Chapter 3 Biological Molecules Flashcards
Covalent Bonding
When atoms share electrons to get a full outer shell.
Hydrogen - 1 bond
Oxygen - 2 Bonds
Nitrogen - 3 bonds
Carbon - 4 bonds
A double bond is when there are two bonds
Condensation reaction
Occurs when molecules are joined together by removing Water.
Monomer + Monomer -> polymer + Water
This happens because a Hydrogen is taken from one monomer and oxygen and hydrogen taken from the end of the other monomer and allows them to join
Hydrolysis reaction
Literally means Water splitting.
Water is being added to the polymer which allows the monomers to form with the hydrogen and oxygen added at the ends.
What are the Monomers and Polymers of these molecules:
Carbohydrates
Proteins
Nucleic acids
- Monosaccharides, Polysaccharides
- Amino acids, Polypeptide
- Nucleotide, DNA + RNA
Hydrogen Bonding
Water = two hydrogen covalently bonded to one oxygen.
Oxygen has more protons which exerts stronger attraction bringing more electrons in the molecule closer to it giving it a negative charge. This leaves the hydrogen with a positive charge.
What makes water so special
Water is a polar molecule since it contains two hydrogen atoms, each covalently bonded to an oxygen atom. The oxygen atom has a greater number of positive protons in its nucleus compared to the hydrogen atoms. This means the shared electrons in the covalently bonded are pulled more towards the oxygen atom than the hydrogen atoms. This makes the oxygen atom slightly negative and the hydrogen atom slightly positive.
properties of water:
- Liquid,
- Reactant
- Density
Liquid - Provides habitats. Major component of tissue. A location for chemical reactions: good transport system.
Reactant - Used as a reactant for example photosynthesis which is an essential biological process. Also used in hydrolysis reactions.
Density - Ice can form which allows ice to float at low temperatures since there is low density. It can serve as a habitat.
properties of water:
- Solvent
- Cohesion & Surface tension
Solvent - can help separate solutes as the positive and negative parts of water can attract the positive and negative parts of water which can help separate them.
Cohesion & Surface tension - The surface tension is created by water particles pishing up and the gravity equalling it out which results in a zero net force.
properties of water:
- High specific heat capacity
- high latent heat of vaporisation
High specific heat capacity - Hydrogen bonding requires a high amount of heat to increase the temperature of water. This means water temp stays relatively still. Creates a stable internal environment.
High latent heat of vaporisation - Due to hydrogen bonding a relatively high amount of heat energy is required to evaporate water. this allows organisms to ocool themselves to maintain a constant body temperature
What is a carbohydrate
“hydrated carbon”
formed of carbon, hydrogen and oxygen.
Functions:
energy source - respiration
energy store - starch
structure - cellulose cell wall.
Can be part of other molecules e.g. nucleic acids.
General formula - (CH2O)n - n is hte number of carbons.
Simple Sugars
- properties
- types
- structure
Monosaccharides are carbohydrate basic units.
Large carbohydrates made by joining these together (disaccharides and polysaccharides)
Properties : soluble in water, sweet and can form a crystal
Types : Triose, Pentose, Hexose
Structure : ring structures or in straight chains.
Isomers of glucose
- Forms
Forms of glucose : chains or rings
Ring glucose can also be in 2 main forms called alpha and beta glucose.
alpha glucose - hydroxyl group below
beta glucose - hydroxyl group above
This states about the hydroxyl group surrounding the Carbon1
Joining Monosaccharides
Condensation reactions are used to join up simple sugars. Convalent bonds formed between monosaccharied are called glycosidic bonds.
Remember one water molecule is released so this is a condensation reaction.
Starch, glycogen and cellulose are polysaccharides.
Carbohydrates and Energy
Glucose is broken down to release ATP through respiration
Each step in respiration is controlled by enzymes
Alpha (a) glucose is often used in respiration. Many carbon hydrogen bonds here.
Beta (B) glucose can be used as an energy source but it is a structural resource.
What are lipids?
Lipids are biological molecules that contain the elements carbon (C), hydrogen (H), and oxygen (O). However, lipids contain a much lower proportion of oxygen than carbohydrates.
Lipids are not made up of long chains of monomers, meaning they are not considered as polymers.
