Topic 1: Biological Molecules Flashcards
(105 cards)
1
Q
Monomers
A
Small, basic molecular units that can form a polymer (e.g. monosaccharides, amino acids and nucleotides).
2
Q
Polymers
A
Large, complex molecules composed of long chains of monomers joint together.
3
Q
Condensation reaction
A
Forms a chemical bond between monomers, releasing a molecule of water.
4
Q
Hydrolysis reaction
A
Breaks the chemical bond between monomers using a water molecule.
5
Q
Hydrogen bond
A
Weak bonds between a slightly positively charged hydrogen atom in one molecule and a slightly negatively shared atom in another molecule.
6
Q
80%
A
What percentage of a cell’s contents does water make up?
7
Q
Metabolite
A
A substance formed in or used by metabolism.
8
Q
Metabolism
A
The chemical processes that occur within a living organism in order to maintain life.
9
Q
Metabolic rate
A
A reaction involved in metabolism.
10
Q
Polar covalent bond
A
A covalent bond in which the atoms have an unequal attraction for electrons, and so the sharing is unequal.
11
Q
Specific heat capacity
A
The energy required to raise the temperature of 1 gram of a substance by 1°C.
12
Q
Latent heat of vaporisation
A
The thermal energy required for a liquid to vaporise to a gas or the amount that is released when a gas condenses to a liquid.
13
Q
δ
A
Slightly
14
Q
Bipolar molecule
A
A molecule which has a slightly negative charge at one end and a slghtly positive charge at the other.
15
Q
Cohesion
A
The attraction between molecules of the same type
16
Q
Sugar
A
A general term for monosaccharides and disaccharides.
17
Q
Monosaccharides
A
The simplest sugars and the building blocks of carbohydrates
18
Q
Carbon, hydrogen and oxygen
A
What elements do all carbohydrates contain?
19
Q
Hexose sugar
A
A monosaccharide with six carbon atoms in each molecule (e.g. glucose)
20
Q
Isomers
A
Molecules with the same molecular formula as each other, but with the atoms connected in a different way (different structures).
21
Q
Hydroxyl group
A
-OH group
22
Q
Disaccharide
A
Formed when two monosaccharides join together (in a condensation reaction).
23
Q
Glycosidic bond
A
The bond that forms in a condensation reaction.
24
Q
Maltose
A
A disaccharide formed by two α−glucose molecules joining together by a glycosidic bond (in a condensation reaction).
25
Sucrose
A disaccharide formed by a glucose molecule and a fructose molecule joined together by a glycosidic bond (in a condensation reaction).
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Lactose
A disaccharide formed by a glucose molecule and a galactose molecule joined together by a glycosidic bond (in a condensation reaction).
27
Reducing sugars
Includes all monosaccharides and some disaccharides.
28
Add Benedict's reagent (blue) to a sample and heat it in a water bath that’s been brought to the boil. If the test's positive it will form a coloured precipitate - solid particles suspended in the solution.
Test for reducing sugars
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Blue (none), green (very low conc.), yellow (low conc.), orange (medium conc.), red (high conc.)
What are the colours formed in the reducing sugars test?
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1. Do Benedict's test and it should stay blue/negative.
2. (with a fresh sample) Boil with acid then neutralise with alkali.
3. Heat with Benedict's reagent and if the test's positive it will form a coloured precipitate - solid particles suspended in the solution.
Test for non-reducing sugars
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Carbohydrates
What are polysaccharides?
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Large numbers of monomers (monosaccharides) bonded together in a condensation reaction
What are polysaccharide molecules made from?
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Quantitative
Numerical results, this data is objective (not effected by personal opinion).
34
Qualitative
Non-numerical results, this data tends to be subjective (affected by personal opinion).
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Semi-quantitative
Results that give some idea about quantities but aren’t very precise.
36
Polysaccharide made of α−glucose monomers bonded together.
What are starch and glycogen?
37
Add iodine in potassium iodide solution (yellow/orange at start).
Positive result: goes blue-black.
What is the test for starch?
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Only in animals
Where is starch found?
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Only in animals
Where is glycogen found?
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Helical - compact.
Polymer of glucose - provides glucose to be respired for energy release.
Insoluble in water - osmotically inactive (doesn’t affect osmosis).
Branched - more ends so faster hydrolysis for glucose release.
Large molecule - cannot escape from cell across cell-surface membrane.
What are the structures and functions of starch and glycogen in cells?
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Soluble
Is glucose soluble or insoluble in water?
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Insoluble
Is glycogen soluble or insoluble in water?
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More ends can be acted on simultaneously by enzymes. It is therefore more rapidly blocked down to form glucose monomers, which are used in respiration. This is important to animals which have a higher metabolic rate and therefore respiratory rate than plants because they are more active.
