Biological Molecules Flashcards
Monomer
single units of a biological molecules - can be joined via condensation reactions
Polymer
result of many monomers joined together - can be hydrolysed
What are the monomers and polymers of proteins
Amino acids
Polypeptides and protein
Which elements make up proteins
C, H, O, N, S
Amino acid structure
All are made of a carboxyl group (-COOH) and an amino group (-NH2) attached to a carbon atom. A Hydrogen molecule is also attached to the central C.
The difference between different amino acids is the variable group (R).
All amino acids contain C,O,H,N and 3 contain S.
Dipeptide vs polypeptide
Dipeptide is formed when 2 amino acids join together
Polypeptide is formed when mored than 2 amino acids join together.
Proteins are made of one or more polypeptides
Condensation reaction (protein)
Joins amino acids by forming a peptide bond.
Hydrolysis reaction (amino acids)
A molecule of water is added to break the peptide bond.
Primary structure of protein
- Sequence of amino acids in the polypeptide chain.
- Different proteins have different sequences of amino acids in their p-structure.
- A change may affect the whole protein structure.
Secondary structure of protein
Hydrogen bonds form between nearby amino acids in the chain (carboxyl of one alpha and amino group of another). This makes it automatically coil into an alpha helix or fold into a beta pleated sheet
Tertiary structure of protein
Overall 3D shape (globular)
More bonds form between different parts of the polypeptide chain
- Disulphide
- Ionic
- Hydrogen
- Hydrophobic/hydrophilic interactions
Ionic bonds (tertiary)
Attractions between negatively charged R-groups and positively charged R-groups on different parts of the molecule.
Hydrogen bonds (tertiary)
Weak bonds between slightly positively charged hydrogen ions in some R groups and slightly negatively charged atoms in other R groups on the polypeptide chain
Disulphide bonds (tertiary)
between any R group containing sulphur
Hydrophobic/hydrophilic interactions
Hydrophobic R groups fold inwards to protect itself from water, hydrophilic stays on outside.
Hydrophobic R groups clump close together in the protein
Quaternary structure of protein
Any protein made of more than 1 polypeptide chain. Joined by R group bonds as an R group
Conjugated protein (e.g. haemoglobin)
Fibrous protein properties
- Long, narrow
- Structural role (strength, support)
- (Generally) insoluble in water
- Repetitive amino acid sequence
- Less sensitive to changes in heat, pH, etc
- E.g. Collagen, myosin, fibrin, actin, keratin, elastin
Globular protein properties
- Rounded/spherical
- Functional role (catalytic, transport, etc)
- (Generally) soluble in water
- Irregular amino acid sequence
- More sensitive to changes in heat, pH, etc
- E.g. Catalase, haemoglobin, insulin, immunoglobin
Haemoglobin
- Globular protein that carries oxygen around the body in red blood cells.
- Conjugated protein as it has a non-protein group attached. This is called a prosthetic group.
- Each of the four polypeptide chains has a prosthetic group called haem. A haem group contains iron, which oxygen binds to.
Insulin
- Hormone secreted by the pancreas.
- Helps to regulate blood glucose levels.
- Soluble so it can be transported in the blood to the tissues were acts.
- Consists of two polypeptide chains, how together by disulphide bonds
Amylase
- Enzyme that catalyses the breakdown of starch in the digestive system.
- Made of a single chain of amino acids.
- Secondary structure contains both alpha helix and beta pleated sheet sections.
- Most enzymes are globular proteins
Collagen
- Found in animal connective tissues, such as bone skin and muscle.
