2. cellular respiration

Question 1

what is respiration

Answer 1

Respiration is a series of metabolic pathways which bring about the release of energy from the breakdown of food molecules e.g. glucose. The energy released is used to regenerate the energy transfer molecule ATP.

Cellular respiration is central to metabolism and is linked to many other pathways.

Question 2

what is a phosphorylation reaction

Answer 2

involves a phosphate group being added to a substrate.

ATP also has a role in carrying out phosphorylation reactions

Question 3

describe the formation of ATP

Answer 3

The formation of ATP from ADP and Pi is a phosphorylation reaction since a phosphate group is added to ADP to form ATP

Question 4

name the 3 sets of reactions in cellular respiration

Answer 4

1) glycolysis
2) citric acid cycle
3) electron transport chain

Question 5

describe the first stage of respiration, glycolysis

Answer 5

is the breakdown of glucose to pyruvate in the cytoplasm.

ATP is required for the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis. This leads to the generation of more ATP during the energy pay-off stage and results in a net gain of ATP.

Question 6

what do dehydrogenase enzymes do

Answer 6

remove hydrogen ions and electrons from the intermediate substrate molecules.

These hydrogen ions and electrons immediately attach to co-enzyme molecules called NAD, forming NADH. These co-enzyme molecules are also known as hydrogen carriers.

Question 7

where does the citric acid cycle take place

Answer 7

the citric acid cycle takes place in the matrix of the mitochondria

Question 8

what is oxygen known as in the electron transport chain stage

Answer 8

the final hydrogen/electron-acceptor

Question 9

how is water made during the final respiration stage

Answer 9

hydrogen ions and electrons are passes along the inner membrane transport chain so then they are free to join with the oxygen molecule to make water

Question 10

describe fermentation

Answer 10

in the absence of oxygen, fermentation takes place in the cytoplasm

results in much less ATP (2ATP) being produced than in aerobic respiration (38ATP).

Question 11

describe fermentation in animal cells

Answer 11

pyruvate is converted to lactate in a reversible reaction

Question 12

describe fermentation in plant/yeast cells

Answer 12

ethanol and CO2 are produced in an irreversible reaction

Question 13

what is the metabolic pathway for fermentation in plants and yeast

Answer 13

glucose —> pyruvate —> ethanol + carbon dioxide

Question 14

what is the metabolic pathway for fermentation in animal cells.

Answer 14

glucose –> pyruvate <—> lactate (lactic acid)

Question 15

describe the 6 stages of the citric acid cycle

Answer 15

-in aerobic conditions, pyruvate is broken down to an acetyl group (and carbon dioxide is released)

-acetyl combines with coenzyme A forming acetyl coenzyme A

-the acetyl group from acetyl coenzyme A combines with oxaloacetate to from citrate

-during a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide

-dehydrogenase enzymes removes hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH (in glycolosis and CCA)

-the hydrogen ions and electrons from NADH are passed to the elcectron transport chain on the inner mitochondria membrane

Question 16

describe the 5 stages of the electron transport chain

Answer 16

-the ETC is a series of carrier proteins attached to the inner mitochondrial membrane

-electrons are passed along the ETC releasing energy

-the energy allows hydrogen ions to be pumped across the inner mitochondrial membrane

-the flow of these ions back through the membrane protein, ATP synthase, results in the production of ATP

-finally, hydrogen ions and electrons combine with oxygen to form water