Ch 12: Energy and Respiration Flashcards
How to overcome activation energy? (e.g. glucose)
- Using enzymes to lower the activation energy
2. Using phosphorylation to raise energy level of glucose
Why is the ATP a good molecule as ‘energy currency’?
- Readily hydrolyzed to release energy
- Small (easy to transport)
- Water-soluble (easy to transport)
The difference between ‘energy currency’ and ‘energy storage’!
Energy currency: immediate donor of energy when a cell needs energy –> first choice of energy supply?
Energy storage: short-term or long-term store of chemical potential energy –> second and third choice of energy supply?
Energy for ATP synthesis comes from what processes? (2 processes)
- Energy released from reorganizing chemical bonds (respiration) –> Krebs cycle and glycolysis
- Electrical potential energy
Explain electron potential energy! (how it happens)
Transfer of electrons by electron carriers (mitochondria and chloroplast)
- Difference in proton (H+ ions) across cell membrane
- Protons flow down their concentration gradient (facilitated diffusion) –> ATP synthase synthesizes ATP (a.k.a. chemiosmosis)
Conditions for chemiosmosis to happen
3 protons create 1 ATP, as long as ADP and a Pi group are available inside the organelle
Phases of chemiosmosis (3 phases)
ATP synthase has 3 binding sites and a part of molecule which rotates as H+ (proton) passes causing changes in the 3 binding sites and hence passing 3 phases:
- ADP and Pi binds
- Tightly bound ATP forms
- ATP is released
Active transport, what goes in and out of cells? (what pumps are used as well?)
pump Na+ (sodium ions) OUT of cell
pump K+ (potassium ions) INTO the cell
Protein (sodium-potassium) pumps on cell surface membrane
Explain sodium-potassium pump!
- A protein
- Spans across cell membrane
- OUTER side: K+ binding site
- INNER side: Na+ and ATP
- Acts as ATPase (releasing energy)
What is ATPase?
Enzyme which catalyzes the hydrolysis of ATP into ADP + Pi, generating energy to drive the pump (change protein pump shape) –> 30.5 kJ/mol
What is Pi?
Inorganic phosphate, H3PO4
For each ATP, how many K+ and Na+ are moved? (also, into or out of cell do they go?)
Two K+ move into the cell
Three Na+ move out of cell
What is the result of the amount of K+ and Na+ not being equal?
Potential difference is created across the membrane. Negative inside compared to the outside.
Sodium and potassium leaks down their diffusion gradient. However, cell surface membranes are much less permeable to Na+, so this ‘leaking’ diffusion actually increases the potential difference across the membrane.
Is ATP used a lot for active transport?
Yes, about 50% of ATP is used to maintain ionic content of cells
What is the purpose of respiration?
Breaking down of organic molecules in a series of stages to release chemical potential energy to synthesize ATP
What are the 4 stages of glucose breakdown? (in order and in which part of the cell they happen)
- Glycolysis (cytoplasm)
(mitochondria)
- The link reaction
- The Krebs cycle
- Oxidative phosphorylation (electron transport chain)
Explain glycolysis extensively! (pt1)
a. Process
a. Process:
1. Phosphorylation using ATP because glucose is stable (increases energy level so that glucose will react)
_glucose (6C) + ATP –> fructose phosphate (6C)
_fructose phosphate + ATP –> fructose biphosphate (6C)
_fructose biphosphate (6C) –> 2 triose phosphate molecules (3C)
- Removal of hydrogen from triose phosphate
2NAD + 2H+ –> 2NADH [reduced NAD]
also produces 2ATP
NAD = nicotinamide adenine dinucleotide - what’s left of triose phosphate is the intermediate and intermediate changing to 2 pyruvates generates 2ATP
Explain glycolysis extensively! (pt2)
b. Reactants and Products @ which process of glycolysis
Used =
2ATP @ phosphorylation
Gained =
2 ATP @ removal of hydrogen from 2 triose phosphates
2 NADH @ removal of hydrogen from 2 triose phosphates
2 ATP @ intermediate turning into 2 pyruvates
net gain 2ATP, 2NADH
Explain the link reaction!
Pyruvate enters mitochondria by active transport.
Through outer and inner membranes into the mitochondrial matrix
(Pyruvate - CO2 - H) + CoA –> acetyl coenzyme A
- decarboxylated and dehydrogenated (H moved to NAD)
- added with coenzyme A
- acetyl coenzyme A is yielded
Pyruvate + CoA + NAD –> acetyl coenzyme A + NADH + CO2
Extra info about link reaction
- component and a feature of coA
- another way of making acetyl coA and its process
- coA = a nucleoside (ribose plus adenine); acts as carrier of acetyl groups to Krebs cycle
- Fatty acids; in cycle of reactions, each cycle turn shortens the fatty acid chain by two-carbon acetyl unit. each react with a coA, producing acetyl coA
Krebs cycle also known as…
aka citric acid or tricarboxylic acid
What are the steps of Krebs cycle?
- Acetyl coA + oxaloacetate……
refer to diagram drawn
Mention Krebs cycle products
2 CO2, 1FAD, 3NADH, 1ATP
Explain why do is there a term like “oxidative phosphorylation AND electron transport chain”?
Where do oxidative phosphorylation happens?
Energy for phosphorylation comes from activity of electron transport chain
Inner mitochondrial membrane
