ATP & Respiration

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  • Created by: Laura
  • Created on: 04-04-14 11:22
What does ATP stand for?
Adenosine triphosphate
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What forms ATP?
organic base - adenine, 5c sugar - ribose & 3 phosphate groups
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Why is ATP a better energy source
releases energy gradually
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Why is a slow energy release a good thing?
So temperature of cell doesn't rise
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How many enzymes does ATP need to release energy?
One
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How many reactions does the hydrolysis of ATP require?
one
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What is activation energy?
amount of energy to start a reaction.
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How is energy released from ATP?
The unstable phosphate bonds are broken
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What enzyme is the hydrolysis of ATP catalysed by?
ATPase
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What is phosphorylation?
adding a phosphate group to a molecule
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What types of phosphorylation are there?
Oxidative, photophosphorylation & substrate-level
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Where does oxidative phosphorylation occur?
membranes of mitochondria
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Where does photophosphorylation occur?
membranes of chloroplasts during photosynthesis
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When does substrate-level phosphorylation occur?
When phosphate groups are transferred from donor molecules to ADP to make ATP
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What is the reaction called when energy is taken up?
endergonic
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What is the reaction called when energy is released?
exergonic
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What are the roles of ATP?
Metabolic reactions: to build more complex molecules e.g. DNA synthesis, Movement; muscle contraction, Active transport: change shape of carrier proteins in plasma membranes allowing molecules/ions to move against a concentration gradient
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..... cont.
Nerve transmission: sodium-potassium pumps actively transport sodium & potassium ions across axon plasma membrane & secretion: packaging and transport of secretory products into vesicles.
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What happens when a phosphate group is transferred from ATP to another molecule?
lowers activation energy so it's more reactive.
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What is aerobic respiration? (obligate anaerobes)
requires oxygen
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What does aerobic respiration produce?
carbon dioxide, water & ATP
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What is anaerobic respiration? (facultative anaerobes)
occurs in the absence of oxygen
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What does anaerobic respiration produce?
lactate (animals), ethanol and carbon dioxide (yeast)
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Where does Glycolysis take place?
cytoplasm
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What type of respiration occurs during glycolysis?
Aerobic & anaerobic respiration
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What happens when 2 molecules of ATP are added to glucose? (phosphorylated)
Becomes more reactive
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What is glucose converted to?
hexose phosphate
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What happens to the hexose phosphate?
splits into 2 molecules of triose phosphate
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What is removed from the molecules of triose phosphate?
Hydrogen
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What is the hydrogen carrier molecule called? And what does it become once hydrogen is transferred to it?
NAD and it becomes reduced NAD
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What are the triose phosphate molecules converted to?
Pyruvic acid
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What is the total yield of ATP in glycolysis for each molecule of glucose?
4 ATP molecules
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What type of phosphorylation is this?
substrate-level phosphorylation
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2 ATP molecules are used to phosphorylate glucose at the beginning, what is the net gain of ATP?
2 molecules
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How many molecules of reduced NAD are produced?
2
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What is pyruvate converted to during anaerobic respiration
lactic acid or ethanol, in order to re-oxidise NAD
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At the end of glycolysis where does the pyruvate diffuse to?
mitochondrial matrix
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What happens to the pyruvate?
decarboxylated & dehydrogenated
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What is decarboxylation?
carbon dioxide is removed
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What is dehydrogenation?
Hydrogen is removed
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What happens to the removed hydrogen?
Its transferred to NAD to form 2 molecules of reduced NAD
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What does decarboyxlation and dehydrogenation form?
2-carbon acetate
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What does the 2 carbon acetate combine with? What does this form?
CoEnzyme A to form acetyl coenzymeA
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What connects glycolysis to the krebs cycle?
The Link Reaction
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What does the krebs cycle do?
Frees up energy for carbon bonds to provide ATP, reduced NAD, reduced FAD and carbon dioxide
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What is the role of NAD & FAD?
deliver hydrogen to electron transport chain
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When the acetyl coenzymeA enters the Krebs cycle what does it combine with?
It combines with a 4 carbon acid forming a 6 carbon compound, allowing the coenzymeA to be regenerated
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What happens to the 6 carbon compound?
Idecarboyxlated and dehydrogenated
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The acetate compound is broken down to leave a 4 carbon residue, what happens to this?
It's converted to regenerate the 4 carbon compound otherwise acetyl coenzymeA would accumulate, so it can bind with more acetyl coA
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What is the ratio of reduced NAD & reduced FAD
3 NADH & 1 FADH
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What is produced in one turn of the krebs cycle?
1 ATP (substrate level phosphorylation), 3 NADH & 1 FADH, 2 carbon dioxide molecules
