Digestion and absorption Flashcards
Through what reaction are biological molecules broken down?
Hydrolysis
What is amylase?
Digestive enzyme
What does amylase do?
Catalyses the breakdown of starch
Where is amylase produced?
Salivary glands
Pancreas
Where is amylase released into?
Mouth
Small intestine
What is starch broken down into?
Glucose molecules
What are membrane-bound disaccharidases?
Enzymes attached to the cell membranes of epithelial cells lining the ileum
What do membrane-bound disaccharidases break down?
Disaccharides into monosaccarides
What are sucrase, maltase and lactase examples of?
Membrane bound disaccharidases
What reaction does sucrase catalyse?
Breakdown of sucrose
What is sucrose broken down into?
Glucose and fructose
What reaction does maltase catalyse?
Breakdown of maltose
What is maltose broken down into?
Glucose and glucose
What do lipase enzymes catalyse the breakdown of?
Lipids
What are lipids broken down into?
Monoglycerides and fatty acids
What bonds in lipids are hydrolysed?
Ester
Where are lipase enzymes mainly made?
Pancreas
Where are lipase enzymes secreted into?
Small intestine
Where are bile salts produced?
Liver
What do bile salts do?
Emulsify lipids
How does the work of bile salts benefit digestion of lipids?
They increase the surface area thats available for the lipase enzymes to work on
What is a micelle?
Tiny structures of bile salts with attached monoglycerides and fatty acids
What enzymes break down proteins?
Peptidases
What are the three types of peptidases?
Endopeptidases
Exopeptidases
Dipeptidases
What bonds in proteins are hydrolysed?
Peptide bonds
Where on a protein do endopeptidases work to hydrolyse the bonds?
in the middle of the polypeptide chain
Where on a protein do exopeptidases work to hydrolyse the bonds?
At the end of the polypeptide chain
What do dipeptidases only work on?
Dipeptide
What is a dipeptide?
Two amino acids in a chain joined by a peptide bond
How is it beneficial to have all three peptidases working together during protein digestion?
The endopeptidases create more ends/more surface area for the exopeptidases and dipeptidases to work on, which makes the process faster
How are glucose and galactose absorbed?
By active transport with sodium ions via a co-tranporter protein
How is fructose absorbed?
Via facillitated diffusion through a different transporter protein
How are monoglycerides and fatty acids absorbed?
The micelles move them towards the epithelium and then break up to release them so they can be absorbed
How are amino acids absorbed?
Sodium ions are actively transported out of the cell into the epithelium and when they diffuse back through a sodium-dependent transporter protein, they bring the amino acids with them
Where is maltase produced?
Small intestine
Describe the role of enzymes of the digestive system in the complete breakdown of starch (5 marks)
1) Hydrolysis of glycosidic bonds
2) by amylase
3) produces maltose which is a disaccharide
4) maltase breaks down maltose by hydrolysing the glycosidic bonds
5) into two molecules of glucose
Suggest and explain why the combined actions of endopeptidases and exopeptidase are more efficient than exopeptidases on their own (2 marks)
- It’s faster
- more ends are made to increase surface area for exopeptidases to work on
Give an advantage of lactase and other digestive enzymes being located in the plasma membranes of cells lining the small intestine rather than being secreted into the lumen of the small intestine (1 mark)
Membrane bound so they aren’t lost through faeces
The concentration of glucose in the blood rises after eating a meal containing carbohydrates. The rise is slower if the carbohydrate is starch rather than sucrose. Why? (3 marks)
1) Starch digested by amylase to maltose
2) Maltose digested by maltase into glucose
3) Sucrose is digested by sucrase into glucose , only a single step
