Biological molecules Flashcards
(57 cards)
1
Q
What makes water polar?
A
Oxygen - slightly negative as it has a greater affinity for electrons in an O-H covalent bond
Hydrogen - slightly positive
2
Q
how is water bonded?
A
- Oxygen forms 2 polar covalent bonds with 2 hydrogens
- hydrogen bonds form between the H and O on other water molecules
3
Q
Why is water a good solvent and how does this help?
A
- it is polar and so are many solutes so it can bind to / attract solutes
- helps transport molecules in and out of cells
- allows for metabolic reactions to happen in it
- plants can absorb minerals or ions
4
Q
Why is water a good transport medium and why does this help?
A
- It is cohesive with other water molecules
- Hydrogen bonds are formed between O and H on different water molecules resulting in them sticking together
- capillary action - water being drawn up a narrow tube against gravity
5
Q
Why is water a coolant and why is this helpful in life?
A
- high specific heat capacity - it takes lots of energy to break H bonds holding them together
- maintains body temp for enzymes in the body with optimal temperatures
- maintains constant temperature in ponds/sea etc to provide a constant environment for fish
6
Q
Why is the density of water helpful in life?
A
- Ice is less dense so floats on top of water because H bonds fix slightly further apart, insulating the water below - providing aquatic creatures with a habitat
- similar high density of water to organisms makes it easier for aquatic animals to float and for oxygen/nutrients to circulate
7
Q
Elements in carbohydrates
A
carbon, oxygen, hydrogen
8
Q
What are complex carbohydrates known as?
A
polysaccharides eg. starch
9
Q
alpha glucose structure
A
- 6 carbons, 5 make up a hexagon with an O molecule
- on carbon 1 - OH on bottom, H on top
(ABBA - alpha below, beta above) - other 4 in hexagon bond to OH and H
- carbon 6 sticks upwards and is CH2OH
10
Q
beta glucose structure
A
- 6 carbons, 5 make up a hexagon with an O molecule
- on carbon 1 - H on bottom, OH on top
(ABBA - alpha below, beta above) - other 4 in hexagon bond to OH and H
- carbon 6 sticks upwards and is CH2OH
11
Q
describe how 2 alpha glucose molecules are joined together
A
- 2 hydroxyl groups on carbon 1 and 4 of glucose molecules interact and form a 1-4 glycosidic bond
- it’s a condensation reaction as a water molecule is released - 2 hydrogen and one oxygen molecule taken from carbon 1 and 4
- this is now maltose which is a disaccharide
12
Q
what makes sucrose?
A
fructose and glucose
13
Q
what makes lactose?
A
galactose and glucose
14
Q
what makes maltose?
A
glucose and glucose
15
Q
What makes starch adapted to its function?
A
- compact, spiral shape for storage
- insoluble due to large size of molecules so no effect on water pot.
- more ‘free ends’ on branched amylopectin so glucose can be readily hydrolysed for respiration
16
Q
amylose properties and what makes it adapted to function
A
- made up of 1-4 glycosidic bonds causing it to have a spiralling structure with H bonds - compact so takes up less space in cell
- unbranched - plants don’t need rapid release of energy
- insoluble - do not affect water pot of cell
17
Q
amylopectin properties that make it adapted to function
A
- made up of 1-4 and 1-6 glycosidic bonds so is branched - can be hydrolysed by enzymes quicker than amylose
18
Q
What makes glycogen adapted to its function?
A
- compact so can store more of it
- insoluble due to large size, no effect on water pot. of cells
- ‘free ends’ bc highly branched so glucose can be quickly added or removed - more rapid for animals
19
Q
how does beta glucose join together?