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What is the electron transport chain?
carriers and pumps
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Where is the electron transport chain?
inner mitochondrial matrix
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What waste product is formed?
Carbon dioxide
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How many molecules of ATP are synthesised if NAD is the initial acceptor?
three
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What about if FAD is the initial acceptor?
two
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What type of phosphorylation occurs on the membranes of mitochondria?
oxidative
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How does the chemiosmotic theory explain synthesis of ATP?
proposes energy for ATP synthesis originates from electrochemical gradient of protons across a membrane
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What does NADH donate to the first electron carrier?
electron from the hydrogen atoms
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Where do the hydrogen ions remain?
mitochondrial matrix
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What does the electron from the hydrogen provide?
Energy for the first proton pump
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Where do the hydrogen ions accumulate?
In the inter-membrane space as inner membrane is impermeable to protons
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What is the concentration difference between the inter-membrane space and the matrix?
concentration in the inter-membrane space is higher than matrix
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How do the hydrogen ions diffuse back into the matrix?
Through special channels, and the electrical potential energy produced is used to produce ATP
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What happens at the end of the electron transport chain?
Electrons combine with hydrogen ions and oxygen (final electron acceptor) to form water. This is essential otherwise hydrogen and electrons would accumulate and stop process.
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How many pumps does the carrier system involving FAD have?
2
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How many pumps does the carrier system involving NAD have?
3
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What is cyanide?
A poison that acts as a non-competitive inhibitor of the final acceptor in electron transport chain which results in an accumulation of hydrogen and electrons
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What process of respiration is the only one that can occur in anaerobic conditions?
Glycolysis
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What happens if NADH can't be reoxidised to pick up more hydrogen ions?
link reaction & krebs cycle can't happen
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In animals muscle tissues, what is pyruvate converted to?
Lactic acid
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When does Lactic acid occur?
When the body can't get enough oxygen to muscle cells, so it's deprived meaning pyruvate acts as the hydrogen acceptor
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In micro-ogranisms e.g. yeast, what is pyruvate converted to?
Ethanol by alcohol fermentation
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How does alcohol fermentation work?
Pyruvate is decarboxylated to produce ethanal, the hydrogen released during glycolysis is transferred to NAD, NADH passes hydrogen to ethanal which is reduced to ethanol
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Where does substrate-level phosphorylation occur?
glycolysis and Krebs cycle
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Where does oxidative phosphorylation occur?
Electron transport chain
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How many ATP molecules are made in Glycolysis?
Net = 2 as 4 molecules are made but 2 were used to phosphorylate glucose molecule.
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How many ATP molecules are made in the link reaction?
6, 2 NADH molecules each capable of producing 3 ATP molecules by oxidative phosphorylation
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How many ATP molecules are made in the krebs cycle?
24 ATP, 6 NADH molecules each capable of producing 3 ATP molecules by oxidative phosphorylation, 2 FADH molecules are each capable of producing 2 ATP by oxidative phosphorylation & 2 ATP molecules are made directly by substrate-level phosphorylation
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During glycolysis, how many ATP, NADH & FADH molecules are formed?
2 ATP, 2 NADH & 0 FADH
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During the link reaction, how many ATP, NADH & FADH molecules are formed?
6 ATP, 2 NADH & 0 FADH
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During the krebs cycle, how many ATP, NADH & FADH molecules are formed?
24 ATP, 6 NADH & 2 FADH
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What happens to the pyruvate during anaerobic respiration?
doesn't enter mitochondria and therefore isn't available for the krebs cycle so only 2 ATPs are formed.
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Name two alternative respiratory substrates?
Lipids & proteins
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When are lipids used as a respiratory substrate?
carbohydrate levels are low
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What must happen to lipids?
split into glycerol and fatty acids by hydrolysis
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Explain what happens to the glycerol?
Glycerol is phosphorylated with ATP, dehydrogenated with NAD & converted into triose phosphate which enters glycolysis pathway
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What happens to the fatty acids?
The chain is split into 2 carbon fragments which enter the krebs cycle as acetyl coA. Very large numbers of ATP are build up, precise number depends on length of the chain. Hydrogen that is released is picked up by NAD and fed into E.T.C.
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How much energy does 1g of fat release compared to 1g carbohydrate
twice as much energy
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When are proteins used as a respiratory substrate?
only when all reserves of fat & carbohydrate are depleted e.g. starvation
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What happens to the tissue protein?
mobilised to supply energy
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What happens if dietary energy supplies are inadequate?
protein component of food is diverted for energy purposes
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What happens to protein?
Protein is hydrolysed into amino acids and deaminated in liver
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What happens to the amino group?
converted to urea & excreted, residue is converted to acetyl coA, pyruvic acid or another krebs cycle intermediate & oxidised.
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Why is a slow energy release a good thing?

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Card 5

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