Chapter 2: Biological Molecules Flashcards
1
Q
What are biological molecules?
A
They are organic substances found in living organisms. including reducing sugars, non-reducing sugars, starch, proteins and lipids.
2
Q
Hows are biological molecules identified?
A
Using chemical tests.
3
Q
What is starch?
A
Is what is produced when many glucose molecules bond by glycosidic bonds.
4
Q
What are proteins?
A
Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.
5
Q
explain how the 4 main biologicala molecules can be formed from the simple monomers.
A
- Monosaccharides link up to form polysaccharides,
- Monosaccharides make nucleotides, which can link up with organic bases to form nucleic acids.
- Amino acids link up to form proteins.
- Fatty Acids and glycerol can link up to mak lipids.
6
Q
What are macromolecules?
A
they are laWhatrge bioloigcal molecules such as a protein, polysaccharide or a nucleic acid.
7
Q
What are Polymers?
A
They are giant molecules made from many similar repeating subunits joined together in a chain; They are also sometimes referred to as macromolecules.
8
Q
What are Monomers?
A
they are relatively simpler molecules which is used as a basic building block for the synthesis of a polymer; many monomers are joined together to make the polymer, usually by condensation reactions; common examples of molecules used as monomers are monosaccharides.
9
Q
What is a Nucleotide?
A
A molecule consisting of a nitrogen containing base,a pentose sugar and a phosphate group.
10
Q
What are carbohydrates?
A
They are macromolecules consisting of carbon, hydrogen and oxygen. Cx(H2O)y where water: carbon in the ratio 2:1 and therefore is a hydrate.
11
Q
what are the three main groups of carbohydrates?
A
Monosaccharides, Disaccharides and Polysacchraides. the sacchride means sugar or swett sbstance.
12
Q
What is a monosaccharide?
A
Is a colecule consisting of a single sugar unit with the general formula (CH2O)n
13
Q
What are the main groups of monosaccharides? Give common examples.
A
- Trioses (3C)
- Pentoses (5C) e.g. Ribose and Deoxyribose.
- Hexoses (6C) e.g Glucose, Fructose, Galactose.
14
Q
describe the ring structured nature of glucose.
A
The presensce of a longer chain of carbon allows the chain to close up on it self, where C1 and C5 joinup together with Oxygen and the C6 does not participate,.
The fact that the OH can easily switch sides allows there to be an α-glucose and a ß-glucose.
15
Q
what are the roles of monosaccharides in living organisms?
A
- They can act as an energy source due to their high abundance of C-H bonds which can be broken down to release energy to make ATP using ADP and a phosphate.
- They are used as building blocks for the creation of much larger molecules like glucose, pentose or ribose. the latter can go on to make RNA and DNA.
16
Q
What is a disaccharide?
A
Is a sugar molecule consisting of two monosaccharides joined together by a glycosidic bond.
17
Q
What are the monsaccharide consitituents of the disaccharide, maltose, fructose and galactose?
A
- Maltose: Glucose + glucose
- Sucrose: Glucose + Fructose
- Lactose: Glucose + Galactose
18
Q
What is a Glycosidic bond?
A
it is a C-O-C link between two monsccharide molecules formed by a condensation reaction.
19
Q
What is the role of enzymes in condensation reactions.
A
The enzyme decides which -OH bond will participate in the formation of a glycosidic bond, which allows for the creation of a variety of molecules.
20
Q
What is Hydrolysis?
A
It is a reaction in which a complex molecule is broken down to simpler ones involving the addition of water.
21
Q
What are reducing sugars?
A
They are the sugars that can carry out reduction where they become oxidised. They include all monosaccharides and some disaccharide like maltose.
22
Q
What is benedict’s reagent?
A
It is copper(II) sulfate in an alkaline solution with a distinctive blue colour.
23
Q
What is the chemical formula for benedict’s test?
A
reducing sugar + Cu2 (blue) -> oxidised sugar + Cu2+ (red brown)
24
Q
Why is excess reagent used in benedict’s test?
A
To ensure that all sugar has reacted.
25
How can we determine the concentration of sugar using a benedict's test?
1. Using colour standards and comparing it OR
| 2. Use a colourimeter to measure the colour accurately.
26
How is benedict's test used in the test for a non reducing sugar?
- The sample is tested with benedicts test, looking for any reducing sugars.
