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A level Biology > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

what % of a cell is water?

A

80

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2
Q

explain what it means that water is a polar molecule

A

The share of the electrons between O and H is unequal, being closer to O, making O slightly negative and H slightly positive.

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3
Q

explain what hydrogen bonding is for water

A

The negative O atoms attract positive H atoms from other water molecules, connecting water molecules together, making water a very stable structure

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4
Q

what is specific heat capacity ?

A

the energy needed to raise the temp of 1 gram of a substance by 1 degrees Celsius

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5
Q

Why does water have a high specific heat capacity ?

A

The H-bonds between water molecules can absorb a lot of energy. This means it takes a lot of energy to heat it up. Doesn’t experience rapid temp changes, making it a good habitat.

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6
Q

Why does water have a high latent heat evaporation ?

A

It takes a lot of energy to break the H-bonds, therefore a lot of energy is needed til the water evaporates.

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7
Q

why is water having a high latent heat evaporation useful?

A

It is useful for organisms’ cooling systems, when mammals sweat, it cools the surface of the skin as energy is needed to break the H-bonds.

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8
Q

what makes water cohesive?

why is this useful ?

A

water is cohesive as it is a polar molecule
this helps water flow, which makes it great for transporting substances
also helps water to be transported up plant stems in transpiration stream

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9
Q

cohesive

A

water - water (same type)

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10
Q

adhesive

A

water - other (diff type)

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11
Q

water as a good solvent

A

the charges on the atoms in water causes it to be a good solvent and dissolve substances

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12
Q

why is ice less dense than water?

A

the water molecules are held further apart because each water molecule forms 4 H-bonds to other water molecules, making a lattice shape, which makes ice float

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13
Q

why is ice useful ?

A

forms an insulating layer on top of water, so the water doesn’t freeze, and organisms don’t freeze and can still move

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14
Q

uses for water as a solvent

A

dissolving ions into the water in blood for it to be transported, digestion, medium for metabolic reactions, transport

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15
Q

why is it useful that water is transparent ?

A

allows photosynthesis for aquatic life and vision

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16
Q

what is a carbohydrate ?

A

polymer of monosaccharides

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17
Q

what is a hexose monosaccaride?

examples??

A

a monosaccharide with 6 carbon atoms

e.g. - glucose / fructose / galactose

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18
Q

hexose sugars info :

A
  • act as respiratory substrates
  • simple and soluble so easily transported
  • easily metabolised
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19
Q

how does glucose’s structure help its function ?

A

its structure makes it (highly) soluble, meaning it can be easlit transported
its bonds also contain lots of energy

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20
Q

what is ribose?

A

It is a pentose sugar (5 carbon atoms) that is the sugar component of RNA nucleotides

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21
Q

Role and solubility of fructose

A

main sugar in nectar / fruit

very soluble

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22
Q

Role and solubility of galactose

A

important role in production of glycolipids and glycoproteins
not very soluble

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23
Q

what is the bond called between monosaccharides ?

A

glycosidic bonds

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24
Q

what is a disaccharide ?

A

two monosaccharides joined together

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25
Q

what is a condensation reaction ?

A

a reaction that joins molecules together with the release of water molecules

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26
Q

what is a hydrolysis reaction?

A

a reaction that breaks larger molecules into smaller molecules using water molecules

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27
Q

what would you call any large molecule ?

A

a macro molecule

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28
Q

what is a dimer ?

A

a molecule composed of two single units (identical or similar)

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29
Q

what is an oligomer ?

A

a molecule composed of several single units (identical or similar)

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30
Q

what is a catabolic reaction ?

A

chemical reaction in an organism that breaks down molecules

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31
Q

what is an anabolic reaction ?

A

chemical reaction in an organism that builds larger molecules from smaller ones

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32
Q

what is maltose made up of ?

A

two alpha glucose molecules with an alpha 1-4 glycosidic bond

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33
Q

what is sucrose made up of ?

A

alpha glucose and fructose with an alpha 1-4 glycosidic bond

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34
Q

what is lacotse made up of ?

A

galactose and either alpha / beta glucose with an alpha / beta 1-4 glycosidic bond

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35
Q

what is the function of sucrose ?