- Very strong
- Minerals can bind to the protein to increase its rigidity
Keratin
Found in many external structures of animals, such as skin, hair, nails, feathers and horns. Can be flexible or hard and tough
Elastin
Found in elastic connective tissue, such as skin, large blood vessels and some ligaments. Elastic so it allows tissues to return to the original shape after stretching
Which elements make up carbohydrates
C, H, O
For every carbon atom, there is normally 2 hydrogen atoms and 1 oxygen atom
What are the monomers and polymers of carbohydrate
Monosaccharides (e.g. glucose)
Polysaccharides (e.g. starch)
Functions of carbohydrates
- Substrate for respiration - glucose
- Hereditary info - pentose sugar (deoxyribose)
- Energy stores - starch, glycogen
- Structural - cellulose, chitin in arthropod exoskeletons and fungal walls
- Recognition of molecules outside a cell (e.g. attached to proteins/lipids on cell surface membrane)
Properties of monosaccharides
- Good source of energy as there are lots of C-H chemical bonds (energy released when broken)
- Sweet
- Small so easily transported in/out of cells
- Soluble so easily transported around the body
- Can be straight chain or ring/cyclic forms
Examples of monosaccharides (LEARN STRUCTURE)
Alpha-glucose - hexose monosaccharide (6 carbons)
Beta-glucose - hexose monosaccharide (6 carbons)
Ribose - pentose monosaccharide (5 carbons)
Deoxyribose - pentose monosaccharide (5 carbons)
What is the structural difference between an alpha and beta glucose molecule
H and OH swaps position on carbon 1
(Isomer - same chemical formula, but different structural arrangement )
What is the structural difference between a ribose and deoxyribose
Deoxyribose loses an oxygen on carbon 2
3
4
5
6 Carbons
triose
tetrose
pentose
hexose
Condensation reaction (carbohydrates)
Monosaccharides are joined together by glycosidic bonds to form disaccharides.
During synthesis, a hydrogen atom on one monosaccharide bonds to a hydroxyl (OH) group on the other, releasing a molecule of water.
Hydrolysis reaction (carbohydrates)
A molecule of water reacts with the glycosidic bond, breaking the disaccharide apart (into monosaccharides)
What is a glycosidic bond
C - O - C
A covalent bond formed between 2 monosaccharides by a condensation reaction. They are named according to which carbons they are linked to.
Disaccharide examples
2 alpha-glucose molecules = maltose
alpha glucose + fructose = sucrose
alpha glucose/beta glucose + galactose = lactose
How are polysaccharides formed + example
More than two monosaccharides join together.
E.g. Lots of alpha glucose molecules are joined together by glycosidic bonds to form amylose
Starch is made up of
straight chained a-amylose and branched chained amylopectin
Amylose is made of
a-glucose molecules (1-4 glycosidic bond) (monomer)
Amylopectin structure
- monomer A-glucose
1,4 AND 1,6 glycosidic bonds
Why is starch a good storage molecule
- Compact - high energy content per mass - energy dense
- Starch is essentially chains of glucose. Glucose monomers can be easily be snipped off by hydrolysis to be used in respiration
- Amylopectin is branched. Branched molecules are more compact and have more free ends. More glucose can be hydrolysed at the same time when lots of energy is required quickly
- Large molecules cannot diffuse out of the cell
- Insoluble - does not affect water potential/the osmotic balance of the cell
Why does amylopectin release more energy
Branches of a-1,6 glycosidic bonds in amylopectin causes the molecule to be branched. The branches creates more free ends. Enzymes hydrolyse the monomer off the free ends. This means a branched molecule can have more monomers hydrolysed more quickly. These monomers can be used in respiration.
Glycogen main role
an energy store in animals (liver and muscle cells)
Glycogen structure
Glycogen is almost identical to amylopectin in that it has 1,4 and 1,6 glycosidic bonds and contains H-bonds to hold it in place.
However, there are more branches (and the branches are shorter). This allows faster breakdown of the molecules during respiration as it means these are more ends which enzymes can start the process if hydrolysis from.
Cellulose
Cellulose is made up of B-glucose molecules. Each alternate glucose molecule flips 180 to allow the bonding of the hydroxyl groups.
A B-1,4 glycosidic bond forms.
This means that the CH20H alcohol group of every other molecule is above the carbon ring and the others are below
Why is cellulose so strong
- Chains run in straight lines parallel to each other.
- H bonds form within the chain. This stops chain spiralling - keeps it a straight chain
- H bonds also form between chains to increase strength
- 60-70 cellulose chains make a microfibril. Up to 400 microfibril are held together by hydrogen bonds to make a macrofibril
- Macrofibril criss-cross to increase strength. Pectin acts like a glue, holding the criss-cross together.
- Any space amongst the macrofibril allows water and ions to be transported in/out of cells.
Which elements make up lipids
C, H, O
Which elements make up nucleic acids
C, H, O, N, P
