5A - photosynthesis and respiration

Question 1

what are the 4 stages of aerobic respiration and where do they occur?

Answer 1

Glycolysis - cytoplasm
link reaction - mitochondrial matrix
krebs cycle - mitochondrial matrix
oxidative phosphorylation - inner membrane / cristae

Question 2

describe gylcolysis

Answer 2

glucose (6C) is phosphorylated due to the hydrolysis of 2ATP into 2ADP +2Pi forming glucose phosphate (6C) . this molecules splits into triose phosphate ( 3C X 2). this molecule is oxidised, losing a hydrogen which is picked up by the co - enzyme, 2NAD being reduced into 2NADH. 2ADP and 2Pi forms 2ATP in a condensation reaction. 2 3C pyruvates are formed.

Question 3

what is the gain of molecules at the end of glycolysis

Answer 3

2ATP, 2NADH and 2 3C pyruvate molecules.

Question 4

describe the link reaction

Answer 4

pyruvate molecule is oxidised and NAD is reduced forming NADH. the pyruvate is decarboxylated releasing CO2 and producing an acetate molecule. acetate reacts with co-enzyme A forming acetyl coenzyme A

Question 5

describe the krebs cycle

Answer 5

acetyl CoA reacts with a 4C molecule producing a 6C moleucle. the 6C molecule is decarboxylated releasing 2 carbons and producing 2 CO2 molecules. it is oxidised releasing hydrogens which are taken up by by 3 NAD enzymes and 1 FAD enzyme, producing 3NADH and 1FADH2. an ATP molecule is produced via substrate level phosphorylation. this will reproduce a 4C molecule.

Question 6

what are the products of the krebs cycle

Answer 6

2CO2, 3NADH,1FADH2 and 1ATP

Question 7

describe oxidative phosphorylation

Answer 7

NADH and FADH2 are oxidised releasing the H. the H splits into an electron and a proton. the electron moves across the etc through cattier proteins, releasing energy which is used in the active transport of protons across the inner membrane space, this forms an electro-chemical gradient. protons move back to the matrix through ATP synthase via facilitated diffusion. this causes rotation- for every 1 proton there is 1 rotation, and 1 ATP molecule is made every 3 rotations-
oxygen acts as the final electron acceptor, joining with 2 electrons and 2 protons to produce 1 water molecule.

Question 8

what happens to lipids before they are used as products

Answer 8

they are hydrolysed by lipase into fatty acids and glycerol. the glycerol is phosphorylated and then converted into triose phosphate, entering glycolyis

Question 9

what happens to the glycerol before entering the process of respiration

Answer 9

the glycerol is phosphorylated and then converted into triose phosphate, entering glycolyis

Question 10

what happens to the fatty acids before entering the process of respiration

Answer 10

the fatty acids are converted into acetyl conenzyeme A, entering the krebs cycle

Question 11

when is protein used at respiratory substrate

Answer 11

severe starvation

Question 12

what happens to proteins inorder to be used as a respiratory substrate

Answer 12

proteins are hydrolysed into amino acids. excess amino acids are deaminated and converted into urea and excreted

Question 13

what is deamination

Answer 13

removal of the amine group NH2

Question 14

what happens to the remaining molecules of a protein

Answer 14

they enter the respiratory pathway depending on the number of carbon atoms. 3C are converted to pyruvates, 4C and 5C enter the krebs cycle directly

Question 15

pathway of alcohol fermentation in anaerobic respiration

Answer 15

occurs in yeast and some plants.
pyruvate will lose a molecule of CO2 and accepts a hydrogen from NADH. this produces ethanol and regenerates NAD

Question 16

pathway of lactate fermentation in anaerobic respiration

Answer 16

occurs in animals and bacteria.
pyruvate accepts a hydrogen from NADH.
this produces lactate and regenerates NAD

