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Biological molecules Flashcards

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

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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
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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
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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
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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
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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
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7
Q

Elements in carbohydrates

A

carbon, oxygen, hydrogen

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8
Q

What are complex carbohydrates known as?

A

polysaccharides eg. starch

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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
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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
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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
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12
Q

what makes sucrose?

A

fructose and glucose

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13
Q

what makes lactose?

A

galactose and glucose

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14
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
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15
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
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16
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
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17
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
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18
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
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19
Q

function of cellulose

A
  • gives cell wall great strength
  • arrangement of macrofibrils allows water to pass through
  • keeps cells turgid
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20
Q

Test for starch

A

Iodine solution
Orange to blue/black
coils in amylose trap iodine molecules

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21
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
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22
Q

explain reducing sugars test

A
  • reducing sugars react with the copper ions in benedict’s
  • results in addition of electrons to blue copper ions reducing them to brick red
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23
Q

test for non-reducing sugars (eg. sucrose)

A
  • test reducing sugars first
  • Heat solution with hydrochloric acid
  • Heat with Benedict’s - brick-red
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24
Q

test for proteins

A
  • add equal volumes of protien solution and biuret reagant
  • lilac solution formed
25
Q

explain protein test

A

the copper ions in biuret’s reagent react with the peptide bonds creating a purple complex

26
Q

test for lipids

A

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

27
Q

What elements are in triglycerides?

A

carbon, oxygen, hydrogen

28
Q

2 main components of triglycerides

A
  • 1 glycerol, 3 fatty acid tails
29
Q

How is a triglyceride formed?

A
  • 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
30
Q

How are triglycerides broken down?

A
  • Lipase breaks the ester bonds holding them together, releasing the glycerol and fatty acid molecules
  • requires 3 water molecules - hydrolysis reaction
31
Q

how are triglycerides adapted to their function?

A
  • 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
32
Q

fatty acid structure

A

An acid group at one end
A hydrocarbon chain between 2-20 carbons long

33
Q

Saturated fatty acids

A
  • 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
34
Q

unsaturated fatty acids

A
  • 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.
35
Q

Structure of phospholipid

A

1 glycerol attached to 2 non-polar hydrophobic fatty acid tails and a polar hydrophilic phosphate head

36
Q

how are phospholipids adapted to their function?

A
  • phosphate head is polar so hydrophillic and soluble in water - forms H bonds with water allowing cell to compartmentalise
  • fatty acid tails are non-polar so hydrophobic and insoluble in water / repel water
  • therefore they can form bilayers in water forming plasma membranes
37
Q

function of lipids

A
  • 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
38
Q

properties of sterols

A
  • 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
39
Q

cholesterol function

A
  • 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
40
Q

what causes high blood cholesterol levels?

A
  • diets with high red meat content - contain large amounts of saturated fats which can lead to large amounts of LDL’s
41
Q

elements in proteins

A

carbon, oxygen, hydrogen, nitrogen, sulfur (depending on the protein)

42
Q

amino acid structure

A

amine group on left (N, H, H)
R group
Carboxyl group on right (COOH)
H R O
N C C
H H OH

43
Q

how do you join 2 amino acids?

A
  • condensation reaction - water molecule released
  • peptide bond catalysed by peptidyl transferase in ribosomes
44
Q

primary structure of protein

A
  • 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
45
Q

secondary structure of protein

A
  • polypeptide chain twists into helix
    beta pleated sheet
  • polypeptide chain folds over itself
  • Hydrogen bonds within the chain hold it in place
46
Q

tertiary structure of protein

A

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)

47
Q

quaternary structure of protein

A
  • same interactions as in tertiary structure but between subunits of proteins rather than within a protein
48
Q

breakdown of peptides

A
  • protease catalyses the hydrolysis reaction
  • water molecule used to break peptide bond
  • amine and carboxylic acid groups reformed
49
Q

Globular proteins

A
  • 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
50
Q

insulin as globular protein

A
  • 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
51
Q

keratin

A
  • 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
  • more disulphide bonds - more strong eg. nails compared to hair
52
Q

elastin

A
  • 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)
53
Q

Conjugated proteins

A
  • Globular proteins with a non protein prosthetic group attached by covalent bond/ionic bond/ hydrogen bond
    eg. haemoglobin and catalase have a haem group
54
Q

haemoglobin protein structure

A
  • quaternary protein with 4 polypeptides - 2 alpha, 2 beta subunits
  • each subunit has a prosthetic haem group
  • the iron II ions in haem groups combine with oxygen
55
Q

catalase protein structure

A
  • enzyme
  • quaternary proteinw with 4 haem groups
  • iron II ions in prosthetic groups allow catalase to speed up breakdown of hydrgen peroxide (byproduct of metabolism)
56
Q

Fibrous proteins

A
  • 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
57
Q

Collagen

A
  • Fibrous protein found in skin, teeth, tendons, bones etc.
  • 3 polypeptide chains wound into rope-like triple helix structure
  • no tertiary structure
  • every 3rd amino acid is glycine - small so chains can pack close together
  • chains held together by many hydrogen bonds - strong quaternary structure with staggered ends allowing many colagen molecules to join together and form tropocollagen fibrils
  • covalent bonds / crosslinks between collagen molecules - strong
  • insoluble- many hydrophobic R groups, unreactive
58
Q

high latent heat of evaporation of water - helpful in life

A

Heat energy is released during the evaporation of sweat which reduces body temperature when hot

59
Q

ribose structure and function

A
  • pentose sugar
  • produced by body from food
  • enhances recovery of muscles
  • in RNA nucleotides
  • part of nucleic acid

Biology (21 decks)

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