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Physiology > L31 - Metabolism 1 > Flashcards

L31 - Metabolism 1 Flashcards

1
Q

What is energy produced from?

A

the breakdown of metabolic fuels: fats, carbohydrates and proteins
broken down to be stored in various parts of the body
further broken down to produce ATP

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2
Q

What is energy input mediated by?

A

hunger/appetite, satiety, social and psychological factors

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3
Q

What is energy output mediated by?

A

voluntary physical activity, non-exercise activity thermogenesis, adaptive thermogenesis, basal metabolic rate

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4
Q

How much of our energy output goes into voluntary physical activity?

A

~20%

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5
Q

What are the characteristics of non-exercise activity thermogenesis and how much of our energy output goes into this?

A

spontaneous muscle contraction, maintaining posture, walking (ambulation), talking, fidgeting
~15%

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6
Q

What are the characteristics of adaptive thermogenesis and how much of our energy output goes into this?

A

thermogenic effects of food (diet-induced thermogenesis), uncoupled respiration (cold)
~10%

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7
Q

What are the characteristics of basal metabolic rate and how much of our energy output goes into this?

A

sustain basic functions such as: macromolecule synthesis and ATP production to maintain essential functions such as respiration, cardiac contraction, kidney and liver functions, brain function
~55%

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8
Q

How does ATP provide energy?

A

energy is released from hydrolysis of phosphate bonds within ATP

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9
Q

What is ATP hydrolysis and therefore energy release catalysed by?

A 
a class of enzymes called ATPases
harness the energy from ATP to drive other chemical reactions that would not otherwise occur
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10
Q

What are some examples of ATPase?

A

metabolic enzymes involved in anabolic processes that need energy and enzymes promoting transport of solutes across membranes

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11
Q

What does low stores of ATP result in?

A

enough energy to survive for ~90 seconds

need to continuously restore ATP levels

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12
Q

What is the mechanism of action of cyanide?

A

inhibits cytochrome c oxidase and prevents ATP synthesis, resulting in impaired contractile force

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13
Q

The complete breakdown of one ATP would produce:

A

adenosine, three inorganic phosphates and energy

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14
Q

What is metabolism?

A

chemical reactions that take place in an organism: extract energy from nutrients, use energy for work, store energy for later use and produce heat

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15
Q

What is catabolism?

A

breakdown of substances to generate energy

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16
Q

What is anabolism?

A

uses energy to synthesise larger molecules from smaller substances

17
Q

What are the challenges faced by cells in metabolism?

A

transport nutrients into cells, store nutrients for times of need, mobilise nutrients from stores when needed, convert nutrient to ATP

18
Q

Which tissues use glucose preferentially?

A

lens and cornea; areas of kidney; RBC’s; exercising muscle

brain uses it almost exclusively

19
Q

What is the distribution of glucose after a meal?

A

50% to storage and 50% for ATP synthesis

20
Q

How is glucose transported into cells?

A

glucose enters and leaves capillaries by simple diffusion through spaces between the cells
glucose is transported into cells by facilitated diffusion; that is, carrier mediated transport

21
Q

What is facilitated transport of glucose mediated by?

A 
by glucose transporters:
GLUT 2 (e.g. liver); gradient driven glucose uptake
GLUT 4 (e.g. muscle and adipose tissue); responsive to insulin
22
Q

How is glucose stored?

A

stored as glycogen
glucose molecules are added to chains of glycogen for storage
the enzyme glycogen synthase catalyses this reaction

23
Q

How is glycogen broken down to glucose?

A

glucose is removed from glycogen to form G-1-P
the enzyme glycogen phosphorylase catalyses this reaction
this can be converted to G-6-P and further broken down through glycolysis for energy production

24
Q

What is the process of glycogen breakdown known as?

A

glycogenolysis

25
Q

How is ATP produced from glucose metabolism?

A

glycolysis -> pyruvate dehydrogenase reaction -> Krebs cycle -> electron transport chain

26
Q

What are the characteristics of glycolysis?

A

occurs in cytoplasm of cells
10 reaction steps
two main functions: immediate energy (ATP) and to generate pyruvate
products: 2 x pyruvate + 2 x ATP + 2 x NADH

27
Q

What are the characteristics of the PDH reaction?

A

PDH is a complex enzyme that exists in an inactive and active form
rate-limiting step for carbohydrate metabolism, transfers pyruvate into mitochondria
products: 1 x acetyl CoA + 1 x NADH

28
Q

What are the characteristics of the Krebs cycle?

A

occurs within the mitochondrial matrix, 8 reactions
main function is to degrade acetyl CoA to ATP and H+ bound to coenzymes -> H+ and e- are passed into the ETC for oxidative phosphorylation

29
Q

What is the role of coenzymes?

A

transfer 2 hydrogen atoms from one reaction to another

30
Q

What are the products of the Krebs cycle?

A

2 x ATP, 6 x NADH (= 15 ATP) and 2 x FADH2 (= 3 ATP) formed

net: 20 ATP produced

31
Q

What are the steps of the ETC?

A

e- from coenzymes donate e- to ETC -> energy released drives H+ across inner membrane, producing a H+ gradient and potential energy -> ATP synthase drives H+ into the matrix and uses the potential energy to promote ATP synthesis -> e- and H+ combine with 1⁄2 O2 to form water

32
Q

When do tissues use fat?

A

most tissues preferentially use fat, especially when energy demand is low

33
Q

How are fatty acids stored?

A

as triglycerides

34
Q

How are fats broken down?

A

lipolysis is catalysed by enzymes called lipases -> glycerol becomes a glycolysis substrate

35
Q

How are fatty acids transported into cells?

A

simple diffusion into the cytosol (medium chain FAs)
protein-mediated transport system (long chain FAs)
e.g. fatty acid translocase translocates from cytoplasm to plasma membranes

36
Q

How are fatty acids metabolised?

A

transfer of fatty acid from the cytosol into the mitochondria -> β-oxidation -> Krebs cycle -> ETC

37
Q

Which enzyme mediates the transfer of fatty acid from the cytosol into the mitochondria?

A

carnitine palmitoyl transferase (CPT1)

38
Q

What are the characteristics of β-oxidation?

A

occurs in the mitochondrial matrix, converts one fatty acyl-CoA to acetyl CoA and reducing equivalents
4 reactions in cycle
net production from one fatty acid (C16:0) ~129 ATP

39
Q

What are the products of β-oxidation?

A

each cycle produces 1 x acetyl CoA + 1 x FADH2 + 1 x NADH except last cycle where only 1 x acetyl CoA produced

Physiology (33 decks)

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