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Biochemistry > Carbs, Their digestion and metabolism > Flashcards

Carbs, Their digestion and metabolism Flashcards

1
Q

types of polysaccharides

A

starch, glycogen, cellulose (fiber)

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2
Q

the goal of breaking down glycosidic bonds

A

using dietary foods to produce energy for body processes through digestion; various enzymes break down starch and disaccharides to monosaccharides for absorption

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3
Q

carbohydrate digestion

A

salivary amylase at the mouth, enzymatic digestion by hydrolysis rxns

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4
Q

starch digestion

A

salivary alpha amylase at the mouth and at the small intestines

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5
Q

pancreatic alpha amylase

A

digests starch into disaccharides, containing bicarbonate ions to raise the pH of stomach contents as they move into the duodenum

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6
Q

starch digestion in the small intestine

A

enzymes in the brush border hydrolyze disaccharides into monosaccharides, each. with activity toward a diff. glycosidic bond/oligosaccharide structure

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7
Q

what type of proteins are carbohydrate-digesting enzymes?

A

integral membrane proteins which are highly glycosylated to prevent digestion from intestinal proteases

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8
Q

what can the body not digest?

A

dietary fibre (cellulose), which is insoluble (not to be confused w/ soluble fibres such as pectin and gums)

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9
Q

lactose intolerance

A

impaired ability to digest lactose due to reduced amounts of the enzyme lactase as you age; secondary lactase deficiency occurs w/ injurt to intestinal absorptive cells (e.g. celiac disease)

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10
Q

what occurs with inability to break down lactose?

A

metabolism of lactose by colonic bacteria (lac operon) into gases and lactic acid

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11
Q

glucose absorption

A

secondary active transport with sodium ions (sodium-glucose cotransporter, also facilitative diffusion)

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12
Q

glucose transport

A

secondary active transport; glucose is polar and cannot freely diffuse through the lipid bilayer

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13
Q

GLUTs (glucose transporters)

A

mechanism used in some glucose transport into the intestine

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14
Q

GLUT4

A

isoform of GLUT that is insulin-sensitive and important for uptake into muscle and adipose tissue

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15
Q

GLUT3

A

isoform of GLUT that is NOT insulin-sensitive and important for uptake into brain; can account for potential for low blood glucose in brain (transported at rate not much faster than it is used)
- less glucose transport = less metabolism = situations associated w/ hypoglycemia

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16
Q

how is glycogen synthesized?

A

in response to blood glucose level signals

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17
Q

what does insulin signal?

A

glucose uptake by muscle and adipose and promotion of glycogen synthesis

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18
Q

what does glucagon signal?

A

glycogenolysis in the liver to control regulate blood sugar levels

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19
Q

glycogen utilization

A
  • fuel source in the muscle when ATP is needed
  • glycogen in the liver controls blood glucose; muscle glycogen cannot contribute to blood glucose
  • the liver (and kidneys) have glucose-6-phosphatase from C6 so glucose can enter the bloodstream
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20
Q

cholera

A

toxin causes Cl- channels to remain open resulting in watery diarrhea
- oral rehydration/rice takes advantage of secondary active transport to return Na+ to the cell and slow the release of water into the intestines

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21
Q

Starch

A

long polymer (many subunits) of glucose

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22
Q

Lactose

A

glucose + galactose- disaccharide

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23
Q

Sucrose

A

glucose + fructose- disaccharide

24
Q

T/ F: Animal products contain very little carbohydrate?

A

true

25
Q

Where do carbohydrates exist?

A

fruits, vegetables, and grains

26
Q

What stores glycogen?

A

liver and muscles

27
Q

Cellulose has what type of bond?

A

B-14 bonds; dont have enzyme for so bond between glucose cant break so it becomes dietary fibre

28
Q

Amylases breaks down

A

starch into individual glucose molecules

29
Q

Sucrases breaks down

A

glucose and fructose (Sucrose)

30
Q

Galactose breaks down

A

galactose and glucose (lactose)

31
Q

Where is bile salt stored?

A

made in liver and stored in gallbladder and released in presence of fats in GI tract

32
Q

T/F: cellulose is soluble?

A

false; insoluble

33
Q

T/F: Pectins and gums are solube?

A

true

34
Q

How do soluble fibres reduce blood cholesterol?

A

by binding bile salts or reducing absorption in the intestines

35
Q

Type One Diabetes

A
  • beta cells are destroyed by autoimmunity
  • GLUT are locked inside cell and can only come to surface of cell
  • cells are starving and go into ketoacidosis
  • blood glucose drops too low- brain not getting enough
  • want glucose out of blood stream and stored back in liver or muscle
  • want GLUT to go back into the cell so glucose is not being taken out of the blood so glucose wont keep dropping
36
Q

Does the brain have insulin sensitive glucose transporters?

A

no

37
Q

Type Two Diabetes

A
  • insulin circulates but receptors arent as sensitive
  • results in hypergylcemia
  • drops in blood glucose= less glucose transport and therefore metabolism
38
Q

What transport does the brain normally use?

A

GLUT 3; not insulin sensitive

39
Q

What is broken down in response to blood glucose level signals?

A

glycogen

40
Q

Ribonucleotide

A

source of energy

41
Q

What is salivary amylases optimal pH? and when is it inactivated?

A

6; by the acidity in the stomach

42
Q

When does starch begin to be digested?

A

in the mouth due to salivary amylases

43
Q

What breaks starch down into smaller units until maltose is produced?

A

alpha amylase in the pancreas

44
Q

Where does maltose reside?

A

intestinal wall

45
Q

Villi and microvilli

A

contain a capillary network and nutrients can get into the rbc and then into the capillary

46
Q

Carb digesting enzyme function

A

wait for disaccharides to come by in order to break them down

47
Q

What happens to the disaccharides that are not digested?

A

enzymes distributed along here not digested may be metabolized by bacteria in the colon to prod. gases or short chain FAs

48
Q

Where should lactose never be?

A

large intestine- it should be digested in the small intestine

49
Q

too much LDL

A

get rid of some bile salts so that the liver takes more LDL out of the blood to remake bile salts

50
Q

Secondary lactase deficiency

A

results from injury to intestinal absorptive cells; lactase is first to shed and last to come back

51
Q

Osmotic diarrhea is caused by?

A

lactose being in small intestine and dragging in water with it to balance the osmolality

52
Q

What happens when you cant break down lactose?

A

metabolism by colonic bacteria by lac operon

53
Q

treatment for diarrhea

A

rehydration of fluids needs to contain glucose and sodium in water in order for absorption to occur

54
Q

symptoms of hypoglycemia

A
  • headache
  • blurred vision
  • hunger
  • irritability
  • weakness, fatigue, feeling tired
  • sweating
  • dizziness
  • fast heartbeat
  • shaking
  • anxiety
55
Q

Blood glucose levels after eating

A

drop

56
Q

Can muscle use glycogen to contribute to blood glucose?

A

NO only use it for energy within the muscle

Biochemistry (22 decks)

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