3.3 Digestion Flashcards
(118 cards)
1
Q
What are the 2 types of digestion
A
- Mechanical/ physical
- Chemical
2
Q
What 2 structures in the body are involved in physical digestion
A
- Teeth and stomach
3
Q
Why is physical digestion important
A
-To break larger pieces into smaller ones
- Providing a large surface area for chemical digestion
- Increasing the rate of digestion
4
Q
What does chemical digestion do
A
It hydrolyses large, insoluble molecules into smaller soluble ones
5
Q
Explain why it is necessary for food to be digested, in order to be absorbed into our body
A
To make it smaller and soluble so that it can be transported across the membrane to be absorbed into the blood plasma
6
Q
What are the 3 functions of mucus
A
- Lubricant
- Neutralises acids
- Protects gut wall from acid erosion
7
Q
Where is amylase secreted from
A
- Salivary glands
- Pancreas
8
Q
What does amylase hydrolyse
A
Starch
9
Q
What are the products of amylase when starch is hydrolysed
A
Maltose
10
Q
Where are the sites of action for amylase
A
-Mouth (salivary glands)
- Duodenum (pancreatic juices)
11
Q
Roughly what is the optimum pH of amylase
A
About 8
12
Q
What type of bond does amylase hydrolyse
A
Glycosidic bonds
13
Q
Where is maltase found
A
In the ileum
14
Q
What is the substrate for endopeptidase
A
Proteins/ polypeptides
15
Q
What is the product from endopeptidase
A
Shorter polypeptides
16
Q
Where are endopeptidases secreted from
A
- Gastric glands
- Pancreas
17
Q
Where are the sites of action for endopeptidases
A
- Stomach
- Duodenum
18
Q
What are the substrates for exopeptidases
A
Short polypeptides
19
Q
What are the products from exopeptidases
A
- Amino acids
- Dipeptides
20
Q
Where are exopeptidases secreted from
A
- Pancreas
- Epithelial cells
21
Q
Where are the sites of action of exopeptidases
A
Duodenum
Ileum
22
Q
What is the substrate for lipase
A
Lipids
23
Q
What are the products from lipase
A
- Monoglycerides
- Fatty acids
24
Q
Where are lipase secreted from
A
Pancreas
25
Where is the site of action for lipase
Duodenum
26
What is the substrate for disaccharidases
Disaccharides
27
What is the product from disaccharidases
Monosaccharides
28
Where are disaccharidases secreted from
Epithelial cells
29
Where is the site of action for disaccharidases
Ileum
30
Do endopeptidases or exopeptidases hydrolyse the bonds at the end of the chain
Exopeptidases
31
Why are endopeptidases secreted inactive
So they don't digest the gut wall before they reach the stomach or the duodenum
32
Where is bile produced
Liver
33
Where is bile stored
Gallbladder
34
What is the name of tube where bile travels from the gallbladder to the duodenum
Bile duct
35
What are the 2 components of bile
- Bile salts
- Sodium hydrogen carbonate
36
What is the name of the process from which lipid droplets become micelles
Emulsification
37
What does sodium hydrogen carbonate do
Neutralises stomach acid
38
Micelles make the lipids more _______ so therefore easier to _______
1. Soluble
2. Transport
39
What is the pH range in the mouth
6.5-7.5
40
What types of digestion happen in the mouth
- Physical/ mechanical
- Chemical
41
What feature in the mouth carries out physical digestion
Teeth - increase the SA for chemical digestion
42
What is digested by chemical digestion in the mouth
Starch only
43
What are the 3 components of saliva
- Amylase
- Mucus
- Mineral ions
44
What is the role of amylase in saliva
To breakdown starch
45
What is the role of mucus in saliva
Lubricant
46
What is the role of mineral ions in saliva
Maintain pH
47
What is the name given to the process where there is co-ordinated contractions
Peristalsis
48
What is the role of goblet cells
To secrete mucus
49
What are the general 2 muscles in the digestive system
- Circular muscle
- Longitudinal muscle
50
What does the contraction of circular muscles do to the gut
Squeeze the gut
51
What does the contraction of the longitudinal muscles do to the gut
Shorten the gut
52
What is the name given to the ball of food that travels down the oesophagus
Food bolus
53
What is the role of mucus in the oesophagus
Lubrication
54
What is the pH in the stomach
pH 2
55
What is the name of the soupy consistancy product formed from the stomach churning
Acidic chyme
56
What biological molecule is chemically digested in the stomach
Proteins only
57
What does the gastric gland secrete
Gastric juice
58
What are the 3 components of gastric juice
- Endopeptidase
- Mucus
- HCl
59
What are the functions of mucus in the stomach
- Lubricant
- Protect the lining from acid erosion
60
What are the functions of HCl in the stomach
- Maintains pH to activate enzymes
- Kill bacteria
61
What part of the digestive system is the main site of chemical digestion
Duodenum
62
What are the 2 external glands to the duodenum
- Liver
