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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
How are long chained fatty acids transported
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
26
What are chylomicrons
lipoprotein particles - mainly triglycerides - also phospholipids, cholesterol, proteins ball structure - allows to interact with receptors and tissues within the tissues
27
where do the chylomicrons travel
first into the lyphatic system and enter the bloodstream through the thoracic duct
28
What do chylomicrons do in the mucosal cells (in the SI)
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
29
What is Apolipoprotien B
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)
30
What does ApoB in the intestine do
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)
31
What does the full-length ApoB-100 do
made in the liver and becomes part of a different lipoprotein very-low density lipoprotein (VLDL)
32
where do chylomicrons transport lipids
from the mucosal cells lining the intestines, through the lymph and the n into the blood
33
What are lipoprotein lipase (LPL)
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
What do chylomicron remnants do
travel to the liver for disposal/recylcling by lysosomes
35
how are FA stored in the body
triglycerides - an efficient and lightweight method of energy storage
36
What are the functions of fatty acids
main source of energy during fasting - B-oxidation - Ketogenesis storage - triaclyglycerols used to make membrane lipids - phospholipids - sphingolipids
37
How are fatty acids broken down
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
What is the starting material for fatty acid syntehsis where does it happen
acytell CoA (2carbon) and combines into larger molecule in the liver
39
what is excess carbs used for
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
What is VLDL produced from
mainly form excess carbs in the liver (FA synthesis) mostly by the liver to circulate excess triglycerides to the body and adipose tissue
41
What happens to remaining glucose in the fed state
converted to triglycerides and packaged into VLDLs with ApoB-100 for release into the bloodstream
42
What happens as VLDL circulates
lipoprotein lipase (LPL) will remove triglycerides and excess carbohydrates from VLDL - it loses density and turns into an intermediate density lipoprotein (IDL)
43
What happens after IDL is formed
IDL can go back to liver or continue to have triglcyerides removed, eventually becoming a low-denstiy lipoprotein (LDL) -- bad cholesterol
44
What is the structure of cholesterol
insoluble in water nad must be transported through the blood within lipoproteins
45
Why is cholesterol important
needed to stablizie cell membranes precursor to hormones and vit D Used to make bile salts
46
Which lipoprotein has high amounts of cholesterol
LDL - high amounts of LDL may indicate excess cholesterol is available
47
What is HDL
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
How does LDL and HDL differ
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
What happens when there is a vascular injury
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
How are proteins digested
mouth (mechanical brekadown by teeth) stomach -- HCL reelased by gastric partietal cells, denature the proteins to make them easier for pepsin to cleave
51
What are zymogens
inactive forms of enzymes that must be activated by cleavage before they are functional enzymes
52
What is an example of a zymogen
pepsinogen, secreted by the chief cells in the stomach is the zymogen form of pepsin
53
What does HCl in the stomach do
causes pepsinogen to change confirmation and cleave itself (autocatalysis), becoming the active form pepsin
54
what releases bicarbonate ions and when
pancreases releases once the food leaves the stomach
55
What does bicarbonate do
neutralizes the acidic chyme and allows enzymes in the intestine to function
56
why is it important that pancreatic proteases are released as zymogens in the pancreas
would start to breakdown the pancreas itself
57
What are the pancreatic proteases
trypsinogen --> trypsin (by enteropeptidase secreted by brush border cells) - actives chrymotrypsinogen --> chymotrypsin - activates proelastase --> elastase - activates procarboxypeptidases --> carboxypeptidasesq
58
Why are there not just one enzyme to giest all proteins
because proteins are made up of various amino acids that have different structures
59
What are endopeptidases
cleave the petide bonds between two aa each peptidase cleaves the peptide bond around a particular type of aa (tyrypis, elastase..)
60
What are exopeptidases
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
how does absorption of aa occur
secondary active tranpsort along with sodium ion faciliatated diffusion
62
what does it mean that each aa transporter have specificity for similar aa
many aa can be transported by more than one carrier
63
what happens to aa once in the blood
travel to the liver and are distributed from there for protein synthesis or energy metabolism or fats for storage
64
Why does the pool of aa in the body form
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
What are the aa in the pool of aa used for
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
What recycles proteins
lysosomal degradation proteosomal degradation
67
What happens if essential amino acids are missing
functional protein must be broken down to provide them
68
What are essential aa
cells cannot make them, and they must be taken in the diet
69
What are nonessential amino acids
we have biological pathways to make them in our bodies
70
What are conditinoally essnetial amino acids
can be made from other compoentns, only if we have enough of those in our diets
71
What is nitrogen balance
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
What is negative nitrogen balance
nitrogen intake < nitrogen output toal body proetin decreases - fasting, not eating enough
73
What is positive nitrogen balance
nitrogen intake > nitrogen output total body protein increases - pregnancy, active growht phase
74
What is the major blood protein
albumin Makes up about 60% of total plasma protein
75
Where is albumin made
in the liver
76
What happens to albumin in conditions of protein malnutrition
albumin synthesis is decreased quickly (not enough aa to make new proteins)
77
What does albumin do
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

Biochem (11 decks)

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