Biological molecules Flashcards
1
Q
State properties of water
A
- metabolite
- solvent
- H bonds
- High specific heat capacity
- High latent heat of vaporisation
- liquid water denser than ice
2
Q
How is water a metabolite
A
Used in hydrolysis, made in condensation
3
Q
How is water a solvent
A
Polar molecule, dissolves solutes for transport/ reactions
4
Q
what does hydrogen bonding in water allow
A
Allows cohesion for transpiration and pond-skater habitat
5
Q
Role of high specific heat capacity in water
A
Acts as a buffer to temperature change
6
Q
Role of high latent heat of vaporisation of water
A
Reduction of body temperature via sweating
7
Q
Role of liquid water denser being than ice
A
Aquatic habitats protected under floating ice as the ice insulates water below
8
Q
Define monomer
A
Individual molecules that can make up a polymer
9
Q
Define polymer
A
Long chain of many individual monomers that have been bonded together in a repeating pattern via condensation reactions
10
Q
What are condensation reactions
A
Occur when two molecules combine to form a more complex molecule with the removal of water
11
Q
What are hydrolysis reactions
A
Occur when larger molecules are broken down into smaller molecules with the addition of water
12
Q
What type of bonds join monomers together
A
Covalent
13
Q
What type of molecules are joined by H bonds
A
- polar molecules
- stabilises larger structures
14
Q
What are monosaccharides
A
Are the simplest carbohydrates, being sweet tasting, soluble and contain many C-H bonds for energy storage
15
Q
What are isomers
A
- Molecules with the same formula but different atom arrangement in space
- example: alpha and beta glucose
16
Q
What are disaccharides
A
Formed when two monomers react in a condensation reaction, forming a glycosidic bond
17
Q
What monomers make maltose
A
a Glucose + a Glucose
18
Q
What monomers make lactose
A
a Glucose + B Galactose
19
Q
What monomers make sucrose
A
a Glucose + Fructose
20
Q
What makes cellobiose
A
B Glucose + B Glucose
21
Q
What is the 1 non-reducing sugar
A
Sucrose
22
Q
What are the 2 reducing sugars
A
- Maltose and lactose
- all monosaccharides are reducing sugars
23
Q
What test is used to qualitatively test the presence of reducing and non- reducing sugars
A
Benedict’s solution
24
Q
What will Benedict’s test look like for reducing sugars
A
- heating with Benedict’s solution changes colour from blue to green, yellow, or orange-red
- reducing sugars reduce Cu^2+ to Cu forming copper (I) oxide precipitate
25
Why can’t you use Benedict’s to directly test for non- reducing sugars
- non-reducing sugars can’t reduce Benedict’s until the glycosidic bond is hydrolysed
26
How do you carry out Benedict’s test on non- reducing sugars
1. Boil with HCl to break into monosaccharides (reducing sugars)
2. Cool and add sodium hydrogen carbonate to neutralise
3. Test with Benedict’s and look for the same colour change as before
27
How can the concentration of reducing sugars be quantitatively measured
Colorimetry
28
How do you carry out colorimetry
1. **Centrifuge** separates ppt and unreacted Benedict’s
2. Supernatant placed in a cuvette and into colorimeter with red filter
3. Transmission of light measured, using zero reading with water
29
what does high transmission/low absorbance mean
high amount of reducing sugars
30
what does low transmission/ high absorbance mean
low amount of reducing sugars
31
what's a calibration curve
uses a series of known concentrations and transmissions used to estimate the concentration of sample sugars
32
what can reducing sugar concentration also be measured with
reagent test strips
33
how are reagent strips used
- strip dipped into the sample solution and the colour is compared to a **calibration card**, showing how colour relates to sugar concentration
34
give an example of what reagent test strips can be used for
urine testing for sugar in diabetics
35
what's starch
a plant-based energy storage molecule made of two types of alpha glucose polymers: amylose and amylopectin
36
what are the properties of starch and why
- insoluble - no effect on water potential