- Then to another sample, it is hydrolysied using HCl and then neutralized with NaOH. this gives the constituent monosaccharides
- Benedicts test is repeated. positive results mean that the sugar were non reducing. a heavier result means that both types were present. should there not be any positive results, then there is no sugars in the sample whatsoever.
27
What is a polysaccharide?
It is apolymer whose subunits are monsaccharides joined together by glycosidic bonds. e.g. starch, glycogen and cellulose. e.g. Starch, glycogen and cellulose.
28
explain the storgae of glucose in animal and plants.
glucose is stored as starch in plants and as glycogen in animals because it is too reactive on its own and is likely to disrupt osmosis if left dissolved in a soltion.
29
What is amylose?
It is a polymer of α-glucose linked by 1,4 linkages forming a curving chain; aylose is a constituent of starch. It is formed by condensation reactions and forms a compact, helical structure.
30
What is amylopectin?
A polymer of α-glucose monomers linked by 1,4 and 1,6 linkages forming a branched chain; amylopectin is a constituent of starch.
31
What is the function of amylose and a in mylopectin?
They form grains which are used as storage chloroplasts, storage organs, legumes etc. these grains can be made visible by simply staining it with iodne solution and viewing it with a microscope.
32
What is glycogen?
It is a polysaccharide made of many glucose molecules linked together; that acts as a glucose store in liver and muscle cells by clumping up and forms granules.
33
Why does the iodine test work for starches?
Starch molecules form large spirals that have holes, through which an iodine molecule can fit through easily. this then forms a complex that produces a very distinctive blue-black colour.
34
How do you carry out the iodine test?
drop the iodine onto the starch.
35
What is cellulose?
It is an structually strong natural polymer used as the main structural component for plants.
36
Why is cellulose so strong?
it is made with ß-glucose molecules whic have to be successively rotated 180°. This forms hydrogen bonds, composed of small charges. this although weak,together with many bonds makes strong microfibrils which can then go on to make a very strong fibre that run in different directions, cross-linked with other molecules to further increase strength.
37
What is a hydrogen bond?
It is a relatively weak bond formed by the attraction between a group with a small positive charge on a hydrogen atom and another group carrying a small negative charge.
38
how does the cell wall give a plant structural support?
cellulose has extremely high tensile strength. which means that it does not stretch very much and therefore it gives the cell turger pressure which can make a cell rigid during osmosis. this gives structural support.
39
What is a dipole?
it is when there is an unequal distribution of electric charges in a covalent bond, where the atoms get slightly more or slightly less of its fair share of charge. They may happen to -OH, CO or NH molecules.
40
Explain how the attractions of dipole molecules can happen.
Hydrogen can form between these groups because they can attract.
41
What does polar mean?
it means that the molecule contains a dipole group which allows it to be hydrophilic and water soluble.
42
What does non polar mean?
It means that it has no dipole groups which makes it hydrophobic, and therefore water hating, and therefore has uses for making cell membranes.
43
What are lipids?
they are a group of chemicals that are all insoluble in water. e.g. fats and oils
44
what are true lipids?
true lipids are esters formed by a fatty acid combining with an alcohol.
45
what is a fatty acid?
it a molecule that has an acid head followed by a hydrocarbon tail.
46
What are unsaturated fats?
They are fats that have carbon double bonds with lesser number of hydrogen atoms. They are usually found in plants as oils. they are easily melted.
47
What are the two forms that an unsaturated fat can be present?
1. Polysaturates: they have more than one C=C bond.
| 2. Monounsaturates: they have only 1 C=C bond.
48
What is a saturated fat?
it is a fat that has no C=C double bonds and the maximum number of Hydrogen possible. these are mainly found in animal lipids and are much harder to melt.
49
What is an alcohol?
It is an organic molecule with a hydroxyl group (-OH).
50
What is an ester?
it a sweet smelling substance formed by the reaction of an alcohol and an acid, by forming an ester bon/ester linkage. it is a condesation reaction where water is formed and can be reversed by hydrolysis.
51
What is a triglyceride?
It is a lipid whose molecules are made up of a glycerol molecule and that three fatty acids.
52
describe the solubility of triglycerides and explain whyit is that way.
