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A-Level Biology - OCR A > 2.1.2 Biological Molecules > Flashcards

2.1.2 Biological Molecules Flashcards

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1
Q

Why do cells need water?

A

Makes up 80% of the cell content:
A reagent of hydrolysis
A solvent
For Transport
For temperature Control
Providing a habitat

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2
Q

What is the structure of water?

A

One Oxygen - two hydrogens

Oxygen and hydrogen share a negitive electron from hydrogen. The pull of electrons is slightly greater towards the oxygen atom.
Hydrogen has a slightly positive charge - forming a polar molecule

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3
Q

How do water molecules bond together?

A

slightly negitive oxygen attracts the slightly positive hydrogen from another molecule - forming a hydrogen bond

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4
Q

What properties does water have?

A

Polar solvent
High specific heat capacity
surface tension
incomprecability
less dence when solid

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5
Q

Why is water a solvent?

A

As water is polar lots of substances can dissolve in water

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6
Q

Why is water important as a solvent?

A

It is a usefull transport medium. Water has the ability to ionise molecules.
Polar molecules disolve in water.
Non-polar molecules do not.

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7
Q

What does a high specific heat capacity mean?

A

Lots of energy is needed to increase the temperature of water.
Lots of energy needs to be lost in order to reduce the temperature of the water.

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8
Q

What is the specific heat capacity of water?

A

4.2j/g/c

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9
Q

Why is the SHC of water important?

A

Acts as a buffer against rapid temperature change.
-it absorbs sun energy during the day and retains it at night.
-it acts as a habitat as the constant temperatures of the water allow organisms to survive

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10
Q

What is cohesion and surface tension?

A

Water molecules ‘sticking together’ due to hydrogen bonds.
Water molecules also stick to ther molecules - cohesion
the strong inwards cohesion force creates surface tension.

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11
Q

What advantage does cohesion and surface tension of water bring?

A

allows the surface of water to act as a habitat for small organisms - like pond skimmers

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12
Q

What is the importance of the dencity of water?

A

Ice is less dence than liquid water so floats on it.
This allows it to act as a habitat for animals to live on top of. It also insulates the water below to provide a habitat for aquatic creatures in sub-zero temperatures

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13
Q

Why is ice less dence than water?

A

Particals have less kinnetic energy at lower temperatures so move slower. meaning more hydrogen bonds form and due to a long bond length spreading the molecules out - decreacing the density

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14
Q

What is important about waters latent heat of vapourisation?

A

Water requires a lot of energy to evaporate.
This allows it to be used as a cooling agent for animals - sweating and panting - and plants - transpiration.

lots of energy is transfered to the water from the organism to cause it to evaporate - cooling it down.

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15
Q

Why is water important for metabilic reactions?

A

Water is a reactant in many reactions.
e.g. hydrollysis and photosynthesis.

It is also a product in many reactions.
e.g. condensation reactions and aerobic respiration

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16
Q

What is the general formula for carbohydrates?

A

CnH2nOn

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17
Q

What are the 3 main categories of carbohydrates?

A

Monosaccharides
Disaccharides
Polysaccharides

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18
Q

What are examples of monosaccarides?

A

Glucose - Fructose - Galactose

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19
Q

What are examples of Disaccarides?

A

Maltose, sucrose, lactose, cellobiose

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20
Q

What monosaccharides make up maltose?

A

Two molecules of a-glucose

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21
Q

What monosaccharides make up sucrose?

A

a-glucose and Fructose

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22
Q

What monosaccharides make up lactose?

A

b-galactose and a-glucose

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23
Q

What monosaccharides make up cellobiose?

A

b-glucose and b-glucose

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24
Q

What type of reaction joins monosaccarides?

A

Condensation (using water)

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25
Q

What type of reaction breaks down monosaccharides?

A

Hydrolysis (needing water)

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26
Q

What are examples of polysaccharides?

A

Glycogen - amylopectin - amylase

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27
Q

What are the features of monosaccarides?

A

Simple sugars
sweet tasting
source of energy
disolve easiy in water
can be streight chains or rings

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28
Q

What are triose sugars?

A

A monosaccharide with 3 carbons. General formula C3H6O3

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29
Q

What are examples of triose sugars?

