During digestion, large biological molecules are broken down by the addition of water into smaller molecules that can cross cell membranes.
What type of reaction is this?
Hydrolysis
Hydrolysis uses water to break bonds between monomers in polymers during digestion.
Which enzyme begins the digestion of starch in the mouth and small intestine by breaking it into maltose?
Amylase
Salivary and pancreatic amylase hydrolyse starch into maltose and other short polysaccharides.
Which enzymes located on the epithelial cell membrane of the small intestine hydrolyse disaccharides into monosaccharides?
Membrane-bound disaccharidases
Examples include maltase, lactase and sucrase on the brush border of the ileum.
What type of carbohydrate molecule is absorbed across the epithelial cells of the ileum after digestion?
Monosaccharides
Carbohydrates must be digested to monosaccharides such as glucose before absorption.
Which enzyme catalyses the digestion of lipids into fatty acids and monoglycerides?
Lipase
Pancreatic lipase acts mainly in the small intestine.
What substance produced by the liver emulsifies lipids and increases the surface area for lipase action?
Bile salts
Bile salts break large fat globules into smaller droplets, improving enzyme access.
What process occurs when bile salts break large fat globules into many small droplets?
Emulsification
Emulsification increases the surface area of lipids for lipase activity.
True or False:
Lipase directly breaks triglycerides into glycerol and three fatty acids in a single step.
False
Lipase typically produces monoglycerides and fatty acids rather than glycerol directly.
Which group of proteases breaks peptide bonds within the middle of a polypeptide chain?
Endopeptidases
Examples include trypsin and pepsin. They produce shorter peptide chains.
Which proteases remove amino acids from the ends of polypeptide chains?
Exopeptidases
They act after endopeptidases to release individual amino acids.
Which enzymes attached to the epithelial cell surface hydrolyse dipeptides into amino acids before absorption?
Membrane-bound dipeptidases
These enzymes are located on the brush border of the ileum epithelial cells.
What transport mechanism moves glucose and amino acids into epithelial cells of the ileum together with sodium ions?
Co-transport
Also called secondary active transport; uses a sodium ion gradient created by active transport.
Fill in the blank:
The movement of sodium ions out of epithelial cells by the ______ pump provides the gradient that drives co-transport of glucose.
Sodium–potassium pump
This pump uses ATP to move Na+ out and K+ into cells, maintaining the Na+ gradient.
What small spherical structures formed by bile salts transport fatty acids and monoglycerides to epithelial cell membranes?
Micelles
Micelles keep lipids soluble and help them diffuse to the epithelial surface for absorption.
True or False:
Micelles allow lipid digestion products to diffuse across the phospholipid membrane of epithelial cells.
True
Fatty acids and monoglycerides leave micelles and diffuse across the membrane.
After entering epithelial cells, fatty acids and monoglycerides are reassembled into which type of lipid before transport in the lymph?
Triglycerides
These combine with proteins to form chylomicrons before entering lacteals.
-
3.1.1 Monomers & Polymers9
-
3.1.2 Carbohydrates22
-
3.1.3 Lipids17
-
3.1.4 Proteins39
-
3.1.5 Nucleic Acids32
-
3.1.6 ATP11
-
3.1.7 Water11
-
3.1.8 Inorganic ions8
-
3.2.1 Cell structure52
-
3.2.2 Cell division20
-
3.2.3 Transport across cell membranes20
-
3.2.4 Cell recognition & the immune system36
-
3.3.1 Surface area to volume ratio13
-
3.3.2 Gas exchange24
-
3.3.3 Digestion & absorption16
-
3.3.4 Mass transport39
-
3.4.1 DNA, genes & chromosomes13
-
3.4.2 DNA & protein synthesis14
-
3.4.3 Genetic diversity & meiosis14
-
3.4.4 Genetic diversity & adaptation20
-
3.4.5 Species & taxonomy20
-
3.4.6 Biodiversity within a community12
-
3.4.7 Investigating diversity12
-
3.5.1 Photosynthesis23
-
3.5.2 Respiration17
-
3.5.3 Energy & ecosystems20
-
3.5.4 Nutrient cycles15
-
3.6.1 Stimuli & Response62
-
3.6.2 Nervous coordination53
-
3.6.3 Skeletal muscles14
-
3.6.4 Homeostasis57
-
3.7.1 Inheritance12
-
3.7.2 Populations15
-
3.7.3 Evolution may lead to speciation22
-
3.7.4 Populations in ecosystems24
-
3.8.1 Gene Mutations and Protein Structure14
-
3.8.2 Control of Gene Expression44
-
3.8.3 Applications of Genome Projects10
-
3.8.4 Gene Technologies and Their Applications46
