Digestion and Absorption Flashcards
1
Q
Digestion Basics
A
- large biological molecules in food too big to cross cell membranes so can’t be absorbed from gut into blood
- during digestion large molecules are broken down into smaller ones so that they can easily move across cell membranes to be absorbed from gut to blood to then be transported around the body fo use by body cells
2
Q
Digestive Enzymes
A
- used to break down biological molecules in food
- variety of different digestive enzymes produced by specialised cells in digestive system of mammals released to mix with food
- they’re released to mix with food
3
Q
Amylase
A
- digestive enzyme that catalyses breakdown of starch
- catalysing hydrolysis reactions that break glycosidic bonds in starch to produce maltose
- produced by salivary glands released in mouth
- produced in pancreas released small intestine
4
Q
Starch
A
-mixture of 2 polysaccharides each mode from long chains of alpha-glucose molecules
5
Q
Membrane-Bound Disaccharides
A
- enzymes attached to the cell membranes of epithelial cells lining the ileum
- helps break down disaccharides into monosaccharides as hydrolysis glycosidic bond
- sucrose- sucrase -glucose + fructose
- maltose- maltase -glucose + glucose
- lactose- lactase -glucose +galactose
6
Q
ileum
A
-final part of small intestine
7
Q
Digestion of Lipids
A
- lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids as it hydrolysis the ester bonds
- lipase made in pancreas and secreted in small intestine where then active
8
Q
Bile Salts
A
- produced by liver and emulsify lipids causing lipids to form small droplets
- not enzymes
- very important in process of lipid digestion
- several small lipid droplets have a bigger surface area then a single droplet
- formation of small droplets greatly increase the surface area of lipids thats available for lipase to work on
9
Q
Lipids broken down
A
- by lipase
- monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles
- help products of lipid digestion be absorbed
10
Q
Digestion of proteins
A
- broken down by combination of dif peptidases
- enzymes that catalyse conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids
11
Q
Endopeptidases
A
- act to hydrolysis peptide bonds within a protein
- trypsin and chymotrypsin
- synthesised in pancreas and secreted into small intestine
- pepsin released into stomach by cells in stomach lining
12
Q
Exopeptidases
A
- act to hydrolyse peptide bonds at end of protein molecule so remove a single amino acid
- dipeptidases’ work specifically on dipeptides and act on 2 separate amino acids that make up a dipeptide by hydrolysing the peptide bond between them
- locates on cell surface membrane of epithelial cells in small intestine
13
Q
Absorption of products of digestion
A
-absorbed across ileum epithelium into bloodstream
14
Q
Monosaccharide absorption
A
- monosaccharides - glucose absorbed by active transport with sodium ions via a co-transporter protein same with galactose
- fructose absorbed via facilitated diffusion through a different transporter protein
15
Q
Monoglycerides and fatty acid absorption
A
- micelles help to move monoglycerides and fatty acids toward the epithelium
- micelles constantly break up and reform they can release monoglycerides and fatty acids allowing them to be absorbed so the whole micelles aren’t taken up across epithelium
- monoglycerides and fatty acids are lipid soluble so can diffuse directly across the epithelial cell membrane