A

Ketose, aldehyde

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30
Q

What is a pentose sugar?

A

A monosaccharide with 5 carbons. General formula - C5H10O5

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31
Q

What are examples of pentose sugars?

A

Ribose, Deoxyribose

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32
Q

Whats the difference between ribose and deoxyribose?

A

OH on carbon 2 or just H.
Deoxyribose only has H on carbon 2 - not OH

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33
Q

Ribose Structure

A

[NO IMAGE]

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34
Q

Deoxyribose Structure

A

[NO IMAGE]

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35
Q

What are hexose sugars?

A

monosaccharides with 6 carbons. General formula C6H12O6

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36
Q

Whats the difference between Alpha and Beta Glucose?

A

The position of the OH group on carbon one.
ABBA - Alpha Below - Beta Above

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37
Q

Alpha Glucose Structure

A

[NO IMAGE]

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38
Q

Beta Glucose Structure

A

[NO IMAGE]

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39
Q

What is an isomer?

A

Two or more compounds that have the same formula but different structure

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40
Q

What are the roles of monosaccharides?

A

Energy source for respiration - C-H bonds are easily oxidised to yeald lots of energy.
Form building blocks for larger molecules.

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41
Q

What is fructose?

A

The main sugar in fruits and vegetables

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42
Q

How many carbons does fructose have?

A

6 carbons - hexose sugar

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43
Q

What is Galactose?

A

Beta Glucose but the OH on Carbon 4 is above the H instead of below.

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44
Q

What is a glycosidic bond?

A

When the hydroxil (OH) group of one carbohydrate bonds with the hydrogen of another hydroxil group to form water - a condensation reaction.

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45
Q

Why is glucose not good for storage?

A

It is reactive and soluble

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46
Q

How is glucose stored in plants?

A

As starch

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47
Q

How is glucose stored in animals?

A

As glycogen

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48
Q

What are the types of starch?

A

Amylose and amylopectin

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49
Q

details about amylose

A

makes up aprox 20% of starch
made of 200-500 units
contains 1,4 glycosidic bonds

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50
Q

details about amylopectin

A

makes up 80% of starch
made of 5,000 - 100,000 units
contains both 1,4 and 1,6 glycosidic bonds

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51
Q

What is the structure of amylose?

A

1,4 glycosidic bonds between Alpha glucose molecules.
It is spiraled due to the hydrogen bonds.
It is not branced.

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52
Q

What is the structure of amylopectin?

A

1,4 and 1,6 glycosidic bonds between alpha glucose molecules.
it has long brances and is only slightly spiraled.
Hydrogen bonds hold the structure together.

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53
Q

What is the structure of glycogen?

A

1,4 and a few (9%) 1,6 glycocidic bonds giving it some short branches and a small amount of sopiraling.
The structure is held by hydrogen bonds

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54
Q

Why is it better to store glucose as starch and glycogen?

A

Easily hydrolised by enzymes.
Branched chains are more compact but branches means that ends can be rapidly hydrolised.

55
Q

What enzymes hydrolise starch and glycogen?

A

Amylase and maltase does 1,4
glucosidase does 1,6

56
Q

How do you test for starch?

A

Using iodine solution

57
Q

What are the positive tests for starch using iodine solution?

A

Goes from orange to:
Starch - Black
Amylase - Deep Blue
Amylopectin - Red/Purple

58
Q

What causes the colour change seen in the starch test?

A

The solution contains I3- Ions that fit between the amylose helix forming a polyiodide starch complex that brings about the colour change.

59
Q

Why is there less of a colour change in the test for starch in amylopectin?

A

Not as dark as the spirals arnt as tight so not as many iodine ions get within the structure.

60
Q

What is cellulose?

A

A polymer of betaglucose molecules held together by glycosidic bonds

61
Q

What is the structure of cellulose?

A

Beta glucose monomers where every other is flipped to allow the OH groups to align.
Forms streight and unbranched chains of up to 15,000 monomers. Hydrogen bonds prevent spiraling.
Formed by condensation reactions

62
Q

What are the proporties of cellulose?

A

High tensil strength
tough
Insoluble
Fiborus

63
Q

How can the structure of cellulose change?