A
- molecules don’t spiral as hydroxyl groups are too far so alternate molecules turn upside down - forms straight chain
- chains can lie close allowing H bonds to form between chains - more strength
- this forms microfibrils then macrofibrils then fibres - strong, insoluble
20
Q
function of cellulose
A
- gives cell wall great strength
- arrangement of macrofibrils allows water to pass through
- keeps cells turgid
21
Q
Test for starch
A
Iodine solution
Orange to blue/black
coils in amylose trap iodine molecules
22
Q
test for reducing sugars
A
- Equal volume of Benedict’s reagent added to sample, heated for 5 mins
- V. low conc - blue
green - Strong conc. - brick red
- semi-quantitative test
23
Q
test for non-reducing sugars (eg. sucrose)
A
- test reducing sugars first with benedict’s solution
- Heat solution with hydrochloric acid
- Heat with Benedict’s - brick-red
24
Q
test for proteins
A
- add equal volumes of protien solution and biuret reagant
- lilac solution formed
25
test for lipids
Place sample in test tube and add ethanol, shake thoroughly.
Pour mixture into test tube 3/4 filled with water
- white emulsion will form on the surface because alcohol mixes with the water
26
What elements are in triglycerides?
carbon, oxygen, hydrogen
27
triglyceride structure and how is it formed
- 1 glycerol forms 3 ester bonds with 3 fatty acid tails
- 3 condensation reactions occur to bond 3 fatty acids to a glycerol molecule
- 3 water molecules released
- 3 ester bonds formed - the C, O, O - esterfication
28
How are triglycerides broken down?
- Lipase breaks the ester bonds holding them together, releasing the glycerol and fatty acid molecules
- requires 3 water molecules - hydrolysis reaction
29
how are triglycerides adapted to their function?
- they're made up of lots of carbon-hydrogen bonds, so when bonds are broken during respiration, lots of ATP is released - store more energy per gram than carbohydrates
- they're hydrophobic and insoluble so don't affect water pot of cells so more can be stored
- they have low density increasing buoyancy
- thermal insulation
- protection of vital organs
30
fatty acid structure
An acid group at one end
A hydrocarbon chain between 2-20 carbons long
31
Saturated fatty acids
- no double bonds, only single
- All possible bonds made with hydrogen
- solids at room temp
- straighter chains, group closer together
- in excess, can lead to coronary heart disease
32
unsaturated fatty acids
- double bonds between 1 or more carbon atoms - less hydrogen can bond to it
- kink in chain
- unable to group close together
- liquids at room temp.
33
Structure of phospholipid
1 glycerol attached to 2 non-polar hydrophobic fatty acid tails and a polar hydrophilic phosphate head
34
how are phospholipids adapted to their function?
- phosphate head is polar so hydrophilic and attracted to water - forms H bonds with water allowing cell to compartmentalise
- fatty acid tails are non-polar so hydrophobic and repel water
- therefore they can form bilayers in water forming plasma membranes
35
function of lipids
- energy source - broken down to CO2 and water in respiration to release energy and ATP
- energy store - insoluble, don't affect water pot.
- insulation
- buoyancy - less dense than water, helps marine animals
- protection - around internal organs
36
properties of sterols
- type of lipid
- complex alcohol molecules
- 4 carbon ring structure with polar hydrophilic hydroxyl group at one end and the rest of the molecule is hydrophobic
- eg. cholesterol
37
cholesterol function
- in biological membranes - positioned between phospholipds
- add stability and regulate fluidity - fluid at low temp, not too fluid at high temp
- in hormones eg. testosterone, oestrogen - allowing them to pass through cell membranes
- used to make vitamin D
- used in liver to produce bile - used in digestion of lipids by lipase
38
what causes high blood cholesterol levels?
- diets with high red meat content - contain large amounts of saturated fats which can lead to large amounts of LDL's
39
elements in proteins
carbon, oxygen, hydrogen, nitrogen, sulfur (depending on the protein)
40
amino acid structure
amine group on left (N, H, H)
R group
Carboxyl group on right (COOH)
H R O
N C C
H H OH
41
how do you join 2 amino acids?
