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OCR AS-level Biology > 2.1.2 biological molecules > Flashcards

2.1.2 biological molecules Flashcards

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1
Q

Name four macro molecules

A

Proteins, fats, water, carbohydrates

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2
Q

Name the components of the macro molecules

A

protein: made up of amino acids
fat: made from glycerol and fatty acids
water: contains hydrogen and oxygen only

Carbohydrate: simple sugars to complex polysaccharides

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3
Q

Name the function of the four macro molecules

A

Protein: Used to make enzymes, hormones and structural components such as muscle

fat: energy source and storage, installation, buoyancy and protection
water: components of tissues, medium for chemical reactions and transport medium
carbohydrate: Source of energy and structural uses

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4
Q

Define a condensation reaction

A

Two molecules join together. A water molecule is removed during the reaction

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5
Q

Define a hydrolysis reaction

A

A molecule is split into two molecules. Water is needed for the reaction to occur

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6
Q

Define a monomer

A

A small molecule that can be bound to other identical monomers by condensation

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7
Q

Describe a polymer

A

A large molecule, made from many monomers

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8
Q

What are the bonding rules

A

bonding can be determined by the number of electrons in the outer orbital.

Carbon atoms can form 4 bonds with other atoms
nitrogen atoms form 3 bonds
oxygen forms 2 bonds
Hydrogen forms 1 bond

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9
Q

Name the monomer and polymer of a carbohydrate

A

monomer: monosaccharide

Polymer: polysaccharide

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10
Q

Name the monomer and polymer of a protein

A

monomer: amino acids

Polymer: polypeptides and proteins

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11
Q

Name the monomer and polymer of nucleic acids

A

monomer: nucleotides

Polymer: DNA and RNA

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12
Q

Name the monomer and polymer of fats

A

monomer : fatty acids and glycerol

Polymer: triglycerides

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13
Q

Why is water described as a polar molecule

A

water is described as polar as it has an unequal distribution of charge in the molecule. Oxygen is slightly negative (delta negative) and hydrogens are slightly positive (delta positive)

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14
Q

How do hydrogen bonds form between water molecules

A

water is polar: oxygen is more electronegative than hydrogen, so attracts electron density in covalent bonds more strongly.

There are intermolecular forces of attraction between a lone pair of oxygen Delta negative of one molecule and hydrogen Delta positive on an adjacent molecule

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15
Q

State some biologically important properties of water

A

it has a high surface tension which enables organisms to walk on water

it has a high specific heat capacity: because of the high amount of hydrogen bonds, it means that it can absorb a lot of heat and provides relatively constant temperatures

universal solvent: it can dissolve many ionic and polar substances which enables many biochemical reactions to take place in the cell cytoplasm and it enables substances to be transported

it provides a habitat

it transports into and around cells in the blood, xylem, lymph fluid

it is a liquid at room temperature which allows the transport, habitat and is a medium for reactions

it has a high latent heat of vaporisation and is a coolant because heat energy is needed to break the hydrogen bonds when the water evaporates

it is dense so ice floats, has an insulating layer

cohesion between molecules

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16
Q

Define cohesion

A

Attraction to other water molecules

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17
Q

Define adhesion

A

Attraction to other polar substances

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18
Q

Why is the incompressible nature of water important for organisms

A

It provides turgidity to plant cells and provides Hydro static skeleton for some small animals like earthworms

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19
Q

Explain why ice floats on water. And why is this important for organisms

A

Ice is less dense than water because hydrogen bonds holding molecules in fixed positions further away from each other. It insulates water in Arctic climates so aquatic organisms can survive and water acts as a habitat

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20
Q

Why is the high surface tension of water important for organisms

A

It slows water loss due to transpiration in plants. Water rises unusually high in narrow tubes, lowering demand on route pressure.