A

60-70 cellulose molecules become tightly cosslinked to form microfibral bundles. These are indigestable by most vertibre.
Hydrogen bonds between chains prevents spiraling and provides extra strength.
Great tensil strength and flexability makes cell walls strong and permiable

64
Q

How does the cell wall form?

A

From crosslinked cellulose fibers.
Gaps between each strand makes it permiable.
Microfibrils running in different directions form a network to provide extra strength.
Other molecules help crosslink the fibers and form a glue like mixture of pectin.

65
Q

What is an amino acid?

A

Amino acids make up proteins. There are aprox 500 amino acids but only 20 are protogenic - can make proteins.
Each amino acid has a different R group so they have slightly different proporties.
Made of carbon, hydrogen, oxygen and nitrogen only

66
Q

Structure of an aminao Acid

A

[NO IMAGE]

67
Q

What properties make amino acids good buffers?

A

They are ampoteric - meaning that they resist changes in PH

68
Q

What is a protein?

A

A chain of amino acids.
The proporties of the protein are dependant on the Amino Acid sequence - allows them to adapt to unique shapes.

69
Q

What are the functions of proteins?

A

Structure.
Enzymes.
Transport.
Pumps.
Motors.
Hormones.
Antibodies.
Receptors.
Storage.
Blood Clotting.
Lubrication.
Toxins.
Antifreeze.

70
Q

How are proteins formed from amino acids?

A

During protein synthesis in ribosomes.
One amino acid looses an OH group from the carboxil group.
The other looses the H from the amino group.
This forms water (condensation)
The amino acids are linked by a covelant bond between the C of one and N of another

71
Q

What is the name of the covalent bond found between amino acids?

A

PEPTIDE BOND

72
Q

What is the priomary struture of a protein?

A

The amino acid chain - the sequence of amino acids within the chain

73
Q

What is the secondary structure of a protein?

A

The twisting of the amino acid chain into a shape.

74
Q

What shapes can the AA chain fold into in the secondary structure?

A

Alpha Helix
Beta Pleted Sheets

75
Q

What is the aplha helix structure?

A

Forms as a result of hydrogen bonds between different amino acids. It has 36 amino acids per 10 terns of the helix.
The NH group of an amino acid is bonded to the CO of the amino acid 4 places ahead of it in the chain.

76
Q

What is the structure of beta pleated sheets?

A

The polypeptide chain folds over itself. Hydrogen bonds form between the NH group of one amino acid and the Co group of another.
R groups extend above and below the plane of the sheet

77
Q

What is the tertiary structure of a protein?

A

The folds that form the precise 3D structure. Has a single polypeptide chain ‘backbone’ with one or more secondary structures. Shape is primeraly caused by the R groups interacting and forming bonds.

78
Q

What is the quaternary structure of a protein?

A

How multiple polypeptide chains are arranged to make the complete protein molecule.
Incluses the addition of prothstetic groups.

79
Q

What is a prothstetic group?

A

Non-protein part of a protein.

A molecule that is perminantly attached to a protein (by covelant/hydrogen/ionic bonds) that are vital for the normal function of the molecule.

Metal ions and moleules derived from vitamins are also prothstetic groups.

80
Q

What is it called when a lipid/carbohydrates combine with proteins?

A

form lipoproteins and glycoproteins.

81
Q

What is a conjugated protein?

A

A globular protein that contains a non-protein part (prothstetic group).

82
Q

What are globular an fibourous proteins?

A

Globular are globe shaped/spherical
Fibourous are shaped in strands like fibers

83
Q

What is a globular protein?

A

Proteins that are compact, water soluble and spherical in shape.

84
Q

What is the structure of a globular protein?

A

Hydrophobic R Groups face inwards while the hydrophyllic groups face outwards. This give it its spherical shape.
The protein is water soluble as water molecules cluster around the protein and attach to it.

85
Q

What are examples of globular proteins?

A

Insulin - pepsin - catalase - haemoglobin

86
Q

What is insulin?

A

A Hormone that binds to glycoprotein receptors on the CSM of the liver and muscle cells to increase glucose transport to cells.

87
Q

What is the structure of insulin?