- condensation reaction - water molecule released
- peptide bond catalysed by peptidyl transferase in ribosomes
42
primary structure of protein
- order of amino acids in polypeptide chain - determined by the gene that codes for it
- the order directly impacts the bonds formed on other levels of structure
- changing just one amino acid can change shape and function of protein
43
secondary structure of protein
- polypeptide chain twists into helix
beta pleated sheet
- polypeptide chain folds over itself
- Hydrogen bonds within the chain hold it in place
44
tertiary structure of protein
polypeptides fold further into a precise 3D shape and interactions occur between R groups:
- Hydrogen bonds - weakest
- Ionic bonds - more strong
- Hydrophobic and hydrophillic interactions between polar and non-polar R groups - hydrophobic on inside, hydrophillic on outside
- Disulphide bonds - between sulphur containing R groups - covalent bond (strong)
45
quaternary structure of protein
- same interactions as in tertiary structure but between subunits of proteins rather than within a protein
46
breakdown of peptides
- protease catalyses the hydrolysis reaction
- water molecule used to break peptide bond
- amine and carboxylic acid groups reformed
47
Globular proteins
- form when proteins fold into tertiary structure where hydrophobic R groups folded into middle, hydrophilic R groups on outside - Soluble in water
- Curl up into a ball shape - compact Eg. haemoglobin
48
haemoglobin as a globular conjugated protein
- compact - fits inside red blood cells
- quaternary structure
- 2 alpha and 2 beta polypeptide chains
- each polypeptide chain contains a haem group (prosthetic group) which contains an iron atom
- each iron atom can reversibly bind to 1 oxygen molecule (O2)
- one haemoglobin can carry 4 oxygen molecules
49
insulin as globular protein
- made up of 2 polypeptide chains help together by disulfide bonds
- hormone involved in regulation of blood glucose conc
- needs to be soluble to be transported in blood
- need to fit specific receptors so need precise shape
50
keratin as fibrous protein
- fibrous proteins in hair, nails, skin
- strong, insoluble in water
- high proportion of cysteine (sulfur containing R group) - used to form lots of disulphide bonds (strong covalent bonds) - very strong molecules
- either flexible or rigid depending on the type of disulfide bonds it contains
51
elastin as fibrous protein
- fibrous protein in alveoli, walls of arteries
- gives flexibility to stretch and recoil to original shape
- made of many soluble tropoelastin molecules to make a large, insoluble, stable crosslinked structure
- tropoelastin can stretch and recoil and contains alternating hydrophobic regions and lysine-rich areas
- hydrophobic regions associate on multiple tropoelastin molecules
- crosslinking covalent bonds involving lysine (amino acid)
52
Conjugated proteins
- Globular proteins with a non protein prosthetic group attached by covalent bond/ionic bond/ hydrogen bond
eg. haemoglobin and catalase have a haem group
53
catalase protein structure
- enzyme
- quaternary protein with 4 haem groups
- iron II ions in prosthetic groups allow catalase to speed up breakdown of hydrgen peroxide (byproduct of metabolism)
54
Fibrous proteins
- Form long strong strands
- Insoluble - high proportion of - hydrophobic R groups
- amino acid sequence quite repetitive - organised structures reflected in their roles
Eg. keratin, collagen, elastin
55
Collagen
- Fibrous protein found in skin, teeth, tendons, bones etc.
- 3 polypeptide chains wound into rope-like triple helix structure - strength and flexibility
- no tertiary structure
- chains held together by many hydrogen bonds
- covalent bonds / crosslinks between collagen molecules - strong
- insoluble- many hydrophobic R groups, unreactive
56
high latent heat of evaporation of water - helpful in life
Heat energy is released during the evaporation of sweat which reduces body temperature when hot
57
ribose structure and function
- pentose sugar
- produced by body from food
- enhances recovery of muscles
- in RNA nucleotides
- part of nucleic acid
