Respiration

Question 1

catabolic reaction

Answer 1

breaking down of complex molecules in to smaller molecules

Question 2

anabolic reaction

Answer 2

builds molecules the body needs

Question 3

stages of respiration and where they take place

Answer 3

glycolysis-cytoplasm of cell
link reaction-matrix of mitochondria
krebs cycle- matrix
electron transport chain- utilises proteins found in membrane of the cristae

Question 4

glycolysis

Answer 4

-first stage of anaerobic and aerobic respiration
-carbohydrate splitting
-occurs in cytoplasm, anaerobic process
2 stages: phosphorylation, oxidation

Question 5

stages of glycolysis

Answer 5

-glucose is phosphorylated into glucose phosphate (6C) by 2xATP
-glucose phosphate splits into 2x3C molecules of triose phosphate (TP)
-TP is oxidised to form 2xpyruvate
-NAD collects H+ ions forming 2 reduced NAD
-net gain of 2x ATP

Question 6

why is there a net gain of ATP

Answer 6

4 ATP are produced, but 2 were used at the start, so net gain of 2 ATP

Question 7

products of glycolysis and where they go

Answer 7

-2 reduced NAD- goes to the ETC
-2 pyruvate- actively transported into mitochondria for link reaction
-2 ATP- used for energy

Question 8

link reaction

Answer 8

-oxidative carboxylation- removal of CO2 and H+ from pyruvate producing acetate.
-H+ ions is accepted by NAD forming reduced NAD
-acetate combines with coenzyme A (CoA) to form acetylcoenzyme A- enters Krebs cycle

Question 9

summary equation for link reaction

Answer 9

pyruvate+ CoA+ NAD-> acetyl CoA+ reduced NAD+ CO2

Question 10

krebs cycle

Answer 10

a series of redox reactions produces:
-ATP by substrate level phosphorylation
-reduced coenzymes
-CO2 from decarboxylation

Question 11

stages of krebs cycle

Answer 11

-acetate is removed from CoA and combines with a 4C molecule of oxoloactic acid to form 6C sugar-citrate
CoA goes back to link reaction
-citrate is decarboxylated and dehydrated - 2H+ions are used to reduce NAD.
-5C molecule now, a phosphate removed to generate ATP=substrate level phosphorylation
-it is decarboxylated + dehydrated again to produce a 4C molecule, another CO2 and NADH.
-the 4C compound is dehydrogenated again and 2H+ ions reduce FAD.

Question 12

what happens in ETC

Answer 12

-electrons released from reduced NAD and FAD undergo successive redox reactions.
-the energy released s coupled to maintaining proton gradient or released as heat.
-oxygen acts as final electron acceptor

Question 13

coenzymes

Answer 13

molecules that some enzymes require in order to function e.g. NAD, FAD, NADP

Question 14

significance of krebs cycle

Answer 14

-breaks down macromolecules into smaller molecules: pyruvate->CO2
-produces H atoms that are carried by NAD to ETC for oxidative phosphorylation, leading to production ATP
–source of immediate compounds used by cells to manufacture other compounds e.g. fatty acids, amino acids

Question 15

oxidative phosphorylation

Answer 15

-reduced NAD and FAD donate the electrons of H atoms they are carrying to first molecule of ETC.
-electrons pass along a chain of electron transfer carrier molecules in a series of redox reactions.
-energy released from redox reactions in ETC causes the active transport of protons (H+ ions) from the mitochondrial matrix into the intermembrane space
-H+ ions move down their concentration gradient from intermembrane into mitochondrial matrix via channel protein ATP synthase.
ATP synthases catalyses ADP+Pi-> ATP

Question 16

benefit of an ETC rather than a single reaction

Answer 16

energy is released gradually
less energy is released as heat

Question 17

2 molecules that can be used as alternative substrates

Answer 17

-amino acids from proteins
-glycerol and fatty acids from lipids

Question 18

how can lipids act as alternative respiratory substrates

Answer 18

-lipids first hydrolysed to glycerol and fatty acids
-glycerol is phosphorylated and converted into TP-used for glycolysis and subsequently krebs cycle
-fatty acid is broken into acetate
-acetate enters the link reaction
-H atoms produced for oxidative phosphorylation

Question 19

how can amino acids act as alternative respiratory substrates

Answer 19

-hydrolysed into amino acids
-deamination-amine group removed & enters respiratory pathway at different points depending on number of C atoms they contain.
-3C compounds->pyruvate for link reaction
-4C/5C compounds->intermediates in Kreb’s cycle

Question 20

anaerobic respiration in animals

Answer 20

only glycolysis continues
reduced NAD+ pyruvate-> oxidised NAD (for further glycolysis) + lactate

Question 21

what happens to lactate produced in anaerobic respiration

Answer 21

transported to liver via the bloodstream, where it is oxidised to pyruvate.
can enter link reaction in liver cells or be converted to glycogen.

Question 22

anaerobic respiration in yeast+ plant cells

Answer 22

only glycolysis continues
pyruvate is decarboxylated to form ethanal
ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis.

Question 23

advantage of producing ethanol/lactate during anaerobic respiration

Answer 23

converts reduced NAD back into NAD so glycolysis can continue

Question 24

disadvantage of producing ethanol during anaerobic respiration

Answer 24

-cells die when ethanol concentration is above 12%
-ethanol dissolves cell membranes

Question 25

disadvantage of producing lactate in anaerobic respiration

Answer 25

acidic, so decreases pH
results in muscle fatigue

Question 26

respiratory quotient

Answer 26

RQ= CO2 produced/ O2 consumed

if RQ>1, anaerobic respiration is occurring

Question 27

compensation point

Answer 27

the light intensity at which the rate of photosynthesis will match rate of respiration

Question 28

advantage of muscle cells having more mitochondria (2)

Answer 28

mitochondria produces ATP from aerobic respiration, more ATP produced so more energy can be released.

Question 29

use of hydrolysis of ATP in cells (2/3)

Answer 29

-provides energy for active transport
-synthesis of molecules e.g protein
-add phosphate to other substances, makes them change

Question 30

in a sprint, why is more energy provided by anaerobic respiration than aerobic (2)

Answer 30

-energy demand is really high, not enough time for oxygen to reach muscles

Question 31

why is less energy released by anaerobic (1)

Answer 31

glucose is only partly broken down as only glycolysis takes place

Question 32

describe how ATP is made in mitochondria (6)

Answer 32

-ATP is produced in kreb’s cycle by substrate level phosphorylation: phosphate group is removed from 5C molecule to produce ATP
-kreb’s cycle + link reaction produce reduced NAD
-electrons released from reduced NAD and FAD enter electron transport chain
-energy is released by -redox reactions of electrons
-energy used for active transprot of H+, H+ move down concentration gradient trough ATP synthase channel
-ATP synthase catalyses the reaction to produce ADP + Pi-> ATP

Question 33

why is it important plants produce ATP in photosynthesis and respiration (5)

Answer 33

-when it is dark, ATP not produced by photosynthesis
-ATP is need to provide energy for active transport of ions
-some tissues e.g. unable to photosynthesise
-ATP cannot be moved from cell to cell
-plants use more ATP than produced in photosynthesis