Cellular Respiration

Topic 3.7 and 3.8

Assessment Statements: SL 3.7.1 Define cell respiration.

3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by

glycolysis

into pyruvate, with a

small yield of ATP

.

3.7.3 Explain that, during

anaerobic

cell respiration, pyruvate can be converted in the cytoplasm into

lactate

, or

ethanol and carbon dioxide

, with no further yield of ATP.

3.7.4 Explain that, during

aerobic

cell respiration, pyruvate can be broken down in the

mitochondrion

carbon dioxide and water with

a large yield of ATP.

into

Cellular Respiration: Standard level

How does the process of cellular respiration yield ATP (chemical energy) from food?

1.What do you already know about cellular respiration?

2.What organelle in the cell is the

“

powerhouse

”

that makes energy for the cell

?

What is ATP?

• • • Energy ‘currency’ used by all cells Adenosine triphosphate Organic molecule containing high-energy phosphate bonds

Chemical Structure of ATP Adenine Base 3 Phosphates Ribose Sugar

How Do We Get Energy From ATP?

By breaking the high energy bonds between the last two phosphates in ATP

ATP hydrolase (ATP’ase)

catalyses the breakdown of ATP into ADP + P i

Each day, you hydrolyse 10 25 ATP molecules

ATP-ase ATP Synthetase

H 2 O HYDROLYSIS (Adding H 2 O)

How is ATP re-made?

• •

Substrate-level phosphorylation

(using enzymes : in the cytoplasm of the cell and the matrix of the mitochondrion)

Chemiosmosis

ATP synthase ) (in the mitochondria, using

Substrate level phosphorylation and chemiosmosis

Definition of cellular respiration

Controlled release of energy from organic compounds to produce ATP

• • • Cells break down organic compounds by SLOW oxidation Chemical energy is stored in covalent bonds By releasing energy in a controlled way, it can be trapped in the ‘useful’ form of ATP

Cellular Respiration

Breakdown of one glucose results in 36 to 38 ATP molecules

• • •

Metabolic Pathway that breaks down carbohydrates Process is exergonic as high-energy glucose is broken into CO 2 H 2 O and Process is also catabolic because glucose breaks into smaller molecules

Equations for aerobic respiration

All of these are fine!....

Equation for Cellular Respiration C 6 H 12 O 6 + 6O 2 YIELDS 6CO 2 + 6H 2 0 + e -

+ heat

+ 36-38 ATP

1.

2.

3.

Stages of Cellular Respiration

Glycolysis ALWAYS OCCURS Anaerobic pathways if no oxygen available

(Lactic acid and Ethanol fermentation)

Aerobic pathways if oxygen available

(Link reaction, Krebs cycle, electron transport chain)

Where Does Cellular Respiration Take Place?

glycolysis occurs in the cytoplasm Krebs Cycle & ETC Take place in the mitochondria

Glycolysis:

Always the initial stage of respiration

• • • • Location: cytoplasm Substrate: glucose Requires input of

2 ATP

Products: pyruvate, (NADH),

4 ATP

Glycolysis is an anaerobic process: no oxygen required the movie...

Glycolysis

If no oxygen is available, glycolysis (anaerobic) is followed by fermentation (anaerobic)

Why fermentation?

In the absence of oxygen, glycolysis soon stops unless there is an alternative acceptor for the electrons produced from the glycolytic pathway

Fermentation

1. Alcoholic fermentation

Pyruvate is converted into ethanol plus carbon dioxide and NAD +

2. Lactate fermentation

Pyruvate is converted into lactate and NAD +

Alcoholic fermentation in yeast

Alcoholic fermentation in yeast • • • • Pyruvate is produced from glycolysis 3-carbon pyruvate is converted to 2-carbon ethanol and carbon dioxide Generation of carbon dioxide helps bread products to rise Yeast is used to produce ethanol

Lactate fermentation in mammals

• • Lactate is a 3 carbon molecule NAD + is regenerated to allow glycolysis to continue

Aerobic respiration

• • • • • Takes place in the mitochondria of eukaryotic cells Substrate : pyruvate

Produces LOTS of ATP (28 – 38 ATP): 90% of total ATP from respiration

Also produces carbon dioxide, water and heat Oxygen is the final electron acceptor

Aerobic respiration: the most efficient pathway for ATP generation

Aerobic respiration

• • • • 2 pyruvate molecules enter the mitochondrion Pyruvate loses a CO 2 molecule and becomes acetyl CoA Krebs cycle produces 2 ATP and CO 2 Electron transport chain produces 34 ATP and water • • Aerobic respiration

completely

oxidises a glucose molecule Anaerobic respiration

does not completely oxidise glucose

– ethanol, lactate and carbon dioxide are by products

Some practice questions on respiration…

1.

How do cells capture the energy released by cell respiration?

A.

They store it in molecules of carbon dioxide.

B.

C.

They produce glucose.

The energy is released as pyruvate.

D.

They produce ATP.

(Total 1 mark)

Some practice questions on respiration…

2.

Which process produces the most ATP per molecule of glucose?

A.

B.

Anaerobic respiration in a yeast cell Aerobic respiration in a bacterial cell C.

Glycolysis in a human liver cell D.

The formation of lactic acid in a human muscle cell

(Total 1 mark)

Some practice questions on respiration…

3. Which of the following is the best definition of cell respiration?

A.

A process needed to use energy, in the form of ATP, to produce organic compounds B.

A process used to provide oxygen to the atmosphere C.

A controlled release of energy, in the form of ATP, from organic compounds in cells D.

A controlled release of energy in the production of food from organic compounds

(Total 1 mark)

Some practice questions on respiration…

4. Which of the following processes produces CO

2 ?

I.

Glycolysis II.

III.

Alcohol (ethanol) fermentation Lactic acid production A.

B.

C.

D.

I only II only I and II only I, II and III

(Total 1 mark)

Some practice questions on respiration…

4. Which of the following processes produces CO

2 ?

I.

Glycolysis II.

III.

Alcohol (ethanol) fermentation Lactic acid production A.

B.

C.

D.

I only II only I and II only I, II and III

(Total 1 mark)

Some practice questions on respiration… 4.

State a word equation for anaerobic cell respiration in humans.

(1 mark)