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Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Name seven important properties of water

A

behaviour as a liquid;
density;
solvent;
cohesion and surface tension;
high specific heat capacity;
high latent heat of vaporisation;
reactant

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2
Q

Why is it difficult for water molecules to become gas?

A

molecules move and hydrogen bonds are made and broken continually, hard to escape

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3
Q

How is water being liquid at room temp important? (4)

A

Habitat;
major component of organisms;
reaction medium;
transport medium

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4
Q

Why is the density of water important for organisms?

A

Any less dense then organisms couldn’t float

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5
Q

Why is it important for ice to be less dense than water?

A

ice floats, layer insulates ponds during winter, stable environment for aquatic organisms.

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6
Q

What happens to density of water when it freezes?

A

gets less dense due to polarity

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7
Q

Why is water a good solvent?

A

Polar, so different charges of solutes attracted to different charges of water molecules;
Water molecules cluster around molecules/ions and keep them separate from one another

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8
Q

How is water useful as a solvent?

A

molecules and ions move around and react together in water, such as cytoplasm;
transport medium

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9
Q

What is cohesion?

A

Forces of attraction between water molecules due to hydrogen bonds holding them together

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10
Q

What is surface tension?

A

Molecules at surface of water attracted to molecules below, water contracts and can resist forces applied to surface

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11
Q

How is cohesion useful?

A

columns of water in plants pulled up as a chain from the roots

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12
Q

How is surface tension useful?

A

Some insects can walk on water

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13
Q

Why is specific heat capacity of water high and how is this important?

A

Stable temp within organisms for enzymes;
Stable environment for aquatic organisms.

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14
Q

Why is the specific heat capacity of water high?

A

need lots kinetic energy to break hydrogen bonds between molecules

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15
Q

Why is high latent heat of vaporisation of water important?

A

Useful to cool down organisms, like when sweat evaporates or when water evaporates from mesophyll cells in plants

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16
Q

Why is the latent heat of vaporisation of water high?

A

need lots kinetic energy to break hydrogen bonds

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17
Q

How is water important as a reactant?

A

part of reactions like photosynthesis and in hydrolysis/breakdown of molecules;
important for digestion and synthesis of large molecules

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18
Q

What is a hydrolysis reaction?

A

molecules broken apart by adding molecule of water

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19
Q

What is a condensation reaction?

A

molecules joined together by the removal of water molecules

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20
Q

What is a hydrogen bond?

A

Weak bond created when slightly negative ion attracted to slightly positive hydrogen ion

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21
Q

Name three functions of carbohydrates and example

A

Source of energy, store of energy and structural units

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22
Q

Give two examples of carbohydrate energy stores

A

starch and glycogen

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23
Q

Give an example of a carbohydrate energy source

A

glucose

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24
Q

Give two examples of carbohydrate structural units

A

cellulose and chitin

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25
Q

State the physical properties of monosaccharide

A

sweet-tasting sugars
soluble in water
solid at room temperature

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26
Q

What bonds are common in monosaccharides?

A

large number of carbon-hydrogen bonds

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27
Q

When are monosaccharides soluble?

A

in water, not in non-polar solvents

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28
Q

Structure of monosaccharides

A

Backbone of carbon atoms, one double bond to oxygen (carbonyl group), found in chain/cyclic form

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29
Q

Hexose and pentose sugars have how many carbons?

A

6 and 5

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30
Q

Describe structure of the isomers of glucose (3)

A

a-glucose, OH group beneath the ring;
B-glucose, OH group above the ring;
both hexose

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31
Q
A
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32
Q

Two physical properties of disaccharides

A

sweet and soluble in water

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33
Q

What are the three most common disaccharides?

A

maltose, sucrose and lactose

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34
Q

which monomers make maltose?

A

a-glucose + a-glucose

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35
Q

Which monomers make up sucrose?

A

a-glucose + fructose

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36
Q

Which monomers make up lactose?

A

B-galactose + a-glucose

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37
Q

Which monomers make up cellobiose?

A

B-glucose + B-glucose

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38
Q

How are monosaccharides bonded together?

A

By glycosidic bond

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39
Q

What is the role of a-glucose?

A

energy source;
component of starch and glycogen

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40
Q

What is the role of B-glucose?

A

energy source;
component of cellulose

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41
Q

What is the role of ribose?

