Biological Molecules Flashcards
1
Q
What are the 4 key elements that make up biological molecules and are essential for all products?
A
- hydrogen
- carbon
- oxygen
- nitrogen
2
Q
What is the function of magnesium in biology?
A
- constituent of chlorophyll
- essential for photosynthesis
- withinout magnesium, chlorosis occurs because the plant cannot make chlorophyll
3
Q
What is the function of iron in biology?
A
- constituent of haemoglobin
- transports oxygen inside red blood cells
- lack of iron = anaemia
4
Q
Why are phosphates important in biology?
A
- used for making nucleic acids (DNA, RNA, ATP)
- constituent in phospholipids
5
Q
Why is calcium important in biology?
A
- structural component o bones and teeth in mammals
- component in plant cell walls
6
Q
What are micronutrients?
A
Inorganic ions needed in minute (trace) amounts e.g. copper and zinc
7
Q
What are macronutrients?
A
Inorganic ions needed in small amounts e.g. magnesium, calcium, iron, phosphates
8
Q
What is polymerisation?
A
The linking together of identical monomers to form larger molecules (polymers)
9
Q
What is a condensation reaction?
A
When two monomers link together to form a polymer and a molecule of water is eliminated
10
Q
What is a hydrolysis reaction?
A
Polymers broken down to form monomers by the chemical insertion of water
11
Q
What are the main functions of carbohydrates?
A
- storage and release of energy
- cellular structures (cellulose cell walls of plant cells)
12
Q
What are the classes of carbohydrate?
A
MONOSACCHARIDE: monomers that form the building blocks for larger carbohydrates
DISACCHARIDE: two monosaccharides joined together by glycosidic bonds during a condensation reaction
POLYSACCHARIDE: large complex carbohydrates formed from very large numbers of monosaccharides joined together by glycosidic bonds
13
Q
What are the main disaccharides?
A
Maltose: 2x alpha glucose = inside seeds, important source of glucose in germination
Sucrose: glucose and fructose = transported through the phloem of all plants
Lactose: glucose and galactose = found in mammalian milk, important source of energy for their young
14
Q
What bonds form between two sugars?
A
Glycosidic bond
Forms between the carbon 1 and carbon 4 of two monosaccharides
Can be broken by the insertion of water in a hydrolysis reaction
15
Q
What are the main functions of glucose?
A
- insoluble so doesn’t affect osmosis + cannot diffuse out of the cell
- compact so can be stored in a small place in the cell
- easily hydrolysed to release the energy for respiration
16
Q
What is starch?
A
- glucose energy storage polysaccharide in plant cells
- made up of 1000s of alpha glucose monomers
- made up of two different molecules: amylose and amylopectin
17
Q
What is amylose?
A
TYPE OF STARCH
- straight chained helical polymer
- alpha 1-4 glycosidic bonds
18
Q
What is amylopectin?
A
TYPE OF STARCH
- branched polymer
- alpha 1-4 and 1-6 glycosidic bonds
- 1-6 bonds form when a branch is formed
19
Q
What is glycogen?
A
- animal glucose energy storage polysaccharide
- found in liver and muscle cells
- highly branched
- alpha 1-4 and 1-6 glycosidic bonds
20
Q
What is cellulose?
A
- polysaccharide made up of beta glucose monomers
- structural carbohydrates formed in plants
- most important component of the plant cells wall
- gives the plant cell rigidity because the cellulose cell walls is inelastic and has high tensile strength to prevent plant lysis
- every other beta glucose monomer rotates by 180 degrees to form a straight chain
- hydrogen cross link bonds form between the straight chains, which form a strong microfibril which go on to form a cellulose bundle
21
Q
What is chitin?
A
- lightweight, waterproof, very strong
- forms exoskeleton of arthropods
- muco-polysaccharide as some OH groups in the beta glucose are replaced by nitrogen containing acetylamine group
- beta glucose chains
22
Q
What makes up triglyceride?
A
- glycerol
- fatty acids
Not polymers because they aren’t made up of identical monomers
23
Q
How do fatty acids differ?
