2.2 Biological Molecules Flashcards
(145 cards)
1
Q
What are examples of molecules needed for sustaining life?
A
Water, proteins, nucleic acids, lipids, vitamins and minerals, carbohydrates.
2
Q
What is a condensation reaction?
A
A reaction that occurs when two molecules are joined together with the removal of water.
3
Q
What is a hydrolysis reaction?
A
A reaction that occurs when a molecule is split into two smaller molecules with the addition of water.
4
Q
What is a hydrogen bond?
A
A weak interaction that can occur wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom.
5
Q
What is a monomer?
A
A small molecule which binds to many other identical molecules to form a polymer.
6
Q
What is a polymer?
A
A large molecule made from many smaller molecules called monomers.
7
Q
What is one of the most important organic molecules?
A
The carbon-hydrogen bond.
8
Q
What are condensation and polymerisation reactions responsible for?
A
Linking and splitting apart biological molecules in living things.
9
Q
What is the monomer and polymer of carbohydrates?
A
Monosaccharide (e.g. glucose); polysaccharide (e.g. starch).
10
Q
What is the monomer and polymer of proteins?
A
Amino acids; polypeptides and proteins.
11
Q
What is the monomer and polymer of nucleic acids?
A
Nucleotides; DNA and RNA.
12
Q
What does water consist of?
A
Two hydrogen atoms, each covalently bonded to one oxygen atom.
13
Q
What is a polar molecule?
A
One end of the molecule is slightly positive and the other end is slightly negative.
14
Q
What are hydrogen bonds weaker than?
A
Covalent bonds.
15
Q
What does having lots of hydrogen between chains of monomers in a polymer do to a biological molecule?
A
Helps to stabilise its structure.
16
Q
What do the hydrogen bonds between water molecules do?
A
Make it difficult for them to escape to become a gas.
17
Q
Why can water flow easily.
A
It has a high viscosity despite its hydrogen bonds.
18
Q
What can water do because it’s a liquid at room temperature?
A
Provide habitats, form major component of tissues in living organisms, provide reaction medium for chemical reactions, provide effective transport medium.
19
Q
What happens to water density as temperature decreases?
A
It becomes more dense until 4 degrees Celsius where it gets less dense until 0 degrees Celsius, due to it’s polar nature.
20
Q
Why is it important that ice is less dense than water?
A
Aquatic organisms have a stable environment to live in through the winter, bodies of water are insulated against extreme cold.
21
Q
What is water good at?
A
Being a solvent for many substances found in living things.
22
Q
Why is water a good solvent?
A
It’s polar so the positive and negative parts of the water molecules cluster around the negative and positive parts of the solute. This helps to separate them causing them to dissolve.
23
Q
Why is it important that water is a good solvent?
A
Molecules and ions can move and react together in water (e.g. in cytoplasm), molecules and ions can be transported around living things.
24
Q
What is surface tension of water?
A
Water molecules at the surface are more attracted to the water molecules beneath them than the air molecules above them, so the surface of the water contracts.
25
What is cohesion of water.
Hydrogen bonds pull water molecules together so they don't spread out.
26
Why is water surface tension and cohesion important?
Columns of water in plant vascular tissue are pulled up the xylem tissue from the roots, insects like pond-skaters can walk on water.
27
What do hydrogen bonds holding water molecules together mean?
A lot of heat energy needs to be put in to increase their kinetic energy and temperature (specific heat capacity).
28
What does water's high specific heat capacity mean?
Water doesn't heat up or cool down quickly.
29
Why is it important that water has a high specific heat capacity?
Living things need a stable temperature for enzyme-controlled reactions to happen properly, aquatic organisms need a stable environment to live in.
30
What does latent heat of vaporisation help with?
Molecules breaking away from each other to become a gas, this is high in water due to lots of hydrogen bonds holding molecules together.
31
Why is it important for water to have a high latent heat of vaporisation?
Water can help to cool living things and keep their temperature stable, e.g. sweat evaporating.
32
What is a carbohydrate?
A group of molecules containing C, H and O.
33
What are the functions of carbohydrates?
A source of energy (e.g. glucose), a store of energy (e.g. starch and glycogen), structural units (cellulose and chitin).
34
What are the three main groups of carbohydrates?
Monosaccharides, disaccharides and polysaccharides.
35
Why are monosaccharides well-suited to being a source of energy?
They have a large number of carbon-hydrogen bonds.
36
What are features of sugars?