A

Two polypeptide chaind (A and B).
A starts with an Alpha Helix section.
B ends with a Beta Pleated Sheets section.
The tertiary structure is held together by disulphide links.
Hydrophyllic R groups point out of the molecule making it water soluble.

88
Q

What is pepsin?

A

An enzyme found in the stomach to digest proteins.

89
Q

What is the structure of pepsin?

A

A single polypeptide chain of 327 amino acids. It folds inot a semetrical structure.
4 basic amino acids means that there are few places for H= ions in the stomaach to bond to and effect the molecules shape.
43 acidic amino acids amkes it stable in the acidic environments.
The tertiary structure is held together by hydrogen bonds and 2 disulphide bridges.

90
Q

What is haemoglobin?

A

A protein found i eurithrocytes that carries oxygen from the lungs to tissues - changes from purple to red as it becomes oxygenated.

91
Q

What is the structure of haemoglobin?

A

Conjugate protein with a non-protein haem group.
Consists of 4 subunits (2x Alpha, 2x Beta) - each is one polypeptide chain with one heam group.

92
Q

What are fibourous proteins?

A

Proteins with a long cylindrical shape - fibers.
They have a regular repeating sequence of amino acids and are usually insoluble in water.

The fiber structure provides strength.

93
Q

What gives fibourous proteins their shape?

A

Parrallel polypeptide chains held together by cross-links. These form long ropelike structures with a high tensil strength.

94
Q

What is the structure of elastin?

A

Mainly crosslinks - coiled to allow for extra stretch

95
Q

What is the function of elastin?

A

Found in the skin to allow it to stretch and return to normal.
It allows the lungs to inflate and deflate, the bladder to stretch and hold urine, blood vessels to stretch and recoil to maintain pressure

96
Q

What is the structure of keratin?

A

Two polypeptide chains intertwined. Its ritch in amino aacids (lycine) so lots of disulphide bridges between the chains of keratin. Hydrogen bonds between the chains make the molecule very strong.

97
Q

What is the function of keratin?

A

Provides a barrier agains disease.
Water proofing.
Forms hard parts of the body - such as hair nails claws hoofs horns scales fur and feathers

98
Q

What is the function of collogen?

A

Mechanical strength in atery walls - to withstand high pressure and prevent them bursting.
Tendens that connect muscle to bone - cartilage and connective tissue made of collogen.
bones are made of collogen and reinforced with calcium phosphate to make them hard

99
Q

What is the structure of collogen?

A

around 20 proteins
forms a tripple helicies - 3 polypeptide chains wrapped around each other forming a rope like structure.

100
Q

What are lipids?

A

Made of carbon, hydrogen and oxygen only.
Higher proportion of hydrogen and lower proportion of oxygen than carbohydrates.
Fats are solid at room temperature - lipids are liquid
Lipids can be fats, oils and waxes.

101
Q

What are the proporties of lipids?

A

insoluble in water.
Excelent souce of energy.
Poor conductors of heat - making them good insulators.
small compared to pollysaccharides.
join together to form globuals.

102
Q

what is the general formula for a lipid?

A

CH3(CH2)nCOOH

103
Q

What are the functions of lipids?

A

protection of vital organs - e.g kidneys.
Prevents evaporation - plants and animals.
waterproofing.
Energy store - ritch in CH bonds.
Insulation.
Hormones.
Electric Insulation - myelin sheath made of lipids.
Metabolic souce of water during formation of ester bonds.
Cell membranes.

104
Q

What are the three main types of lipids?

A

Triglycerides.
Phospholipids.
Cholestorol.

105
Q

What is a triglyceride?

A

3 fatty acid molecules attached to glycerol. Consists of a COOH group attached to a hydrogen tail.

106
Q

What are satturated and unsatturated fatty acids?

A

Satturated contain single bonds only between carbons:
C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-…

unsatturated contain both single and double bonds between carbons:
C-C-C-C-C=C-C-C=C-C-C-C-C-C-C–C=-C-C-…

107
Q

What type of bond do tryglycidides make?

A

Ester bonds - between the glycerol and the fatty acid. A condensation reaction.

108
Q

What is the function of a phospholipid?

A

Makes up the cell surface membrane - phosphilipid bilayer.
Hydrophobic tails prevent the membrane coming apart.
prevents polar molecules passing through the membrane due to the hydrophobic tails.

