23. Absorbtion of Nutrients

Question 1

what are the stwo absobtion states?

Answer 1

absorptive state and post-absorptive state

Question 2

when does the absorptive state occur? what occurs in the body (3 points) and how long does it last (1 point)

Answer 2

after we have eaten.

1. nutrients enter the bloodstream
2. glucose is readily available for ATP production
3. increased blood glucose switches on absoptive state metabolic pathways

its lasts 4 hours - which is the typical meal absorbtion time

Question 3

when does post absorbtive state occur and what are two points about what occurs?

Answer 3

occurs during fasting.

1. absorbtion of nutrients from the gastrointential tract is ocmplete
2. energy needs must be met by fuels already in the body

Question 4

where does nearly the absorbtion of nutrients take place

Answer 4

in the small intestine

Question 5

describe the digestion of carbohydrates

Answer 5

starch and disacchrides are digested in the mouth by salivary amylase and in the lumen of the small intestine by pancreatic amylase

oligosacchardies and disaccharides further digested by brush boarder enymes

they are turned into monosaccharides and are absorbed across eptihelial cells by either:

facilitated diffusion

or active transport

Question 6

how does glucose get absobed across the epithelium of the gut?

Answer 6

1. there is facilliated diffusion to get glucose into the cells
2. glycogenesis converts glucose into glycogen to be stored energy
3. adipocytes take up excess glucose and convert them into triglyceridedes for energy storate

Question 7

give three steps of the digestion and absorbtion of protein (hydrophillic) then give a step of how and where they are transported to

Answer 7

1. pepsin and HCl in the stomach denature and lyse proteins into large polypeptides
2. pancreatic enymes in the small intestine (trypisn chymostrypis and carboxypeptidase) reduce the polypeptides to small peptides
3. brush boarder enymes break down small peptides into amino acids.
4. amino acids enter the villi capillary blood and then transported to the liver - via the hepatic portal vein

Question 8

what is speical about lipid digestion and absorbtion and give three steps on how it occurs

Answer 8

lipids are able to diffuse across the plasma membrane because theyre hydrophobic, however the membrane is made from lipids, unlike carbs or protein who are hydrophillic and require transport

lipids enter the lymphatic system via a lacetal (a lymphatic capillary) unlike carbs and fats which are hydrophillic and go to the liver

dlipids arent broken down into monomers like protein and carbs, they are split into fatty acids and triglycerides

Question 9

what is the process of lipid abosrbtion?

Answer 9

lipids emulsion droplet broken down into a miscelle

miscelle broken down in to free fatty acids and monoglycerides

fatty acids and monoglycerides enter the enterocyte (cell of intestinal lining)

chylomicrons are formed in the smooth ER

chymomicrons exit the cell via exoctysosis

enter the lymphatic system

Question 10

what is the first step in glycogenolysis to gain energy back in a post - absobtive state?

Answer 10

the alpha cells in the endocrine pancreas convert liver glycogen into glucose that enters the blood

Question 11

what is the second nutrient to be broken down once all the glucose has been secreted from the beta cells? what is the process of this?

Answer 11

lids are broken down! the process is called lipolysis which is where triglycerides are broken down to glycerol and fatty acids

1. the glycerol and fatty acids are obtained from the adipose tissue

Question 13

what happens to the glycerol when its broken down from adipose tissue after all of liver glycogen has been used?

Answer 13

glycerol is convereted to glucose through the stimulation of adrelanin, cortisol into the blood stream

Question 14

what happens to the fatty acids from the adipose tissue after all the glucose has been used from liver glycogen?

Answer 14

fatty acids produce ATP and produce ketone bodies for energy

Question 15

define glucogenesis and an example

Answer 15

synthesis of glucose from non-carbohydrates

eg lactic acid from exercise

Question 16

what is glycogenesis

Answer 16

the breakdown of muscle glycogen stores into glucose

Question 17

what is the process in three steps of how muscle glycogen can produce energy

Answer 17

1. muscle glycogen is convered into glucose 6-phosphate
2. glucose 6-phosphate can become ATP or Pyruvic acid
3. when its pyruvic acid it can either become -

reduced (aerobic, loss of O2) which produces ATP

or it can be oxidised (anaerobic) which forms lactic acid - lactic acid in the blood becomes glucose

Question 18

what is the last resort of glucogenesis?

Answer 18

the breakdown of proteins, amino acids converted into glucose in the liver

Question 19

how does ketogenesis work?

Answer 19

hepatocytes convert fatty acids into ketone bodies

ketone bodies convert into glucose for energy

Question 20

what are the bodies responses to eating? fours steps (whats released, what does it stimulate)

Answer 20

gastrin secreted y the stomach secretes HCl and pepsinogen secretion

this stimulates the release of secretein, CCK and GIP

this inhbits acid secretion (stop HCl)