A

provides energy for animals

translocated in phloem

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36
Q

what is the function of maltose ?

A

sugar produced from starch in germination

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37
Q

what is the function of lacotse ?

A

respiratory substrate in milk

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38
Q

what is amylose made up of ?

A

lots of alpha glucose molecules joined by alpha 1-4 glycosidic bonds

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39
Q

what is starch made up of ?

A

amylose and amylopectin

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40
Q

Describe amylose and how its structure helps its function

A

It is a long, unbranched chain of alpha glucose in a coiled structure, which makes it compact, so its really good for storage because you can fit more in a small space

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41
Q

Describe glycogen and how its structure helps its function

A

polysaccharide of alpha glucose, with lots of short side branches, meaning that the stored glucose can be released quickly
it is also very compact

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42
Q

Describe cellulose and how its structure helps its function

A

long, unbranched chains of beta glucose, held together by H-bonds to form microfibrils, which then bunch to form macrofibrils, giving it high mechanical strength

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43
Q

what happens when beta glucose molecules bond together ?

A

they form straight cellulose chains

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44
Q

which polysaccharides have a 1-6 glycosidic bond?

A

glycogen and amylopectin

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45
Q

which polysaccharides are soluble ?

A

none

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46
Q

which polysaccharides branch ?

A

glycogen (highly) and amylopectin

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47
Q

what are the chemical elements in lipids ?

A

carbon, hydrogen and oxygen

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48
Q

what is a triglyceride ?

A

a marcomoleucle, made up of a glycerol with 3 fatty acids attached to it by an ester bond

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49
Q

Describe esterification (synthesis of triglycerides)

A
  • synthesised by the formation of an e bond between fatty acid and glycerol
  • each e bond is formed by a condensation reaction
  • triglycerides break down in a hydrolysis reaction
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50
Q

what is a saturated fatty acid ?

A

fatty acid that does not contain double bonds between the carbon atoms, meaning they can pack closer

51
Q

general formula for a saturated fatty acid …

A

Cn H(2n+1) COOH

52
Q

what is an unsaturated fatty acid ?

A

fatty acid with at least one carbon double bond, causing the chain to kink

53
Q

what is a phosopholipid ?

A

macro molecule similar to triglycerides however replace one fatty acid with a (hydrophilic) phosphate group, that make up the phospholipid bilayer

54
Q

why are triglycerides good for storage ? (hydrocarbon chain)

A

The long hydrocarbon fatty acid tails contain lots of chemical energy, so lots is released when they are broken down. Lipids contain x2 energy as carbohydrates because of this.

55
Q

why are triglycerides good for storage ? (insoluble)

A

They are insoluble, so they don’t cause water to enter the cells which would make them swell. They bundle up as insoluble droplets because the fatty acid tails are hydrophobic, meaning they face inwards.

56
Q

functions of triglycerides :

A
  • major energy store / source
  • protect organs
  • waterproofing
  • insulation
  • buoyancy
  • store carbon (bacteria)
57
Q

why is the structure of a phospholipid suitable for cell membrane ?

A

The heads are hydrophilic, while the tails are hydrophobic, so they form a double layer, with the heads facing out both sides. The centre is hydrophobic, so water cannot pass through easily

58
Q

describe the structure of cholesterol

A

Hydrocarbon ring structure attached to a hydrocarbon tail. The ring structure has a polar hydroxyl group attached to it

59
Q

State the functions of cholesterol

A
  • helps strengthen cell membrane

- needed to make vit D / hormones and bile

60
Q

State how the structure of cholesterol helps its functions

A
  • small size and flattened shape, allowing it to fit in between phospholipid molecules
  • bind to the hydrophobic tails, causing them to pack closer, making the membrane less fluid and more rigid
61
Q

Describe test for solid lipid

A
  • crush food and place in test tube
  • add ethanol and shake
  • allow time to settle
  • decant into another tube
  • add equal vol of water (deionized)
  • cloudy white suspension shows lipid presence
62
Q

Describe test for liquid lipid

A
  • add drops to test tube
  • add equal vol of ethanol and water
  • cloudy white suspension shows lipid is present
63
Q

what are the factors that affect cholesterol :

A

genes / diet / gender / age

64
Q

what is high cholesterol ?