And some insects can skim across the surface of water

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21
Q

Why is water an important solvent for organisms

A

polar universal solvent dissolves and transports charged particles involved in intra and extracellular reactions

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22
Q

Why are the high specific heat capacity and latent of vaporisation water important for organisms

A

Acts as a temperature buffer which enables endotherm is to resist fluctuations in core temperature, to maintain optimum enzyme activity. Cooling affect when water evaporates from skin surface as sweat/from mouth when panting

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23
Q

Name the elements found in carbohydrates, lipids, proteins and nucleic acids

A

carbohydrates and lipids: carbon, hydrogen, oxygen ( CHO)

proteins: carbon, hydrogen, oxygen, nitrogen, sulfur ( CHONS)

nucleic acids: carbon, hydrogen, oxygen, nitrogen, phosphorus ( CHONP)

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24
Q

carbohydrates: Draw the structure of alpha glucose and beta glucose

A

they are both hexose monosaccharides with a ring structure

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25
Q

carbohydrates: State the three carbohydrates and the example molecules

A

monosaccharide are small, simple sugars e.g. glucose, fructose and ribose

disaccharides are large sugars e.g. lactose and sucrose

Polysaccharides are long chain carbohydrates e.g. glycogen, Celulose and starch

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26
Q

carbohydrates: describe glucose

A

glucose is an abundant and very important monosaccharide. It contains six carbon atoms so it is a hexose sugar and its general formula is C6 H12 O6

Glucose is the major energy source for most cells. It is highly soluble and is the main form in which carbohydrates are transported around the body of animals

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27
Q

carbohydrates: How do we make disaccharides and polysaccharides

A

Condensation reaction

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28
Q

carbohydrates: Describe pentose monosaccharides

A

They contain five carbon atoms. Two important pentose molecules are the structural isomers ribose and deoxyribose. The only difference between them is that ribose has one hydrogen atom and 1 OH group attached to carbon 2, whereas deoxyribose has two H atoms and no OH group

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29
Q

carbohydrates: How is maltose formed (disaccharide)

A

Glucose + glucose = maltose

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30
Q

carbohydrates: How is sucrose formed (disaccharide)

A

glucose + fructose

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31
Q

carbohydrates: How is lactose formed (disaccharide)

A

glucose + galactose = lactose

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32
Q

carbohydrates: What are polysaccharides

A

Polysaccharides are polymers containing many monosaccharides linked bike like acidic bonds. Like disaccharides, polysaccharides are formed by condensation reactions

The major polysaccharides are starch and cellulose in plants and glycogen in animals

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33
Q

carbohydrates:

What type of bond forms when monosaccharides react

A

(1,4 or 1,6) glycosidic bonds

two monomers= one chemical bond = disaccharide

multiple monomers = many chemical bonds = polysaccharides

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34
Q

carbohydrates: do you find it in humans or plants

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = Plants

(II) amylopectin =Plants

(III) glycogen =Animals

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35
Q

carbohydrates: Where in the organism is it stored

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose= Grains in the chloroplasts

(II) amylopectin =Grains in the chloroplasts

(III) glycogen =Liver and muscles

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36
Q

carbohydrates: Is it a form of starch

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = Alpha glucose

(II) amylopectin = Alpha Glucose

(III) glycogen = Alpha Glucose

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37
Q

carbohydrates: Is it branched

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = No it is straight

(II) amylopectin = Yes

(III) glycogen = Yes loads of branches

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38
Q

carbohydrates: Is it soluble

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = No

(II) amylopectin = No

(III) glycogen = Yes

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39
Q

carbohydrates: Which glycosidic bonds does it have

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = 1,4

(II) amylopectin 1,4 and 1,6

(III) glycogen 1,4 and 1,6

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40
Q

carbohydrates: are they spiralled

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = Yes

(II) amylopectin =No

(III) glycogen = No

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41
Q

carbohydrates: Are hydrogen bonds important in holding the structure in place

(I) amylose

(II) amylopectin

(III) glycogen

A

(I) amylose = Yes

(II) amylopectin = no

(III) glycogen = no

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42
Q

carbohydrates: Describe glycogen

A

Animals do not store carbohydrate as starch but as glycogen. Glycogen is stored as small granules, particularly in muscles and liver. Glycogen is less dense and more soluble than starch and breaks down more rapidly. And the reason glycogen is more soluble than starch is because it has loads of branches which make it more compact enabling it to store more energy

43
Q

carbohydrates : What is Celulose

A

Celulose is another polysaccharide and is the main part of plant cell walls.

Unlike starch, Celulose is very strong, and prevents cells from bursting when they take in excess water.

Celulose consist of long chains of beta glucose molecules joined by beta 1,4 glycosidic bonds.

The glucose chains form ropelike microfibrils which are layered to form a network

44
Q

lipids: What are the characteristics of lipids

A

lipids contain C, H and O.