- compact granules - take up little space
- branching - multiple sites for rapid hydrolysis
- large molecule - many glucose for respiration
37
what are the two types of starch
- amylose
- amylopectin
38
explain structure of amylose
- long chain of a-glucose molecules
- has 1-4 glycosidic bonds
- amylose coils into spiral shape
- OH groups holding the spiral in place
- OH group on C 2 situated are on inside of coil, making the molecule less soluble and allowing H bonds to form to maintain the coil's structure
- no branches
39
describe the structure of amylopectin
- a-glucose chain joined by 1,4 glycosidic bonds but in addition have branches formed by 1-6 glycosidic bonds
- coils into spiral shape but also has branches
40
what's glycogen
animal- based energy storage polysaccharide made of a-glucose
41
state the properties of glycogen and why
- insoluble - no effect on water potential
- compact granules - takes up little space
- branching - multiple sites for rapid hydrolysis
- large molecule - many glucose molecules for respiration
42
describe the structure of glycogen
- a-glucose chain joined by 1-4 glycosidic bonds, branches formed by 1-6 glycosidic bonds
43
how does the structure of glycogen differ from that of amylopectin
- **glycogen chains smaller** so has less tendency to coil
- **glycogen has more branches**, makes it more compact and easier to remove monomers ( for quicker enrgy release as animals are more active)
44
what's cellulose made of
- long chains of B-glucose joined by 1-4 glycosidic bonds
- found in plant cell walls
45
describe and explain the structure of cellulose
- straight, unbranched chains run parallel to one another due to B-glucose inverting 180 degrees alternatively. This allows H bonds to form between B glucose molecules
- hydrogen bonds provide strength as they produce microfibrils of 60-70 chains
- hydroxyl group on C2 sticks out so H bonds form between chains
46
why is cellulose insoluble
- doesn't affect water potential but permeable to solutes
47
why do macrofibrils in cellulose run in different directions
for extra strength
48
what's the test for starch
- iodine
- yellow to blue-black for +ve test
49
what are lipids are made from
- glycerol and fatty acids
50
how many -OH groups does glycerol have
3
51
what do fatty acids contain
- COOH group and hydrocarbon chain
52
what are saturated fatty acids
fatty acids with only single bonds in hydrocarbon chain
53
what are unsaturated fatty acids
fatty acids with double bonds
54
what's the difference in structure of triglycerides and phospholipids
- triglyceride: glycerol + 3 fatty acids
- phospholipid: glycerol + 2 fatty acids + 1 phosphate
55
where are ester bonds formed
- form between fatty acids and glycerol
- covalent bonds formed in condensation and broken in hydrolysis
56
are fatty acids in triglycerides all the same
no, they can be different
57
what type of molecules are lipids
macromolecules ( very large organic molecules)
58
explain the role of phospholipids in in the phospholipid bilayer/ miscelle
- phospholipids are polar with hydrophilic phosphate heads oriented towards water and hydrophobic fatty acids tail facing away from water
59
what is meant by membranes being selectively permeable
allow only small non-polar particles to pass
60
what's cholesterol (steroid alcohol) and what's its role
- lipid with 4 carbon rings
- regulates bilayer fluidity by preventing it from being too fluid at high temp or too rigid at low temp
61
give an example of a steroid hormone formed form cholesterol
oestrogen
62
what's the test for lipids
- emulsion test
1. sample mixed with ethanol
2. filter the solution and add to clean test tube of water
3. a cloudy- white emulsion indicates a +ve test as lipids form from droplets
63
what are proteins made of
amino acids
64
what functional groups do amino acids have
- NH2 (amino group)
- COOH (carboxyl group)
H2N(HCR)COOH
65
can animals synthesise essential amino acids
no
66
how many essential amino acids are there
9
67
can plants synthesise all their amino acids
yes provided that they have enough nitrogen
68
R groups can vary in...