Roles of lipids
The main functions of lipids:
Energy supply - Lipids can be oxidised to provide energy to cells.
Structural components - Phospholipids are used in cell membranes.
Waterproofing - Insoluble lipids are used to form water-resistant barriers.
Insulation - Lipids can help retain heat or act as electrical insulators.
Protection - Delicate organs are surrounded by a layer of fat.
Fatty acids
Most lipids are made up of fatty acids combined with an alcohol (usually glycerol).
Fatty acids consist of a carboxyl group (-COOH) attached to a hydrocarbon chain (R group).
Saturated fatty acids:
These have hydrocarbon chains that are ‘saturated’ with hydrogen, meaning all carbon atoms are bonded to the maximum number of hydrogen atoms.
The hydrocarbon chain has no carbon-carbon double bonds.
Lipids that contain saturated fatty acids have higher melting points and so are usually solid at room temperature (fats).
Unsaturated fatty acids
These have hydrocarbon chains that do not contain the maximum number of hydrogen atoms bonded to the carbon atoms.
The hydrocarbon chain has at least one carbon-carbon double bond, which causes the chain to kink.
Lipids that contain unsaturated fatty acids have lower melting points and so are usually liquid at room temperature (oils).
Monosaturated
Polysaturated
Mono - One double bond
Poly - Two or more double bonds
Testing for lipids
To find out whether a sample contains lipids, you must carry out the emulsion test.
Place your food sample in a test tube.
Add 2 cm3 of ethanol.
Shake.
Add 2 cm3 of distilled water.
If lipids are present, a milky white emulsion will appear.
Triglycerides
A triglyceride is a type of lipid used as a store of energy in animals, plants, and some bacteria.
A triglyceride consists of a glycerol backbone attached to three fatty acid tails. Each fatty acid tail contains a hydrocarbon chain (R) which can vary in length and may be saturated or unsaturated
Saturated and Unsaturated
There are no double bonds in fatty acid chains so they are called saturated because all the carbon atoms form the maximum number of bonds with hydrogen atoms.
A fatty acid with double bonds between some of the carbon atoms is called unsaturated.
one double bond = monounsaturated
two or more double bonds = polyunsaturated
Phospholipids
Have two fatty acids with a phosphate group instead of another fatty acid. All attached to the glycerol. The phosphate ions have extra electrons so are negative charged and soluble in water.
Have a charged hydrophilic head and non-polar hydrophobic tails.
The will form a layer on the surface of water with the phosphate heads in the water and the fatty acids tails sticking out of the water. They are called surface active agents.
They can also form strucures based on a two layered sheet (a bilayer) with all their hydrophobic tails pointing towards the middle.
Sterol - Cholesterol
Cholesterol is a type of lipid known as a sterol and is used by animal cells to increase the stability of the cell membrane.
Cholesterol is also used to make vitamin D, steroid hormones, and bile.
Like phospholipids, cholesterol is a polar molecule. The hydroxyl group (OH) is hydrophilic whereas the rest of the molecule is hydrophobic.
Proteins are made up of amino acids
Amino acids are the building blocks of proteins, which are essential macromolecules involved in various functions within living organisms.
Amino acids are monomers and can join together via peptide bonds to form dimers (dipeptides) and polymers (polypeptides).
What are the roles of proteins?
Enzymes - These proteins are used to breakdown and synthesise molecules.
Antibodies - These proteins are involved in the immune response.
Transport - Some proteins can move molecules or ions across membranes.
Structural components - Proteins like keratin and collagen are used to create strong fibres.
Hormones - Some of these are proteins that act as chemical messengers in the body.
Muscle contraction - Muscles are made up of proteins.
Amino Acid Structure
They all have the same general structure:
A central carbon atom
An amino group (-NH2)
A carboxyl group (-COOH)
A hydrogen atom (-H)
An R group or a variable side group
Dipeptide synthesis and breakdown
They are synthesised through peptide bonds when there is a condensation reaction. Here the hydroxyl group from the carboxyl group is removed aswell as a hydrogen from the other amino acids, amino acid group to form water and a peptide bond.
Testing for proteins
To find out whether a sample contains peptide bonds (and hence, proteins), you must carry out the Biuret test.
Place your food sample in a test tube.
Add an equal volume of Biuret solution (sodium hydroxide and copper sulfate).