- Pancreas
63
What does the liver secrete
Bile
64
What are the 4 components of pancreatic juice
- Amylase
- Endo and Exopeptidases
- Lipase
- Hydrogen carbonate ions
65
What is the name of the gland in the gut wall of the duodenum
Brunner's gland
66
What is secreted from the Brunner's gland, and what is its function
Mucus
- Neutralise stomach acid
- Protect the lining from acidic erosion
67
Where is the final region of chemical digestion
The ileum
68
Where are the enzymes in the ileum
In the microvilli, so the wall before the lumen
69
What is absorbed in the colon
- Water
- Vitamins
70
Why is water absorbed in the colon
To produce solidified faeces
71
Why do we need to have solidified faeces
In order to stimulate peristalsis
72
What synthesises the vitamins in the colon
The bacteria
73
Why is cellulose needed in the diet if it cannot be digested
It provides bulk since the fibres provide the solidity to the faeces
74
How do bile salts help the digestion of lipids
They emulsify them which increases the surface area for lipase
75
Why are hydrogen carbonate ions secreted into the duodenum
To neutralise the stomach acid
76
What is assimilation
How molecules are used by the cell, used for their relative process
77
What are amino acids used for by the cell
Protein synthesis
78
What are fatty acids and monoglycerides used for by the cell
Formation of cell membrane
79
What type of surface is the ileum
Exchange surface
80
What are the 4 features of the ileum that increase absorption efficiency
-Villi and microvilli
- Thin gut wall
- Muscle layer
- Blood flow carries the products away
81
How do villi and microvilli increase absorption efficiency in the ileum
They increase the surface area, so more carrier proteins therefore more molecules can pass through the membrane at one time
82
How does the ileum having a thin gut wall increase absorption efficiency
Shorter diffusion pathway, so increased rate of absorption
83
How do the muscle layers in the ileum increase absorption efficiency
They ensures that the molecules are in contact with the villi, so a concentration gradient is maintained
84
Why does blood flow carrying products away in the ileum increase absorption efficiency
It maintains the concentration gradient
85
Once molecules are absorbed into the lumen of the ileum, which 2 'tubes' can the be absorbed into
- Capillary
- Lacteal
86
What product of digestion is absorbed into the lacteal
Products of lipid digestion
87
What products of digestion are absorbed into capillaries
Products of protein and carbohydrates digestion
88
Before lipids are absorbed into the epithelial cells of the ileum, what do the fatty acids and monoglycerides leave first
The micelle
89
Once inside the epithelial cell of the ileum, what happens to the fatty acids and the monoglycerides
The reform as triglycerides
90
Once triglycerides have been formed in the epithelial cells of the ileum, what happens to them- what are they combined with, what is the new name of them
- The triglycerides are chemically modified in the golgi body
- Triglycerides are combined with proteins
- Forming chlyomicrons
91
Once the chlyomicrons are formed in the epithelial cells of the ileum, what is the name of the process by which they leave the epithelial cell
Exocytosis
92
Once chlyomicrons leave the epithelial cell of the ileum, where do they go
Into the lacteal
93
What is the name of the duct that the chlyomicrons are transported to once in the lacteal
Thoracic duct - then into the blood stream
94
Why do chlyomicrons have to go through the lacteal and the lymphatic system instead of diffusing directly into the blood stream
Because its too large to fit through the fenestrations of the capillary
95
What is the name of the pump which starts the absorption process of glucose or amino acids
Sodium, potassium pump
96
When absorbing glucose/ amino acids, what is the 1st step of the process, bonus points if you can name the type of co-transporter protein it is
Sodium ions are actively out of the ileum into the tissue fluid through a antiporter while potassium ions are actively transported into the ileum
97
When absorbing glucose/amino acids, what happens after the sodium ions have been pumped out of the ileum
This sets up a concentration gradient for sodium between the lumen of the ileum and the ileum wall
98
When absorbing glucose/ amino acids, what happens once a sodium concentration gradient has been set up, bonus points for the name of the co-transporter protein
Sodium is transported down it's concentration gradient through a symport protein, while pulling glucose/ amino acids into the ileum wall too- by indirect active transport
99
When absorbing glucose/ amino acids, how does the glucose/ amino acids enter the tissue fluid from the ileum wall