Why is glycogen more branched than starch?
44
In plants. It makes up the cell walls and makes it string and stops the cell from bursting due to osmotic pressure.
Where is cellulose found?
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A long, straight and unbranched chain of β-glucose monomers joined to each other by glycosidic bonds.
What is a cellulose molecule?
46
Hydrogen bonds
What are cellulose molecules joined to get her by?
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Microfibrils (which provide rigidity/strength to the cell)
What do cellulose molecules joined together by hydrogen bonds form?
48
β-glucose monomers are used rather than α-glucose monomers.
β-glucose monomers are alternately flipped over with respect to each other.
Why are cellulose molecules straight rather than helical?
49
Strong
Hydrogen bonds are individually weak, but are many of them together in a network strong or weak?
50
Starch/glycogen contains alpha glucose; Cellulose contains beta glucose.
Starch/glycogen is helical/coiled; cellulose is straight.
Starch/glycogen is branch; cellulose is unbranched.
Starch/glycogen can’t form microfibrils; cellulose can for microfibrils.
All of the glucose monomers in starch/glycogen are the same way up; the glucose monomers in cellulose are alternately flipped over with respect to each other.
Describe four ways in which the structure of starch/glycogen is different from the structure of cellulose.
51
Cellulose molecules are straight which allows them sit sit parallel to each other and make a strong network of many hydrogen bonds.
Why can cellulose form microfibrils?
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Both are polysaccharide made up of glucose monomers.
Both contain glycosidic bonds (between monomers).
Both contain carbon, hydrogen and oxygen.
Describe three ways in which the structure of cellulose is similar to the structure of starch.
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Long/straight/unbranched chains (of glucose);
(joined to each other by) hydrogen bonds;
Form microfibrils;
Provide rigidity/strength/support.
The structure of cellulose is related to its role in plant cell walls. Explain how.
54
Lipids
What is the cell-surface membrane in cells and membranes around organelles made up of?
55
The flexibility for membranes and the transfer of lipid-soluble substances across them.
What does the phospholipids in cell membranes contribute to the cells?
56
Energy store, waterproofing, insulation, protection.
What are the roles of lipids?
57
When oxidised (reacted with oxygen), lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water.
Explain why lipids are a good energy store.
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Lipids are insoluble in water and therefore useful as a waterproofing. Both plants and insects have want, lipid cuticles that conserve water, while mammals produce an oil secretion from the sebaceous glands in the skin.
Explain how lipids are used in waterproofing.
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Fats are slow conductors if heat and when stored beneath the body surface help to retain body heat. They also act as electrical insulators in the myelin sheath around nerve cells.
Explain how lipids are used as insulation.
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Fat is often stored around delicate organs, such as the kidney.
Explain how lipids are used for protection.
61
Add ethanol then add water and shake.
Positive result: white/milky emulsion.
What is the test for lipids?
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Lipids are insoluble in water, so when water is added and shaken, the lipids (which are dissolved in the ethanol) collect together to form an emulsion of lips droplets in the water.
How does the emulsion test for lipids work?
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The condensation of one molecule of glycerol and three molecules of fatty acid. The condensation reaction between glycerol and each fatty acid (RCOOH) forms an ester bond and a molecule of water is given off.
How are triglycerides formed?
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RCOOH
What is the general formula for a fatty acid?
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A carboxyl group
What does COOH represent?
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A hydrocarbon chain, consisting of only hydrogen and carbon atoms. It can vary in length and in the number of double bonds between carbon atoms.
What is the R group in fatty acids?
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Saturated fatty acids have no double bonds between carbon atoms.
Unsaturated fatty acids have at least one double bond between carbon atoms.
What is the difference between saturated and unsaturated fatty acids?
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Mono-unsaturated
Why is a fatty acid with one double bond between carbon atoms called?
69
Polyunsaturated
What is a fatty acid with more than one double bond between carbon atoms called?
70
They make the molecule bend. Therefore, they cannot be packed together so closely, making them liquids.
What do the double bonds in fatty acids cause?
71
Triglycerides and phospholipids
What are two types of lipid?
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Triglycerides
What is the main chemical that makes up fats and oils?
73
High ratio of energy-storing carbon-hydrogen bonds to carbon atoms.
Low mass to energy ratio.
Large, non-polar molecules.
High ratio of hydrogen to exogenous atoms.
What is the structure of triglycerides?
74
They are an excellent source if energy because C-H contain a large amount of chemical energy.
Explain the importance of triglycerides having a high ration of energy-storing carbon-hydrogen bonds to carbon atoms.
75
This makes them good storage molecules because lots of energy can be stored in a small volume. This is especially beneficial to animals as it reduces the mass they have to carry as they move around.
Explain the importance of triglycerides having a low mass to energy ration.