size, charge and polarity
69
what are the bonds between amino acids and how are they formed
- peptide bonds
- formed from condensation reactions between carboxyl and amino groups of adjacent amino acids
70
the peptide bond is a covalent bond and amino acids join to make a.....
polypeptide
71
what's primary structure
- the sequence of amino acids, determines the higher structure levels
72
what's secondary structure
- due to H bonds and forms a- helices and B-pleated
73
what's tertiary structure
- overall 3D shape formed by ionic, disulfide and H bonds, plus hydrophobic/hydrophilic interaction
74
what's quaternary structure
- formed when multiple polypetides bind, often with prosthetic groups
75
features of fibrous proteins
- contain repeating sequences of amino acids and are insoluble, forming structural fibres, such as collagen or keratin
- metabolically inactive
76
what's a prosthetic group
**non-protein component** that forms a permanent part of a protein molecule
77
what's the function of collagen
provides mechanical support
78
where's collagen found
- in artery walls, prevents artery bursting when withstanding high bp
- tendon which connect muscle to bone allowing them to move
- cartilage
79
structure and function of keratin
- **rich in cysteine** so lots of disulfide bridges in addition to H bonds make it very strong
- provides mechanical protection but also provides an impermeable barrier to infection
80
where's keratin found
nails, hair, claws
81
structure and function of elastin
- cross-linking and coiling make elastin strong and extensible
- allows stretching
82
where's elastin found
- skin
- lungs, allowing them to inflate and deflate
- in blood vessels to help them stretch and recoil to help maintain pressure
83
feature of globular proteins
- spherical shape with core of hydrophobic interactions
- hydrophilic R groups on the outside
- metabolically active
84
structure of Hb
- 4* structure of Hb consists of for polypeptides: 2 a and 2 B (each has its own 3* structure)
- each polypeptide has a haem group with an iron ion (prosthetic group)
- **conjugated protein** = globular protein with a prosthetic group
85
function of Hb
- carries O2 from lungs to tissues
- one oxygen molecule binds to each iron ion
86
function of pepsin
enzyme that digests protein in the stomach
87
structure of pepsin
- very few amino acids with basic R groups, helps maintain stability as there are few basic groups to accept H+ so little effect on structure
- 3* structure held together by **2 disulfide bridges and H bonds**
88
test for proteins
- biuret test
1. a sample is added to clean test tube
2. **biuret A contains NaOH**, added to sample
3. **Biuret B contains Copper (II) Sulphate**, added to sample
4. +ve state causes a colour change from **blue to lilac** as Cu2+ react with nitrogen atoms in the polypeptide chain
89
what do biosensors do
measure a chemical variable by turning it into an electrical signal
90
important application of biosensors
- detecting contaminants in food
- detecting air-borne bacteria
91
how do biosensors work
1. molecule to be measured binds to receptors in biological layer
2. chemical variable converted into electrical signal
92
what's chromatography used for
separates a mixture into components based on the speed of movement through phases
93
what's the stationary phase in TLC
chromatography paper made of cellulose, or TLC plate with free OH- groups. Sample molecules adhere to this
94
what's the mobile phase in TLC
solvent carrying sample of biological molecules, often water or ethanol
95
how do you calculate Rf
Rf = distance moved by spot/ distance moved by solvent
96
colourless solutions in TLC can be observed using:
- UV light
- ninhydrin
- iodine
97
why do polar molecules move slower than non-polar ones
polar molecules adhere to the -OH groups on the stationary phase (TLC plate) strongly (more attracted)
98
properties and function of insulin
- made up of 2 polypeptide chains
- A chain begins with a- helix and B chain ends with section of B pleat
- both chains fold into 3* stricture bonded by disulfide links
hydrophilic R groups on outside making it soluble
- insulin binds to receptors in muscle and liver cells causing them to increase their uptake of glucose
