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Biochem > 10 > Flashcards

10 Flashcards

1
Q

What are lipoproteins

A

liporproteins in blood are used to transport triglycerides, cholesterol and fat-soluble molecules between tissues

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2
Q

Where does lipid digestion occur

A

some in mouth and stomach
majority in small intestine

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3
Q

What do bile salts do

A

solubilize lipids – allowing lipases to release the fatty acids which can be absorbed by the cells of the small intestines

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4
Q

What are lipoproteins

A

packaged triglycerides

lipoproteins enter the circulation and are used by peripheral tissues

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5
Q

What bonds triglycerides

A

ester linkages – means more susceptible to hydrolysis

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6
Q

What are triglycerdies

A

major source of dietary fat

consist of a glycerol backbone with 3 fatty acids attached (C1, C2, C3)

hydrolzyed to fatty acids and 2-monoglycerol in the small intestine by lipase

triglycerides are packaged into lipoproteins for transport in the body

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7
Q

Where are lingual (mouth) and gastric (stomach) lipases most active

A

in short and medium chain fatty acids

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8
Q

Why are lipoproteins necessary

A

triglycerides are nonpolar and need protein to transport htem through polar bonds

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9
Q

What is the structure of triglycerides

A

nonpolar/hydrophobic and not soluble in aqueous environments of the intestine (or the blood)

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10
Q

How are bile salts syntheized

A

from cholesterol in the liver

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11
Q

What does it mean that bile salts are amphipathic

A

hydrophobic on one side
hydrophillic on the other

phospholipids

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12
Q

Where are bile salts secrted

A

gall bladder where they are stored

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13
Q

What do bile salts do

A

emulsifiers – surround the lipids and allow them to form smaller micelles
- take big fat globules and make them smaller

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14
Q

What are micelles

A

lipid particles that come very close to brush border of SI allowing them to be absorbed

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15
Q

what does cholecytokinin (CCK) do

A

stimulates bile salts to be released from the gall bladder and enzymees to be released from the pancreas

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16
Q

when is CCK released

A

once the chyme (fat) enters the duodenum in response to fats and proteins in the chym

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17
Q

When is bicarbonate released
What does it do

A

due to the signal from secretin to neutralize pH and allow the enzymes to function

increase to pH of the acidic chyme of stomach

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18
Q

When do micelles form

A

when the bile salts reach a concentration greater than the “critical micelle concentration”, below which the bile salts are soluble

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19
Q

how do micelles form

A

with polar heads around the outside surrounding the hydrophobic materials within

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20
Q

when is colipase released

A

by the pancreas and binds to the lipids and bile salts around emulsion droplets

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21
Q

what does the lipase colipase do

A

breaks down the triglycerides (TGs) in the micelles into fatty acids and monoglycerides
- can be absorbed by the muscosal cells of the small intestines

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22
Q

What happens to bile salts that are left behind in the intestines

A

reabsorbed further down the intestine to be used again in another digestive cycle
- liver doesn’t need to make more

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23
Q

what fatty acids do not require bile salts for absorption

A

medium and short chain fatty acids
- smaller and more water soluble –> polar acid group makes up a larger proportion of the molecule, allowing water to form hydration shell around it

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24
Q

what transport protein transports medium and short fatty acids after entering blood

A

they are bound to albumin

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25
Q

How are long chained fatty acids transported

A

mucosal cells in the SI package triglycerides into the lipoprotein chylomicron
1. fats digested and absorbed into mucosal cells
2. reassembled into triglycerides and packed within proteins to allow travel in water-based blood

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26
Q

What are chylomicrons

A

lipoprotein particles
- mainly triglycerides
- also phospholipids, cholesterol, proteins

ball structure
- allows to interact with receptors and tissues within the tissues

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27
Q

where do the chylomicrons travel

A

first into the lyphatic system and enter the bloodstream through the thoracic duct

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28
Q

What do chylomicrons do in the mucosal cells (in the SI)

