Topic 3B - More Exchange and Transport Systems Flashcards
How are carbohydrates digested? (2)
- Amylase — Amylase catalyses the breakdown of starch. It works by catalysing hydrolysis reactions that break the glycosidic bonds in starch to produce maltose.
- Membrane-bound disaccharidases — These are enzymes which help breakdown disaccharides into monosaccharides. This is done by catalysing the hydrolysis of glycosidic bonds.
Where is amylase produced? (2)
- The salivary glands — this releases amylase into the mouth.
- The pancreas — this releases amylase into the small intestine.
Where are membrane-bound disaccharidases found?
Attached to the cell membranes of epithelial cells lining the ileum.
What makes up sucrose?
Glucose + Fructose
What makes up maltose?
Glucose + Glucose
What makes up lactose?
Glucose + Galactose
What is the disaccharidase of sucrose?
Sucrase
What is the disaccharidase of maltose?
Maltase
What is the disaccharidase of lactose?
Lactase
How are lipids digested? (2)
- Lipase enzymes — They catalyse the breakdown of lipids into monoglycerides and fatty acids. This is done by catalysing the hydrolysis of the ester bonds in lipids.
- Bile salts — These emulsify lipids (form small droplets), which are then easier to be hydrolysed by lipases as they’ll have a greater surface area.
Where are lipases produced?
The pancreas — they are then secreted into the small intestine.
Where are bile salts produced?
The liver
How are proteins digested? (3)
- Endopeptidases — They act to hydrolyse peptide bonds within a protein.
- Exopeptidases — They hydrolyse peptide bonds at the end of protein molecules. They remove single amino acids from proteins.
- Dipeptidases — They are exopeptidases that work specifically on dipeptides. They act to separate the two amino acids that make up dipeptides by hydrolysing the peptide bond between them.
Where are endopeptidases produced? (2)
- Some endopeptidases (Trypsin & Chymotrypsin) are produced in the pancreas — they are secreted into the small intestine.
- Another endopeptidase (Pepsin) is produced in the cells lining the stomach — it is then secreted directly into the stomach.
How are monosaccharides absorbed into the bloodstream? (3)
Glucose is absorbed by active transport with sodium ions via a co-transporter protein.
Galactose is absorbed in the same way by the same co-transporter protein.
Fructose is absorbed via facilitated diffusion through a different transporter protein.
How are monoglycerides and fatty acids absorbed into the bloodstream?
Micelles help to move monoglycerides and fatty acids towards the epithelium. As micelles constantly break up and reform they can ‘release’ monoglycerides and fatty acids, allowing them to be absorbed. Monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across the epithelial cell membrane.
How are amino acids absorbed into the bloodstream?
Sodium ions are actively transported out of the epithelial cells into the ileum itself. They then diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membranes, carrying the amino acids with them.