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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
What does GLUT1 do
Moves glucose from the blood into RBCs and across the blood brain barrier
26
What does GLUT2 do
moves glucose from the mucosal cells to the blood, and from the blood into the liver and pancreas
26
What does GLUT3 do
moves glucose from the blood into the neurons
27
What does GLUT4 do
moves glucose into muscle and adipose cells in response to insulin
28
What does GLUT5 do
moves fructose from the SI to the mucosal cells
29
why is glucose the primary fuel for the brain what is the significance
lipoproteins (carry fatty acids) do not easily cross the blood brain barrier neural cells account for the potential low blood glucose in the brain
30
How is the glucose concentration gradient established
glucose is transported into the brain ata rate faster than it is used - glucose is always lower in the brain then in the blood
31
What would happen at a decrease in blood glucose concentration in the brain
less glucose tranpsort into the neural tissue and decreased energy production hypoglcemia
32
How is ATP generated
by breaking the bonds in molecules (carbs, lipids, proteins), that allow proteins to harness that energy and make ATP
33
Where is energy stored
in chemical bonds which are shared electrons between atoms
34
What are the different electron carriers
NAD+/NADH NADP+/NADPH FAD+/FADH2
35
When is ATP synthesized
on demand, only when needed
36
Where does glycolysis occur
in the cytoplasm and does not require the mitochondria
37
Does glycolysis produce energy with or wihtout ocygen
both
38
which cell types is glycolysis presnet in
all
39
What molecule does glycolysis start with
glucose
40
What is needed to breakdown glucose in glycolysis
2 ATP
41
What is the end product of glycolysis
2 pyruvates
42
What is generated in glycolysis
4 ATP directly - substrate-level phosphorylation - phosphate is transferred
43
What is the first step of glycolysis What is the purpose
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
What is glucose 6 p used for
generate energy (glycolysis) stored for later (as glycogen in liver or muscle cells) used to make new molecules
45
What is fructose converted to in glycolysis
DHAP and glyceraldehyde-3-phosphate
46
What is galactose converted into in glycolysis
glucose-6-phosphate
47
what turns off enzymes in glycolysis how is it turned off
increased concentrations of ATP or metabolic products (G6P, citrate, Acetyl-CoA) signal it binds to active site or allosteric site to turn off
48
What signals enzymes to be turned on to replenish energy in glycolysis
increased concentrations of energy metabolites that indicate low energy reserves (AMP, ADP)
49
What will happen to pyruvate in cells with mitochondria and when oxygen is available
converted to Acetyl-CoA and enter the TCA cycle
50
What will happen to pyruvate in the absence of mitochondria and oxygen
pyruvate will be converted to lactate
51
Why is the conversion of pyruvate into lactate necessary
to regenerate NAD+
52
What does glycolysis require
coenzyme NAD+
53
What happens when NAD+ is depleted
pyruvate converted to lactate to regenerate NAD+
54
can metabolic acidosis occur when lactate levels are increased
yes and no due to mitochondria dysfunction
55
What causes the accumulation of H+ that causes metabolic acidosis
ATP hydrolysis results in gerations of ADP, P and H+ NOT generated from dissociation of lactic acid to lactate
56
What cells and tissues obtain energy from anaerobic glycolysis only
RBC tissues in the eye - dont have mitochondria
57
What happens to lactate
taken in by the liver and converted back to glucose glucose can then be returned to blood to be used as energy
58
where does glycolysis occur
cytoplasm
59
how do cells relying on anaerobic glycolysis overcome ATP inefficiency (as much less is generated)
produce many more glycolytic enzymes to increase reaction rates
60
how does the impermeable inner membran of mitochondria help
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
which mitochondrial membrane is permeable, to which molecules
outer membrane to small ions (to pyruvate)
62
What does the mitochondrial matrix contain
location of all the enzymes in the TCA cycle nad the mitochondrial DNA
63
What hapenns when pyruvate enters the matrix of mitochondria
pyruvate dehydrongenase enzyme complex (PDC) converts pyruvate to acetyl-CoA
64
What does PDC do pyruvate dehydrongenase complex
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
What starts the TCA cycle
Acetyl-CoA combines with oxalacetate to produce citrate 2 carbons are oxidized to CO2 -- regernates oxaloacetate in the proces
66
What is the role of TCA cycle
producing GTP directly and NADH and FADH2 -- electorn carriers for the ETC
67
What ist he centre of energy metabolism
Acetyl-CoA
68
What are the two phases of energy metabolism
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
When are NAD+ and FAD reduced
in the tca cycle and glycolysis - gain electrons for molecules in the pathway
70
When are NADH and FADH2 oxidized
in the ETC - donate elextrons, converting them back to NAD+ and FAD
71
How does the ETC work
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
What is the purpose of the ETC
to move more and more H+ from the matrix into the intermembrnae space and establish a H+ gradient
73
What is produced from 1 glucose molecule in glycolysis
2 pyruvate 2 ATp 2 NADH
74
What is produced from 1 glucose molecule in PDC
2 acetyl-CoA 2 NADH
74
What is produced from 1 glucose molecule in TCA cycle
2x (3 NADH + 1 FADH2 + 1 GTP)
75
what is the total amount of ATP produced from one glucose molecule
32 atp
76
is anaerobic or aerobic faster
anaerobic faster
77
What regulates the energy metabolism
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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