A
- length of hydrocarbon chain
- whether hydrocarbon chain is saturated
24
Q
What are saturated and unsaturated triglycerides?
A
Saturated= contains no carbon-carbon double bonds in the fatty acid chains
Unsaturated= contains at least one carbon-carbon bond in the fatty acid chains
25
How are triglycerides formed?
Three fatty acids are linked to the glycerol molecule by an ester bond following a condensation reaction
26
What are low density lipoproteins?
LDLs contain and transport saturated fats and can cause harm as fatty acids can block major artieris with plaque and cause a heart attack
Often solid at room temperature
27
What are high density lipoproteins?
HDLs contain and transport unsaturated fats and carry harmful fats away into the liver for disposal and a high proportion in the blood lowers the risk of heart disease
Often liquid
28
How can a high fat intake be dangerous?
Fat deposits called atheroma can build up inside the coronary arteries and narrow the vessel (atherosclerosis)
This can restrict blood flow to the heart and cause damage to the heart muscle resulting in angina, or if blood flow is completely blocked, a heart attack
29
What are the properties of lipids?
- insoluble in water, but soluble in organic solvents
- fats are solid at room temperature (butter, margarine)
- oils are liquid at room temperature (olive oil)
30
What are the functions of lipids?
- energy storage = release 2x more energy per gram than carbohydrates when used as alt respiratory substrates
- shock absorption to protect vital organs = laid down around delicate internal organs, protect surface cuticles of plants
- thermal insulation to reduce heat loss especially in cold aquatic mammals
- buoyancy = less dense than water so will float on the top so used in maintaining buoyancy of fish
- produce metabolic water when oxidised by respiration = helps desert animals e.g. camel (hump made of fat)
- waterproof the exoskeletons of insects and cuticles of plant leaves = waxes are hydrophobic = prevents water loss
31
What are phospholipids?
Glycerol, two fatty acids, phosphate group
Fatty acid heads = HYDROPHILIC = attracted to water
Fatty acid tails = HYDROPHOBIC = repel water
Important cell membrane component
32
How are phospholipids important in maintaining the cell membrane?
Hydrophilic heads face the water, hydrophobic tails face away from the water
Phospholipids form droplet spheres with water when mixed
33
What are amino acids?
Building blocks for proteins
Contain carbon, hydrogen, oxygen, and nitrogen
Also have a variable group which represents the rest of the molecule and determine what amino acid is present
34
What is a dipeptide and how are they made?
Two amino acids that have been combined in a condensation reaction to form peptide bonds
35
What are polypeptides?
Many amino acids joined together by peptide bonds
Polypeptides form proteins with either a primary, secondary, tertiary, or quaternary structure
36
What is the primary structure of a polypeptide?
The number and sequence of amino acids in a polypeptide chain
Responsible for the overall structure of the protein
Functional proteins have 10-100s of amino acids
37
What is the secondary structure of a protein?
Primary structure can coil to form either an alpha helix structure, or a beta pleated sheet
Alpha helix if held together by hydrogen bonds in a spiral shape
Beta pleated sheet is the flat zigzag structure
Both structures can be present in the same protein
38
What is the tertiary structure of the protein?
Secondary structure folds to form complex 3D shapes held together by bonds and interactions
Bonds:
- hydrogen bonds
- ionic bonds
- disulphide bridges
- hydrophobic R group interactions (inside protein)
-hydrophilic R group interactions (outside protein)
Hydrogen, ionic and disulphide maintain the shape of the protein
39
What is the quaternary structure of the protein?
Occurs when more than one polypeptide chain (each with tertiary structure) combine to form a larger protein complex
Same bonds as quaternary (ionic, hydrogen, disulphide and hydrophobic interactions)
Also contain non protein groups sometimes (prosthetic groups)
40
What are fibrous proteins?
Keratin and collagen (secondary proteins)
Carry out structural functions
- tough
- non-specific
- insoluble in water
- have a regular repetitive sequence of amino acids
41
What are collagen and keratin?
COLLAGEN: main component of connective tissue such as cartilage and tendons
KERATIN: main component of hard structures like hair and nails
elongated polypeptide chains with an alpha helix structure - 3x chains twist around each other an closely bind into rope like strands
42
What are globular proteins?