Taste sweet, soluble in water, insoluble in non-polar solvents.
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How are monosaccharides structured?
Straight chains or in ring or cyclic forms, have a single-bonded carbon atom backbone, one carbonyl group (carbon double bonded to oxygen).
38
What are the most common disaccharides?
Maltose (reducing), sucrose (non-reducing) and lactose (reducing).
39
What forms maltose?
α-glucose + α-glucose
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What forms sucrose?
α-glucose + fructose
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What forms lactose?
β-glucose + α-glucose
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What forms cellobiose?
β-glucose + β-glucose
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How is a glycosidic bond formed?
Two hydroxyl groups line up next to each other, a water molecule is removed, an oxygen atom is left to link the two monosaccharide units together, a condensation reaction.
44
How are disaccharides broken down?
Hydrolysis reaction, addition of water molecule provides hydroxyl group and hydrogen which break glycosidic bond.
45
What is the role of α-glucose in the body?
Energy source, component of starch and glycogen which act as energy stores.
46
What is the role of β-glucose?
Energy source, component of cellulose which provides structural support in plant cell walls.
47
What is the role of ribose in the body?
Component of ribonucleic acid (RNA), ATP and NAD.
48
What is the role of deoxyribose in the body?
Component of deoxyribonucleic acid (DNA).
49
What percentage of atoms in the human body are carbon?
60%
50
What percentage of atoms in the human body are hydrogen?
11%
51
What are macro-nutrients?
Main elements, ions required in large amounts in humans and plants.
52
What are micro-nutrients?
Trace elements, ions required in small amounts in humans and plants.
53
When do humans and plants have deficiency symptoms?
When not enough of a particular ion is consumed.
54
What does a deficiency in copper cause?
Young plants to die back.
55
What is the bond that forms between glycerol and a fatty acid?
An ester bond.
56
What is the molecule formed when an ester bond is made?
A water molecule.
57
What are the two variations of glycosidic bond?
1-4 and 1-6.
58
What are three molecules that are insoluble in water?
Triglyceride, phospholipid, and cholesterol.
59
What are functions of lipids?
Energy storage in adipose cells, insoluble so are transported in the blood by lipoproteins.
60
What is an unsaturated fatty acid?
A fatty acid that contains at least one double bond between two carbon atoms, so contains fewer hydrogen atoms.
61
What is the function of glucose?
To release energy to make ATP via aerobic respiration.
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What is the structure of glucose?
Small so can be transported, soluble in water, can be broken down into smaller molecules to produce ATP, lots of H atoms so can produce lots of ATP.
63
How are polysaccharides formed?
monomers of a molecule are joined by glycosidic bonds.
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Why are polysaccharides arranged in chains?
So glucose can be easily 'snipped off' when it's needed via hydrolysis reaction.
65
How are polysaccharides stored in plants?
As starch (amylose and amylopectin).
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How are polysaccharides stored in humans?
Glycogen.
67
What is the structure of amylose?
A store of energy in plants, made of alpha glucose monomers, forms an unbranched chain that coils into a spiral with H bonds holding its structure.
68
What are the pros of the structure of amylose?
Coiled shape means more can fit in a small space so it's compact, OH groups are within the coil so it's less soluble and doesn't affect the water potential of the cell.
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What is the structure of amylopectin?
Store of energy in plants, monomers of glucose bonded together with 1-4 glycosidic bond, branches formed by 1-6 glycosidic bonds.
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What are the pros of the structure of amylopectin?
Coiled and branched shape means more can fit in a small space so it's compact, OH groups are within the coil so it's less soluble, easy to remove glucose through hydrolysis.
71
What is the structure of cellulose?
Found in all plants, made of beta glucose monomers with 1-4 glycosidic bonds, every second glucose molecule is rotated 180 degrees, long straight unbranched chains, form cross-links, many hydrogen bonds.
72
What are the pros of the structure of cellulose?
Cross-links stop it spiraling, hydrogen between chains give strength and rigidity.
73
What is the structure of glycogen?
Store of energy in humans, 1-4 and 1-6 glycosidic bonds, branches formed between glucose monomers, less coils because of smaller chain length.
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What are the pros of the structure of glycogen?
OH groups make it less soluble, more branches than amylopectin so more compact and easier to hydrolyse.
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What are features of micro and macro-fibrils?
Have immense strength due to glycosidic bonds and H bonds making them good for cell walls, beta 1-4 glucose bonds make it hard to digest.