A

component of RNA, ATP and NAD

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42
Q

What is the role of deoxyribose?

A

component of DNA

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43
Q

How does the structure of deoxyribose differ from ribose?

A

Bottom right, deoxyribose has H instead of OH

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44
Q

Name for polysaccharide made of same and different monomers

A

same: homopolysaccharide,
different: heteropolysaccharide

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45
Q

Give an example of a homopolysaccharide

A

starch

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46
Q

What is a homopolysaccharide?

A

a polysaccharide made up of one type of monosaccharide

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47
Q

What is a heteropolysaccharide?

A

a polysaccharide made up of different monosaccharides

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48
Q

Four reasons polysaccharides are good energy stores

A

compact, dense grains, glucose can be snipped off by enzymes;
branched chains more compact and lots glucose can be released quickly;
less soluble in water

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49
Q

Why are branched chains better energy stores?

A

more compact, lots energy can be released quickly

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50
Q

Name the enzyme used to hydrolyse 1-6 glycosidic bonds

A

glucosidase

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51
Q

Name the enzyme used to hydrolyse 1-4 glycosidic bonds

A

amylase

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52
Q

Explain what a 1-4 or 1-6 glycosidic bond means

A

Bond between carbon 1 of one molecule and carbon 4 or 6 of another

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53
Q

Why is it important for energy stores to be insoluble?

A

If sugar dissolves in tissues, water potential reduces and water disrupts functioning of the cells

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54
Q

Why are polysaccharides less soluble in water?

A

Size;
Regions which could hydrogen bond with water hidden within molecule;
Amylose forms double helix, hydrophobic exterior

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55
Q

How does structure of amylose make it insoluble?

A

double helix, has hydrophobic exterior

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56
Q

Describe the structure of amylose (3)

A

Chain of a-glucose, 1-4 bonds;
Coils into spiral by hydrogen bonds;
hydroxyl groups on carbon 2 situated on inside of coil, less soluble

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57
Q

Where are amylose and amylopectin found?

A

in plants

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58
Q

Describe the structure of amylopectin (2)

A

1-4 bonds but also branches joined by 1-6 bonds;
Coils into spiral with branches emerging

59
Q

Describe the structure of glycogen (3)

A

1-4 bonds and branches connected by 1-6 bonds;
1-4 chain usually smaller so doesn’t coil;
More branches so more compact and easy to remove monomers as it has more ends

60
Q

State three physical features of cellulose

A

Tough=, Insoluble, Fibrous

61
Q

What is cellulose made of?

A

long chains B-glucose molecules

62
Q

Describe the structure of cellulose (4)

A

Every other B-glucose inverted so that hydroxyl groups align;
1-4 bonds and hydrogen bonds within/between chains;
Prevents spiralling;
Hydroxyl group on carbon 2 sticks out to form hydrogen bonds

63
Q

How do cellulose chains form cell wall (4)

A

chains form microfibrils;
microfibrils bundled together form macrofibrils;
These embed in pectins (like glue) to form cell wall;
criss-cross in different directions for strength

64
Q

What is the role of the cell wall? (4)

A

stops cell bursting when turgid;
cells press against one another providing more stability;
protects cell membrane;
permeable for water and ions to pass in/out of cells

65
Q

How is the structure of the cell wall useful?

A

glycosidic and hydrogen bonds make it strong and difficult to digest,
macrofibrils criss-cross for strength

66
Q

How can the macrofibril cell wall be reinforced? (3)

A

cutin and suberin are waxes which blocks spaces making it waterproof;
lignin does same in xylem;
in woody part of trees cell wall is extra thick to support weight

67
Q

Describe the structure of bacterial cell walls (2)

A

Long polysaccharide chains lying in parallel;
cross-linked by short peptide chains

68
Q

What are bacterial cell walls made of?

A

peptidoglycan

69
Q

Describe structure of exoskeletons

A

made of chitin, forms cross-links between long parallel chains of acetylglucosamine

70
Q

How does chitin differ to cellulose?

A

acetylamino group on carbon 2

71
Q

What type of molecules are lipids?

A

macromolecules

72
Q

What are the three most important lipids in organisms

A

triglycerides, phospholipids and steroids

73
Q

Describe the structure of glycerol

A

three carbon, bonded to hydrogen and three OH groups

74
Q

Describe the structure of fatty acids

A

-COOH group on one end attached to hydrocarbon tail

75
Q

What does saturated mean?

