respiration(change name )

Question 1

how does photosynthesis work

Answer 1

photosynthesis transfers energy in the form of sunlight in to the chemical energy of carbohydrates. instead cells use ATP as their immediate energy source . the formation of ATP from the breakdown of glucose takes place during the process of cellular repiration depending on whether oxygen is involved or not

Question 2

what are the stages of aerobic respiration

Answer 2

• glycolysis - the splitting of glucose into 2 pyruvate molecules
  -link reaction - the pyruvate molecules enter into a series of reactions which leads to the formation of the acetyl coenzyme A
  krebs cycle - the introduction of acetyl coenzyme A into a cycle of oxidation -reduction reactions that yield some ATP and a large quantity of NAD and FAD
  -oxidative phosphorylation - the use of the electrons associated with reduced NAD and FAD released from the krebs cycle to synthesis ATP with water as a by product

Question 3

what is glycolysis

Answer 3

glycolysis is the initial stage of both aerobic and anaerobic respiration. it occurs in the cytoplasm of all living cells and is the process by which glucose is split into two molecules of pyruvate
it has 2 stages , phosphorylation - addition of phosphate groups as ATP-> ADP + Pi
oxidation and reduction - addition and loss of hydrogen respectively (for glycolysis)

Question 4

what is NAD

Answer 4

NAD transfers electrons from one molecule to another within cells . it exists in two forms reduced NAD (NADH) and NAD+ (without hydrogen)

Question 5

what are mitcondria

Answer 5

mitocondria are the site of aerobic repsiration , producing the vast majority of ATP molecules used by the cell to release energy

Question 6

why do mitocondria have a double membrane

Answer 6

they have a double membrane which determine the molecules that can pass into and out of the mitocondrion

Question 7

what is the actual process of glycolysis

Answer 7

1) glucose is phosphorylated by the addition of two phosphate molecules to produce phosphorylated glucose. the phosphate groups come from the hydrolysis of two ATP molecules to ADP. this also provides the energy to activate glucose
2) each glucose molecule is split into 2 triose phosphate( 3 carbon molecule)
3) each triose phosphate molecule is oxidised to remove a hydrogen molecule which is transferred to NAD to produce NADH ( reduced NAD), each triose phopshate is then converted into pyruvate which releases 2 molecules of ATP per molecule and reduced NAD per molecule therefore 2 reduced NAD produced

Question 8

what is the summary for glycolysis

Answer 8

• net gain of 2 ATP molecules
  -2 molecules of reduced NAD
• 2 molecules of pyruvate

Question 9

what is the link reaction

Answer 9

after glycolysis these pyruvate molecules posess potential energy that can only be released in a process called the krebs cycle . but before they can enter the cycle these pyruvate molecules must first be oxidised in the ink reaction. both the krebs cycle and link reaction takes place inside the mitocondria

Question 10

what happens in the link reaction

Answer 10

reduced NAD and pyruvate in the cytoplasm actively transported into the matrix of the mitoncdria

Question 11

what happens in the link reaction

Answer 11

the pyruvate is oxidised to acetate . the 3 carbon pyruvate loses a carbon dioxide molecule to form acetate ( a 2 carbon molecule) and also hydrogen which goes to NAD to form reduced NAD. the acetate combines with coenzyme A to produce acetylcoenzyme A ( a 2 carbon molecule )

Question 12

what is the overall equation for the link reaction

Answer 12

pyruvate + NAD + coenzyme A -> acetyl coenzyme A + reduced NAD + Co2

Question 13

how many times does the link reaction occur

Answer 13

twice ( two pyruvate molecules produced per glucose molecule) therefore in total 2 acetylcoenzyme A produced , 2 co2 produced and 2 reduced NAD produced

Question 14

what is the krebs cycle

Answer 14

involves a series of oxidation- reduction reactions that take place in the matrix of the mitocondria

Question 15

what happens in the krebs cycle

Answer 15

1) the 2 carbon acetylcoenzyme A from the link reaction combines with a 4 carbon molecule to produce a 6 carbon molecule
2) this coenzyme A is released
3)then in a series of reactions this 6 carbon molecule loses 2 carbon dixoides and hydrogens to produce a 4 carbon molecule , reduced NAD , 2 carbon dioxide and reduced FAD and ATP

Question 16

what are the products of the krebs cycle

Answer 16

per cycle
-3x reduced NAD
-2 carbon dioxide
-1 ATP
-1 FAD
per glucose molecule
-6 nad
- 4 carbon dioxide
-2 atp
-2 fad

Question 17

In endurance sports, such as long distance running, stores of glucose in the body are often depleted after around two hours.

Using your knowledge of aerobic respiration, suggest how athletes are able to run for longer than two hours

Answer 17

After glucose stores have been used up in aerobic respiration, triglycerides and amino acids can be used in respiration. Triglycerides are broken down into glycerol and three fatty acids. Glycerol is converted into triose phosphate which can take part in glycolysis. The fatty acids are converted into acetyl CoA molecules that can take part in the Krebs cycle. The majority of amino acids with three carbons are converted into pyruvate which is used in the link reaction, whereas 4−

and 5−

carbon amino acids are converted into intermediates in the Krebs cycle. By using amino acids and triglycerides, ATP continues to be produced in the absence of glucose stores. This means ATP is available for use as an energy source for the contraction of muscles that allows the athlete to keep running.

Question 18

what happens in oxidative phosphorylation

Answer 18

We’ve seen that the energy ATP synthase needed to catalyse the production of ATP is provided by chemiosmosis: the diffusion of protons down the proton gradient through ATP synthase.

In order to make sure that ATP synthase has enough energy to keep producing ATP, the proton gradient needs to be maintained.

To maintain the proton gradient, protons are actively transported from the matrix to the intermembrane space. This ensures that there’s always a higher concentration of protons in the intermembrane space compared to the matrix.