A

when you have too much cholesterol in your body that it builds in the artery walls, increasing blood pressure and increasing chances of heart diseases

65
Q

how to avoid high cholesterol

A
  • balanced diet
  • exercise regularly
  • give up smoking
  • take statins / aspirin which thin the blood
66
Q

what are the effects of high cholesterol ?

A

causes atherosclerosis, which is the accumulation of cholesterol in artery walls, reducing blood flow, causing … high blood pressure / blood clots / heart attacks / stroke

67
Q

why might cholesterol info be flawed ?

A
  • subjects underestimate what they eat / lie / don’t record info precisely
  • difficult to compare individuals (correlation is not causation)
68
Q

what is the glucose colour range ?

A

blue / green / yellow / brown - orange / brick red

69
Q

how do glucose strips work ?

A

they are embedded with a chemical that changes colour in the presence of a molecule

70
Q

how could you test for diabetes ?

A

dip glucose strip in sample, if glucose is present, suggest diabetes (as glucose shouldn’t be in urine)

71
Q

what is a qualitative test?

A

test which doesn’t provide range / numbers, instead provides a ‘present’ or ‘absent’, or even a description

72
Q

state the elements present in carbohydrates

A

carbon, oxygen and hydrogen

73
Q

what is a triose sugar and give an example

A

simple sugar containing 3 carbon atoms

Glyceraldehyde

74
Q

what are furanoses and pyranoses ?

A

furanose - cyclic sugar containing 5 membered ring

pyranose - cyclic sugar containing 6 membered ring

75
Q

define electronegativity

A

the measure of the ability of an atom to attract electrons

76
Q

define dipole

A

a molecule that has both positive and negative charges

77
Q

what are the monomers in a protein ?

A

amino acids

78
Q

what is a dipeptide / polypeptide ?

A

two amino acids joined together / more than 2

79
Q

how many polypeptides make up a protein ?

A

one or more

80
Q

what is the general structure of an amino acid?

A 
carboxyl group (COOH), amino acid group (NH2) and hydrogen atom attached to a carbon atom 
the difference is from the variable (R) group
81
Q

what are the elements in a protein ?

A

carbon, oxygen, hydrogen, nitrogen and sometimes sulfur

82
Q

what joins amino acids together ?

A

peptide bonds

83
Q

what reaction joins amino acids together ?

A

condensation reaction (reverse is hydrolysis to break)

84
Q

what is the primary structure ?

A

The sequence the amino acids are condensed together in a polypeptide chain. A change in just one amino acid may change the structure of the whole protein.

85
Q

what is the secondary structure ?

A

When H-bonds begin to form between nearby NH+ and COO- groups, making alpha helices and beta pleated sheets. H-bonds are weak but collectively give strength

86
Q

what is the tertiary structure ?

A

Chain of amino acid coils and folds further.
New R side chains able to interact with each other.
Held by 3 bonds: disulfide, ionic, H- bonds
This 3D structure that allows active site formation and gives functionality.

87
Q

strength of - disulfide bonds
- ionic bonds
- H bonds
(proteins)

A

disulfide - fairly strong (double bond)
ionic - weaker (easily broken by pH change)
H-bonds - numerous and easily broken

88
Q

what is the Quaternary structure ?

A

For proteins made up of several different polypeptide chains, the Quaternary structure is the way they are held together.

89
Q

bonds in primary structure ..

A

peptide bonds

90
Q

bonds in secondary structure ..

A

H-bonds

91
Q

bonds in tertiary structure ..

A

ionic , disulfide, hydrophobic and hydrophilic interactions, H-bonds

92
Q

Describe ionic bonds in proteins

A

Attractions between -ve R groups and +ve R groups on different parts of the molecule.
Easily broken by pH change

93
Q

Describe disulfide bonds in proteins

A

Fairly strong (double) bond between sulfur in cysteine and another sulfur

94
Q

Describe H bonds in proteins

A

Weak bonds between slightly +ve H atoms and slightly -ve other atoms in R groups

95
Q

Describe hydrophobic/hydrophilic interactions in proteins

A

Hydrophobic R groups clump together, causing hydrophilic R groups to be pushed outside, affecting the way a protein folds

96
Q

Describe a globular protein

A

Spherical, soluble proteins with a range of functions.
They are soluble due to hydrophilic R groups being pushed to the outside (caused by hydrophobic and hydrophilic interactions)

97
Q

what will heating a protein do?

