3.3 Digestion and absrobtion

Question 1

what are the two functions of the mouth

Answer 1

mechanical - chew to increase surface area
chemical - salivary glands secrete amylase

Question 2

what is the function if the oesophagus

Answer 2

muscular - peristalsis (rhythmical contractions pushing food to stomach)
ring of cartilage - flexible and protects

Question 3

what are the two functions of the stomach

Answer 3

mechanical - muscular to churn food
chemical - hydrochloric acid to kill pathogens and acidic as pepsin needs pH2

Question 4

what is the function of the liver

Answer 4

produces bile to emulsify fats to increase surface area

Question 5

what is the function of the gall bladder

Answer 5

stores bile

Question 6

what is the function of the pancreas

Answer 6

pancreatic juice - enzymes and neutralises acids with bicarbonate to a pH of around 7

Question 7

what is the function of the small intestine

Answer 7

absorb nutrients produces all enzymes
is one cell thick and has microvilli

Question 8

what is the function of the large intestine

Answer 8

absorbs excess water and has bacteria that can break down complex carbohydrates

Question 9

what is the function of the rectum

Answer 9

stores feaces

Question 10

what is the function of the anus

Answer 10

expeles

Question 11

what are the three enzymes in digestion

Answer 11

carbohydrates, lipases and proteases

Question 12

what do carbohydrates work on

Answer 12

carbohydrates into disaccharides and then monosaccharides

Question 13

what do lipases work on

Answer 13

lipids into fatty acids and glycerol

Question 14

what do proteases work on

Answer 14

proteins into amino acids

Question 15

describe the process of amylase

Answer 15

1. the salivary gland excretes saliva and it thoroughly mixed with the food while chewing.
2. saliva contains the enzyme salivary amylase, this starts hydrolysing any starch in the food to maltose. it also contain mineral salts that help maintain the pH at optimum rate
3. the food is swallowed and enters the stomach where the acidic conditions denote the amylase preventing further hydrolysis
4. the food is passed into the small intestine where it mixes with the pancreatic juice from the pancreas
5. the pancreatic juice contains the enzyme pancreatic amylase, this continues to hydrolyse any remaining starch to maltose. alkaline salts are produced by the pancreas which help maintain the optimum pH
6. muscles in the intestine wall push food along the ileum, and its epithelial lining produces the disaccharide maltase, the malted is a membrane bound as it is not released into the lumen of the ileum, membrane bound allows a shorter diffusion distance

Question 16

what does surcease hydrolyse

Answer 16

the single glycosidic bond in the sucrose molecule, producing glucose and fructose

Question 17

what does lactase hydrolyse

Answer 17

the single glycosidic bond in lactose, producing glucose and galactose

Question 18

define endopeptidases

Answer 18

acts to hydrolyse peptide bonds within protein to break down increasing the surface area for exopeptidase

Question 19

define exopeptidase

Answer 19

acts to hydrolyse peptide bonds at the end of proteins molecules, breaking the protein chain into single amino acids

Question 20

define dipeptidases

Answer 20

specifically work on two amino acids that make up a dipeptide by hydrolysing the peptide bond between them.

Question 21

what are triglycerides broken down into

Answer 21

2 fatty acids and a monoglyceride

Question 22

steps of lipid digestion

Answer 22

1. big lipid droplet mixes with bile salts and forms smaller droplets
2. lipases into monoglycerides and fatty acids
3. these are called micells (a group of monoglycerides and fatty acids) and are absorbed separately as it moves to the epithelial cells
4. once in the cell the endoplasmic reticulum reforms the triglycerides
5. a vesicle of triglycerides called a chylomicron is released by exocytosis into the lymphatic system then the bloodstream

Question 23

6 steps of glucose transport

Answer 23

1. the transporter is initially facing into the lumen and is able to bind to sodium but not the glucose
2. Na+ bonds which induces a conformational change in the protein that opens the glucose binding site
3. glucose bonds and the protein reorients in the membrane so that the sites holding glucose and Na+ are moved into the cell
4. the Na+ dissociates and goes into the cytoplasm, the glucose binding then destabilises
5. The glucose then dissociates into the cytoplasm and the protein then reorients back into its original position.