1
Q
What is digestion?
A
The process by which large molecules are hydrolysed by enzymes into small ones which can be absorbed
2
Q
Where is the liver and gall bladder?
A
Next to stomach
3
Q
Where is the pancreas?
A
Underneath the stomach
4
Q
Where is the duodenum + ileum?
A
Duodenum = top ½ small intestine Ileum = bottom ½ small intestine
5
Q
Where are the ascending + descending colons?
A
Large intestine
6
Q
What is the purpose of the oesophagus?
A
Thick muscular wall to transport food to get digested/absorbed
7
Q
What is the role of the stomach in digestion?
A
- muscular wall: churn, peristalsis
- stomach acid: protease, amino acids, kills bacteria, pH for protease
- gland: mucus, protect stomach
8
Q
What is the purpose of peristalsis?
A
Increase surface area of food for chemical digestion
9
Q
What happens in the duodenum?
A
- pancreatic juice: lipase, carbohydrase, protease
- liver juice: bile = neutralizes, emulsifies fats
10
Q
What is the purpose of the gall bladder?
A
Store bile
11
Q
What happens in the ileum?
A
- intestine wall juice: carbohydrase (glucose), protease (amino acids), lipase (fatty acids + glycerol)
- absorption: villi, surface area
- epithelial: microvilli
12
Q
How is the ileum evolved to suit it’s function of absorption?
A
- large surface area
- short diffusion distance to blood (one cell thick)
- capillary (carbs + pro’s) + lymph vessel (fat) in every villus, carry molecules away, diffusion gradient
13
Q
What does the large intestine do?
A
Water re absorbed into blood
14
Q
What molecules do these enzymes break down?
A
- lipase > fats > fatty acids/glycerol
- carbohydrate > carbs > glucose
- amylase > starch > maltose
- protease > protein > amino acids
15
Q
What is the order of digestion?
A
- Mouth
- Oesophagus
- Stomach
- Duodenum (pancreas + liver)
- Ileum
- Large intestine
- Rectum
- Anus
16
Q
What happens in the mouth?
A
- teeth cut up food, S/A
- salivary glands: amylase, starch
17
Q
What is an example of physical + chemical digestion?
A
Physical: peristalsis, chewing
Chemical: stomach acid, pancreatic juice, bile
18
Q
How do enzymes digest?
A
Hydrolysis: split up molecules by adding water + breaking bonds
19
Q
What is assimilation?
A
The distributing and re-assembling of digested molecules through the rest of the body
20
Q
Where is amylase produced?
A
Salivary glands
Pancreas
21
Q
Where is protease produced?
A
Stomach
Pancreas
22
Q
Where is lipase produced?
A
Pancreas
23
Q
What do glands produce?
A
Enzymes (and hormones)
24
Q
what are carbohydrates? (definition)
A
A group of substances used as energy sources + structural materials
25
What is the formula of glucose?
C6 H12 O6
26
name 3 monosaccharides (simple sugars)
- glucose
- galactose
- fructose
27
What are disaccharides formed from?
two monosaccharides
28
what disaccharide does glucose + glucose form?
maltose
29
what two monosaccharides form lactose?
glucose + galactose
30
what disaccharide does glucose + fructose form?
sucrose
31
what enzyme breaks down lactose?
lactase
32
name 3 polysaccharides
- glycogen
- cellulose
- starch
33
what two polysaccharides contain alpha glucose?
glycogen + starch
34
how are polysaccharides different from each other if they are all made up of many monosaccharides?
different structures
35
what polysaccharide contains beta glucose?
cellulose
36
what two polysaccharides are found in plants?
cellulose + starch
37
glucose contains 6 carbon atoms, what does this mean?
it's a hexose sugar
38
draw the structure of a ring of glucose
*check from book*
39
what is the difference between alpha + beta glucose?
the -OH group on carbon 1 is above the carbon in beta glucose (opposite to alpha)
40
how is fructose different to glucose?
more soluble, sweeter than glucose
41
how is galactose different to glucose?
less soluble, makes glycolipids + glycoproteins
42
what is a pentose sugar?
contains 5 carbon atoms
43
what are two examples of pentose molecules?
ribose + deoxyribose
44
what is the difference between ribose + deoxyribose structurally?
