Week 8: Obtaining energy Flashcards

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1
Q

what is metabolism

A

the sum of all chemical reactions

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2
Q

what is catabolism

A

the breakdown of nutrients to release energy

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3
Q

what is anabolism

A

synthesis of molecules within cells

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4
Q

Catabolic pathways

A

breakdown fuel molecules to produce H2O, CO2

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5
Q

Anabolic pathways

A

build macromolecules from building blocks

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6
Q

Metabolic pathway

A

transforming substrates into products, via specific intermediates/metabolites

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7
Q

Chemical reaction

A

loss of free energy

molecules move to a lower energy state

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8
Q

Activation energy

A

The energy required to overcome the hill is called the activation energy

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9
Q

Why do we need enzymes

A

Enzymes act by lowering the activation energy & making it easier for a reaction to occur

Enzymes increase reaction rates

They allow reactions to occur under much milder conditions: low temperature, atmospheric pressure, approx. neutral pH…ie. physiological conditions!

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10
Q

How does an enzyme work

A

Enzymes have an active site, a cleft into which substrate molecules fit
They are highly selective

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11
Q

How to obtain energy from food

A

food is oxidised by chemical reactions

energy is converted into ATP

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12
Q

Indirect synthesis of ATP

A

Co-enzymes “trap” the packets of energy from the reactions as electrons & an H+ (= H-) eg. NAD+ accepts electrons and hydrogen to become NADH

Energy trapped in NADH is then used to synthesize ATP

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13
Q

Direct ATP synthesis

A

substrate - level phosphorylation

High-energy phosphate groups are directly transferred from phosphorylated substrates to ADP (adenosine diphosphate)
Occurs in glycolysis and the Krebs cycle

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14
Q

what is NAD+

A

nicotinamide adenine dinucleotide
a carrier molecule (like ATP)
a coenzyme
carries electrons

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15
Q

what has a lower chemical potential energy NADH or NAD+

A

NADH

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16
Q

How are macronutrients broken down to acetyl CoA

A

Glucose is broken down to acetyl CoA via the glycolysis pathway, generating NADH

Fatty acids are broken down to acetyl CoA via the β-oxidation pathway, generating NADH

Amino acids are broken down to acetyl CoA via a variety of pathways

17
Q

What is the breakdown of macronutrients

A

Glycolysis, breakdown of fats or amino acids all can produce acetyl CoA

Citric acid cycle in the mitochondria

Electron transfer &
Oxidative phosphorylation in the mitochondria

18
Q

how to convert pyruvate to acetyl CoA in the mitochondria

A

The ‘bridge reactions between glycolysis and Krebs cycle - via pyruvate dehydrogenase enzyme complex

Occurs in the mitochondrial matrix

Each pyruvate yields: 1x Acetyl CoA, 1x NADH, 1x CO2

19
Q

what is the citric acid cycle

A

Acetyl CoA combines with oxaloacetate
Gradual oxidation of citrate

Each acetyl CoA yields:
3x NADH (yield 3 ATP each)
1x FADH2 (yield 2 ATP each)
1x ATP
2x CO2

The initial acceptor molecule oxaloacetate is also reformed

20
Q

Glycolysis vs Citric Acid Cycle

A

Glycolysis:

  • linear pathway
  • cytosol
  • no oxygen

Krebs

  • cyclic
  • mitochondria
  • aerobic
21
Q

Oxidative phosphorylation

A

NADH & FADH2 are used to drive the synthesis of ATP from ADP & Pi (inorganic phosphate)

Consists of 2 processes:
Electron transport chain
ATP synthesis

In eukaryotic cells this takes place in the mitochondria

22
Q

Electron Transport Chain

A

Re-oxidation of NADH to NAD+

Releases 2 “high energy” electrons which are passed along the electron transport chain, which is a series of membrane-bound proteins/enzymes that accept the electrons (are reduced).

The electrons lose energy as they pass through the chain of proteins

This energy is then used to pump H+ ions across the inner mitochondrial membrane into the intermembrane space

This generates an H+ gradient which is used to drive ATP synthesis

At the end of the chain, electrons combine with O2 to form H20

23
Q

what is ATP synthase

A

Large multi-subunit proteins in inner mitochondrial membrane

Act as energy generating molecular motors

Converts energy from the flow of H+ (protons) down the concentration gradient into mechanical energy

ATP synthase has 2 sets of proteins – rotating stalks that push against stationary heads and cause a change in conformation of the subunits of the heads

the mechanical energy is converted into chemical bond energy – ie. a bond is formed between ADP & Pi & ATP is produced

100 molecules of ATP produced per second
approx. 3 H+ moved to produce 1 ATP