Biological Molecules 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
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
3
Q
How is water being liquid at room temp important? (4)
A
Habitat;
major component of organisms;
reaction medium;
transport medium
4
Q
Why is the density of water important for organisms?
A
Any less dense then organisms couldn’t float
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.
6
Q
What happens to density of water when it freezes?
A
gets less dense due to polarity
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
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
9
Q
What is cohesion?
A
Forces of attraction between water molecules due to hydrogen bonds holding them together
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
11
Q
How is cohesion useful?
A
columns of water in plants pulled up as a chain from the roots
12
Q
How is surface tension useful?
A
Some insects can walk on water
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.
14
Q
Why is the specific heat capacity of water high?
A
need lots kinetic energy to break hydrogen bonds between molecules
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
16
Q
Why is the latent heat of vaporisation of water high?
A
need lots kinetic energy to break hydrogen bonds
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
18
Q
What is a hydrolysis reaction?
A
molecules broken apart by adding molecule of water
19
Q
What is a condensation reaction?
A
molecules joined together by the removal of water molecules
20
Q
What is a hydrogen bond?
A
Weak bond created when slightly negative ion attracted to slightly positive hydrogen ion
21
Q
Name three functions of carbohydrates and example
A
Source of energy, store of energy and structural units
22
Q
Give two examples of carbohydrate energy stores
A
starch and glycogen
23
Q
Give an example of a carbohydrate energy source
A
glucose
24
Q
Give two examples of carbohydrate structural units
A
cellulose and chitin
25
State the physical properties of monosaccharide
sweet-tasting sugars
soluble in water
solid at room temperature
26
What bonds are common in monosaccharides?
large number of carbon-hydrogen bonds
27
When are monosaccharides soluble?
in water, not in non-polar solvents
28
Structure of monosaccharides
Backbone of carbon atoms, one double bond to oxygen (carbonyl group), found in chain/cyclic form
29
Hexose and pentose sugars have how many carbons?
6 and 5
30
Describe structure of the isomers of glucose (3)
a-glucose, OH group beneath the ring;
B-glucose, OH group above the ring;
both hexose
31
32
Two physical properties of disaccharides
sweet and soluble in water
33
What are the three most common disaccharides?
maltose, sucrose and lactose
34
which monomers make maltose?
a-glucose + a-glucose
35
Which monomers make up sucrose?
a-glucose + fructose
36
Which monomers make up lactose?
B-galactose + a-glucose
37
Which monomers make up cellobiose?
B-glucose + B-glucose
38
How are monosaccharides bonded together?
By glycosidic bond
39
What is the role of a-glucose?
energy source;
component of starch and glycogen
40
What is the role of B-glucose?
energy source;
component of cellulose
41
What is the role of ribose?
component of RNA, ATP and NAD
42
What is the role of deoxyribose?
component of DNA
43
How does the structure of deoxyribose differ from ribose?
Bottom right, deoxyribose has H instead of OH
44
Name for polysaccharide made of same and different monomers
same: homopolysaccharide,
different: heteropolysaccharide
45
Give an example of a homopolysaccharide
starch
46
What is a homopolysaccharide?
a polysaccharide made up of one type of monosaccharide
47
What is a heteropolysaccharide?
a polysaccharide made up of different monosaccharides
48
Four reasons polysaccharides are good energy stores
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
49
Why are branched chains better energy stores?
more compact, lots energy can be released quickly
50
Name the enzyme used to hydrolyse 1-6 glycosidic bonds
glucosidase
51
Name the enzyme used to hydrolyse 1-4 glycosidic bonds
amylase
52
Explain what a 1-4 or 1-6 glycosidic bond means
Bond between carbon 1 of one molecule and carbon 4 or 6 of another
53
Why is it important for energy stores to be insoluble?
If sugar dissolves in tissues, water potential reduces and water disrupts functioning of the cells
54
Why are polysaccharides less soluble in water?
Size;
Regions which could hydrogen bond with water hidden within molecule;
Amylose forms double helix, hydrophobic exterior
55
How does structure of amylose make it insoluble?
double helix, has hydrophobic exterior
56
Describe the structure of amylose (3)
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
57
Where are amylose and amylopectin found?
in plants
58
Describe the structure of amylopectin (2)
1-4 bonds but also branches joined by 1-6 bonds;
Coils into spiral with branches emerging
59
Describe the structure of glycogen (3)
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
State three physical features of cellulose
Tough=, Insoluble, Fibrous
61
What is cellulose made of?
long chains B-glucose molecules
62
Describe the structure of cellulose (4)
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
How do cellulose chains form cell wall (4)
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
What is the role of the cell wall? (4)
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
How is the structure of the cell wall useful?
glycosidic and hydrogen bonds make it strong and difficult to digest,
macrofibrils criss-cross for strength
66
How can the macrofibril cell wall be reinforced? (3)
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
Describe the structure of bacterial cell walls (2)
Long polysaccharide chains lying in parallel;
cross-linked by short peptide chains
68
What are bacterial cell walls made of?
peptidoglycan
69
Describe structure of exoskeletons
made of chitin, forms cross-links between long parallel chains of acetylglucosamine
70
How does chitin differ to cellulose?
acetylamino group on carbon 2
71
What type of molecules are lipids?
macromolecules
72
What are the three most important lipids in organisms
triglycerides, phospholipids and steroids
73
Describe the structure of glycerol
three carbon, bonded to hydrogen and three OH groups
74
Describe the structure of fatty acids
-COOH group on one end attached to hydrocarbon tail
75
What does saturated mean?
no C=C bonds
76
What does monounsaturated mean?
one C=C bond
77
What does polyunsaturated mean?
more than one C=C bond
78
How does a C=C bond affect a fatty acid?