A

no C=C bonds

76
Q

What does monounsaturated mean?

A

one C=C bond

77
Q

What does polyunsaturated mean?

A

more than one C=C bond

78
Q

How does a C=C bond affect a fatty acid?

A

Creates a kink in chain at double bond;
pushes molecule apart, more fluid, lower melting point.

79
Q

Fatty acids in animals are usually…?

A

saturated

80
Q

The melting point in saturated fatty acids is…?

A

higher

81
Q

Fatty acids in animals are usually ________ which means the melting point is ________ and they are usually ________ at room temperature

A

saturated; high

82
Q

At room temperature, saturated fatty acids are usually…?

A

solid

83
Q

What is the structure of triglycerides?

A

three fatty acids ester bonded by -COOH groups to a glyceride molecule

84
Q

State five functions of triglycerides

A

Energy source;
energy store;
insulation;
buoyancy;
protection

85
Q

How do triglycerides function as an energy source? (3)

A

hydrolyse ester bonds, glycerol and fatty acids can be fully broken down to carbon dioxide and water;
produces more water than respiration of sugar

86
Q

How are triglycerides effective as energy stores?

A

Insoluble in water;
release twice as much energy as glucose

87
Q

Why do triglycerides release more energy than glucose?

A

Have higher proportion of hydrogen atoms and almost no oxygen

88
Q

How do triglycerides act as insulation? (3)

A

Adipose cells beneath skin acts as heat insulator;
lipid in nerve cells acts as electrical insulator;
animals preparing to hibernate store extra fat

89
Q

Describe the structure of phospholipids

A

two fatty acids and a phosphate group bound to the glycerol by ester bonds, often one saturated fatty acid and one unsaturated, often have even number of carbon atoms

90
Q

How do triglycerides provide buoyancy?

A

Fat less dense than water, used help organisms stay afloat

91
Q

How do phospholipids respond to water and why? (3)

A

head is hydrophillic, tail is hydrophobic;
Could form layer on surface of water with tails sticking out;
or submerged micelles, balls of phospholipids with tails inside and heads facing outwards

92
Q

what is a micelle?

A

ball of phospholipids in water with tails hidden inside

93
Q

Describe the structure of a phospholipid bilayer

A

double layer of phospholipids forms with tails hidden within.

94
Q

What are two important features of the phospholipid bilayer?

A

Phospholipids free to move;
hydrophobic tails provide stability;
selectively permeable, only small non-polar molecules pass through, controls what enters and leaves cell.

95
Q

What does selectively permeable mean?

A

only allows small non-polar molecules to pass through, controls what enters and leaves the cell

96
Q

Where is cholesterol made?

A

liver

97
Q

What type of molecule is cholesterol?

A

steroid alcohol (sterol), not made from glycerol or fatty acids, hydrophobic

98
Q

What is the role of cholesterol?

A

regulates the fluidity of the membrane

99
Q

Name the cholesterol derivative found in animals

A

stigmasterol

100
Q

Name three steroid hormones made from cholesterol

A

testosterone, oestrogen and vitamin D

101
Q

Give one property of steroid hormones

A

small and hydrophobic to pass through cell membrane

102
Q

When happens to plant steroids when ingested?

A

converted to animal hormones

103
Q

Describe the structure of proteins (3)

A

Large polymers of amino acids;
one or more chains;
adopt specific shapes

104
Q

What is the role of proteins?

A

form structural components, used in membranes for transport, enzymes

105
Q

How do plants get amino acids?

A

plants can make all of them if have access to fixed nitrogen (nitrate)

106
Q

Describe the structure of amino acids

A

carbon atom bonded to a hydrogen, NH2 (amino) group, -COOH group and an R group which differs between molecules

107
Q

How are amino acids bonded together?

A

covalent peptide bonds

108
Q

How does a peptide bond form?

A

-COOH group and NH2 group of amino acids bonds covalently C-N

109
Q

What is the primary structure of a protein?

A

Sequence of amino acids, determines the function of protein.

