3.3.3 Digestion + Absorption Flashcards
1
Q
What are the 2 types of digestion
A
Physical digestion
Chemical digestion
2
Q
2 examples of physical digestion
A
Teeth chew food to mechanically break down food into smaller pieces
Walls of stomach contain muscle tissue that contracts to churn food
3
Q
What do enzymes do in chemical digestion
A
Hydrolyse food into smaller molecules
4
Q
What are the 3 main enzymes in chemical digestion
A
Carbohydrases
Lipases
Proteases
5
Q
What does carbohydrase do
A
Digests carbohydrates into monosaccharides
6
Q
What do lipases do
A
Hydrolysed fats into glycerol and fatty acids
7
Q
What do proteases do
A
Hydrolyse proteins into amino acids
8
Q
What are the 2 main carbohydrate digestion enzymes
A
Amylase
Maltase
9
Q
Where is amylase enzyme made (2)
A
Salivary gland - saliva
Pancreas
10
Q
What does amylase enzyme do and produce
A
Hydrolyses alternate glycosidic bonds in starch to produce maltose (disaccharide)
11
Q
Where is maltase enzyme made
What does it do
A
In the ileum
Hydrolyses maltose to produce alpha glucose
12
Q
What is maltase known as as it isn’t secreted but is bound to the lining of the ileum
A
Known as a membrane-bound disaccharide
13
Q
3 places where carbohydrate digestion occurs
A
Mouth
Stomach
Small intestine
14
Q
What happens to the amylase enzyme from the salivary gland (mouth) in the stomach
A
Stomach acid dentures the amylase
15
Q
What in the liver neutralises stomach acid
A
Bile
16
Q
What enzymes does the small intestine receive/have (2)
A
Pancreatic amylase
Maltase
17
Q
2 other carbohydrates (disaccharides)
A
Sucrose
Lactose
18
Q
What’s sucrose found in
A
Fruits
19
Q
What happens to sucrose
A
It’s hydrolysed by sucrase (produce by ileum)
Produces glucose + fructose (2x monosaccharides)
20
Q
What’s lactose found in
A
Milk (yoghurt, cheese)
21
Q
What happens to lactose
A
Hydrolysed by lactase (produced by ileum)
Produces glucose + galactose (2x monosaccharides)
22
Q
What’s the lack of lactose production also known as
A
Lactose intolerance
23
Q
When do babies produce large amounts of lactose
A
When they feed on milk
24
Q
Where is lactose hydrolysed
What does this produce
A
Not on the small intestine but in the colon
Produces small,soluble molecules(sugars) + gas - diarrhoea
25
What’s the role of the colon
To absorb water into the bloodstream to produce solid faeces
26
How can the colons Job be disrupted
How is faeces produced
If water potentials are changed
Water potential in the colon’s lumen is lowered
So water is drawn into the lumen from the epithelial cells by osmosis
This causes faeces
27
What enzymes digest lipids + how
| What forms
Pancreatic lipase enzymes hydrolyse Ester bonds
| Fatty acids + monoglycerides are formed
28
What process assists lipid digestion
| What does it involve
Emulsification
Bile salts made by the liver split the lipids into micelles (fat droplets)
29
What does emulsification into micelles do to help lipase work
It increases the surface area of the lipid to speed up lipase action
30
What’s the bile salt like in lipid digestion
| So how are they arranged
1 end of bile salt is soluble in water (hydrophobic) but not lipid soluble (lipophobic)
The other end is lipophilic but hydrophobic
The salts are arranged so the lipophilic/hydrophobic end is attached to the lipid
31
What does the lipophobic end of bile salt do
Sticks out repelling other lipids
32
What do micelles transport and where to
Digested lipids + vitamins to the epithelial cells of the small intestine
33
What do micelles do at epithelial cells
Micelles fuse with epithelial cells
| They then release the lipids/vitamins into epithelial cells allowing it to be absorbed
34
What are proteins hydrolysed by
Peptidase enzymes (proteases)
35
3 different types of peptidase enzymes in the digestive system
Endopeptidases
Exopeptidases
Dipeptidases
36
What do endopeptidases do and form
Hydrolyse the peptide bonds between amino acids in the central region of the protein -> forming peptide molecules
37
Who do exopeptidases do and form
Hydrolyse peptide bonds at terminal amino acids on peptide chains formed by endopeptidase -> forming dipeptides + amino acids
38
What do dipeptidases do and form
Hydrolyse bonds between the 2 amino acids of a dipeptide -> producing single amino acids
39
What are dipeptidases like in the small intestine
Membrane bound
40
How do things get absorbed in the small intestine
Through villi + microvilli
41
What’s villi
Finger-like projections 1mm long that increase SA for absorption
42
What is each villus separated by
| How does this speed up nutrient absorption
Each villus separated by a capillary
| Reduces diffusion distance speeding up absorption
43
What gives villi a larger surface area
They’re folded and have microvilli on the epithelial cells there
44
What do villi have to reduce diffusion distance
Thin membrane
45
What do villi contain that allows them to move to maintain diffusion gradients
Muscle tissue that contracts
46
What does villi moving do (2)
Mixes the food in the ileum
| Maintains concentration gradient to maximise food absorption
47
How’s the small intestine adapted to maximise nutrient absorption (4)
Long organ