A
  1. moves fatty acids the smooth endoplasmic reticulum and are reassembled into the triglycerides
  2. combines with the ApoB-48 the protein component of the lipoproteins
  3. excreted out
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29
Q

What is Apolipoprotien B

A

translated into 2 different ApoB molecules due to RNA editing – a form of regulation of gene expression
- have differential gene expression
(same gen info but produces different proteins)

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30
Q

What does ApoB in the intestine do

A

a modification to the mRNA is made that produces a new stop codon, much earlier in the mRNA
- the shorter mRNA codes for ApoB-48 (for chylomicrons)

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31
Q

What does the full-length ApoB-100 do

A

made in the liver and becomes part of a different lipoprotein very-low density lipoprotein (VLDL)

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32
Q

where do chylomicrons transport lipids

A

from the mucosal cells lining the intestines, through the lymph and the n into the blood

33
Q

What are lipoprotein lipase (LPL)

A

enzyme that removes triglycerides from chylomicrons

lines the capillaries in muscle and adipose tissue, breaking down triglycerides into FA that can be absorbed by surrounding cells

34
Q

What do chylomicron remnants do

A

travel to the liver for disposal/recylcling by lysosomes

35
Q

how are FA stored in the body

A

triglycerides
- an efficient and lightweight method of energy storage

36
Q

What are the functions of fatty acids

A

main source of energy during fasting
- B-oxidation
- Ketogenesis

storage
- triaclyglycerols

used to make membrane lipids
- phospholipids
- sphingolipids

37
Q

How are fatty acids broken down

A

beta oxidation
- bond between alpha and beta carbon broken in successive rounds to create 2-carbon acetyl CoA molecules
- releases two carbon model called acetyl CoA and FADH and

38
Q

What is the starting material for fatty acid syntehsis
where does it happen

A

acytell CoA (2carbon) and combines into larger molecule

in the liver

39
Q

what is excess carbs used for

A

converted into fatty acids for storage (synthesis of FA)
excess FA sent to other tissues to be used for energy or to adipose tissue for storage

40
Q

What is VLDL produced from

A

mainly form excess carbs in the liver (FA synthesis)
mostly by the liver to circulate excess triglycerides to the body and adipose tissue

41
Q

What happens to remaining glucose in the fed state

A

converted to triglycerides and packaged into VLDLs with ApoB-100 for release into the bloodstream

42
Q

What happens as VLDL circulates

A

lipoprotein lipase (LPL) will remove triglycerides and excess carbohydrates from VLDL
- it loses density and turns into an intermediate density lipoprotein (IDL)

43
Q

What happens after IDL is formed

A

IDL can go back to liver or continue to have triglcyerides removed, eventually becoming a low-denstiy lipoprotein (LDL) – bad cholesterol

44
Q

What is the structure of cholesterol

A

insoluble in water nad must be transported through the blood within lipoproteins

45
Q

Why is cholesterol important

A

needed to stablizie cell membranes
precursor to hormones and vit D
Used to make bile salts

46
Q

Which lipoprotein has high amounts of cholesterol

A

LDL
- high amounts of LDL may indicate excess cholesterol is available

47
Q

What is HDL

A

high density, not a lot of lipid, lots of protein

can take cholesterol from LDL and peripheral cells amd bring it back to the liver where it can be recycled effectively

48
Q

How does LDL and HDL differ

A

LDL: cells with LDL receptors can bind to LDL particles and engulf them – then allow them to use the cholesterol inside
- then releases empty HDL particles

HDL: participate in reverse cholesterol transport – soak up cholesterol from vascular cells adn return it to the liver

49
Q

What happens when there is a vascular injury

A

small dense LDL is able to penetrate through into the intima where it is suscpetible to be oxidized in response to inflammation – absorbs more and more cholesterol – becomes foam cells
- hyperproliferation: precludes blood flow
- forms thrombus over time (BAD!)

