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Biochem > 09 > Flashcards

09 Flashcards

1
Q

Where does the energy for cells come from
What is it used for

A

enzymes breakdown molecules and release the energy stored in chemical bonds

used for proteins to power other cellular process

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2
Q

monosaccharide

A

single sugar
are in an equilibrium in solution

linear sugar can react and form a ring structure

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3
Q

What i the significance of the OH group at C1 carbon

A

hydroxyl group (-OH) at the C1 carbon can be in the alpha (bottom) or beta (top) position

posiition of the hydroxyl group at C1 and which carbon it is linked to on the other sugar will change the shape

functional group and forms bonds with other sugars and impacts how enzymes interact with it

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4
Q

disaccharades and polysaccharides

A

sugar molecules bonded together to form polymers
- glycosidic bonds

disacharides = 2
oligosaccharides = 3-15
polysacharrides = 15+

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5
Q

where does digestion start and stop

A

start in the mouth with salivary amylase

stops in the stomach, before continuing in the small intestine with pancreatic amylase

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6
Q

Why is salivary amylase no longer able to break down carbs once it reaches the stomach

A

pH it too low
proteins denautre

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7
Q

Why is pancreatic amylase able to re-start the process after the stomach

A

pancreatic juice contains bicarbonate and gets released in the SI to raise the pH back to 6.5 (functional again)

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8
Q

what reaction breaks down carbs

A

hydrolysis

process utilizes covalent catalysis and acid-base catalysis

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9
Q

what do enzymes in the brush border of SI do

A

catalyze the final hydrolysis reaction producing monosaccharides that can be absorbed
(carbohydrate digestion)

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10
Q

What happens to nutrients absorbed into capillaries

A

takes digested carbs into the hepatic circulation and to the liver

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11
Q

where are the carb-digesting enzymes located

A

in the membrane of SI (integral membrane proteins)

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12
Q

What keeps the carb-enzymes from being digested themselves

A

enzymes are highly glycosylated (post translational modification) to keep from being digested by the intestinal proteases

glycosylation: adding glucose (other things wont’ break it down)

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13
Q

What is fibre

A

indigestible carbs b/c we don’t have the enzymes to break down the bonds in the carbs

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14
Q

what are the soluble and insoluble types of fibre

A

cellulose = insoluble
pectins and gums = soluble

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15
Q

What are the benefits of soluble fibres

A

reduce blood cholesterol levels by binding bile salts or reducing resportion in the intestines

soluble fibres also slow down absorption of nutrients

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16
Q

What does lactase do

A

enzyme that breaks down lactose to its monosaccharides – galactose and glucose

enzyme expressed in early age and decreases in efficiency while aging

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17
Q

what causes secondary lactase deficiency

A

results from injury to intestinal absorptive cells

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18
Q

what happens as a result of the inability to break down and absorb lactose

A

moves to the large intestine where bacteria can metabolize it for energy – to gases and lactic acid (results in lactose intolerance symptoms)

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19
Q

Why can’t glucose move into cells without protein transporters

A

polar (hydroxyl group)
can’t cross non polar membrane

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20
Q

how do glucose molecules cross the lipid bilayer

A

hydroxyl groups of glucose form hydrogen bonds with amino acids on the protein
- causes conformational change and are released into the interior of the cell

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21
Q

What are the different glucose transporters

A

sodium glucose cotransporter (SAT)

glucose transporter (facilitated diffusion)

fructose tranporter (facilitated diffusion)

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22
Q

Where do monosacharrides get transported to and from

A

from intestine into mucosal cells lining the intesting and then into the blood

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23
Q

What does SGLT1 do

A

moves glucose and sodium from the SI to the mucosal cells

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24
Q

What does SGLT2 do

A

moves glucose and sodium from the renal tubule into the epithelial cells
(type 1 diabetes)

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25
Q

What does GLUT1 do

A

Moves glucose from the blood into RBCs and across the blood brain barrier

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26
Q

What does GLUT2 do

A

moves glucose from the mucosal cells to the blood, and from the blood into the liver and pancreas

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26
Q

What does GLUT3 do

A

moves glucose from the blood into the neurons

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27
Q

What does GLUT4 do

A

moves glucose into muscle and adipose cells in response to insulin

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28
Q

What does GLUT5 do

A

moves fructose from the SI to the mucosal cells

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29
Q

why is glucose the primary fuel for the brain
what is the significance

A

lipoproteins (carry fatty acids) do not easily cross the blood brain barrier

neural cells account for the potential low blood glucose in the brain

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30
Q

How is the glucose concentration gradient established

A

glucose is transported into the brain ata rate faster than it is used
- glucose is always lower in the brain then in the blood

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31
Q

What would happen at a decrease in blood glucose concentration in the brain

A

less glucose tranpsort into the neural tissue and decreased energy production

hypoglcemia

32
Q

How is ATP generated

A

by breaking the bonds in molecules (carbs, lipids, proteins), that allow proteins to harness that energy and make ATP

33
Q

Where is energy stored

A

in chemical bonds which are shared electrons between atoms

34
Q

What are the different electron carriers

A

NAD+/NADH
NADP+/NADPH
FAD+/FADH2

35
Q

When is ATP synthesized

A

on demand, only when needed

36
Q

Where does glycolysis occur

A

in the cytoplasm and does not require the mitochondria

37
Q

Does glycolysis produce energy with or wihtout ocygen

A

both

38
Q

which cell types is glycolysis presnet in

A

all

39
Q

What molecule does glycolysis start with

A

glucose

40
Q

What is needed to breakdown glucose in glycolysis

A

2 ATP

41
Q

What is the end product of glycolysis

A

2 pyruvates

42
Q

What is generated in glycolysis

A

4 ATP directly
- substrate-level phosphorylation
- phosphate is transferred

43
Q

What is the first step of glycolysis
What is the purpose

A

conversion of glucose to glucose-6-phosphate
- traps the glucose molecule in the cell (only glucose can be exported form the cell, not glucose 6 P)
- only liver cells have an enzyme that can reverse this step