Lipids are nonpolar molecules, so are insoluble in water but they are soluble in organic solvents. They are generally water repelling(hydrophobic) The building blocks of fatty acids and glycerol and they do not form polymers

45
Q

lipids: What are triglycerides

A

triglycerides are lipids made from glycerol and 3 fatty acid chains

46
Q

lipids: How do triglycerides form

A

Condensation reaction between one molecule of glycerol and three fatty acids which forms ester bonds

47
Q

lipids: describe a fatty acid’s structure

A

A fatty acid has a hydrocarbon chain, ending in an acidic carboxyl group
- COOH

A carboxyl group is what makes the hydrocarbon chain acidic

48
Q

lipids: What are the differences between fats and oils

A

Fats are solid at room temperature and oils are liquid at room temperature

49
Q

lipids: What are the differences between saturated and unsaturated fatty acids

A

Saturated: contain only single bonds, straight chain molecules have many contact points, higher melting point which means they are solid at room temperature, and they are found in animal fats

unsaturated: contain C=C double bonds, kinked molecules have fewer contact points, Lower melting point which means they are liquid at room temperature and are found in plant oils

50
Q

lipids: Relate the structure of triglycerides to their function

A

High energy: mass ratio = hi calorific value from oxidation (energy storage)

insoluble hydrocarbon chain = No affect on water potential of cells and used for waterproofing

slow conductor of heat = thermal insulation eg adipose tissue

less dense than water = Buoyancy of aquatic animals

51
Q

lipids: Describe the structure of phospholipids

A

amphipathic: glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head

phospholipids can form a layer on the surface of water and they can form a sphere

They do not dissolve in water

They are selectively permeable because only nonpolar molecules can get past the polar head of a phospholipid

52
Q

lipids: Describe the function of phospholipids

A

they form a phospholipid bilayer in water = component of membranes

tails can splay outwards = waterproofing e.g. for skin

Phospholipids heads can shuffle around but also always protect the tails and this provides stability

53
Q

lipids: Are phospholipids and triglycerides polymers

A

No. They are not made from a small repeating units, they are macro molecules

54
Q

lipids: Describe the structure and function of cholesterol

A

steroid structure of four hydrocarbon rings. Hydrocarbon tail on one side, hydroxyl group - OH on the other side

cholesterol adds stability to cell-surface phospholipid bilayer by connecting molecules and reducing fluidity

55
Q

proteins: What are proteins made of

A

Proteins are made of repeating units of amino acids

56
Q

Describe an amino acid structure

A
  • COOH carboxyl/ carboxylic acid group

R variable side group consists of carbon chain and includes other functional groups

NH2 = amino/ amine group

All amino acids have the same general structure, the only difference between each one is the nature of the R group. The R group therefore defines an amino acid

57
Q

proteins: How do polypeptides form

A

condensation reactions between amino acids form peptide bonds. There are four levels of protein structure

58
Q

proteins: Define primary structure of a protein

A

Sequence, number and type of amino acids in the polypeptide, determined by sequence of codons on mRNA

mclaird definition = Simple long chains with no intramolecular bonds or interactions. The order of amino acids determines the primary structure

59
Q

proteins: define the secondary structure

A

hydrogen bonds form between oxygen Delta negative attach to -C=O and hydrogen Delta positive attached to -NH

mclaird definition : Hydrogen bonds form causing the molecule chain to either foil or coil

60
Q

proteins: Describe the two types of secondary protein structure

A

alpha helix: all N-H Bonds on same side of protein chain, spiral shape, H-bonds Parallel to helical axes

beta pleated sheets: N-H and C=O groups alternate From one side to the other

61
Q

Define tertiary structure of a protein and describe the bonds present

A

3-D structure formed by further folding.

Disulphide bridges: strong covalent S-S Bonds between molecules of the amino acid cysteine

ionic bonds: relatively strong bonds between charged r groups (pH changes cause these bonds to break)

hydrogen bonds: numerous and easily broken

mclaird definition: Hydrophilic/phobic interactions, hydrogen bonds, ionic bonds and disulphide bonds hold the molecules together in shape. Disulphide bonds are formed only when sulfur is present in the r group

62
Q

proteins: define quaternary structure of a protein

A

Functional proteins may consist of more than one polypeptide. Precise 3D structure held together by the same types of bond as tertiary structure. May involve addition of prosthetic groups e.g. metal ions of phosphate groups

mclaird definition : These are the same as tertiary but with two separate polypeptide chains interlinked