If proteins are present, the solution will turn from blue to purple. If no protein is present, the solution remains blue.
Primary Structure
The primary structure is made up of the unique sequence of amino acids in the polypeptide chain. This structure is held together by peptide bonds. A change to just one of the amino acids in this chain can result in a change to the protein’s structure and function
Secondary Structure
The secondary structure involves hydrogen bonds forming between the amino group of one amino acid and the carboxyl group of another amino acid further down the chain. This causes the polypeptide chain to coil into either an alpha-helix or a beta-pleated sheet structure
Tertiary Structure
This specific structure is held together by many bonds, including:
Hydrogen bonds - These are individually weak but provide strength in large numbers.
Ionic bonds - These form between positive and negative R groups.
Disulfide bridges - These form between R groups that contain sulphur (such as cysteine).
Hydrophobic and hydrophilic interactions - These are weak interactions between polar and non-polar R groups.
Quaternary Structure
The quaternary structure involves two or more polypeptide chains held together by the same bonds found in the tertiary structure of a protein (hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic and hydrophilic interactions)
It can also involve the addition of non-protein groups known as prosthetic groups.
Globular proteins
Globular proteins
Globular proteins are compact, spherical, and soluble proteins.
Enzymes - These speed up chemical reactions in the body.
Hormones - These are chemical messengers that travel in the bloodstream.
Antibodies - These bind to and prevent the spread of pathogens.
Fibrous Proteins
Fibrous proteins form long strands and are not usually soluble in water.
Keratin - This is found in the skin, hair, and nails.
Collagen - This is found in connective tissues such as bone and muscle.
Elastin - This is found in elastic connective tissue.
What allows Haemoglobin to transport oxygen around the body.
Four polypeptide chains - This means that four molecules of oxygen (O2) can be carried at a time.
Haem group - This contains iron that reversibly binds to oxygen.
Compact globular structure - This allows haemoglobin to fit inside red blood cells.
Insulin
Insulin is made up of two polypeptide chains held together by disulfide bonds
Amylase
Amylase is a globular protein known as an enzyme. It is responsible for the breakdown of starch into maltose.
This enzyme is made up of a single polypeptide chain folded using both alpha-helixes and beta-pleated sheets.
Collagen
Collagen is a fibrous protein used as a structural component in skin, tendons, cartilage, bones, teeth, and walls of blood vessels.
Collagen is made up of three polypeptide chains wound around each other in a rope-like structure. This provides strength and flexibility to the molecule.
Keratin
Keratins are a group of fibrous proteins found in the hair, skin, and nails.
These proteins contain a large number of the amino acid cysteine (contains the element sulphur) which allows disulfide bonds to form. This creates strong and insoluble molecules.
Keratin can be either flexible or rigid, depending on the number of disulfide bonds it contains.
Elastin
Elastin is a fibrous protein found in elastic connective tissue such as in the walls of blood vessels.
It is elastic which allows the tissues to expand and then return to their original shape.
Roles of Cations: Calcium ions(ca2+)
Necessary for never impulse transmission, muscle contraction
Roles of cations: sodium ions(Na+)
Necessary for nerve impulse transmission, kidney function
Roles of cations: potassium ions(k+)
necessary for never impulse transmission, stomatal opening
Roles of cations: Hydrogen ions(H+)
Necessary for catalysis of reactions, pH determination
Roles of cations: Ammonium ions(NH4+)
Necessary for production of nitrate ions by bacteria
Roles of anions: nitrate ions(NO3-)
Necessary for nitrogen supply to plants for amino acid and protein production
Roles of anions: Hydrogen carbonate ions(HCO3-)
Necessary for maintenance of blood pH
Roles of anions: chloride ions(cl-)
Necessary for balance positive charge of sodium and potassium ions in cells
Roles of anions: phosphate ions(PO4 3-)
Necessary for cell membrane formation, nucleic acid and ATP formation, bone formation
Roles of anions: Hydroxide ions(OH-)
Necessary for catalysis of reactions, pH determination
Which element are present in:
Carbohydrates
Lipids
Proteins
Nucleic acids
Carbohydrates: C,H,O
Lipids: C,H,O
Proteins: C,H,O,N,S
Nucleic acids: C,H,O,N,P