76
What are the two types of lipids?
Fatty acids and glycerol.
77
What are sources of lipids in the diet?
Any fat/oil and any fatty/oily food.
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What are the functions of lipids?
Provide source of energy, store energy, insulate, metabolic source of water, protects organs, insoluble in water.
78
What are features of lipids?
Usually contain fatty acids and glycerol, broken down by lipase, contains the element carbon, large complex molecules but not polymers.
79
How are triglycerides formed?
One glycerol and three fatty acids, also produces water, called esterification.
80
What are fatty acids made from?
A carboxylic group and a hydrocarbon tail.
81
What are the three types of fatty acids?
Saturated (no double bonds), mono-unsaturated (one double bond), poly-unsaturated (many double bonds).
82
What does more double bonds in a fatty acid mean?
More kinks so it's more likely to be fluid.
83
What are the properties of triglycerides?
Release twice as much energy as the same amount of a carbohydrate, very compact, stored in adipose tissue which insulates, far less dense than water,protects organs by surrounding them, lots of hydrogen to release lots of energy.
84
What are the properties of phospholipids?
Same structure as triglycerides but one fatty acid replaced by a phosphate group with a negative charge when in water (polar), fatty acid tails are hydrophobic (non-polar), less energy than triglycerides as they have one less fatty acid.
85
What are the properties of cholesterol?
Made from 4 carbon-based rings, comprises testosterone, oestrogen and vitamin-D, small hydrophobic molecule which sits in the middle of the phospholipid area, found in liver of animals, insoluble so good for energy storage.
86
What are the three groups in an amino acid?
Carboxylic group, R group, amine group.
87
What does the R group do?
Determines the different properties of an amino acid and represents the side chain.
88
What is the bond created when a dipeptide is formed?
A peptide bond (covalent) which can only be broken down by an enzyme (protease).
89
What are three examples of protease activity?
Digestion, hormone regulation, ageing.
90
What is the primary structure?
Sequence of amino acids in a polypeptide chain, every protein has a unique primary structure, determines the function of each protein.
91
What are the four levels of protein structure?
Primary, secondary, tertiary, quaternary.
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What do the linked amino acids that make up a polypeptide possess?
Both -NH and -C=O groups on either side of every peptide bond.
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What is the secondary structure?
The -NH and -C=O groups form hydrogen bonds which cause the peptide chains to be twisted into a 3D shape.
94
What are the two different types of secondary structures?
α helix (coils) and β pleated sheets (folded).
95
What are features of the alpha helix structure?
Right hand coil, hydrogen bonds between oxygen and hydrogen atoms, stabilises the protein.
96
What are features of the beta helix structure?
Folded up on itself forming anti-parallel chains, hydrogen bonds formed between oxygen and hydrogen atoms, stabilises the protein.
97
What is the tertiary structure?
Secondary structure twisted and folded to give complex, often unique 3D structure of each protein.
98
Which bonds maintain the tertiary structure?
Disulfide bonds, ionic bonds, hydrogen bonds, hydrophobic and hydrophilic interactions.
99
How do disulfide bonds maintain the tertiary structure?
Form between cysteine residues and help to stabilise the structure.
100
How do ionic bonds maintain the tertiary structure?
Negatively charged R groups attracted to positively charged R groups.
101
How do hydrogen bonds maintain the tertiary structure?
Slightly positively charged H atoms in some R groups bonded to slightly negatively charged O atoms in other R groups.
102
How do hydrophobic and hydrophilic interactions maintain the tertiary structure?
Hydrophobic R groups clump together, so hydrophilic R groups are pushed to the outside.
103
What is vital to each function of a protein?
Its tertiary structure (e.g. enzymes shape for active sites, hormone receptors shape for binding, collagen's shape for strength).
104
What is the quaternary structure?
Proteins made of more than one polypeptide chain.
105
What are features of the quaternary structure?
May have an inorganic component, can't function without all components.
106
What are features of globular proteins?
Ball shaped, compact, hydrophobic amino acids turn inwards and hydrophilic interactions turn outwards making them water soluble, e.g. haemoglobin, insulin, pepsin.
107
What are features of fibrous proteins?
Form fibres which give strength due to cross-links, unreactive, regular repetitive amino acid sequences which run parallel to each other, usually insoluble due to few hydrophilic gaps, e.g. collagen, keratin, elastin.
108
What is the structure, function and use of collagen?
