3.3 Digestion & Absorption Flashcards
Where does stage 1 of protein digestion occur in the body?
Stomach
What is the first stage of protein breakdown?
Break long polypeptide chains in shorter chains
How do endopeptidases speed up the digestion of proteins?
Hydrolyse bonds in the middle of the chain
Create more ends/greater surface area for exopeptidases
What bonds do peptidases hydrolyse?
Peptide
Where does the second stage of protein breakdown occur?
Duodenum (small intestine)
What enzyme carries out stage 2 of protein breakdown?
Exopeptidases
What is the product in stage 2 of protein breakdown?
Dipeptides
What is a dipeptide?
2 amino acids joined by peptide bond
What enzyme carries out stage 3 of protein breakdown?
Dipeptidases
What is the product in stage 3 of protein breakdown?
Single amino acids
What is the first stage of starch breakdown?
Some starch is hydrolysed to maltose
Where does stage 1 of starch breakdown occur?
Mouth/salivary glands
What kind of biological molecule is starch?
Carbohydrate
What bonds does amylase hydrolyse?
Glycosidic
What reaction does amylase catalyse?
starch -> maltose
What kind of digestion is done by the teeth?
Mechanical
Why is it important to rip and grind food into smaller pieces?
Increase surface area:volume to increase enzyme action
What reaction does lactase catalyse?
lactose -> galactose + glucose
What reaction does sucrase catalyse?
sucrose -> glucose + fructose
What reaction does maltase catalyse?
disaccharides -> glucose
What is found in epithelial cells making up the wall of the ileum (small intestine)?
Dipeptidases
Lactase
Maltase
Sucrase
What problem is there with digestion of hydrophobic fats?
Form large globules in the body that have a small surface area:volume making enzyme action slow
What is bile?
A chemical produced in the liver that increases the surface area:volume of fats
Where is bile secreted?
Small intestine
How does bile increase the surface area:volume of fats?
Emulsifies fats into smaller droplets
What reaction does lipase catalyse?
fats -> fatty acids + glycerol
Where does lipase act?
Small intestine
What forms micelles?
Bile salts and fatty acids
Why are micelles important?
More soluble in water
Transport fatty acids to epithelial cell membrane
Ensures higher concentration of fatty acids outside of epithelial cell than inside
How do fatty acids move into epithelial cell?
Diffusion
Lipid soluble so can move straight through phospholipid bilayer
Name two membrane bound dipeptidases.
Endopeptidase
Exopeptidase
Where are endopeptidases produced?
Stomach
What is the role of endopeptidases?
Hydrolyse bonds in the middle of protein chains
What is the role of exopeptidases?
Hydrolyse bonds at the end of protein chains
How do endopeptidases make exopeptidase action quicker?
Make more ends to increase surface area for exopeptidases
How are amino acids absorbed into the blood?
Facilitated diffusion
How are amino acids absorbed into epithelial cells?
Co transport
How is glucose absorbed into epithelial cells?
Co transport
How is glucose absorbed into the blood?
Facilitated diffusion
Name 4 adaptations of epithelial cells for absorption.
Microvilli = large surface area
Mitochondria = active transport
Many protein channels = facilitated diffusion
Many protein carriers = active transport
Where are dipeptidases found?
Membrane of epithelial cells
How are fats absorbed into epithelial cells and into the blood?
Diffusion
Why does cotransport stop when respiration is prevented?
Sodium concentration gradient is no longer maintained