A

break the ionic / hydrophobic and hydrophilic interactions / H-bonds, which will change the 3D shape

98
Q

Describe haemoglobin

A
  • globular protein that carries oxygen round body in RBCs
  • conjugated protein as non-protein group is attached, called a prosthetic group
  • each of 4 polypeptide chains have a haem (prosthetic) group
  • haem groups have iron, which oxygen binds to
99
Q

Describe the globular protein insulin

A
  • hormone secreted by pancreas
  • helps regulate blood glucose level
  • solubility is important as must travel in blood
  • consists of two polypeptide chains, held by disulfide bonds
100
Q

Describe amylase

A
  • globular protein
  • enzyme that catalyses the breakdown of starch
  • made of a single chain of amino acids
  • secondary structure consists of both alpha helices and beta pleated sheets
101
Q

what are fibrous proteins ?

A

Tough, insoluble, rope - shaped proteins that are structural and fairly unreactive

102
Q

Describe fibrous protein collagen

A
  • found in animal connective tissues (bone/skin/muscle)
  • very strong
  • minerals can bind to increase rigidity (e.g. calcium for bones)
103
Q

Describe fibrous protein keratin

A
  • found in external structures like hair, skin, nails, feathers
  • can be flexible or hard and tough
104
Q

Describe fibrous protein elastin

A
  • found in elastic connective tissues like walls of blood vessels / some ligaments
  • elastic so allows tissues to stretch and return to original shape
105
Q

what is the role of calcium ?

A
  • transmission of nerve impulses
  • release of insulin
  • co factor for enzymes
  • bone formation
106
Q

what is the role of sodium ?

A
  • generating never impulses
  • muscle contraction
  • regulating fluid balance
107
Q

what is the role of potassium ?

A
  • same 3 as sodium

- activates enzymes for photosynthesis

108
Q

what is the role of hydrogen ?

A
  • affects pH

- photosynthesis reactions in thylakoid membranes in chloroplast

109
Q

what is the role of ammonium ?

A
  • important source of nitrogen used to make amino acids (in plants)
110
Q

what is the role of nitrate ?

A
  • another source of nitrogen for plants
111
Q

what is the role of hydrogencarbonate ?

A
  • buffer which helps maintain pH of blood
112
Q

what is the role of chloride ?

A
  • ‘chloride shift’
  • co factor for amylase
  • some nerve impulses
113
Q

what is the role of phosphate ?

A
  • photosynthesis / respiration reactions

- synthesis of nucleotides / phospholipids and calcium phosphate

114
Q

what is the role of hydroxide ?

A
  • affects pH
115
Q

test for reducing sugar :

A
  • add Benedict’s (blue) and heat

- colour precipitate : blue / green / yellow / orange / brick red

116
Q

what is a reducing sugar ?

A

monosaccharides (glucose) and some disaccharides (maltose / lactose)

117
Q

test for non - reducing sugar :

A
  • after reducing test, add HCl and heat to break down to monosaccharide
  • neutralise with NaHCO3
  • add Benedict’s
118
Q

test for glucose …

A
  • test strips with reagent that changes colour in presence

- compare to chart to determine concentration

119
Q

test for starch ..

A
  • add potassium iodide solution

- brown to blue - black

120
Q

test for proteins ,,,

A
  • add NaOH to make solution alkaline
  • add copper (II) sulfate solution
  • turn blue to purple
121
Q

test for lipids …

A
  • shake with ethanol
  • pour into water
  • white suspension will form
122
Q

what is a biosensor ?

A

device that uses a biological molecule (enzyme) to detect a chemical

123
Q

Rf value =

A

distance traveled by spot / distance by solvent

124
Q

outline process of testing glucose conc

A
  1. set up diff concentrations of glucose
  2. do Benedicts test on each, then remove precipitate
  3. use colorimeter to measure absorbance of remaining solution
  4. make calibration curve

A level Biology (26 decks)

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