6.9- ENZYMES AND DIGESTION Flashcards
What is the human digestive system made up of?
long muscular tube + its associated with glands
What do the glands associated with the digestive system produce?
enzymes that hydrolyse large molecules into small ones ready for absorption
What is the digestive system used for?
exchange surface through which food substances absorbed
What are the main parts of the digestive system? (7)
oesophagus stomach ileum large intestine rectum salivary glands pancreas
What does the oesophagus do?
carries food from mouth to stomach
What is the stomach?
muscular sac with inner layer that produces enzymes
What is the role of the stomach?
store + digest food, especially proteins
What does the stomach have which digest protein?
glands that produce enzymes which digest proteins
What is the ileum?
long muscular tube
What is done to food in the ileum?
food further digested in ileum by enzymes produced but its walls + glands that pour their secretions into it
What are the inner walls of the ileum folded into?
villi
What does the inner walls of the ileum being folded into villi give them?
large surface area
What is the surface are of the villi of the ileum further increased by?
millions of tiny projections, called microvilli, on epithelial cells of each villus
What does the increased surface of the ileum from the villi and microvilli adapt the ileum for?
its purpose of absorbing products of digestion into bloodstream
What do the large intestines do?
absorbs water
What is most of the water absorbed by the large intestines from?
water from secretions of many digestive glands
What is the final section of the intestines?
rectum
What is stored in the rectum?
faeces
How is the faeces removed from the rectum?
via anus in process called egestion
Where are the salivary glands situated?
near the mouth
How do the salivary glands pass their secretions?
via duct into mouth
What does the secretion of the salivary glands contain?
enzyme amylase, which hydrolyses starch into maltose
What is the pancreas?
large gland situated below stomach
What is the secretion of the pancreas called?
pancreatic juice
What does the pancreatic juice contain?
proteases to hydrolyse proteins, lipase to hydrolyse lipids + amylase to hydrolyse starch
What are the two stages of digestion in humans?
1 physical breakdown
2 chemical digestion
If the food is large, how is it broken down into smaller pieces in physical breakdown?
by means of structures i.e. teeth
What does food being broken down into smaller pieces by the teeth make possible?
ingest food + provides large SA for chemical digestion
How is food physically broken down in the stomach?
food churned by muscles in stomach
What does chemical digestion do?
hydrolyses large. insoluble molecules into smaller, soluble ones
What is chemical digestion carried out by?
enzymes
What do all digestive enzymes function by?
hydrolysis
What is hydrolysis?
splitting up of molecules by adding water to chemical bonds that hold them together
How many enzymes is needed to hydrolyse a large molecule?
more than one
How does hydrolyses of a large molecule usually happen?
one enzyme hydrolyses large molecules into sections + these sections then hydrolysed into smaller molecules by one/more additional enzymes
What are 3 particularly important digestive enzymes?
carbohydrases
lipases
proteases
What do carbohydrases hydrolyse and into what?
carbohydrates to ultimately monosaccharides
What do lipases hydrolyse and into what?
lipids (fats + oils) into glycerol + fatty acids
What do proteases hydrolyse and into what?
proteins, ultimately into amino acids
Where is amylase produced?
mouth + pancreas
What does amylase hydrolyse?
alternate glycosidic bonds of starch molecules to produce disaccharide maltose
What is the maltose produced from amylose hydrolyses, hydrolysed by?
by maltase into monosaccharide α-glucose
What is maltase produced by?
lining of ileum
Amylase working in humans: saliva (1)
saliva enters mouth from salivary glands +t thoroughly mixed with food during chewing
Amylase working in humans: what does saliva contain?
salivary amylase
Amylase working in humans: what does the salivary amylase in the saliva do? (2)
starts hydrolysing any starch in food to maltose
Amylase working in humans: what else does the saliva contain? (2)
mineral salts that help maintain pH at around neutral
this is optimum pH for salivary amylase to work
Amylase working in humans: where does the food go from the mouth? (3)
swallowed + enters stomach, where conditions are acidic
Amylase working in humans: what happens to the amylase in the stomach? (3)
acid denatures amylase + prevents further hydrolysis of starch
Amylase working in humans: where does the food go from the stomach? (4)
after time food passed into small intestine, where it mixes with secretion from pancreas called pancreatic juice
Amylase working in humans: what does the pancreatic juice contains?
pancreatic amylase
Amylase working in humans: what does the pancreatic amylase in the pancreatic juice do? (5)
continues hydrolysis of any remaining starch to maltose
Amylase working in humans: what does the pancreas + intestinal wall produce and why? (5)
alkaline salts produced by pancreas + intestinal walls to maintain pH at around neutral so amylase can function
Amylase working in humans: what do the muscles in the intestines do? (6)
muscles in intestine walls push food along ileum
Amylase working in humans: what does the epithelial lining of the intestine produce? (6)
produces disaccharidase maltase
Is maltase release into the lumen of the ileum?
no
Amylase working in humans: what is the disaccharidase maltase part of? (6)
cell-surface membranes of epithelial cells that line the ileum
As the maltase is a part of the cell-surface membranes of epithelial cells that line the ileum, what is it called?
membrane-bound disaccharidase
Amylase working in humans: what does the maltase do to the maltose? (6)
maltase hydrolyse maltose from starch breakdown into α-glucose
What are two other common disaccharides other than maltose in the diet that are hydrolysed?
sucrose and lactose
Where can sucrose be found in food?
sucrose found in many natural foods, especially fruits
Where can lactose be found in food?
in milk, + hence milk products such as yoghurt + cheese
What does sucrase do?
hydrolyses single glycosidic bonds in sucrose molecules
What does the sucrase hydrolysing sucrose produce?
hydrolysis produces two monosaccharides glucose + fructose
What does lactase do?
hydrolyses single glycosidic bond in lactose molecule
What does the lactase hydrolysing lactose produce?
hydrolysis produces two monosaccharides glucose + galactose
What are lipids hydrolysed by?
enzymes called lipases
Where are lipases produced?
pancreas
What do lipases do?
hydrolyse ester bonds found in triglycerides to form fatty acids + monoglycerides
What is a monoglyceride?
glycerol molecules with single fatty acid molecule attached
What happens to the lipids first in lipid digestion?
split into tiny droplets called micelles by bile salts
What are bile salts produced by?
liver
What is the process of fats being split into tiny droplets called micelles by bile salts called?
emulsification
What does emulsification do?
increases SA of lipids so action of lipases speeded up
What are proteins?
large, complex molecules
What are proteins hydrolysed by?
group of enzymes called peptidases (proteases)
What are the different types of peptidases? (3)
endopeptidases
exopeptidases
dipeptidases
What do endopeptidases do?
hydrolyse peptide bonds between amino acids in central region of protein molecule forming series of peptide molecules
What do exopeptidases do?
hydrolyse peptide bonds on terminal amino acids of peptide molecules formed by endopeptidases
in this way they progressively release dipeptides + single amino acids
What do dipeptidases do?
hydrolyse bond between two amino acids of dipeptide
What type of enzymes are dipeptidases?
membrane-bound, being part of cell-surface membrane of epithelial cells lining the ileum
