9- Metabolism 1 - glycolysis Flashcards

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1
Q

what is anabolism?

A

assimilation of molecules & complex structures from the building blocks of life
= requires energy

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2
Q

what is catabolism?

A

breakdown of molecules to obtain the anabolic “building blocks” of life and substrates for energy
= breakdown of molecules to yield energy

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3
Q

what is metabolism a balance between?

A

anabolism & catabolism

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4
Q

is anabolism
a) endergonic or exergonic?
b) reductive or oxidative?

A

a) endergonic
b) reductive

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5
Q

is catabolism
a) endergonic or exergonic?
b) reductive or oxidative?

A

a) exergonic
b) oxidative

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6
Q

what happens in anabolism?

A

it takes oxidised precursors (products of catabolism) and with NADPH and H+ assembles them together to make biosynthetic products and NADP+ which can be used in catabolism

= anabolism is essential for process of growth & storage

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7
Q

what happens in catabolism?

A

reduced fuel is broken down into oxidised products and NADH and H+ is used for oxidative phosphorylation of O2 to H2O which helps make energy

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8
Q

what does metabolism always require?

A
  • precursor→product
  • reducing equivalent (that either accepts or donates electrons) to drive process forward
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9
Q

what glucose molecules are in plants & animals?

A

plants = starch & cellulose
animals = glycogen

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10
Q

what cells require glucose as an energy source?

A
  • erythrocytes
  • retina
  • renal medulla
  • brain (the brain accounts of about 20% of the oxygen requirement in a resting person even though only 2% of body weight of an individual - highly oxidative organ)
  • all cancer cells
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11
Q

what is structure of glucose?

A

6 carbon carbohydrate
- not naturally in linear form, usually circular

oxygen at top right corner - can think that it holds it in shape and holds likke spring so if you remove that O and do in controlled way you can release energy (glycolysis = breaking of glucose)

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12
Q

what are disaccharides?

A

2 glucose that join together very easily, in lots of different orientations making a family

lactose, maltose, sucrose, cellabiose

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13
Q

why is lactose so good for newborns?

A

it’s very easily broken down so good for supporting metabolism in newborn baby

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14
Q

what are polysaccharides?

A

lots of glucose joined together

cellulose = glucose molecules linked in carbon 1-4 orientation

glycogen = glucose linked together, can make branches which means you can pack together so have ready source of glucose that can be tapped into in times of starvation

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15
Q

if oxygen starved - what happens to pyruvate?

A

pyruvate converted to lactate

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16
Q

what are the 3 different pathways of glucose?

A
  1. converted to PYRUVATE by oxidation through aerobic glycolysis
  2. converted to LACTATE by fermentation by anaerobic glycolysis
  3. converted to RIBOSE-5-PHOSPHATE by oxidation through the pentose phosphate pathway
17
Q

what is ribose-5-phosphate?

A

precursor for nucleotide synthesis & DNA repair = essential for growth (ties into warburg effect of cancer cells = glucose use for cancerous tumours is double whammy; for providing energy & for precursor of growth

18
Q

how is glucose transported into cell?

A

via Na+/glucose symporters

19
Q

what are examples of glucose symports?

A

GLUT 1 = in brain, low Km
GLUT 2 = in liver and B cells, high Km & insulin dependant
GLUT 3 = in brain, low Km
GLUT 4 = in muscle and adipose tissue, insulin dependant
GLUT 5 = in gut, fructose transport

20
Q

what is process of GLUT 1 transporter?

A
  • binding of glucose to the outside triggers conformational change
  • binding site faces inwards
  • glucose can be released in the inside
  • Conformational change regenerates the binding site on the outside
21
Q

what is process of stage 1 of glycolysis?