```
ribose = 1 H atom + 1 -OH group
deoxyribose = 2 H atoms
```
45
how are disaccharides formed?
condensation reaction
46
what is produced in the formation of a disaccharide?
water + glycosidic bond
47
how are disaccharides broken down?
glycosidic bond = add water, hydrolysis reaction
48
why is a glycosidic bond a 1-4 alpha bond?
the Oxygen bond is between the 1 (left) carbon and the 4 (right) carbon
49
is the bond between the disaccharide, lactose, alpha or beta?
beta
50
what is a polysaccharide? (definition)
polymers containing many monosaccharides linked by glycosidic bonds
51
what two types of alpha glucose make up starch?
amylose + amylopectin
52
describe the structure of amylose
1-4 glycosidic bonds
linear chains
helical structure
53
describe the structure of amylopectin
1-4 + 1-6 glycosidic bonds
| highly branched chains
54
why is starch predominantly made up of amylopectin rather than amylose?
branched structure of amylopectin = faster to break down for energy release for respiration
55
what is the main purpose of starch?
stored as energy reserve in plants in starch grains
56
what is the main purpose of cellulose?
holds together plant cell walls, stops cells bursting from osmosis
57
how is cellulose adapted to its purpose?
- glucose linear chains form microfibrils by layering chains on top of each other with hydrogen bonds
- not easily broken down so able to support plant
58
explain the structure of cellulose
- every other beta glucose molecule rotates 180deg
- hydroxyl groups on each molecule are adjacent
- condensation reactions form glycosidic bonds
59
what is the purpose of glycogen?
energy store in granules in animal cells
60
how is glycogen adapted to its purpose?
- many alpha 1-6 bonds that produce highly branched structure = more SA to break down quickly
- compact
- insoluble = doesn't affect water potential
61
why is the structure of glycogen more branched than amylopectin in starch?
glycogen more dense + soluble because animals have higher metabolic requirements (plants don't move much)
62
amylopectin contains alpha + beta glucose - true/false?
true
63
how does the structure of starch relate to it's function?
- compact
- insoluble in water = won't make cell burst
- branched = easily hydrolysed for energy release
64
what is a reducing sugar?
reduction = gain of electrons
| reducing sugar = donate electrons
65
what is the process to test for a reducing sugar?
1. grind up solid foods in water = liquid
2. add food sample to test tube
3. add equal volume of Benedict's reagent
4. heat mixture in water bath for 5 mins
5. reducing sugar = red precipitate present
66
how is the Benedict's test for reducing sugar semi-quantative?
differences in colour = can be used to estimate approx amount of reducing sugar in a sample
67
what is an example of a reducing sugar?
maltose (all monosaccharides also)
68
what should be carried out if no colour change occurs after the Benedict's test?
the test for non-reducing sugars present
69
what is an example of a non-reducing sugar?
sucrose (most disaccharides)
70
what is the process to test for a non-reducing sugar?
1. grind up solid foods in water
2. add sample to to Benedict's reagent in test tube
3. put test tube in water bath 5 mins, if still blue continue
4. add liquid food sample to equal volume of hydrochloric acid
5. put in water bath 5 mins
6. add sodium hydrogencarbonate solution to test tube, use pH paper to check alkali
7. add benedict's reagent + boil in water bath 5 mins
8. orange - brown = non-reducing sugar present
71
what is the purpose of adding hydrochloric acid to test for a non-reducing sugar?
it hydrolyses any disaccharide into it's monosaccharide components
72
what is the purpose of adding sodium hydrogencarbonate to test for a non-reducing sugar?
neutralises the hydrochloric acid so that Benedict's solution will work
73
what is the test for starch?
- add solution being tested to test tube
- add two drop of iodine solution
- blue-black colour = starch present
74
what enzymes hydrolyse the disaccharides?
- maltase
- sucrase
- lactase
75
explain why people are lactose-intolerant
- don't produce enzyme lactase to break down lactose in intestines
- lactose fermented by bacteria
- water moves into intestines by osmosis = diarrhoea
76
what is a solution to lactose-intolerance?
add enzyme lactase to milk before drinking it
77
what are proteins made up of?
long chains of amino acids
78
what are the 4 roles of proteins?