It is insoluble in water, as it does not have anyolairty and does not dissolve,
It is soluble in certain organic solvents like ether, chloroform or ethanol etc. that have very small polarities and can induce a polarity onto the triglyceride.
53
What are the roles of triglycerides?
1. It has a high calorific value: it will make more CH bonds, so it works wall as an energy source.
2. it acts as a metabolic store for water because its bonds can be oxidised to give water, which is useful in harsh conditions like the deserts.
54
What are phospholipids?
They are substances whose molecules are made up of a glycerol molecule two fatty acids and a phosphate group; a bilayer of phospholipids forms the basic structure of cell membranes.
55
Describe the solubilities of phospholipids.
they can dissolve in water as it is polar, although the tails still remain hydrophobic.
56
describe how lipids can be tested for.
1. The sample is first dissolved in absolute ethanol.
2. Then the ethanol is poured into water. the ethanol dissolves in the water.
3. if there were lipids in there it would form an emulsion as the lipids will not be able to dissolve into the water.
57
List out a few reasons why proteins are essential.
1. Enzymes
2. Essential components of the cell membrane
3. Hormones
4. Heamoglobin and Myglobin
5. Collagen in skin and arteries
6. Keratin in hair, nails and skin surfaces,
7. Actin and myosin in muscle contraction.
58
What are proteins made of?
Amino acids.
59
Explain what an amino acid is.
It is a molecule formed when an amine group (-NH2) links with a carboxylic acid group (-COOH). the thrid bond is always a hydrogen bond. the 4th bond is linked to any possible R-group.
60
What is a peptide bond?
It is a C-N link between two amino acid molecules formed by a condensation reaction.
61
What is a polypeptide?
It is a long chain of amino acids formed by condensation reactions between the individual amino acids; proteins are made of one or more polypeptide bonds.
62
What happens to polypeptides in the stomach and small intestine?
They get hydrolyzed to form amino acids that can get absorbed into the blood.
63
what happens to amino acids in the ribosomes?
they can get linked up to form polypeptides.
64
what is the meaning of 'primary structure' of a polypeptide?
it is the sequence of amino acids in a polypeptide or protein.
65
what happens if you change the an amino acid in a primary structure?
it ay cause a majot chnage in the properties of the polypeptide or protein.
66
What is an α-helix structure?
It is a helical structure formed by a polypeptide chain, held in place by hydrogen bonds; an α-helix structure is an example of a secondary structure in a protein.
67
What is a secondary structure?
it is the structure of a protein molecule resulting from the regular coiling or folding of the chain of amino acids, e.g. a α- helix or a ß-pleated sheet.
68
Why do secondary structures occur in proteins?
The polar characteristics of the -CO- and the -NH- groups cause hydrogen bonds that give the primary structures a shape.
69
what is a ß-pleated sheet?
It is a loose, sheet-like structure formed by hydrogen bonding between parallel polypeptide chains; ß-pleated sheet is an example of secondary structures.
70
what are the two factors that Hydrogen bonds are vulnerable to?
1. High temperatures
2. High pH
[this is why enzymes denature at these conditions]
71
what is a tertiary structure?
It is the compact structure of a protein molecule resulting from the three-dimensional coiling of the already folded chain of amino acids.
72
Name the 4 tertiary structure bonds.
1. Hydrogen bonds: by strongly polar groups like -OH-, -CO- and OH-
2. Disulfide bonds: between cystein molecules. they are stong covalent bonds and are oxidized to form. it is S-H-H-S -> S-S
3. Ionic bonds: it is between ionized amine and ionized COO-. it can be broken down by pH. NH3+ and COO-
4. Weakly hydrophobic bonds: caused by the collective repulsion from water of the non-polar R groups of proteins.
73
What is the Quaternary structure?
It is the three dimensional arrangement f two or more polypeptides, or of a polypeptide and a non protein component such as haem in a protein.
74
What is a globular protein?
It is a protein whose molecules are folded into a relatively spherical shape and which is often water - soluble and metabolically active. e.g. insulin and hemoglobin.
75
Explain why globular proteins are soluble.
Outside the spherical structure is a the hydrophilic R-groups while inside the the structure is the hydrophobic R-groups. it is therefore soluble.
76
What is a fibrous protein?
It is a protein whose molecules have a generally long, thin structure that is generally insoluble and metabolically inactive and whose function is usually structural. E.g Keratin for nails and hair and collagen in the skin.
