2.1.2: Biological molecules Flashcards
1
Q
Catabolic reaction
A
Large molecule broken down to smaller molecules e.g. hydrolysis
⟶ Energy given out (to surroundings)
2
Q
Anabolic reaction
A
Smaller molecules built up to large molecule e.g. condensation reaction
⟶ Energy taken in (required)
3
Q
Features of a hydrolysis reaction
A
- “Splitting with water”
- Catabolic
- Covalent bond broken
4
Q
Features of a condensation reaction
A
- Water molecule produced
- Anabolic
- New covalent bond formed
5
Q
Hydrogen bonding occurs when…
A
- Slightly negatively charged part of molecule contacts & attracts slightly positively charged part of molecule.
- Between H and O.
6
Q
Individual hydrogen bonds are ____
A
weak but due to large numbers their effect can be big.
7
Q
Effect of H-bonding on polymers
A
Strengthens and stabilises polymers.
8
Q
Properties of water
A
- High SHC
- High latent heat of vaporisation
- Cohesion
- Surface tension
- Polar so can form H-bonds
- Expands when freezes
- Can act as solvent
9
Q
Water’s high SHC
A
• Due to H-bonding, water molecules stick to one another
• Hard to separate molecules
• Higher boiling point than expected
• High SHC
⟶ Acts as a buffer to sudden temp. changes, keeps an environment stable
10
Q
Water’s high latent heat of vaporisation
A
• Due to H-bonding, water molecules stick to one another
• Lots of energy needed to evaporate 1 gram of water
⟶ Sweating = effective cooling mechanism in mammals
11
Q
Cohesion in water
A
Cohesion: tendency of water molecules to stick to each other
⟶ Allows water to be pulled up tube (xylem)
12
Q
Surface tension in water
A
Body of water moves as one mass
• Water molecules at the edge of a body of water are pulled back in rather than escaping
⟶ Allows pond skater to skate across pond
13
Q
Water’s density when freezing
A
• Water becomes less dense when it freezes
⟶ Ice floats, insulating water beneath and allowing organisms to survive
14
Q
Water as a solvent
A
• Polar, interacts with other polar molecules
• Interaction of +ve and -ve charges keeps solute molecules apart hence it dissolves
⟶ Molecules in solution can move/react with other molecules –> water = basis for metabolic reactions
15
Q
Functions of carbohydrates
A
- Energy source
- Energy store
- Structure (cellulose in wall)
- Parts of larger molecules (nucleic acids)
16
Q
Generalised formula of a monosaccharide
A
C𝒏(H₂O)𝒏
17
Q
Types of simple sugars
A
- Triose
- Pentose
- Hexose
Prefix = no. of carbons
18
Q
Arrangements of glucose
A
- Chain
* Ring
19
Q
Forms of glucose ring
A
Alpha
Beta
20
Q
Alpha glucose
A
H above OH on C1
21
Q
Beta glucose
A
OH above H on C1
22
Q
Glycogen contains _ glucose
A
𝛂
23
Q
Cellulose contains _ glucose
A
β
24
Q
Glycosidic bond
A
Covalent bond between two monosaccharides
25
Sucrose
Glucose + fructose
26
Lactose
Glucose + galactose
27
Maltose
Glucose + glucose (both 𝛂)
28
Elements that make up carbohydrates
C
H
O
29
Elements that make up lipids
C
H
O
30
Elements that make up proteins
```
C
H
O
N
S
```
31
Elements that make up nucleic acids
```
C
H
O
N
P
```
32
Example of a pentose monosaccharide
Ribose
33
Carbohydrate polymers are stores of
potential energy
34
Large polysaccharides are ______ so do not affect ______
Large poysaccharides are insoluble so do not affect osmosis
35
Where is the glycosidic bond in amylose
1,4 glycosidic bond
36
Amylose arranged in coil so
very compact
37
Glycogen arrangement
* Branched (v. compact)
| * Can be hydrolysed quickly
38
Where are the glycosidic bonds in glycogen?
* 1,4 glycosidic bond
| * 1,6 linkage (forms branches)
39
Why is glycogen good for storage?
* Insoluble
* Very compact
* Large enough = doesn't diffuse out easily
* Branches at 1,4; linkage at 1,6 --> lots of potential enzyme attachment, hydrolysis sites
40
Why high conc. glycogen = good athletic performance
* Glucose stored as glycogen
* Glucose used for respiration to produce ATP
* ATP needed for muscle contraction etc.
41
Conjugated proteins contain...
a prosthetic group
42
Globular proteins
* spherical, water soluble proteins
* hydrophilic outside, hydrophobic core
* Have chemical functions in living organisms, e.g. enzymes, hormones
43
Fibrous proteins
* Long, insoluble structural proteins
* Lots of hydrophobic R groups
* Examples: keratin, elastin, collagen
44
Collagen
* 3 polypeptide chains twisted around each other
* 35% glycene
* Make up tendons, cartilage, artery walls
45
Elastin
* Many soluble tropoelastin molecules linked to form one stable, cross-linked structure
* Interactions between hydrophobic regions, crosslinks = covalent bonds --> gives strength and elasticity to skin, tissues
46
Primary structure
the sequence of amino acids in a protein
47
Basic chain
the order of the amino acids
48
Secondary structure
the initial folding of the primary structure
49
Secondary structure types
* Alpha helix
| * Beta pleated sheet
50
Alpha helix structure
Hydrogen bonds form
between H-N....C=O
every 4 amino acids
51
Beta pleated sheet structure
Hydrogen bonds form
between H-N...C=O
but not at regular intervals
52
Tertiary structure
provides a protein's 3D shape.