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This makes them insoluble in water. As a result their storage does not affect osmosis in cells or the water potential of them.
Explain the importance of triglycerides being large, non-polar molecules.
77
Triglycerides release water when oxidised and therefore provide an important source of water, especially for organisms living in dry deserts.
Explain the importance of triglycerides having a high ratio of hydrogen to oxygen atoms.
78
Lipids provide more energy per gram than carbohydrates when aerobically respired.
Therefore a lower mass of lipid needs to be stored relative to carbohydrate.
Lipid is therefore a lighter energy storage product - major advantage if an organism (or see) needs to move around.
Why do organisms that move (e.g. animals) and parts of organisms that move (e.g.some plant seeds) use lipids rather than carbohydrates as an energy store?
79
Fish need to be flexible to swim. Fat, which is solid, would make this difficult.
Fish oils are rich in polyunsaturated fatty acids that keep the lipid liquid, even at the low temperatures encountered in the water.
Why do fish tend to store their lipids as oils rather than fats?
80
What is a triglyceride with 3 of the same fatty acids called?
A simple triglyceride
81
What is a triglyceride which doesn’t have 3 of the same fatty acids called?
A mixed triglyceride
82
How are phospholipids different from triglycerides?
One of the fatty acids of a triglyceride is substituted by a phosphate-containing group.
83
What elements do a phosphate group contain?
Phosphorus and oxygen
84
What is in the hydrophilic head of a phospholipid?
Glycerol, phosphate group
85
Why is the head in a phospholipid hydrophilic?
It contains polar covalent bonds and is the rife polar. This allows the head to be attracted towards water molecules.
86
Why is the head in a phospholipid hydrophobic?
It has absolutely no charge and is therefore non-polar. This means that they are repelled by water.
87
What is the phospholipid bilayer?
A double layer of phospholipids with the heads facing out towards from on either side and the tails pointing in away from the water on the inside.
88
What is a NH2 group?
Amine group
89
What is the R group in a protein?
A side chain
90
What are the 4 different types of R groups in proteins?
Non-polar, polar, negatively charged, positively charged
91
Describe how a peptide bond is formed between two amino acids to form a dipeptide. [2]
Condensation reaction;
Between amine and carboxyl
92
What is a peptide bond?
The bond that holds amino acids together. It is formed in a condensation reaction between the OH group in the carboxyl in one amino acid and a H in the amine groups in another amino acid. The result is a covalent bond between carbon and nitrogen and a water molecule is given off.
93
What are polypeptides?
Polymers formed by the condensation of many amino acids.
94
What is primary structure in a protein?
The sequence of amino acids in a polypeptide chain.
95
Describe how monomers join to form the primary structure of a protein.
Condensation reaction between amino acids;
Forming peptide bonds;
Creating a (specific) sequence/order of amino acids
96
What is secondary structure in a protein?
The folding of a polypeptide chain due to hydrogen bonding between the N-H group of one peptide bond and the C=O group of another to create a structure such as an alpha helix or beta pleated sheet.
97
The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how. [2]
Hydrogen bonds;
Between N-H (group of one amino acid) and C=O (group of another amino acid);
Forming β pleated sheets / α helix
98
What is tertiary structure?
The specific three-dimensional folding of a protein due to the relative positioning of binding between R groups, specifically hydrogen bonds, ionic bonds and disulphide bonds.
99
What is a disulphide bridge?
A covalent bond between two sulfur atoms, each on a different R group.
100
It is possible for two proteins to have the same number and type of amino acids, but different tertiary structures. Explain why. [2]
Different primary structure;
Forms ionic/hydrogen/disulphide bonds in different places.
101
What is quaternary structure?
Two or mor polypeptide chains are bonded together to make the final protein. Not every protein has quaternary structure.
102
Describe how the structure of a protein depends on the amino acids it contain. [5]
Structure is determined by (relative) position of amino acids/R groups/interactions;
Primary structure is sequence of amino acids;
Secondary structure formed by hydrogen binding (between amino acids);
Tertiary structure formed by interactions (between R groups);
Creates active site in enzymes / Creates complementary shapes in antibodies/carrier proteins/receptor (molecules);
Quaternary structure contains >1 polypeptide chain
Or
Quaternary structure formed by interactions/bonds between polypeptides.
103
What is the test for proteins? [2]
Add biuret (reagent);
(Positive result) purple/lilac/violet
104
A dipeptide consists of two amino acids joined by a peptide bond. Dipeptide may differ in the type of amino acids they contain. Describe two other ways in which all dipeptide are similar and one way in which they might differ. [3]
All contain an amine group/NH2 (at end);
All contain a carboxyl group/COOH (at end);
All contain two R groups;
All contain C, H, N and O;
The R groups may be different
105
What is the meaning of hydroxylating?
Addition of hydroxyl group