A

2 ATP →2 ADP energy helps convert glucose to fructose-1,6-biphosphate

  • 1 ATP used by hexokinase for glucose →glucose-6-phosphate and (phosphoglucose isomerase →fructose-6-phosphate)
  • 1 ATP used by phosphofructokinase to make fructose-1,6-biphosphate
22
Q

what is the net gain of ATP in glycolysis?

A

2 ATP (2 used at start and then 4 made so 4-2 = 2)

23
Q

what happens in stage 2 of glycolysis?

A

fructose-1,6-biphosphate converted into two 3-carbon triose phosphates

= 2 interconvertible 3-carbon molecules, triose phosphates, are formed

24
Q

what happens in stage 3 of glycolysis?

A

triose phosphate then used 2 NAD →2 NADH + 2H+ and 4ADP →4 ATP to make 2 pyruvate

(both triose phosphate undergo reaction so reaction happens twice →2 pyruvate)

pyruvate kinase catalyses last step to pyruvate making final bit of ATP

25
Q

what are the 2 main cellular needs of glycolysis?

A
  • production of ATP
  • provision of building blocks for synthesis reactions
26
Q

what are the 3 control points in glycolysis?

A
  1. hexokinase = takes 1 ATP and energises glucose (labels glucose for entry into glycolytic pathway) →phosphorylates glucose to glucose-6-phosphate = very 1st step
  2. phosphofructokinase = control rate of flow of glucose-6-phosphate →fructose-1,6-bisphosphate, important in acting like energy sensor, also uses 1 ATP
  3. pyruvate kinase = controls exit of pyruvate from glycolytic pathway (inhibited by high ATP concentration)
27
Q

what is reaction catalysed by pyruvate kinase?

A

phosphoenolpyruvate + ADP + H+ →pyruvate + ATP

28
Q

what is reaction catalysed by phosphofructokinase?

A

fructose-6-phosphate + ATP →fructose-1,6-phosphate + ADP + H+

29
Q

what is reaction catalysed by hexokinase?

A

glucose + ATP →glucose-6-phosphate + ADP + H+

30
Q

what is each control point of glycolysis inhibited by?

A

hexokinase = inhibited by glucose-6-phosphate

phosphofructokinase = inhibited by ATP

pyruvate kinase = inhibited by ATP

31
Q

what are some inhibitors of metabolism?

A

ATP = will slow glycolysis if energy abundant

citrate = TCA cycle intermediate, slows downstream pyruvate entry to TCA cycle if energy abundant

H+ = slows glycolysis if too much lactic acid being produced

32
Q

what are activators of glycolysis?

A

AMP and fructose-2,6-biphosphate →will increase glycolysis if energy is needed

33
Q

what is the ATP/AMP ratio, energy change?

A

it’s the idea that if all adenylate nucleotides are in ATP form then cell fully charged

if cell only contains AMP & Pi then discharged

34
Q

why is AMP not ADP positive regulator?

A

if ATP is rapidly used up …
ATP → ADP + Pi

= adenylate kinase can salvage some of the energy in ADP…
2 ADP → ATP + AMP

(so if lots of energy being used, low energy - then high AMP)

35
Q

where does the 2 NADH + 2H+ go from stage 3 of glycolysis?

A

to electron transport chain & ATP synthesis

36
Q

what is the warburg effect?

A

= up-regulation of anaerobic glycolysis in cancer cells

cancer cells rely on aerobic glycolysis as their primary energy-producing pathway even in presence of sufficient oxygen (contrast to normal cells where they typically generate energy through oxidative phosphorylation in mitochondria)

  • cancer cells have low Km hexokinase
37
Q

what are the advantages to cancer cell’s way of energy production?

A
  • Rapid energy production
  • Supports other pathways for nucleotide synthesis (needed for growth)
  • Supports rapid cell growth (proliferation)
38
Q

what are the disadvantages to cancer cell’s way of energy production?

A
  • Produces H+and lactate as end products
  • Very inefficient ATP synthesis
  • High glucose consumption demand
  • Cancer patients lose weight