- structural: tissues
- catalytic: enzymes
- signalling: hormones/ receptors
- immunological: antibodies
79
Draw the general structure of an amino acid
*refer to diagram*
80
what defines an amino acid?
the R group
81
what are the 4 groups that make up an amino acid?
- carboxylic acid group
- amino group
- hydrogen atom
- R group
82
what kind of bond is formed between two amino acids?
peptide bond
83
what reaction forms a dipeptide?
condensation
84
what does a peptide bond look like?
C - N
85
how is a protein formed?
one or more polypeptide chains folded into a 3D shape
86
what is the primary structure of a protein?
the sequence of amino acids in a polypeptide chain
87
what is the secondary structure of a protein?
- alpha-helix: coiled, H bonds
| - beta-pleated sheet: folded, H bonds
88
what is the tertiary structure of a protein?
- more coiling/folding
- hydrogen
- ionic
- disulphide bonds
- hydrophobic interactions
89
what is the quaternary structure of a protein?
- more than 1 polypeptide chain
| - prosthetic group
90
how is the 3D structure of a protein maintained?
- H+ bonds
- hydrophobic interactions: between non-polar
- disulphide bonds
91
what is the test for proteins?
Biuret Test:
1. add equal volume of sodium hydroxide solution (room temp)
2. add drops of dilute copper sulphate solution
3. remains blue = no protein
purple = peptide bonds
92
what are 3 examples of fibrous proteins?
collagen, keratin, silk
93
what is the molecular structure of a fibrous protein?
1. primary: unbranched polypeptide chain
2. secondary: chain tightly wound
3. tertiary: twisted into helix
4. quat: 3 wound + twisted chains
94
why are fibrous proteins strong?
long chains of twisted polypeptide chains that run parallel + joined by cross-links, insoluble
95
give 3 examples of globular proteins
transport proteins (haem), enzymes, hormones
96
explain the structure of globular proteins
- polypeptide chains tightly folded
- spherical
- hydrophobic groups on inside + hydrophilic on outside = soluble
97
how does a protein denature?
break bonds that hold shape together
98
what happens when fibrous proteins denature?
lose structural strength
99
what happens when globular proteins denature?
insoluble
100
how are enzymes biological catalysts?
lowers activation energy of reactions by creating transition state (enzyme-substrate complex)
101
what is the activation energy?
the initial boost needed to start a reaction
102
why is it important that enzymes lower the activation energy?
so reactions can take place at the low body temp of 37deg
103
explain the lock + key model of an enzyme
substrate is complementary in shape to the active site
104
what is the induced fit model?
explains how enzyme is flexible + inhibitors can bind
105
why is the induced fit model better than the lock + key model?
- explains how other molecules affect enzyme activity
| - how activation energy is lowered
106
why does the R of R of enzymes increase when temp increases?
enzyme + substrate more KE = more frequent collisions
107
what happens when the optimum temp for enzymes is exceeded?
R of R decreases, enzyme denatures, bonds of tertiary structure break, active site changes site
108
how does pH affect enzyme activity?
H+ / -OH ions interact with amino acids in enzyme, breaks bonds + active site changed
109
what enzymes work well in acidic / neutral conditions?
acidic = pepsin
| pH 7 = amylase
110
how does substrate concentration affect enzyme activity?
- R of R increases (lots of free active sites to bind with substrates)
- R of R plateaus as all active sites occupied
111
how does enzyme concentration affect rate of reaction?
- R of R increases until there are more active sites than substrate molecules
112
how do competitive inhibits affect enzyme activity?
inhibitor has similar shape to substrate, binds to active site of enzyme, substrate can only bind once it's left, slows reaction
113
how do you reverse the effects of a competitive inhibitor on enzyme activity?
increase substrate, will out-compete for active site
114
why is it better to use inhibitors to slow reaction?
using heat would destroy enzyme forever
115
how do non-competitive enzymes affect enzyme activity?
inhibitor similar shape to substrate, binds to allosteric site = changes shape of active site, substrate can't bind until inhibitor leaves
Biology Unit 1
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