ |
Example: Faeces |
|
Excretory System |
Digestive System |
Example
Excretion
Cells
↓
Urea
↓
Kidney
↓
Urine
Egestion
Food
↓
Undigested Matter
↓
Anus
↓
Faeces
Why is Excretion Necessary?
Waste substances can become harmful.
Examples:
Carbon Dioxide
Excess CO₂ lowers blood pH.
Urea
Excess urea damages tissues and organs.
Excess Salts
Can disturb water balance.
Excess Water
Can alter blood volume and pressure.
Therefore excretion is essential for survival.
Major Excretory Products in Humans
|
Waste Product |
Source |
|
Carbon dioxide |
Respiration |
|
Urea |
Protein metabolism |
|
Uric acid |
Nucleic acid breakdown |
|
Creatinine |
Muscle metabolism |
|
Excess water |
Metabolism & food |
|
Excess salts |
Food intake |
Human Excretory System
The human excretory system consists of:
1.
Kidneys
2.
Ureters
3.
Urinary
Bladder
4.
Urethra
Diagrammatic Flow
Kidneys
↓
Ureters
↓
Urinary Bladder
↓
Urethra
↓
Outside Body
1. Kidneys
What are Kidneys?
Kidneys are bean-shaped organs.
Humans have:
Two kidneys
Located on either side of the vertebral column.
Functions of Kidneys
1. Remove nitrogenous wastes
Such as:
- Urea
- Uric
acid
- Creatinine
2. Maintain Water Balance
Prevents excessive water loss.
3. Maintain Salt Balance
Regulates electrolytes.
4. Maintain Blood pH
Keeps blood slightly alkaline.
Structure of Kidney
Each kidney contains:
About 1 Million Nephrons
Nephron is the:
Structural and Functional Unit of Kidney
Just as:
Cell → Basic Unit of Life
Nephron → Basic Unit of Kidney
Nephron
What is Nephron?
A microscopic filtering unit.
Every nephron filters blood and forms urine.
Main Parts of Nephron
Glomerulus
↓
Bowman's Capsule
↓
Proximal Convoluted Tubule
↓
Loop of Henle
↓
Distal Convoluted Tubule
↓
Collecting Duct
Detailed Structure
1. Glomerulus
A network of capillaries.
Function:
Blood Filtration
Acts like a sieve.
2. Bowman's Capsule
Cup-shaped structure surrounding glomerulus.
Function:
Collects filtered fluid.
Together They Form
Malpighian Corpuscle
Glomerulus
+
Bowman's Capsule
=
Malpighian Corpuscle
Formation of Urine
Urine formation occurs in three steps:
1.
Ultrafiltration
2.
Selective
Reabsorption
3.
Tubular
Secretion
Step 1: Ultrafiltration
Occurs in:
Glomerulus
What Happens?
Blood enters under high pressure.
Small substances pass through.
Examples:
✔
Water
✔
Salts
✔
Glucose
✔ Urea
✔
Amino acids
What Does NOT Pass?
✘
Blood Cells
✘
Platelets
✘
Large Proteins
Result:
Glomerular Filtrate
Step 2: Selective Reabsorption
Occurs mainly in:
Proximal Convoluted Tubule (PCT)
What Happens?
Useful substances are reabsorbed into blood.
Examples:
- Glucose
- Amino
acids
- Vitamins
- Most
water
- Important
ions
Why?
The body should not lose valuable nutrients.
Step 3: Tubular Secretion
Occurs mainly in:
Distal Convoluted Tubule
What Happens?
Certain wastes are actively added into filtrate.
Examples:
- Hydrogen
ions
- Potassium
ions
- Drugs
- Toxins
This helps regulate:
- Blood
pH
- Salt
balance
Final Urine
After all modifications:
Remaining substances become:
Urine
Contains:
- Urea
- Excess
water
- Excess
salts
- Uric
acid
- Creatinine
Path of Urine
Nephron
↓
Collecting Duct
↓
Renal Pelvis
↓
Ureter
↓
Urinary Bladder
↓
Urethra
↓
Outside Body
Ureters
Humans have:
Two ureters
Function:
Carry urine from kidneys to bladder.
Urinary Bladder
A muscular storage sac.
Function:
Stores urine temporarily.
Urethra
Final tube of urinary system.
Function:
Removes urine from body.
Composition of Urine
Average urine contains:
Water
About 95%
Solutes
About 5%
Including:
- Urea
- Uric
acid
- Salts
- Creatinine
Artificial Kidney (Dialysis)
Sometimes kidneys fail.
This condition is called:
Kidney Failure
What Happens?
Waste products accumulate in blood.
This can be dangerous.
Dialysis
A machine removes waste from blood.
This machine is called:
Artificial Kidney
Principle
Works on:
Diffusion
Waste moves from blood into dialysis fluid.
Kidney Transplant
Permanent treatment for severe kidney failure.
A healthy kidney from a donor is transplanted.
Other Excretory Organs
Kidneys are not the only excretory organs.
Lungs
Remove:
Carbon Dioxide
and
Water Vapour
Skin
Contains sweat glands.
Removes:
- Water
- Salts
- Small
amounts of urea
Liver
Detoxifies harmful substances.
Produces urea from ammonia.
Excretion in Plants
Plants do not have kidneys.
Yet they also remove wastes.
Methods
1. Diffusion
Gases leave through:
- Stomata
- Lenticels
2. Storage
Wastes stored in:
- Leaves
- Bark
- Fruits
3. Shedding
Old leaves fall off carrying wastes.
4. Secretions
Plants produce:
- Resins
- Gums
- Latex
These often contain waste substances.
Osmoregulation
Definition
Maintenance of proper water and salt balance in the body.
Kidneys play a major role in osmoregulation.
Complete Flow Chart
Metabolism
↓
Waste Formation
↓
Blood
↓
Kidneys
↓
Nephron
↓
Filtration
↓
Reabsorption
↓
Urine Formation
↓
Ureter
↓
Urinary Bladder
↓
Urethra
↓
Outside Body
One-Line Summary
Excretion is the process of removing metabolic waste products
from the body, primarily through the kidneys, where millions of nephrons filter
blood, reabsorb useful substances, and produce urine to maintain internal
balance and protect the body from toxic waste accumulation.
Safar-e-ilm mein thak kar jo kahīñ baith gayā,
Woh manzil se nahīñ, apne irādoñ se bichhaṛā.
Translation:
"The one who grew weary on the journey of learning and
stopped to rest,
Did not lose touch with the destination, but with his own determination."
Explanation:
A person gets tired during the journey of gaining knowledge
and gives up, the real loss is not that the destination becomes impossible to
reach. The real loss is that the person becomes separated from their own
determination, courage, and commitment.
ALAMIN
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