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Y1 Fundamentals of Life Science > L10: Glycolysis > Flashcards

L10: Glycolysis Flashcards

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Biology 101 flashcards
1
Q

Why do we eat?

A
  • Maintain cell integrity and barrier function
  • Replenish blood cells
  • Replace cells undergoing apoptosis
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2
Q

What are the core energy providing nutrients?

A

Protein, carbohydrates, fats and lipids

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3
Q

What are the three main phases of cellular respiration?

A

1) Glycolysis
2) The TCA Cycle (Kreb’s)
3) Electron Transport Chain

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4
Q

What are the monomers for carbohydrates?

A

Monosaccharides

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5
Q

What are the monomers for fats/lipids?

A

Fatty acids and glycerol

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6
Q

What are the monomers for proteins?

A

Amino acids

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7
Q

Where are polymers broken down into their constituent monomers?

A
  • Liver
  • Adipose tissue where lipolysis of fatty acids take place
  • Muscles - act on amino acids
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8
Q

Where is glycogen stored?

A
  • High concentrations in the liver - releasable into circulation
  • High amounts in the muscles - for local use only during exercise/fasting as muscles do not have an enzyme to allow glucose to be exported back into circulation
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8
Q

What is meant by anabolism and catabolism?

A
  • Anabolism is the synthesis of complex polymers from monomers or simple polymers
  • Catabolism is the metabolism/break down of complex polymers into monomers or simple polymers
  • This is an energy driven process
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9
Q

What happens to lipids in the fed state?

A
  • Lipids enter the gut by absorption
  • Lipids pass into the liver and package lipids into triglycerides through very low density lipids (VLDL) proteins and pass into the adipose tissue
  • Some to the muscles when required
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10
Q

What happens to glucose in the fed state?

A
  • Glucose enters the gut by absorption
  • Glucose is distributed everywhere to include the liver, muscles, adipose
  • Most to the brain - main carbon source here
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11
Q

What happens to amino acids in the fed state?

A
  • Amino acids enter the gut by absorption
  • To muscle to be used as a fuel source
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12
Q

How can glucose be stored?

A

Glycogen

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13
Q

What is the structure of glycogen?

A
  • Highly branched glucose polymer with a1,4 and a1,6 linkages
  • Stored as granules in the cytosol of cells
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14
Q

What is the benefit of branching in glycogen?

A

Allows for more glucose to be stored and more free ends available to be metabolised quickly

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15
Q

How is the synthesis and metabolism of glycogen regulated?

A

Glucagon and insulin will control the synthesis of glycogen and tell the body when to store or when to utilise glycogen

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16
Q

What happens in the fasted state?

A
  • Adipose tissue releases some fatty acids back into circulation to be converted to energy
  • Glycogen is broken down by the liver into glucose for the brain to be metabolised
  • Glycogen into glucose for muscles if necessary
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17
Q

What happens in the starved state?

A
  • Accelerates the release of free fatty acids from adipose tissue to the liver to convert into energy
  • Glucose released in gluconeogenesis - converts acetyl CoA from fatty acids into glucose for the brain
  • Ketones provide a source of energy - last resort for energy
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18
Q

What ways can energy be regenerated in starvation?

A
  • Lactate from the muscles in anaerobic metabolism
  • Amino acids in transamination from cooperation between muscles and liver to detoxify resultant urea
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19
Q

What is the main source of energy in the human body? How much ATP is produced?

A
  • Glucose is the main energy source
  • Produces 28-32 ATP molecules to drive energetic processes
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20
Q

What is the structure of glucose?

A
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21
Q

What is glycolysis?

A
  • Breaking glucose (6 carbon sugar) into two pyruvate molecules
  • Net production of 2 ATP
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22
Q

What cycle does pyruvate enter after glycolysis, to generate more ATP?

A

TCA/Kreb’s cycle

23
Q

What other ways can pyruvate be processed/

A
  • Transaminate pyruvate into alanine (for gluconeogenesis) - addition of NH3 group
  • Anaerobic respiration (fermentation) to produce lactate from exercise, and yeast can form ethanol
24
Q

What conditions are required for the metabolism of glucose to produce ATP?

A

Aerobic conditions

25
Q

What are the two main phases to glycolysis?

A
  • Investment phase
  • Pay-off-phase
26
Q

What is the investment phase of glycolysis?

A
  • Take glucose and add 2 ATP
  • Splits glucose (6 carbon) into two 3 carbon molecules
27
Q

What is the pay-off phase of glycolysis?

A
  • Convert 3 carbon sugars into pyruvate
  • Generating 4 ATPs (net of 2)
28
Q

What are the 3 different aspects to the 10 different enzymatic reactions in glycolysis?

A

1) The trap - adding a phosphate whilst using ATP, commiting glucose to the pathway
2) The split - 6 carbon glucose becomes two 3 carbon molecules
3) Pyruvate maker

29
Q

What mechanism allows cells take up glucose?

A
  • Facilitated diffusion through a family of hexose transporters
  • No energy involved
30
Q

Where is Glut1 transporter found?