Structure: three long chains, lots of glycine, minerals bind to proteins, Function: strong, flexible, rigid when minerals added, Use: bones, cartilage, connective tissue, artery walls, tendons.
109
What is the structure, function and use of keratin?
Structure: Lots of cysteine, number of disulfide bonds dictates flexibility, Function: can be tough or flexible, Use: hair, nails, skin, feathers.
110
What is the structure, function and use of elastin?
Structure: lots of soluble tropelastin molecules cross-linked, Function: large, strong, stable, stretch and recoil, insoluble, Use: skin, bladder, lungs.
111
What is the structure, function and use of haemoglobin?
Structure: 2 α globulin chains, 2 β globulin chains, conjugated protein, prosthetic group (haem), Function: specific shape, haem contains iron that oxygen bonds to, Use: transport.
112
What is the structure, function and use of insulin?
Structure: α helix chain and β pleated chain joined by disulfide bridges, Function: soluble in water, specific shape, Use: binds to glycoprotein receptor to increase rate of glucose uptake.
113
What is the structure, function and use of pepsin?
Structure: single polypeptide chain, symmetrical 3D structure, lots of H bonds, 2 disulfide bridges, 327 amino acids with acidic R groups, Function: specific shape, stable in stomach, Use: enzyme.
114
What do calcium ions (Ca2+) do?
Bone formation, involved in transmission of nerve impulses and release of insulin from pancreas, co-factor for many enzymes.
115
What do potassium ions (K+) do?
Important in generation of nerve impulses, muscle contraction, and regulating fluid balance in the body, activates essential enzymes in photosynthesis.
116
What do sodium ions (Na+) do?
Important in generation of nerve impulses, muscle contraction, and regulating fluid balance in the body
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What do hydrogen ions (H+) do?
Affects pH of substances, important in photosynthesis reactions.
118
What do ammonium ions ([NH4]+) do?
Important source of nitrogen used to make amino and nucleic acids.
119
What do chloride ions (Cl-) do?
Co-factor for amylase, involved in chloride shift to help maintain pH.
120
What do hydroxide ions (OH-) do?
Affects pH of a substance.
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What do nitrate ions ([NO3]-) do?
Important source of nitrogen used to make amino and nucleic acids.
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What do hydrogen carbonate ions ([HCO3]-) do?
Acts as buffer, maintains pH of blood.
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What do phosphate ions ([PO4]3-) do?
Involved in photosynthesis and respiration, needed in synthesis of many biological molecules.
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What is chromatography used for?
To separate components in a mixture, can be qualitative or quantitative.
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What is the stationary phase of chromatography?
A solid or a liquid supported on a solid, either chromatography paper or a TLC plate.
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What is the mobile phase of chromatography?
A liquid or a gas, either water (for polar molecules), or ethanol (for non-polar molecules).
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What is a TLC plate?
Thin layer chromatography plate, sheet of plastic or glass coated with silica gel of aluminium hydroxide.
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What do TLC plates and chromatography paper have in common?
Both have exposed -OH groups pointing outwards in contact with the mobile phase to make the surface very polar and allow molecules to form H bonds with it.
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How will different components move in chromatography?
At different rates, depends on solubility in the solvent and polarity.
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What will a highly polar substance do in chromatography?
Form less or no bonds and therefore move very quickly.
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How is the RF value calculated in chromatography?
Distance travelled by solute / distance travelled by solvent
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What is validity?
Whether the data answers the question being investigated?
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What things affect validity?
Control variables, sample size, starting temperature, taking accuracy into account.
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What is accuracy?
How close measurements or calculations are to the true value.
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What does the quality of results depend on?
How accurately you measure particular solutions or take down your data.
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What factors improve accuracy?
Use more intermediate values around the closest, use more sophisticated equipment to remove human error and obtain quantitative results, take samples at more regular intervals.
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What is precision?
How close the points are to each other (can be a random error).
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What factors improve precision?
Use correct apparatus and techniques, reduce error by using more sensitive equipment.
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What is a systematic error?
An error that is the same throughout the investigation.
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What is the consequence of a systematic error?
Results may still be precise, but not accurate.
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How can a systematic error be resolved?
If the cause of the systematic error is identified, repeat the experiment or use a correction factor.
142
What is a random error?
An error that occurs when the procedure is not carried out in the same way each time it is performed.
143
What is the consequence of a random error?
Some results will be affected but not all, may cause one or more anomalous result.
144
How can a random error be resolved?
Remove anomalies and repeat data to find an average.