50
Q

How are proteins digested

A

mouth (mechanical brekadown by teeth)
stomach – HCL reelased by gastric partietal cells, denature the proteins to make them easier for pepsin to cleave

51
Q

What are zymogens

A

inactive forms of enzymes that must be activated by cleavage before they are functional enzymes

52
Q

What is an example of a zymogen

A

pepsinogen, secreted by the chief cells in the stomach is the zymogen form of pepsin

53
Q

What does HCl in the stomach do

A

causes pepsinogen to change confirmation and cleave itself (autocatalysis), becoming the active form pepsin

54
Q

what releases bicarbonate ions and when

A

pancreases releases once the food leaves the stomach

55
Q

What does bicarbonate do

A

neutralizes the acidic chyme and allows enzymes in the intestine to function

56
Q

why is it important that pancreatic proteases are released as zymogens in the pancreas

A

would start to breakdown the pancreas itself

57
Q

What are the pancreatic proteases

A

trypsinogen –> trypsin (by enteropeptidase secreted by brush border cells)
- actives chrymotrypsinogen –> chymotrypsin
- activates proelastase –> elastase
- activates procarboxypeptidases –> carboxypeptidasesq

58
Q

Why are there not just one enzyme to giest all proteins

A

because proteins are made up of various amino acids that have different structures

59
Q

What are endopeptidases

A

cleave the petide bonds between two aa
each peptidase cleaves the peptide bond around a particular type of aa

(tyrypis, elastase..)

60
Q

What are exopeptidases

A

cleave the peptide bond at hte end of a polypeptide, releaseing a single aa
exopeptidases are found at the brush border and within the intestinal cells
they finish the job of prtoeolytic lceavage into individual aa

61
Q

how does absorption of aa occur

A

secondary active tranpsort along with sodium ion
faciliatated diffusion

62
Q

what does it mean that each aa transporter have specificity for similar aa

A

many aa can be transported by more than one carrier

63
Q

what happens to aa once in the blood

A

travel to the liver and are distributed from there for protein synthesis or energy metabolism or fats for storage

64
Q

Why does the pool of aa in the body form

A

because we don’t store protein in our body
- dietary protein is broken down into amino acids
- functional proteins are constantly being made nad broken down

65
Q

What are the aa in the pool of aa used for

A

used for energy
converted to glucose or fatty acids and stored for energy
used to make nitrogen-containing compounds
- protein is the source of nitrogen in our diet

66
Q

What recycles proteins

A

lysosomal degradation

proteosomal degradation

67
Q

What happens if essential amino acids are missing

A

functional protein must be broken down to provide them

68
Q

What are essential aa

A

cells cannot make them, and they must be taken in the diet

69
Q

What are nonessential amino acids

A

we have biological pathways to make them in our bodies

70
Q

What are conditinoally essnetial amino acids

A

can be made from other compoentns, only if we have enough of those in our diets

71
Q

What is nitrogen balance

A

the balance of intake vs extresion in our body (nitrogen)
- our bodies cannot store protein
- anything we consume in excess of our needs is converted ot energy and the nitrogen is excreted

nitrogen intake = nitrogen output
everything coming in is being excreted

72
Q

What is negative nitrogen balance

A

nitrogen intake < nitrogen output
toal body proetin decreases
- fasting, not eating enough

73
Q

What is positive nitrogen balance

A

nitrogen intake > nitrogen output
total body protein increases
- pregnancy, active growht phase

74
Q

What is the major blood protein

A

albumin
Makes up about 60% of total plasma protein

75
Q

Where is albumin made

A

in the liver

76
Q

What happens to albumin in conditions of protein malnutrition

A

albumin synthesis is decreased quickly (not enough aa to make new proteins)

77
Q

What does albumin do

A

maintains osmotic pressure
general transporter in the blood
- binds to fatty acids and amny rugs helping those non-polar molecules move around the blood

78
Q
A

Biochem (11 decks)

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