77
What is Haemoglobin?
The red pigment found in red blood cells, whose molecules contain four iron atoms within a globular protein made up of four polypeptides and that combines reversibly with oxygen.
78
What is Globin?
It is a protein whose molecules are folded into a relatively spherical shape and which is often water-soluble and metabolically active. e.g insulin and haemoglobin.
79
What happens to RBC's in sickle cell anemia?
An amino acid on the outside is replaced. Glutamic is replaced with Valine, which is non-polar , making it much less soluble.
80
What is a prosthetic group?
It is a non-protein component that is attached to a protein to form a complex molecule; it aids the protein in its function; an example is the iron-containing heam group, which is attached to α-globin and ß-globin to form heamoglobin.
81
how does heamoglobin function
The hemoglobin molecule can carry 4 oxygen atoms and becomes red. it will become purplish if the Oxygen is lost.
82
What is the biuret test?
It is a test for the presence of amine groups and thus for the presence of proteins; biuret reagent is added to the unknown substance and a change from pale blue to purple indicates the presence of a protein.
83
What is Biuret reagent?
potassium hydroxide or sodium hydroxide mixed with cupper (II) sulfate.
when it is ready made, sodium potassium tartrate or sodium citrate is added to prevent the copper hydroxide precipitate from forming.
84
Why does the biuret test work?
When a Na atom comes with a Cu2- atom it becomes purple.
85
Whats is collagen?
It is a common, insoluble fibrous protein that is present in skins, tendons, cartillage, bones, teeth and blood vessels. it is present is all for structural purposes, making up up to 25% of the proteins.
86
Explain the compostion of a collagen strand.
It is a triple helix with 3 polypeptide chains which is held together by hydrogen and covalent bond. every 3rd amino acid is glycine.
87
What is a collagen fibril?
It is a covalent bonding of R-groups to lay side by side forming cross links
88
What is a collagen fibre?
it is when strong bundles are formed by fibres lining up side by side.
89
what is the main feature of collagen?
It is very tensile. this tensile arrangement is arrangeed in different ways as it is needed. for example, in tendons, it is arrange straight and parralled to stretch upward bt in skin it is arranged randomly to stretch in all directions.
90
Why is it so hard to make water a gas?
the strong hydrogen bonds require large amounts of energy to be broken
91
describe water's role as a solvent.
Water is attracted to ions/polar molecules which collect and separate, ionizing the particles, which allows them to go on and react in metabolic reactions.
however in hydrophobic/non-polar molecules, the ions are pushed together as water molecules are attracted to themselves.
92
What is water's role as a transport medium.
As a solvent, it can transport particles in flood, lymphatic and excretory and digestive systems.
93
Describe te high specific heat capacity of water and its biological consequences.
The specific heat capacity is the heat energy required to raise the temperature of 1 kg of water by 1°C.
Water has a high specific heat capacity because it takes a lot of energy to break the hydrogen bonds.
this means that temperatures in organisms can be maintained rather well.
it also means that temperatures at water bodies wont change as much and gives a stable habitat for aquatic life.
94
Describe the high latent heat of vaporization of water and its biological consequences.
latent heat is the heat energy required to comvertwater from a liquid form to vapor form.
the hydrogen bond are strong and so water has a high specific latent heat.
therefore when vaporized lots of energy is taken from the surrounding it, thereby cooling it.
this allows animals to sweat to cool and for plants to cool by transpiration.
finally, it also means that it is unlikely to freeze and so is also good for aquatic life in water bodies.
95
Describe water's density and freezing properties. what is the biological consequence of this?
When water freezes, the ice becomes less dense than the water. thus is floats and it melts, preventing water bodies from freezing.
these changes in densities and volumes means that there are currents which will cycle nutrients in the ocean.
96
Describe water's high surface tension and its cohesion and the biological consequence of this.
cohesion is when the water molecules stick together.
This allows water to move in long unbroken columns in vascular bundles.
high cohesion means that there is a high surface tension. small insects can exploit this to skate on the water itself.
97
Describe water's role as a reagent.
1. Photosynthesis: The hydrogen in the waters is removed using the energy taken in by chlorophyll from sunlight and is used to make glucose, which is an energy store.
2. water is used in digestion in hydrolysis to break down large molecules.