A concentration gradient has been set up so glucose/ amino acids can now facilitated diffuse down their own gradient into the tissue fluid
100
When there is excess glucose/ amino acids what is the name of the vein that takes it away from the ileum, and where does this vein take it
- Hepatic portal vein
- From ileum to liver
101
What is excess glucose converted into at the liver, and why is it converted to this
Into glycogen so it can be stored in the liver
102
What is the name of the process that happens to excess amino acids in the liver
Deamination
103
What is deamination
Where the liver removes the amino group and the hydrogen on the amino acid
104
Why does deamination occur
Because amino acids in high concentrations are toxic, so removing the ammonia from the amino acid and converting into urea to excrete is beneficial
105
Explain why it is more efficient for the endopeptidase enzymes to act before the exopeptidases
- Endopeptidases hydrolyse the internal peptide bonds
- Therefore increasing the surface area
- For exopeptidases to act on
- So a faster rate of break down
106
What is ingestion
The taking in of food
107
What does the epiglottus do
Blocks the trachea when swallowing food
108
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5 marks)
- Micelles contain bile salts and fatty acids/ monoglycerides
- Make fatty acids/ monoglycerides more soluble in water
- Fatty acids/ monoglycerides absorbed by diffusion
- Triglycerides reformed in cells
- Vesicles move to cell membrane
109
The movement of Na+ ions out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how. (2 marks)
- Generates a concentration gradient for Na+ ions
- Na+ ions moving in by facilitated diffusion, brings glucose with it
110
Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3 marks)
- Micelles include bile salts and fatty acids
- Make the fatty acids more soluble in water
- Brings fatty acids to the lining of the ileum
- Maintain higher concentration of fatty acids to the lining of the ileum
- Fatty acids absorbed by diffusion
111
Describe the role of enzymes in the digestion of proteins in a mammal (4 marks)
- Hydrolysis of peptide bonds
- Endopeptidase act in the middle of protein/ polypeptide
- Exopeptidases act at end of protein/ polypeptide
- Dipeptidases acts on dipeptides/ between 2 amino acids
112
Explain the advantages of lipid droplet and micelle formation (3 marks)
- Droplets increase surface area for lipase action
- So faster hydrolysis of lipids/ triglycerides
- Micelles carry fatty acids and glycerol through membrane to cells
113
Cell lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how. (3 marks)
- Sodium ions actively transported from ileum cell to blood
- Forms diffusion gradient fro sodium ions to enter cells from guy and with it glucose
- Glucose enters by facilitated diffusion with sodium ions
114
What are microvilli (1 mark)
Highly folded cell surface membrane
115
Vitamin A is a fat-soluble substance.
Micelles are involved in the process of Vitamin A absorption.
Describe the process of vitamin A absorption into cells lining the ileum (3 marks)
- Combine with bile salts
- Makes more soluble in water
- Micelles breakdown close to cells
- Diffuses into cells
116
Describe how the anti-toxin antibody would be digested ( 3 marks)
- Peptide bonds hydrolysed
- Endopeptidases break internal peptide bonds
- Exopeptidases break terminal peptide bonds
- Dipeptidases break dipeptides to amino acids
117
Describe and explain 2 features you would expect to find in a cell specialised fro absorption (2 marks)
1. Folded membrane/microvilli so large surface
area (for absorption);
2. Large number of
co-transport/carrier/channel proteins so fast
rate (of absorption)
OR
Large number of co-transport/carrier proteins
for active transport
OR
Large number of
co-transport/carrier/channel proteins for
facilitated diffusion;
3. Large number of mitochondria so make
(more) ATP (by respiration)
OR
Large number of mitochondria for aerobic
respiration
OR
Large number of mitochondria to release
energy for active transport;
4. Membrane-bound (digestive) enzymes so
maintains concentration gradient (for fast
absorption);
118
Describe the role of epithelial cell membranes in the ileum in the absorption of amino acids
- Sodium ions are actively transported out of the epithelial cells into the blood via the sodium/potassium pump lowering the sodium ion concentration inside the cell
- Sodium ions diffuse back into the epithelial cell from the lumen via co-transport protein, bringing amino acids with them
- Amino acids are transported out of the epithelial cell into the blood via a specific carrier protein in the membrane
- The epithelial cell membrane contain microvilli, which increase the surface area for amino acid absorption, maximising efficiency
