2.1.2 Biological molecules Flashcards
Define monomer
Smaller units that join together to form larger molecules
Define polymer
Molecules formed when many monomers are joined together
Define condenstion reaction
A chemical bond forms between to molecules and a water molecule is produced
Define hydrolysis reaction
A chemical bond is broken between two molecules and a water molecule is used
Describe how hydrogen bonding occurs between water molecules
Hydrogen bonding is the intermolecular force of attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen atom of another water molecule.
Water is polar as oxygen is more electronegative than hydrogen
Define cohesion and adhesion of water
Cohesion is the hydrogen bonding between water molecules
Adhesion is the attraction between water molecules and other polar molecules
Explain the importance water as a transport medium in organisms
Cohesion and adhesion lead to capillary action in an organism.
This is the movement of water up a narrow tube against gravity
Explain the importance of water as a habitat for organisms
- Temperature of water is stable, providing a constant environment
- Floating ice insulates water for aquatic organisms
- Surface tension is strong enough to support small insects
Explain the importance of water as a solvent in organisms
- Water is polar
- Water dissolves and transports many biological molecules
- This allows these molecules to undergo metabolic reactions
Explain the importance of water as a coolant in organisms
- High latent heat capacity
- This helps to maintain a stable internal temperature and protect cells from heat damage
- High latent heat of vapourisation
- Evaporation of water cools the surface of organisms
Define high latent heat of vaporisation of water and high specific heat capacity.
The hydrogen bonding between water molecules is very strong
Vaporisation - the thermal energy required for a liquid to vaporize to a gas or the amount that is released when a gas condenses to a liquid
Heat capacity - the energy required to raise the temperature of 1 gram of water by 1 degree Celsius
Explain why ice floats
- Hydrogen bonds fix positions of water molecules further apart when water is solid
- This forms a giant, rigid, open structure
- Ice is therefore less dense than water
- This causes ice to float
State the biological elements that make up carbohydrates
- Carbon
- Hydrogen
- Oxygen
Draw the structures of an α- and a β-glucose molecule
Hexose monosaccharides - 6 carbon monosaccharides
Look up answer to confirm
Draw the structure of a ribose sugar
Pentose monosaccharide - 5 carbon sugar
Look up answer to confirm
State the important properties of glucose
- Glucose is polar and soluble
- This is due to hydrogen bonding between hydroxyl groups and water molecules
- Glucose can dissolve in the cytoplasm of a cell
State the bond formed between monosaccharides and the chemical reaction
Glycosydic bond
Condensation reaction
State three disaccharides
Explain how they are formed
Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose
A condesation reaction between two monosaccharides forms a glycosydic bond
State the function and structure of starch
Amylopectin and Amylose
Energy store for plants
Amylopectin
* 1-4 and 1-6 glycosydic bonds
* Branched shape
Amylose
* 1-4 glycosydic bonds
* Helix shape with intermolecular hydrogen bonding
Alpha glucose polysaccharide
State the function and structure of glycogen
Energy store for animals
* 1-4 and 1-6 glycosydic bonds
* Branched shape
Alpha glucose polysaccharide
State the function and structure of cellulose
Cellulose provides strength and rigidity to plant cell walls
* 1-4 glycosydic bonds
* Straight chain molecules
* Microfibrils form due to hydrogen bonding between parallel chains
Beta glucose polysaccharide
Explain how the structure of glycogen relates to it’s function
Branching
* Many free ends where glucose can be added or removed - speeds up release and storage of glucose
* Compact - ideal for storage
Large and insoluble
* No osmotic effect on cells
* Does not diffuse out of cells
Explain how the structure of starch relates to it’s function
Helix shape
* Compact - ideal for storage
Branching
* Many free ends for removal and addition of glucose - speeds up release and store of glucose
* Compact - ideal for storage
Large and insoluble
* No osmotic effect on cells
* Does not diffuse out of cells
Explain how the structure of cellulose relates to it’s function
Microfibrils - hydrogen bonding between parallel chains of cellulose
* Microfibrils form fibres
* Fibres are strong and insoluble
* Fibres provide high tensile strength to plant cell wall
* Unreactive molecule
* Flexible molecule
State the biological molecules which make up lipids
- Carbon
- Hydrogen
- Oxygen
Describe the structure of a triglyceride
State the molecules, bonds and chemical reaction
Condesation reaction between a glycerol molecule and three fatty acids which form ester bonds
Example of a macromolecule
Constrast unsaturated and saturated fatty acids
Unsaturated
* Contain at least one C=C double bond
* Bent molecule
Saturated
* Only contain C-C single bonds
* Straight chain molecule
Describe the structure of a phospholipid
State the molecules, bonds and chemical reaction
Condensation reaction between a phosphate head and two fatty acids forming ester bonds
Example of a macromolecule
Outline the properties of triglycerides related to their function in organisms
- Energy store
- Thermal insulation to reduce heat loss
- Waterproofing/physical protection of organism surfaces
- buoyancy for aquatic animals
Define the term macromolecule
Macromolecules are large complex molecules. Lipids are a macromolecule.