110
Q

What is the secondary structure of a protein? (4)

A

shape after primary structure;
can twist into an a-helix or fold into a B-pleated sheet;
held by hydrogen bonds between -NH groups and the -CO groups
Some molecules may take different forms at different ends of chain

111
Q

What is the tertiary structure of a protein? (3)

A

specific structure;
held by many bonds between amino acids;
May adopt supercoiled shape or spherical shape

112
Q

What is the quaternary structure of a protein?

A

More than one polypeptide chain, quaternary structure make complete molecule;
same bonds as tertiary structure (various types) to hold together

113
Q

How do ionic bonds form within protein structure?

A

Form between carboxyl (-COOH) and amino (NH2) groups forming NH3+ and COO- ions

114
Q

How do disulphide links form within protein structure?

A

R groups containing sulphur (e.g. cysteine) form covalent disulphide links

115
Q

How does hydrophobic/phillic behaviour affect proteins? (2)

A

hydrophobic parts of R groups associate together in centre of polypeptide, hydrophillic on outside;
Commonly causes twisting of the chain as often surrounded by water.

116
Q

Describe fibrous proteins (4)

A

regular repetitive amino acids;
usually insoluble;
form fibres;
tend to have structural function

117
Q

Three examples of fibrous proteins

A

collagen and elastin in connective tissue;
keratin in hair

118
Q

Describe globular proteins (4)

A

Spherical shape;
hydrophobic R groups in centre and hydrophilic on outside;
Water soluble, molecules easily cluster and bind to them;
specific shapes for roles as enzymes, hormones and haemoglobin

119
Q

State the role of collagen

A

mechanical strength

120
Q

Which tissues are made from collagen?

A

cartilage and connective tissue

121
Q

Role of collagen in bones?

A

collagen reinforced with calcium phosphate makes bones hard

122
Q

What is the role of collagen in the arteries?

A

prevent bursting under blood pressure

123
Q

Role of collagen in tendons?

A

strength allows muscles to pull on bones

124
Q

What is the role of keratin?

A

for protection, impermeable barrier to infection;
waterproof to prevent entry of water-borne pollutants

125
Q

Where is keratin found?

A

nails, hair, claws, hoofs

126
Q

Describe the role of elastin with four examples

A

cross-linking and coiling make it strong and extensible;
skin can stretch due to elastin;
allows lungs to inflate and deflate;
bladder holds urine by expanding;
helps blood vessels stretch and recoil under different pressures

127
Q

Role of elastin in blood vessels?

A

vessels can stretch and recoil under varying pressures

128
Q

Role of elastin in the lungs?

A

allows them to inflate and deflate

129
Q

What type of protein is collagen?

A

Fibrous

130
Q

What type of protein is keratin?

A

Fibrous

131
Q

Why is keratin strong?

A

Rich in cysteine, many disulphide bonds

132
Q

How does the structure of elastin help its function?

A

cross-linking and coiling makes it strong and extensible

133
Q

Describe the structure of haemoglobin (4)

A

four polypeptides (two a-globin and two B-globin);
bonds give specific shape;
Each chain has haem group with iron ion which are prosthetic groups;
conjugated protein.

134
Q

Which prosthetic group is found in haemoglobin?

A

four haem groups with iron ion

135
Q

What kind of protein is haemoglobin?

A

globular

136
Q

State the function of haemoglobin

A

Transports oxygen from lungs to tissues, binds to iron and is released when reaches the tissues

137
Q

Describe the structure of insulin

A

two polypeptide chains;
A chain begins with a-helix and B chain ends with B-pleat, joined by disulfide links;
Hydrophilic R groups on outside of molecule, soluble in water

138
Q

What type of protein is insulin?

A

globular

139
Q

What is the role of insulin?

A

Binds to glycoprotein receptors on outside of muscle and fat cells, increase uptake and consumption of glucose from the blood

140
Q

What kind of protein is pepsin and describe its structure? (4)

A

single polypeptide chain, folds into symmetrical tertiary structure;
43 acidic R groups, stable in acidic environments;
Not many normal R groups to accept H+ ions;
structure held by hydrogen bonds and disulfide bonds

141
Q

What kind of protein is pepsin?

A

globular

142
Q

State the role of pepsin

A

enzyme which digests proteins in the stomach

143
Q

How is water polar?

A

oxygen has six protons compared to hydrogens one, attracts shared electrons, pulls towards oxygen, causing hydrogen gain slightly negative charge

Biology (18 decks)

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