12.1 Glycolysis

Question 1

What is aerobic respiration

Answer 1

Glucose can’t be used directly by cells as a source of energy so cells use ATP as their immediate energy source

Requires oxygen and produces CO2, water and lots of ATP

Question 2

What is anaerobic respiration

Answer 2

Takes place in the absence of oxygen and produces lactate in animals
Or ethanol and CO2 in plants/fungi

Only a small amount of ATP is produced in both cases

Question 3

What are the 4 stages of aerobic respiration

Answer 3

. Glycolysis: Split 6 carbon glucose into two 3 carbon pyruvate molecules

. Link reaction: The Pyruvate molecules enter into series of reactions to make acetylcoenzyme A which has 2 carbons

. Krebs cycle: Introduction of acetylcoenzyme A into a cycle of oxidation-reduction reactions that make some ATP and and a large quantity of reduced NAD and FAD

.Oxidative phosphorylation: Using electrons, associated with FAD and NAD, released from krebs cycle to synthesise ATP with water produced as a by-product

Question 4

What part of the cell does glycolysis occur and why

Answer 4

In the cytoplasm of all living cells.
The enzymes required for it are in the cytoplasm so it doesn’t need an organelle or membrane to occur

Question 5

Does glycolysis occur for only aerobic respiration?

Answer 5

Glycolysis occurs for both aerobic and anaerobic, because it doesn’t require oxygen.

But after pyruvate is made there are two separate reactions depending on if its aerobic or not.
It can be converted into lactate or ethanol if anaerobic occurs

Question 6

There are 4 stages of glycolysis.

Describe stage 1: The phosphorylation of glucose to glucose phosphate

Where do the phosphate molecules come from for this

Answer 6

. Before it can be split in two, glucose has to be made more reactive
. So two phosphate molecules are added to it
This is called phosphorylation

Phosphate molecules come from hydrolysis of two ATP molecules to ADP. This provides the energy to activate glucose and lowers the activation energy for the enzyme reaction to occur

Question 7

Stage 2: Splitting of phosphorylated glucose

Answer 7

Each glucose molecule is split into a 3 carbon molecule
Each known as triose phosphate

Question 8

Stage 3: Oxidation of triose phosphate

Answer 8

Hydrogen is removed from each of the two triose phosphate and is transferred to a hydrogen carrier molecule known as NAD to form reduced NAD (NADH)

because pyruvate is an acid to releases the hydrogens

Question 9

Stage 4: The production of ATP

Answer 9

Enzyme controlled reactions convert each triose phosphate into another 3 carbon molecule called pyruvate

In the process, two molecules of ATP are regenerated from ADP

Question 10

What is the net yield of ATP

Answer 10

Four molecules of ATP are produced in stage 4 (including both triose phosphates)
However two ATPs were used up at the initial phosphorylation of glucose

So overall, two ATPs are produced

Question 11

Net yield of NADH

Net yield of pyruvate

Answer 11

Two molecules in total of NADH are produced

Two molecules of pyruvate produced