Biological Molecules,, Flashcards
Basic functions of water
A reactant in a chemical reactions (hydrolysis)
Solvent
Transports substances
Habitat
Functions of water related to its structure
High specific heat capacity – hydrogen bonds between molecules can absorb a lot of energy, it takes a lot of energy to heat it up
High latent heat of vaporisation – takes a lot of energy to break the bonds between molecules, a lot of energy is used when water evaporates
Cohesive – due to polarity
Solvent – ions can be totally surrounded by water molecules (dissolved)
Less dense when solid – water molecules are held further apart in ice than liquid, useful for habitats
Structure of water
One oxygen atom and two hydrogen atoms
Water is polar The oxygen nucleus is slightly negative charged and the hydrogen nucleus is slightly positively charged
Atoms are connected by hydrogen bonds
Carbohydrate structure
Mostly polymers Made from monosaccharides
Made from carbon hydrogen and oxygen
Polymer
A molecule made from smaller molecules (monomers)
Glucose
A hexose monosaccharide
Two forms – alpha and beta
Soluble
Ribose
Pentose monosaccharide
Disaccharides and polysaccharides
Monosaccharides joined together by glycosidic bonds
Hydrogen atom on one monosaccharide bonds to a hydroxyl group on the other releasing a molecule of water (condensation reaction)
A disaccharide is two monosaccharides joined together
A polysaccharide is when more than two monosaccharides joined together
Hydrolysis breaks the glycosidic. 
Starch
Main energy store in plants.
Cells get energy from glucose and plants store excess glucose as starch
Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.
Starch is insoluble in water so it doesn’t cause water to enter cells by osmosis which makes it good for storage
Amylose
Long unbranched chain of alpha glucose
Coiled structure
Compact therefore good for storage
amylopectin
Long branched chain of alpha glucose
Side branches allow enzymes to break glycosidic bonds easily so glucose can be released quickly
Glycogen
Main energy store in animals
Animals get energy from glucose and starch excess glucose as glycogen (polysaccharide of alpha glucose)
Lots of branches so starch glucose can be released quickly
Very compact – good for storage
Cellulose
Component of cell wall implants
Long on branched chain of beta glucose
Beta glucose molecules bond and form straight cellulose chains linked by hydrogen bonds to form strong microfibrils to provide structural support
Triglycerides
Contain carbon hydrogen and oxygen
Have one molecule of glycerol with three fatty acids
Fatty acid molecules have long tails of hydrocarbons, tails or hydrophobic (repel water molecules) making lipid insoluble in water
Ester bond forms between fatty acid and glycerol by a condensation reaction
Triglycerides can be broken down by hydrolysis which breaks the ester bond
Can be saturated or unsaturated
Ester bond
In triglycerides between fatty acid and glycerol
Phospholipids
One glycerol, two fatty acids and a phosphate group
Phosphate group is hydrophilic (attracts water molecules) and fatty acid tails a hydrophobic
How is triglycerides structure related to the function
Mainly used as an energy store
Long hydrocarbon tails contain lots of chemical energy – lots of energy is released when they’re broken down
Insoluble so they don’t cause water to enter the cells by osmosis making them swell
How is phospholipids structure related to their function
Found in the cell membrane is making up the phospholipid bilayer
Hydrophilic heads and hydrophobic tails from a double layer with the heads facing out towards the water
The centre is hydrophobic so water soluble substances can easily passed through acting as a barrier
How is the structure of cholesterol related to its function
Structure has a pole hydroxyl group attached to it
In eukaryotic cells it helps strengthen the cell membrane by interacting with the phospholipid bilayer
Cholesterol is small which allows it to fit in between the phospholipid molecules in the membrane
They bind to the hydrophobic tails of phospholipids causing them to pack closely together – make the membrane less fluid and more rigid
Proteins
Long chains of amino acids (Monomers)
Polymers
Dipeptide is when two amino acids join together
Polypeptide is one more than two amino acids join together
Proteins are made from one or more polypeptide
Amino acids
Made from: a carboxyl group (minus COOH) and an amino group (minus NH2) attached to a carbon atom, Variable R group.
Contain carbon, oxygen, hydrogen and nitrogen. Sometimes sulphur
Joined by peptide bond to form dipeptides and polypeptides a condensation reaction
Hydrolysis reaction breaks the peptide bond
Peptide bond
Joins amino acids together
Structural levels of protein
Primary structure
Secondary structure
Tertiary structure
Quanternary structure
Primary structure
Sequence of amino acids in the polypeptide chain
Different proteins have different sequences
Peptide bonds between amino acids
Secondary structure
Hydrogen bonds formed between amino acids make a coil into an alpha helix or fold into a beta pleated sheet
Tertiary structure
Chain of amino acids called and folded further
More bonds form between different parts (ionic bonds, disulphide bonds, hydrogen bonds)
If proteins are made from a single polypeptide chain the tertiary structure is the final structure
Quaternary structure
If proteins are made from several different polypeptide chains the quaternary structure is the way that these chains are assembled together
(For example haemoglobin is made from four polypeptide chains)
Globular proteins
Hydrophilic our groups are pushed to the outside of the molecule making globular proteins soluble so that easily transported in fluids
Haemoglobin
Insulin
Amylase
Haemoglobin – globular protein function
Carries oxygen around the body in red blood cells
Conjugated protein – a protein with a non-protein group attached (prosthetic group)
In haemoglobin each of the four polypeptide chains has a prosthetic group called haem
Insulin – globular protein function
Hormone secreted by the pancreas
Regulate blood glucose level
Solubility means it can be transported in the blood where it acts
Consists of two polypeptide chains held together by disulphide bonds
Amylase – globular protein function
Enzyme that catalyses the breakdown of starch in the digestive system
Single chain of amino acids
Most enzymes a globular proteins
Fibrous proteins
Insoluble and strong
Fairly unreactive
Collagen
Keratin
Elastin
Collagen – fibrous protein
Found in animal connective tissues
Strong
Minerals can bind to the protein to increase rigidity
Keratin – fibrous protein
Found in many external structures of animals
Can be flexible (Skin)
Can be Hard and tough (nails)
Elastin – fibrous proteins
Found in elastic connective tissues
Elastic, so allows tissues to return to original shape after being stretched
Inorganic ions
Ion is an atom that has an electrical charge
Positive charge is cation
Negative charge is anion
Cations
Calcium – involved in the transmission of nerve impulses and the release of insulin from the pancreas. Important for bone formation. Acts as a cofactor for many enzymes.
Sodium – important for generating nerve impulses, muscle contraction and regulating fluid balance in the body.
Hydrogen – effects the pH of substances. Also important for photosynthesis reactions.
Ammonium – absorbed by the soil and plants and is important source of nitrogen.
Anions
Nitrate – absorbed from the soil by plants, important source of nitrogen.
Hydrocarbonate – acts as a buffer which helps maintain the pH of the blood.
Chloride – involved in the chloride shift helps maintain pH of blood during gas exchange. cofactor for amylase. Involved in nerve impulses.
Phosphate – involved in photosynthesis and respiration reactions. Needed for synthesis of many biological molecules (nucleotides, Phospholipids and calcium phosphate.)
Hydroxide – affects the pH of substances.