Large SA - folded villi + microvilli
Mitochondria - active transport
Carrier proteins - active transport/facilitated diffusion
Blood supply close by
Enzymes to digest carbohydrates,fats + proteins
Cotransport (sodium + glucose)
48
What’s celiac disease
Intolerance to gluten
49
What’s gluten
A protein in wheat,rye + barley
50
What can eating gluten if you have celiac disease do to you
Stimulate the immune system to damage the small intestine, causing malnourishment
51
What does gluten attack in celiac disease
| So what do this make difficult for this body
Gluten attacks the villi that lines the small intestine
| so your body can’t take in nutrients from food in the bloodstream
52
How do most nutrients get into epithelial cells (sodium)
By moving passively from the lumen of the small intestine into the epithelial cell
53
E.g of a nutrient that can’t move passively into epithelial cells
Glucose
54
What’s the co-transport pump in the small intestine
Sodium-glucose symporter
55
In the sodium-glucose symporter what must happen before the molecules can be moved by the protein
Both sodium + glucose must bind
56
What makes it easier for the other molecule to bind in the sodium-glucose symporter
The binding of 1 molecule
57
What keeps the sodium-glucose symporter pump moving in the right direction
The concentration gradient of sodium
58
If sodium levels in the epithelial cells were allowed to accumulate what would happen
Sodium actively pumped out of epithelial cells and into body by Na/K+ pump
Maintains concentration gradient to allow glucose co-transport
Glucose passes into blood via facilitated diffusion (uniporter)
59
How are triglycerides absorbed (7)
1. Micelles break down when come into contact with epithelium of ileum
2. Monoglycerides + fatty acids (non-polar) diffuse across membrane into epithelial cells
3. They’re transported to ER in epithelial cells to reform triglycerides
4. Bind to cholesterol and lipoproteins in ER and Golgi to form chylomicrons
5. Chylomicrons enter lacteals
6. They travel through lymphatic system + pass into blood stream
7. Triglycerides are then hydrolysed by lipase enzymes + enter cells that need them
60
What 3 things are involved in absorbing triglycerides
Micelles (bile salts), monoglycerides + fatty acids
61
What are monoglycerides and fatty acids formed from
Lipase enzyme
62
What do monoglycerides and fatty acids reform at the ER in epithelial cells
Triglycerides
63
What do triglycerides bind to in ER + Golgi
| What does this form
Bind to cholesterol and lipoproteins
| Forms Chylomicrons
64
What are lacteals
Lymphatic capillaries
65
What’s the lymphatic system
A series of thin tubes filled with lymph
| Contains large number of white blood cells (lymphocytes)
66
What produces the enzymes that hydrolyse molecules for absorption
Glands
67
What does the oesophagus do
Carries food from mouth to stomach
68
What’s the ileum
Long muscular tube
69
What does the large intestine do
Absorbs water
70
What’s the process called when faeces are removed by the anus
Egestion
71
What’s the pancreas
Large gland below the stomach
72
What is the solution called that pancreas secretes containing enzymes
Pancreatic juice
73
What does the saliva contain to help maintain the pH for enzymes around neutral
Mineral salts
74
What are micelles
Tiny fat droplets
75
What are villi well supplied with to maintain diffusion gradient
Blood vessels
76
What do micelles do when they come into contact with the epithelial cells lining the villi of the ileum
Break down, releasing the monoglycerides and fatty acids
77
Why do monoglycerides and fatty acids easily diffuse into epithelial cells
As they’re non-polar
78
Where are monoglycerides and fatty transported to once they’re in the epithelial cells
What happens
The endoplasmic reticulum
| Recombined to form triglycerides
79
What do the triglycerides form in the endoplasmic reticulum and Golgi apparatus
Form chylomicrons
80
What 2 things do triglycerides associate with to form chylomicrons
Cholesterol
| Lipoproteins
81
What are chylomicrons adapted for
Transport of lipids
82
What do chylomicrons enter after they’ve exited the epithelial cells (exocytosis) to enter the bloodstream
Lymphatic capillaries (lacteals)
83
How are glucose and amino acids absorbed from small intestine
Co-transport
84
Why is it co-transport
As either glucose/amino acids are drawn into cells with sodium ions that have been actively transported out by the sodium-potassium pump
85
Where is the higher concentration of sodium ions when they’re transported out of epithelial cells by the pump
In the lumen of the intestine rather than epithelial cells
86
What do sodium ions diffuse into the epithelial cells through
What are they now carrying
Through a co-transport protein
| Either amino acids molecules/glucose molecules
87
How do the glucose/amino acids pass into the blood plasma after this, by using a different carrier
Facilitated diffusion
88
What molecules move against their concentration gradient in do-transport
The glucose
89
Where is bile made and stored
Made - liver
| Stored - gall bladder
90
What type of digestion is bile
Physical and it has no enzymes