Tertiary or quaternary proteins
- compact and folded into spherical molecules
- specific shape
- soluble in water + have a wide range of amino acids
43
What are examples of globular proteins?
- transport proteins such as haemoglobin
- enzymes such as lipase and DNA polymerase
- hormones such as insulin
44
What is the test for proteins?
Biuret test
- add a few drops to th solution and gently shake
- if proteins are present, solution will change colour rom light blue to purple
- if no proteins are present, solution will remain blue
NO HEAT REQUIRED
45
What is the test for reducing sugars?
Benedict’s reagent
- add Benedict’s reagent to test tube with sample and boil for 5 minutes in a water bath
- if reducing sugar is present, light blue reagent will turn brick red
- if lower concentrations of reducing sugars are present, then the results at range between yellow, green, orange or brick red as the test is semi-quantitative
- if no reducing sugars present, colour will not change and will remain blue
GLUCOSE, GALACTOSE, FRUCTOSE, MALTOSE, LACTOSE
46
What is the test for non reducing sugars?
If Benedicts reagent initially yields a negative result, more testing can be done
- add HCl to the test sample and boil for 5 minutes in a water bath to hydrolyse any glycosidic bonds that are present
- add hydrogen carbonate powder (alkali) to neutralise the HCl
- add Benedict’s reagent and boil for 5 minutes in a water bath
- if non-reducing sugars are present, the light blue colour will change to brick red
- if there is no non-reducing sugar present, no colour change will be observed
NORMALLY SUCROSE
47
What is the test for starch?
Iodine solution
- if starch present, the colour will change from orange-brown to a blue-black colour
- qualitative test so accurate concentration cannot be determined
48
What is the test for lipids?
Ethanol test
- mix the test solvent with equal amounts ethanol to dissolve any lipids
- add equal volume of water and shake gently
- if lipids are preset, the lipids will form droplets and appear as a cloudy white emulsion
49
What is water?
- polar molecule, uneven distribution of charges
- oxygen end has the more -ve charge, whilst the hydrogen end has the more +ve charge
- when two water molecules are in close contact, their opposing charges attract each other and form hydrogen bonds
50
What are hydrogen bonds?
Form between opposites charged atoms in water molecules
- weak individually
- many of them will form a strong lattice
- can cause water molecules to stick together (cohesion)
51
Why does water have surface tension?
Water molecules form hydrogen bonds with other water molecules, but not with any molecules in the air
These cohesive forces produces the uneven distribution of forces called surface tension, forming a skin over the after which can support insects (e.g. pond skater) and aquatic plants (lilies)
52
Why is water the universal solvent?
Because water is a polar molecule, it will attract and dissolve other charged particles like ions and polar molecules like glucose
This means water can act as a transport medium
In animals, blood transports substances around the body
In plants, xylem vessels transport water and dissolved mineral ions
Lipids don’t dissolve in water as non polar molecules are hydrophobic
53
Why is water a metabolite?
It is a reactant in photosynthesis and hydrolysis and is also produced in respiration and condensation reactions
54
Why does water have a high specific heat capacity?
- lots of energy is required to break the hydrogen bonds to increase the temperature of water
Provides a more stable environment for aquatic organisms by preventing dramatic temperature changes of water
Allows enzymes to catalyse reactions without being denatured in the body from high temperatures
55
Why does water have a high latent heat capacity?
A lot of heat energy is required to break the hydrogen bonds and change water from a liquid to a vapour
Lots of energy is required to evaporate water from the surface of an organism to provide a cooling effect
56
Why is waters density good?
Water is less dense in its solid state (ice) than in its liquid state meaning it floats on the surface of water, providing an insulating layer to allow aquatic organisms to survive in water beneath the ice whilst providing a habitat fr other organisms above the ice
57
Why is the transparency of water good?
It allows light to pass through it to underwater aquatic plants to allow them to photosynthesise
58
Why is the transparency of water good?
It allows light to pass through it to underwater aquatic plants to allow them to photosynthesise
