Cellular respiration

Grade 10
Life Sciences
Cellular Respiration: Releasing Energy
from Food
• Definition: Cellular respiration is the process where cells
break down organic compounds (glucose) to release energy
in the form of ATP.

• Requirements: Requires glucose and usually oxygen.

• Products: The main products are carbon dioxide, water, and

ATP.
Cellular Respiration Equation:

Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)

C₆H₁₂O₆ + O₂ → CO₂ + H₂O + ATP
Uses of Energy (ATP):

• Energy is essential for all life functions. It is used for:

1. Growth: Making large molecules (proteins, fats) and new cell

components.
2. Movement: The contraction and relaxation of muscles (e.g., heart, blood
vessels).
3. Cell Division: Powering DNA replication and chromosome movement.
4. Maintaining Body Temperature: Heat released during the reactions is
used by endothermic organisms (whose body temperature stays
constant).
5. Active Transport: Moving substances against a concentration gradient.
Structure of the Mitochondrion:

• Definition: The mitochondrion is an oval-shaped organelle found in both plant

and animal cells where aerobic respiration is completed.

• Double Membrane: The outer membrane is permeable, allowing substances like

oxygen and pyruvic acid to enter.
• Cristae: The inner membrane is folded into finger-like projections called cristae.
These folds increase the surface area for cellular respiration to occur.
• Matrix: The ground substance inside the inner membrane, containing DNA,
ribosomes, and enzymes.
• Enzymes: Manufactured by ribosomes and are crucial for the respiration
process.
• Number of Mitochondria: A cell's energy needs are reflected in the number of
mitochondria it contains.
 Mitochondrial Eve
is the name given to the
matrilineal most recent
common ancestor of all
living humans.
She is not the first woman
of our species, but rather
the woman whose
mitochondrial DNA
(mtDNA) is carried by all
humans today.
This means that all humans
alive today can trace their
direct maternal lineage
back to her.

Mitochondrial DNA (mtDNA)

is passed down exclusively
from mother to child.

Therefor, all humans alive

today share the same mtDNA,
meaning they all trace their
ancestry back to a single
female ancestor.
Types of Respiration:
Aerobic Respiration: Anaerobic Respiration :

• Occurs in the presence of • Occurs in the absence of

oxygen. oxygen.
• Very efficient, producing a net • Very inefficient, producing a net
gain of 36-38 ATP molecules. gain of only 2 ATP molecules.
• Takes place in the cytoplasm • Takes place only in the
and mitochondria. cytoplasm.
• The glucose is not completely
broken down.
• (Fermentation)
Anaerobic Respiration in Detail:

• Begins with glycolysis in the cytoplasm. Glucose is broken

down into two pyruvic acid molecules.

• In Plant & Yeast Cells: Pyruvic acid is converted into ethanol

and carbon dioxide.
• In Animal Cells: Pyruvic acid is converted into lactic acid.
Anaerobic Respiration in Detail:

Glucose (6-carbon molecule)

[Glycolysis in Cytoplasm]

Pyruvic Acid (2 x 3-carbon molecules)

In Animal Cells In Plant Cells/Yeast
→ Lactic Acid + ATP → Ethanol + Carbon Dioxide + ATP
Anaerobic Respiration in Detail: (continued)

• Oxygen Debt: During intense exercise, when oxygen supply

cannot meet the energy demand, an oxygen debt occurs, and
anaerobic respiration takes over. The resulting lactic acid
buildup causes muscle soreness and stiffness.

• Paying the Debt: After exercise, breathing and heart rate

remain high to repay the oxygen debt. Oxygen is used to
convert lactic acid back into glucose or break it down into
carbon dioxide and water.
Similarities & Differences:

Table showing the similarities and difference between Aerobic and Anaerobic respiration

Aerobic Respiration Anaerobic Respiration

Oxygen Dependent on oxygen Independent of oxygen

Energy Net gain of 36 ATP (more) Net gain of 2 ATP (less)
Products Carbon dioxide and water Animals: Lactic acid and carbon
dioxide
Plants & yeast: Ethanol and
carbon dioxide
Location Mitochondria and cytoplasm Cytoplasm only
Role of Anaerobic Respiration in Industry
(Biotechnology): https://www.youtube.com/shorts/oHStaGCayLc

1. Fermentation: A type of anaerobic respiration in microorganisms

like yeast.
2. Products: Produces alcohol and carbon dioxide as byproducts.
3. Applications: Used in industries to make products like beer, wine,
and bread.
4. Bread-making: Yeast ferments sugars in the dough, releasing
carbon dioxide that causes the bread to rise. The alcohol is
burned off during baking.
5. Winemaking: Yeast ferments sugars from crushed grapes in a vat,
producing alcohol and carbon dioxide.
Energy as ATP:

• ATP (Adenosine Triphosphate): An energy-rich compound

that is the primary energy currency of the cell.
• ATP/ADP Cycle: Energy released from respiration is used to
combine a phosphate molecule with ADP (Adenosine
Diphosphate) to form ATP.
• Energy Release: When a cell needs energy, a phosphate bond
is broken, releasing approximately 34 kJ of energy and forming
ADP again.
• Transport: ATP molecules move freely within the cell to supply
energy wherever it is needed.
Terminology:

• Cellular Respiration: The process where glucose is broken down to release

energy.
• ATP: Stands for Adenosine Triphosphate, an energy-rich compound.
• Aerobic Respiration: Respiration in the presence of oxygen.
• Anaerobic Respiration: Respiration in the absence of oxygen.
• Cristae: Finger-like projections in the mitochondrion that increase surface area.
• Phosphorylation: The addition of a phosphate molecule to glucose with the
addition of energy.
• Pyruvic acid: A 3-carbon molecule formed from the breakdown of glucose.
• Oxygen debt: Occurs when available oxygen cannot meet energy demands.
• Fermentation: Anaerobic respiration in microorganisms.
• Biotechnology: Using biological processes for industrial production.
 QUESTION 1

The energy rich compound associated with respiration is…

A. ATP
B. ADP
C. P
D. None of the above
 QUESTION 2

The processes that requires energy in the body are…

A. Growth, passive transport and cell division

B. Mitosis, meiosis and passive transport
C. Growth, mitosis and meiosis
D. Both A and C
 QUESTION 3

The organelle in which cellular respiration occurs is…

A. Chloroplast
B. Nucleus
C. Mitochondrion
D. Golgi apparatus
 QUESTION 4

The mitochondrion contains the following components…

A. DNA, stoma, crista

B. Nucleus, crista, stroma
C. DNA, crista, nucleus
D. DNA, crista, matrix
 QUESTION 5

The phase of respiration that occurs in the mitochondrion is…

A. Kreb’s cycle
B. Glycolsis
C. Oxidative phosphorylation
D. Both A and C
 QUESTION 6

The phase of respiration that occurs in the cytoplasm is…

A. Kreb’s cycle
B. Glycolsis
C. Oxidative phosphorylation
D. Both A and C
 QUESTION 7

The energy released from the energized hydrogen atom during oxidative phosphorylation
is used to…

A. Combine ADP + P to form ATP

B. Produce pyruvic acid

C. Break down pyruvic acid

D. Break down glucose

 QUESTION 8

Energized hydrogen atoms and carbon dioxide is released during…

A. Glycolysis
B. Kreb’s cycle
C. Oxidative phosphorylation
D. Both B and C
 QUESTION 9

Energized hydrogen atoms are transferred from one co-enzyme carrier to the next during…

A. Glycolysis

B. Kreb’s cycle

C. Oxidative phosphorylation

D. Both B and C
 QUESTION 10

The 6 carbon molecule undergoes a step wise break down to form two pyruvic acids
during…

A. Glycolysis

B. Kreb’s cycle

C. Oxidative phosphorylation

D. Both B and C
 QUESTION 11

______ is an adaptation that increases the surface area for respiration.

A. Smooth outer membrane

B. Permeable outer membrane
C. Presence of cristae
D. Presence of DNA and ribosome
 QUESTION 12

______ is an adaptation that allows oxygen and glucose to enter the mitochondrion for
respiration.

A. Smooth outer membrane

B. Permeable outer membrane

C. Presence of cristae

D. Presence of DNA and ribosome

 QUESTION 13

______ is an adaptation that allows for easy movement of the mitochondrion around the
cytoplasm.

A. Smooth outer membrane

B. Permeable outer membrane

C. Presence of cristae

D. Presence of DNA and ribosome

 QUESTION 14

______ is an adaptation that allows for the production of enzymes for respiration.

A. Smooth outer membrane

B. Permeable outer membrane
C. Presence of cristae
D. Presence of DNA and ribosome
 QUESTION 15

During anaerobic respiration in plants the products are…

A. ATP, carbon dioxide and water

B. ATP, alcohol and carbon dioxide
C. ATP, lactic acid and carbon dioxide
D. ATP, alcohol and water
 QUESTION 16

During aerobic respiration the products formed are…

A. ATP, carbon dioxide and water

B. ATP, alcohol and carbon dioxide
C. ATP, lactic acid and carbon dioxide
D. ATP, alcohol and water
 QUESTION 17

During fermentation in bacteria the products formed are…

A. ATP, carbon dioxide and water

B. ATP, alcohol and carbon dioxide
C. ATP, lactic acid and carbon dioxide
D. ATP, alcohol and water
 QUESTION 18

The enzyme that is used to curdle milk is…

A. Called rennin
B. An example of a protease
C. Used during the production of alcohol
D. Both A and B
 QUESTION 19

Bread is able to rise when baked because of…

A. Anaerobic respiration
B. Aerobic respiration
C. The presence of alcohol
D. Both A and C
 QUESTION 20

A similarity between aerobic and anaerobic respiration is that…

A. Both require oxygen

B. Both release alcohol

C. Both release water

D. Both require glucose

 Solutions Final assessment Questions

1. A 11. C
2. C 12. B
3. C 13. A
4. D 14. D
5. D 15. B
6. B 16. A
7. A 17. C
8. B 18. D
9. C 19. A
10. A 20. A