63
Q

proteins: Describe the structure and function of globular proteins

A

they are spherical and compact. Hydrophilic R groups face outwards and hydrophobic R groups face inwards = usually water soluble

they are involved in metabolic processes e.g. enzymes such as amylase, insulin and haemoglobin

64
Q

proteins: Describe the structure and function of fibrous proteins

A

They can form long chains of fibres, insoluble in water and are useful for structure and support e.g. collagen in skin

65
Q

List the functions of collagen, elastin and keratin

A

collagen: component of bones, cartilage, connective tissues and tendons
elastin: provides elasticities to connective tissue, arteries, skin, lungs, cartilage, ligaments

Keratin: structural components of hair, nails, whose, horns, epithelial cells of outer layer of skin

66
Q

proteins: Describe the structure and function of conjugated proteins

A

they are globular proteins that contain a nonprotein component called a prosthetic group. It functions in interaction with other non-polypeptide chemical groups attached by covalent bonds. E.g. haemoglobin

67
Q

proteins: Describe the structure of haemoglobin

A

globular conjugated protein with prosthetic group.

Two alpha chains, two beta chains, four prosthetic haem groups.

Water soluble also dissolves in plasma.

Fe 2+ haem group forms coordinate bond with O2

tertiary structure changes so it is easier for subsequent oxygen molecules to bind (cooperative bonding)

68
Q

Describe how to test for proteins in a sample

A

biuret

add an equal volume of biuret solution and observe the colour change.

If the sample is positive for protein it will go from blue to lilac

and if the sample is negative for protein it will stay blue

69
Q

Describe how to test for lipids in a sample

A

emulsion test:

add ethanol to the food to dissolve the fat, then add water and shake

If the sample is positive for lipids then a milky white emulsion will form with a white or cloudy appearance

If the sample is negative it stays colourless

70
Q

describe how to test for reducing sugars

A

add benedicts solution to the food and boil in a water bath for five minutes

if the sample is positive for reducing sugars it will form a brick red precipitate

If the sample is negative it will stay blue

71
Q

Describe the benedicts test for non-reducing sugars

A

add the test sample with dilute hydrochloric acid. Neutralise the test sample by adding sodium hydrocarbonate. And heat the test sample with benedicts solution

if the sample is positive for a non-reducing sugar it forms a brick red precipitate

if the sample is negative It stays blue

72
Q

Describe the test for starch

A

add 2 to 3 drops of iodine on the specimen

if the sample is positive for starch then the colour will change from Orange to blue / black

If the sample is negative it will stay orange / brown

73
Q

Outline the principles and process of chromatography

A

Use capillary tube to spot solution onto pencil start line 1 cm above bottom of paper

place chromatography paper in solvent, the origin should be above solvent level

let solvent to run until it almost touches the other end of the paper. Molecules in mixture move different distances based on relative solubility in the solvent/attraction to paper

74
Q

chromatography : what are Rf Values and how can they be calculated

A

ratios to allow comparison of how far molecules have moved in chromatograms

Rf value = Distance between origin and centre of pigment spot ÷ Distance between origin and solvent front

also known as Rf = distance moved by the solute ÷ distance moved by the solvent

75
Q

ppq: Name the bond that joins the unit in a molecule of sucrose

A

glycosidic bond

76
Q

ppq: Name the type of reaction that breaks a glycosidic bond

A

Hydrolysis reaction

77
Q

ppq: Name the precise group of carbohydrate molecules of which glucose is an example

A

Monosaccharides

78
Q

ppq: State and explain two ways in which the glucose molecule is well suited to its function in living organisms

A

Glucose is a ready source of energy e.g. in cellular respiration energy is released from glucose which helps make ATP. And it is highly soluble in water which allows the glucose fuel to be transported easily e.g. in the bloodstream

79
Q

ppq: How does the structure of glycogen help its function as an energy storage molecule

A

Glycogen has many short branches, which are easily digested by carbohydrase enzymes

80
Q

ppq: How are the bonds between triglycerides broken

A

The ester bonds are broken by a hydrolysis reaction

81
Q

ppq: Haemoglobin has a high affinity for oxygen, how does the shape of haemoglobin aid its function

A

Each subunit of the quarternary protein contains an iron based haem group. Each heam groups binds a molecule of oxygen

82
Q

ppq: Which is the strongest bond strength

A

disulphide is the strongest bond strength

It goes hydrogen, ionic, disulphide

83
Q

ppq: Name the covalent bond between two adjacent amino acids in a chain of amino acids

A

Peptide bond

84
Q

ppq: Name the type of reaction involved in breaking a peptide bond and describe what happens in this reaction

A

hydrolysis and in this reaction water is needed

85
Q

ppq: lipids form an essential part of a balanced diet. Some food, such as Mycoprotein is produced by micro organisms.