Outline the properties of phospholipids in related to their function in organisms
- Fatty acid tails are hydrophobic, point away from water, inward/towards each-other
- Phosphate group is hydrophilic, forms H-bonds with water and points outwards
- Formation of phopholipid bilayer in the cell membrane
Describe the structure and function of cholesterol
Structure
* Four hydrocarbon rings
* Hydroxyl (OH) group at one end
Function
* Adds stability to the cell membrane by reducing
the fluidity of the phospholipid bilayer
State the biological elements that make up proteins
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Sulphur
Draw the general structure of an amino acid
Look up answer to confirm
Outline the synthesis of peptide chains
State the monomer, chemical reaction and bond
Condesation reaction between amino acids forms polypeptide chains with peptide bonds
Describe the primary structure of a protein
The sequence of amino acids in a peptide chain
Describe the secondary structure of a protein
State bonding present
Hydrogen bonding in the peptide chain form alpha-helix or beta pleated sheet structures
Describe the tertiary structure of a protein
State bonding present
The 3D structure of a protein
* Hydrophobic and hydrophilic interactions - between polar and non-polar R-groups
* Hydrogen bonding
* Ionic bonding - between oppositely charged R groups
* Disulphide bonding - covalent bonding between R groups containg sulphur atoms (cysteine amino acids)
Describe the quarternary structure of a protein
Two or more polypeptide chains
Describe the properties and function of globular proteins
Properties:
* Spherical and compact
* Water soluble - hydrophilic R-groups face outwards and hydrophobic R-groups face inwards
* Have a tertiary shape complimentary to another molecule
* May be conjugated proteins
Functions:
* Involved in metabolic processes
* Examples include: enzymes such as catalase, hormones such as insulin, and molecules such as haemoglobin
Describe the structure and function of Haemoglobin
Haemoglobin is a named example of a globular conjugated protein
Haemoglobin
* 2 alpha subunits, 2 beta subunits
* Each subunit contains a prosthetic haem group
* Fe2+ ion in the haem group can bind an to oxygen molecule
* Haemoglobin can transport oxygen around the body
State the definition of a conjugated protein
A globular protein with a non-protein component - known as a prosthettic group
Describe the structure and function of catalase
Catalase is a named example of an enzyme globular protein
- Quaternary structure
- Four prosthetic haem groups
- Fe2+ ions allow catalase to break down hydrogen peroxide which is damaging to cells
Describe the structure and function of insulin
Hormone which regulates blood glucose concentration
Water soluble - hydrophilic R groups point outwards. Hydrophobic R groups point inwards
Specific shape caused by hydrophilic, hydrophobic interactions and bonding in the tertiary structure - to fit into specific cell surface receptors
Why must every other beta glucose moleucle be oriented oppositely in a beta glucose polysaccharide
Due to the position of the OH group and the H atom on carbon 1 of a beta glucose molecule, alteernate molecules must be oriented 180 degrees for a glycosydic bond to form.
Why do unsaturated triglycerides have a low boiling point?
Fewer hydrogen atoms/more carbon carbon double bonds
Kinked chain, unable to uniformly pack together
Describe the function and properties of fibrous proteins (give names examples)
Properties:
* Insoluble
* elongated strands
* strong and tough
* flexible
Functions:
* Structure: Collagen in bones
* Protection: Keratin in skin, hair and nails
* Elasticity: Elastin in blood vessels
* Contraction: muscle movement, movement in cilia/flagella