44
Q

What is glucose 6 p used for

A

generate energy (glycolysis)
stored for later (as glycogen in liver or muscle cells)
used to make new molecules

45
Q

What is fructose converted to in glycolysis

A

DHAP and glyceraldehyde-3-phosphate

46
Q

What is galactose converted into in glycolysis

A

glucose-6-phosphate

47
Q

what turns off enzymes in glycolysis
how is it turned off

A

increased concentrations of ATP or metabolic products (G6P, citrate, Acetyl-CoA) signal it

binds to active site or allosteric site to turn off

48
Q

What signals enzymes to be turned on to replenish energy in glycolysis

A

increased concentrations of energy metabolites that indicate low energy reserves (AMP, ADP)

49
Q

What will happen to pyruvate in cells with mitochondria and when oxygen is available

A

converted to Acetyl-CoA and enter the TCA cycle

50
Q

What will happen to pyruvate in the absence of mitochondria and oxygen

A

pyruvate will be converted to lactate

51
Q

Why is the conversion of pyruvate into lactate necessary

A

to regenerate NAD+

52
Q

What does glycolysis require

A

coenzyme NAD+

53
Q

What happens when NAD+ is depleted

A

pyruvate converted to lactate to regenerate NAD+

54
Q

can metabolic acidosis occur when lactate levels are increased

A

yes and no
due to mitochondria dysfunction

55
Q

What causes the accumulation of H+ that causes metabolic acidosis

A

ATP hydrolysis results in gerations of ADP, P and H+

NOT generated from dissociation of lactic acid to lactate

56
Q

What cells and tissues obtain energy from anaerobic glycolysis only

A

RBC
tissues in the eye

  • dont have mitochondria
57
Q

What happens to lactate

A

taken in by the liver and converted back to glucose
glucose can then be returned to blood to be used as energy

58
Q

where does glycolysis occur

A

cytoplasm

59
Q

how do cells relying on anaerobic glycolysis overcome ATP inefficiency (as much less is generated)

A

produce many more glycolytic enzymes to increase reaction rates

60
Q

how does the impermeable inner membran of mitochondria help

A

helps to establish a hydrogen ion gradient that can be used to drive ATP synthesis

enzymes of the ETC are embedded in the inner membrane

61
Q

which mitochondrial membrane is permeable, to which molecules

A

outer membrane

to small ions (to pyruvate)

62
Q

What does the mitochondrial matrix contain

A

location of all the enzymes in the TCA cycle nad the mitochondrial DNA

63
Q

What hapenns when pyruvate enters the matrix of mitochondria

A

pyruvate dehydrongenase enzyme complex (PDC) converts pyruvate to acetyl-CoA

64
Q

What does PDC do
pyruvate dehydrongenase complex

A

converts 3-carbon pyruvate molecule to the 2 carbon acetyl-CoA

generates an NADH and CO2 in the process

acetyel-CoA can enter the TCA cycle and the NADH can go to the ETX

65
Q

What starts the TCA cycle

A

Acetyl-CoA combines with oxalacetate to produce citrate

2 carbons are oxidized to CO2 – regernates oxaloacetate in the proces

66
Q

What is the role of TCA cycle

A

producing GTP directly
and NADH and FADH2 – electorn carriers for the ETC

67
Q

What ist he centre of energy metabolism

A

Acetyl-CoA

68
Q

What are the two phases of energy metabolism

A
  1. breakdown fuels (fules are oxidized to CO2, generating NADH and FADH2)
  2. generating ATP
    - where all the oxygen comes in
    - uses NADH and FADH2
69
Q

When are NAD+ and FAD reduced

A

in the tca cycle and glycolysis
- gain electrons for molecules in the pathway

70
Q

When are NADH and FADH2 oxidized

A

in the ETC
- donate elextrons, converting them back to NAD+ and FAD

71
Q

How does the ETC work

A
  1. NADH donates electrons to complex 1
  2. energy created can be used to move H+ out of matrix and into intermermembrane
    - against concentration gradient
  3. electron gets passed to CoQ, Complex 3, cytochrome C, complex 4 and then to a O2
  4. ATP synthase uses the movement of H+ back into the mitochondrial matrix with its concentration gradient to make ATP
72
Q

What is the purpose of the ETC

A

to move more and more H+ from the matrix into the intermembrnae space and establish a H+ gradient

73
Q

What is produced from 1 glucose molecule in glycolysis

A

2 pyruvate
2 ATp
2 NADH

74
Q

What is produced from 1 glucose molecule in PDC

A

2 acetyl-CoA
2 NADH

74
Q

What is produced from 1 glucose molecule in TCA cycle

A

2x (3 NADH + 1 FADH2 + 1 GTP)

75
Q

what is the total amount of ATP produced from one glucose molecule

A

32 atp

76
Q

is anaerobic or aerobic faster

A

anaerobic faster

77
Q

What regulates the energy metabolism

A

ratio of NADH/NAD+

surplus of NADH = a lot of potential energy in the cell
NADH causes TCA cycle enzyme to turn off
excess NAD+ indicates energy being used up quickly

Biochem (11 decks)

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