How might the lipid content of mycoprotein differ from food that comes from animals

A

Overall they have less fat,

less saturated fat and more unsaturated fat

86
Q

ppq: why is the ability of water to act as a solvent important for the survival of organisms

A

it means they are a medium for metabolic reactions and because it allows ionic compounds to separate

87
Q

ppq: State the name given to the sequence of amino acids in a protein molecule

A

Primary structure

88
Q

ppq: State one property of collagen that makes it a useful component of blood vessel walls

A

It is very strong

89
Q

ppq: Describe the structure of the collagen molecule

A

there are peptide bonds, between amino acids and every third amino acid is coiled.

Alpha helix which is left-handed

glycine allows closeness

three polypeptide chains

hydrogen bonds between polypeptide chains and a few hydrophilic r groups on the outside of the molecule

90
Q

ppq: State one function of haemoglobin

A

Transport of oxygen

91
Q

ppq: Haemoglobin contains a prosthetic group, collagen does not contain a prosthetic group.

Describe three other ways in which the structure of haemoglobin differs from that of collagen

A

haemoglobin is globular,

has hydrophobic r groups on the inside and hydrophilic r groups on the outside.

and have four chains (polypeptide)

The subunits are two different types: alpha, helix.

And has a wider range of amino acids

92
Q

ppq: Name the polymer formed from a chain of amino acids

A

Polypeptide

93
Q

ppq: Name the bond that is formed when two amino acids are joined together. And describe the formation of this bond

A

peptide bond

between, amine Group of one amino acid and carboxyl group of another, H from amine combines with OH (carboxyl) through a condensation reaction

94
Q

ppq: describe ways in which the physical properties of water allow organisms to survive over a range of temperatures

A

large amount of heat needed to change from liquid to gas (high latent heat of vaporisation )

Evaporation is an efficient cooling mechanism e.g. sweating, painting, transpiration

water is thermally stable (high specific heat capacity) which enables a thermally stable environment for aquatic organisms and aquatic organisms use less energy on temperature control

Ice is less dense than water and this therefore means that the surface of ice provides habitats for organisms e.g. polar bears on ice.

water beneath us is insulated and doesn’t freeze and therefore aquatic organisms do not freeze and can still swim

it is an effective solvent and is therefore a medium for reactions and is able to delete toxic substances

it has surface tension which creates a habitat for invertebrates

it is transparent so allows underwater photosynthesis

and has high density so allows floatation

95
Q

ppq: List three examples of where hydrogen bonds are found in biological molecules

A

protein secondary structure (alpha helix, beta pleated sheet)

protein tertiary structure

Between polypeptide chains in quaternary structure

96
Q

ppq: State two roles of cholesterol in living organisms

A

regulates fluidity of membranes e.g. phospholipid bilayer

Waterproof the skin and makes vitamin D

97
Q

ppq: Identify one way in which the molecular structure of cholesterol is similar to the molecular structure of a carbohydrate

A

both contain C H O

98
Q

ppq: cholesterol was transported in the blood within molecules of low-density lipoprotein (LDL)

Name two molecules that combine with cholesterol to form LDLs

A

Triglycerides and proteins

99
Q

ppq: Suggest why diets with a high red meat content or associated with high blood cholesterol

A

Red meat contains large amounts of saturated fats and saturated fats lead to increased amount of LDLs

100
Q

ppq: Describe the structure of a triglyceride molecule

A

One glycerol and three fatty acids with an ester bond between the glycerol and fatty acids

101
Q

ppq: State three roles of lipids in living organisms

A

thermal insulation

Energy store

protection

Waterproofing

102
Q

ppq: suggest one difference between lipids from animals and those from plants

A

saturated fatty acids have fewer double bonds

And animal fats are solid at room temperature

103
Q

ppq: give three differences between the structure of glycogen and collagen

A

Glycogen: polysaccharide, alpha glucose units, identical units, glycosidic bonds, branched, one chain per molecule, no cross links, contain C H O

Collagen: polypeptide, amino acid units, different amino acid units, peptide bonds, three chains per molecule, cross links between chains, contains C H O N

OCR AS-level Biology (12 decks)

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