A
  • Blood
  • Blood-brain barrier
  • Heart (lesser extent)
31
Q

Where is Glut2 transporter found?

A
  • Liver
  • Pancreas
  • Small intestines
32
Q

Where is Glut3 transporter found?

A
  • Brain
  • Neurons
  • Sperm
33
Q

Where is Glut4 transporter found?

A
  • Skeletal muscle
  • Adipose tissue
  • Heart
34
Q

What glucose transporter is the main transporter for the uptake of glucose?

A
  • Glut4
  • Made available in the plasma membrane through the action of insulin
35
Q

What does insulin promote in glucose uptake by Glut4?

A

Promote a loop for transport of glucose into the muscle, where it can be converted into glucose six phosphate and used in glycolysis, or stored as muscle glycogen

36
Q

Where is insulin produced?

A

Pancreas

37
Q

Summarise the pathway of glycolysis, including the main enzymes

A
38
Q

At what point are two of each molecule produced in glycolysis?

A
  • From glyceraldehyde-3-phosphate downwards
  • Also produces two of each of the intermediates (4 ATP and 2 NADH)
39
Q

What are the 3 irreversible steps in glycolysis?

A
  • Glucose-6-phosphate back to glucose
  • Fructose-1,6-bisphosphate back to fructose-6-phosphate
  • Pyruvate back to phosphoenolpyruvate
40
Q

What happens if there is an enzyme deficiency/dysfunction at any of the 3 irreversible steps?

A

Build of metabolites

41
Q

Why is glucose synthesis from pyruvate important?

A
  • Glucose synthesis needed to supply the brain with enough glucose
  • Catabolism and anabolism occur at the same time
  • Often spatially separated
42
Q

How can pyruvate be converted into glucose?

A

Using bypass reactions to replace the irreversible steps with alternative activities in gluconeogenesis

43
Q

How is pyruvate converted to phosphoenolpyruvate?

A

1) Pyruvate to oxaloacetate using enzyme pyruvate carboxylase - uses 1 ATP and CO2
2) Oxaloacetate to phosphoenolpyruvate using enzyme phosphoenolpyruvate carboxykinase - uses 1 GTP and produces CO2
- This produces 1 molecule of each

44
Q

How is fructose-1,6-bisphosphate converted into fructose-6-phosphate?

A

1) Bypass 2
2) Uses enzyme fructose-1,6-bisphosphatase
- A phosphate is produced
- No energy involved

45
Q

How is glucose-6-phosphate converted into glucose?

A
  • Bypass 3
  • Uses enzyme glucose-6-phosphatase
  • A phosphate is produced
  • No energy is involved
46
Q

What is the energy costs to go from pyruvate to glucose via irreversible reactions?

A
  • 4 ATP
  • 2 GTP
  • 2 NADH/glucose synthesised
47
Q

How is glycogen converted to glucose-6-phosphate?

A
48
Q

How is fructose inputted into glycolysis?

A
  • Enzyme fructokinase
  • Converted into fructose-6-phosphate
  • Or fructose in converted to fructose-1-phosphate at inputted into glyceraldehyde-3-phosphate
49
Q

How is mannose inputted into glycolysis?

A

Hexokinase to mannose-6-phosphate then fructose-6-phosphate

50
Q

How are lactose and sucrose inputted into glycolysis?

A
  • Lactose to glucose by lactase
  • Glucose to glucose-6-phosphate by hexokinase
  • Sucrose to either glucose or fructose using sucrase
  • Glucose and fructose inputted to glucose-6-phosphate and fructose-6-phosphate by hexokinase
51
Q

How is galactose inputted into glycolysis?

A
  • To glucose-1-phosphate by UDP-Galactose
  • Enters the same pathway as glycogen
52
Q

What happens to pyruvate under anaerobic conditions?

A
  • Pyruvate to lactate
  • Uses enzyme lactate dehydrogenase
  • Reversible reaction
  • Often more pyruvate than lactate - driven towards lactate formation
  • Regenerates NAD+ from NADH and H+
53
Q

Why is the regeneration of NAD+ in anaerobic metabolism significant?

A
  • Need NAD+ to generate NADH in glycolysis
  • Lots of NADH means a lower concentration of NAD+ - need to regenerate NAD+
54
Q

What happens to lactate when formed?

A
  • Can enter the Cori cycle in the liver
  • Detoxifies lactate into pyruvate which can form glucose
  • Short term 2 ATP generated
  • Need to input 6 ATP to regenerate (net loss of 4 ATP)
55
Q

What is lactate acidosis?

A
  • High levels of lactate can build up above 5mM
  • Can cause fatigue and stiffness in muscles
56
Q

What happens to pyruvate in aerobic metabolism?

A
  • Generates NADH + H+ through enzyme pyruvate dehydrogenase
  • Coenzyme A is a carrier protein that forms acetyl-CoA and CO2
  • NADH can be used to generate energy in the electron transport chain

Y1 Fundamentals of Life Science (17 decks)

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