Question 17

negatives of respiring anaerobically in animals

Answer 17

accumulation of lactate causes cramp and muscle fatigue. as lactate is acidic it will reduce the pH affecting enzymes

Question 18

what is anerobic respiration and where does it occur

Answer 18

respiration in the absence of oxygen. occuring in the cytoplasm of the cell

Question 19

why is NADH oxidised

Answer 19

to regenerate NAD to be reused in glycolysis

Question 20

what is the efficiency of aerobic respiration

Answer 20

38 molecules of ATP produced = 32% efficiency

Question 21

what is the net production of ATP in anaerobic respiration

Answer 21

2 molecules

Question 22

word equation for photosynthesis

Answer 22

carbon dioxide + water -> glucose + oxygen

Question 23

what type of reaction is photosynthesis

Answer 23

endothermic

Question 24

why do plants need energy

Answer 24

photosynthesis
active transport
DNA replication
protein synthesis
mitosis + meiosis

Question 25

what is photosynthesis

Answer 25

a series of biochemical reactions which occur in different part of the chloroplast, where energy from sunlight is used to make glucose from carbon dioxide and water

Question 26

structure of an ATP molecule

Answer 26

adenine, ribose sugar and 3 phosphate groups

Question 27

why is ATP a good energy source

Answer 27

1. releases energy in small and manageable amounts so no energy is wasted
2. ATP is easily broken down so energy is easily released
3. cant leave the cell so there is always an energy source

Question 28

location of the dependent and independent reactions

Answer 28

dependent - thylakoid membrane of the chloroplasts
independent - stroma of the chloroplast

Question 29

thylakoid membrane

Answer 29

folded membrane containing chlorophyll
embedded with transmembrane electron carrier proteins

Question 30

chlorophyll

Answer 30

located on the thylakoid membrane
different proteins that absorb light
different proportions of each pigment leads to different colours of leaves

Question 31

light-dependent reaction

Answer 31

first stage of photosynthesis
occurs in the thylakoid membrane
uses light energy and water to produce ATP and NADH for the light-independent reaction
involves photoionisation of chlorophyll, photolysis and chemiosmosis

Question 32

photolysis

Answer 32

light energy absorbed by chlorophyll, splitting water into oxygen, H+ and e-

Question 33

products of photolysis

Answer 33

oxygen - used in respiration or diffuses out the stomata
H+ - picked up by NADP to form NADPH
e- - passed along the chain of electron carrier proteins

Question 34

photoionisation of chlorophyll

Answer 34

light energy absorbed by the chlorophyll excites electrons so they move to a higher energy level, leaving the chlorophyll
some of the energy released is used to make ATP and NADPH

Question 35

chemiosmosis

Answer 35

electrons gain energy and move across the electron carrier proteins in the thylakoid membrane
they release energy which pumps protons across the thylakoid membrane
an electrochemical gradient made protons pass back across via ATP synthase producing ATP

Question 36

what happens to the protons after chemiosmosis

Answer 36

combine with NADP to become NADPH

Question 37

products of the light independent reaction

Answer 37

ATP
NADPH
oxygen

Question 38

light independent reaction

Answer 38

calvin cycle
uses CO2, NADPH and ATP to form glucose
occurs in the stroma which contains the enzyme rubisco

Question 39

1st step of the calvin cycle

Answer 39

CO2 combines with ribulose bisphosphate (5c) to form 2 glycerate - 3- phosphate (3c) molecules
catalysed by rubisco

Question 40

2nd step of the calvin cycle

Answer 40

GP is reduced to form triose phosphate
the energy is provided by the hydrolysis of 2 ATP molecules
NADPH is also oxidised for the H+

Question 41

3rd step of the calvin cycle

Answer 41

5/6 turns of the calvin cycle produce RuBP from triose phosphate
this also uses energy from the hydrolysis of ATP

Question 42

production of hexose sugars in the LIR

Answer 42

1/6 turns of the calvin cycle