53
Hydrophobic interaction in a protein
interaction pushing apart parts of molcule
54
Ionic bonds in a protein
polar interactions between R groups, help maintain shape, stronger than H-bonds
55
Disulfide bridges
very strong covalent bonds, offer further suppport.
| 2 R groups with sulphur required
56
Cellulose structure
* Contains β glucose
* 1,4 glycosidic bond
* Alternate β glucose molecules rotated 180°
* Hydroxyl groups projected either side of chain --> allows H-bonding to occur between chains
57
Where do plant cell walls get their strength
* From cellulose microfibrils --> bundles of 60-70 cellulose molecules lie parallel
* H bonding between hydroxyl groups of neighbouring chains
58
Fat
lipid that is solid at RTP
59
Oil
lipid that is liquid at RTP
60
Lipis are __________ so _________
Lipids are non-polar so insoluble
61
Triglyceride
Contains glycerol and 3 fatty acids
62
Glycerol
3 carbon molecule with 3 OH groups
63
Saturated
all available bonds in the hydrocarbon chain have a hydrogen attached.
64
Unsaturated
not all available bonds in the hydrocarbon chain have a hydrogen attached
65
Where are saturated triglycerides found?
In animal products
66
Where are monounsaturated triglycerides found?
in cell membranes
67
Where are polyunsaturated triglycerides found?
in vegetable oil e.g. olive oil
68
How is a triglyceride formed?
* Condensation reaction repeated 3 times
* 3 water molecules produced
* 3 ester bonds formed
69
Why are triglycerides good energy stores?
* Insoluble: hydrophobic charges all around molecule, cannot H bond with water, does not affect ψ
* High calorific value: gives out 2x as much energy as the same mass of carbohydrates would
70
Differences between triglycerides and phospholipids
* Phospholipids contain a phosphate group
* Triglycerides contain 3 fatty acids, phospholipids contain 2
* Triglycerides are totally hydrophobic, phospholipids have a hydrophilic head and hydrophobic tail
71
How are lipids respired?
* Can be respired directly
* Hydrolysis of ester bond required
* Glycerol and fatty acids completely broken down into carbon dioxide and water
* Releases energy used to make ATP
72
Cholesterol
* Small, made from 4 carbon-based rings
* Narrow and hydrophobic
* Found in membranes, between tails of phospholipids
* Helps regulate strength and fluidity of membrane
73
Steroid hormones
* Made from cholesterol
| * Lipid based, can pass through phospholipid bilayer into target cell
74
Cholesterol is needed for
Plasma membrane
| Hormones
75
Cholesterol is made in
many cells especially those in the liver
76
In excess, cholesterol
can cause formation of gall stones, build up in arteries and lead to stroke, heart attack
77
Where is starch found?
In chlorolplasts and plant storage organs
78
What is starch made from?
2 polysaccharides:
• Amylose (20%)
• Amylopectin (80%)
79
Starch is soluble/insoluble?
Insoluble, so does not affect ψ.
80
Starch and glucose - shared features
✔︎ Energy storage molecules
✔︎ Insoluble --> do not affect ψ
✔︎ Long chains (of glucose); can be hydrolysed for respiration to produce ATP
81
Ca²⁺ uses
* Nerve impulse transmission
| * Muscle contraction
82
Na⁺ uses
* Nerve impulse transmission
| * Kidney function
83
K⁺ uses
* Nerve impulse transmission
| * Stomatal opening
84
H⁺ uses
* Catalysis of reactions
| * pH determination
85
NH₄⁺ uses
• Production of nitrate ions by bacteria
86
NO₃⁻ uses
• Nitrogen supply to plants, for amino acid and protein formation
87
HCO₃⁻ uses
Maintenance of blood pH
88
Cl⁻ uses
• Balance positive charge of sodium and potassium ions in cells
89
OH⁻ uses
* Catalysis of reactions
| * pH determination
90
Benedict's test method - reducing sugars
1) Add sample to test tube. If solid, grind up into water.
2) Add benedict's reagent.
3) Heat mixture gently in water bath set to 80°C for 5 mins.
91
Benedict's test method - non-reducing sugars
1) Add dilute hydrochloric acid to sample in test tube.
2) Heat for a few minutes to hydrolyse the glycosidic bond.
3) Add sodium hydrogencarbonate powder to neutralise the solution. The solution should fizz.
4) Add Benedict's reagent.
5) Heat mixture gently in water bath set to 80°C for 5 minutes.
92
Benedict's test results
```
✘ Blue
✔︎ Green - v. low
✔︎ Yellow - low
✔︎ Brown - medium
✔︎ Brick-red/orange - high
```
93
Emulsion test - method
1) Add ethanol to test sample
2) Shake thoroughly so that any lipids in the sample are dissolved
3) Add water and shake gently
94
Emulsion test - results
✘ Colourless and transparent
| ✔︎ Formation of cloudy white emulsion
95
Emulsion test - safety
* Ethanol is highly flammable
| * Goggles should be worn when ethanol is handled
96
Iodine Iodide test - method
1) Add a few drops of Iodine Iodide solution to the test sample
97
Iodine Iodide test - results
✘ Yellow/brown
| ✔︎ Blue-black
98
Biuret test - method
1) Sample in solution in test tube
2) Add an equal volume of sodium hydroxide at RTP
3) Add a few drops of dilute copper sulphate and mix gently
99
Biuret test - results
✘ Blue (pale because dilute)
| ✔︎ Lilac/purple colouration
100
Food test for starch
Iodine Iodide test
101
Food test for proteins
Biuret test
102
Food test for simple sugars
Benedict's test
103
Food test for lipids
Grease spot/emulsion
104
Name of process in which triglycerides are formed
Esterification