Creates a kink in chain at double bond;
pushes molecule apart, more fluid, lower melting point.
79
Fatty acids in animals are usually...?
saturated
80
The melting point in saturated fatty acids is...?
higher
81
Fatty acids in animals are usually ________ which means the melting point is ________ and they are usually ________ at room temperature
saturated; high
82
At room temperature, saturated fatty acids are usually...?
solid
83
What is the structure of triglycerides?
three fatty acids ester bonded by -COOH groups to a glyceride molecule
84
State five functions of triglycerides
Energy source;
energy store;
insulation;
buoyancy;
protection
85
How do triglycerides function as an energy source? (3)
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
How are triglycerides effective as energy stores?
Insoluble in water;
release twice as much energy as glucose
87
Why do triglycerides release more energy than glucose?
Have higher proportion of hydrogen atoms and almost no oxygen
88
How do triglycerides act as insulation? (3)
Adipose cells beneath skin acts as heat insulator;
lipid in nerve cells acts as electrical insulator;
animals preparing to hibernate store extra fat
89
Describe the structure of phospholipids
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
How do triglycerides provide buoyancy?
Fat less dense than water, used help organisms stay afloat
91
How do phospholipids respond to water and why? (3)
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
what is a micelle?
ball of phospholipids in water with tails hidden inside
93
Describe the structure of a phospholipid bilayer
double layer of phospholipids forms with tails hidden within.
94
What are two important features of the phospholipid bilayer?
Phospholipids free to move;
hydrophobic tails provide stability;
selectively permeable, only small non-polar molecules pass through, controls what enters and leaves cell.
95
What does selectively permeable mean?
only allows small non-polar molecules to pass through, controls what enters and leaves the cell
96
Where is cholesterol made?
liver
97
What type of molecule is cholesterol?
steroid alcohol (sterol), not made from glycerol or fatty acids, hydrophobic
98
What is the role of cholesterol?
regulates the fluidity of the membrane
99
Name the cholesterol derivative found in animals
stigmasterol
100
Name three steroid hormones made from cholesterol
testosterone, oestrogen and vitamin D
101
Give one property of steroid hormones
small and hydrophobic to pass through cell membrane
102
When happens to plant steroids when ingested?
converted to animal hormones
103
Describe the structure of proteins (3)
Large polymers of amino acids;
one or more chains;
adopt specific shapes
104
What is the role of proteins?
form structural components, used in membranes for transport, enzymes
105
How do plants get amino acids?
plants can make all of them if have access to fixed nitrogen (nitrate)
106
Describe the structure of amino acids
carbon atom bonded to a hydrogen, NH2 (amino) group, -COOH group and an R group which differs between molecules
107
How are amino acids bonded together?
covalent peptide bonds
108
How does a peptide bond form?
-COOH group and NH2 group of amino acids bonds covalently C-N
109
What is the primary structure of a protein?
Sequence of amino acids, determines the function of protein.
110
What is the secondary structure of a protein? (4)
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
What is the tertiary structure of a protein? (3)
specific structure;
held by many bonds between amino acids;
May adopt supercoiled shape or spherical shape
112
What is the quaternary structure of a protein?
More than one polypeptide chain, quaternary structure make complete molecule;
same bonds as tertiary structure (various types) to hold together
113
How do ionic bonds form within protein structure?
Form between carboxyl (-COOH) and amino (NH2) groups forming NH3+ and COO- ions
114
How do disulphide links form within protein structure?
R groups containing sulphur (e.g. cysteine) form covalent disulphide links
115
How does hydrophobic/phillic behaviour affect proteins? (2)
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
Describe fibrous proteins (4)
regular repetitive amino acids;
usually insoluble;
form fibres;
tend to have structural function
117
Three examples of fibrous proteins
collagen and elastin in connective tissue;
keratin in hair
118
Describe globular proteins (4)
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
State the role of collagen
mechanical strength
120
Which tissues are made from collagen?
cartilage and connective tissue
121
Role of collagen in bones?
collagen reinforced with calcium phosphate makes bones hard
122
What is the role of collagen in the arteries?
prevent bursting under blood pressure
123
Role of collagen in tendons?
strength allows muscles to pull on bones
124
What is the role of keratin?
for protection, impermeable barrier to infection;
waterproof to prevent entry of water-borne pollutants
125
Where is keratin found?
nails, hair, claws, hoofs
126
Describe the role of elastin with four examples
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
Role of elastin in blood vessels?
vessels can stretch and recoil under varying pressures
128
Role of elastin in the lungs?
allows them to inflate and deflate
129
What type of protein is collagen?
Fibrous
130
What type of protein is keratin?
Fibrous
131
Why is keratin strong?
Rich in cysteine, many disulphide bonds
132
How does the structure of elastin help its function?
cross-linking and coiling makes it strong and extensible
133
Describe the structure of haemoglobin (4)
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
Which prosthetic group is found in haemoglobin?
four haem groups with iron ion
135
What kind of protein is haemoglobin?
globular
136
State the function of haemoglobin
Transports oxygen from lungs to tissues, binds to iron and is released when reaches the tissues
137
Describe the structure of insulin
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
What type of protein is insulin?
globular
139
What is the role of insulin?
Binds to glycoprotein receptors on outside of muscle and fat cells, increase uptake and consumption of glucose from the blood
140
What kind of protein is pepsin and describe its structure? (4)
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
What kind of protein is pepsin?
globular
142
State the role of pepsin
enzyme which digests proteins in the stomach
143
How is water polar?
oxygen has six protons compared to hydrogens one, attracts shared electrons, pulls towards oxygen, causing hydrogen gain slightly negative charge