109
Q

What is the structure of a phospholipid?

A

A glycerol with 2 fatty acids and a phosphate group. The OH on the phosphoric acid forms an ester with the glycerol. The phosphate group is ionising and gains electrons. The phosphate head attracts water so is hydrophillic. Fatty acid tails are hydrophobic.

110
Q

What is an amphiphilic molecule?

A

One with both non-polar and polar regions

111
Q

What is the function of cholestorol?

A

In the hydrophobic part of the Plipid bilayer it reduses membrane permiability to water ions and polar molecules.
It maintains the regidity of the CSM by binding to the polar heads and non-polar tails of the phospholipids.
Controlls fluidits - prevents solidifying at low temps and too much fluidity at high temperatures.
Cholesterol in the liver can produce steroids - testosterone, oestrogen and vit D

112
Q

What is the structure of cholesterol?

A

A lipid without fatty acid or glycerol.
Contains 4 carbon based rings (isoprene units)
All steroids have a 4 ring structure made of cholesterol.

113
Q

What are cations?

A

Positively charged ions

114
Q

What are anions?

A

Negatively charged ions

115
Q

What is the calcium cation?

A

Ca2+

116
Q

What is the sodium cation?

A

Na+

117
Q

What is the potassium cation?

A

K+

118
Q

What is the hydrogen cation?

A

H+

119
Q

What is the ammonium cation?

A

NH4+

120
Q

What is the nitrate anion?

A

NO3^-

121
Q

What is the hydrogencarbonate anion?

A

HCO3-

122
Q

What is the chloride anion?

A

Cl-

123
Q

What is the phosphate anion?

A

PO4^3-

124
Q

What is the hydroxide anion?

A

OH-

125
Q

What is the calcium cation (Ca^2+) used for?

A

Increases the rigidity of bones, teeth and cartilage.
A component of the exoskeleton of crustaceans.
Important in clotting blood and muscle contraction.
Activator for enzymes.
Stimulates muscle contraction.
Regulates transmission of nervous impulses.
Regulates cell permeability.
Formation of cell wall in plants.
Formation of middle lamella between cell walls.

126
Q

What is the sodium cation (Na+) used for?

A

Regulation of oncotic pressure.
Regulates water levels in body fluid.
PH.
Adsorption of carbohydrates in the intestine.
Absorption of water in the kidney.
Nervous transmission.
Muscle contraction.
Vacuoles in plants - to maintain turgidity.

127
Q

What does the potassium cation (K+) do?

A

Water levels in body fluid.
Body PH.
Active transport.
Synthesis of glycogen and protein.
Breakdown of glucose.
Leaves in flowering plants.
Nervous transmission.
Muscle contraction.
Vacuoles to maintain turgidity.

128
Q

What does the hydrogen cation (H+) do?

A

Photosynthesis.
respiration.
Transport of oxygen and CO2 in the blood.
Blood PH.

129
Q

What does the ammonium cation (NH4+) do?

A

Part of amino acids, proteins, vitamins and chlorophyll.
Makes up some hormones.
Part of nucleic acids.
PH maintenance.
Nitrogen cycle.

130
Q

What does the nitrate anion (NO3-) do?

A

Part of amino acids, proteins, vitamins and chlorophyll.
Makes up some hormones.
PH maintenance.
Nitrogen cycle.

131
Q

What does the hydrogencarbonate anion (HCO3-) do?

A

Regulate blood PH.
Transport of CO2 in the blood.

132
Q

What does the chloride anion (Cl-) do?

A

Production of urine.
Maintaining water balance.
Transport of CO2 in and out of the blood.
Regulates affinity of haemoglobin to oxygen (allosteric effects).
Regulates blood PH.
Produce HCl in the stomach.

133
Q

What does the phosphate anion (PO4^3-) do?

A

Increases the rigidity of bones, teeth and cartilage.
A component of the exoskeleton of crustaceans.
Part of phospholipids, ATP, Nucleic Acids, and enzymes.
Regulates blood PH.
Root growth in plants.

134
Q

What does the hydroxide anion (OH-) do?

A

Regulates blood glucose

A-Level Biology - OCR A (16 decks)

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