2.1.2 Biological Molecules Flashcards
How does hydrogen bonding occur between water molecules
Oxygen and hydrogen do not share electrons equally in a covalent bond, oxygen has greater share (is negative)
This means water molecules have slight positive and negative charges and are polar
The positive and negative regions attract eachother and form hydrogen bonds
Why is water a good solvent
Because its polar it can act as a medium for chemical reactions and helps transport dissolved compounds in/out of cells
Why is water a good transport medium
Cohesion means water molecules stick together when being transported through the body
Adhesion occurs between water molecules and other polar molecules and surfaces
Cohesion and adhesion result in water exhibiting capillary action which is how water can rise up a narrow tube against the force of gravity
How does water act as a coolant
Due to high specific heat capacity and high latent heat of vaporisation
How is water effective as a habitat
Habitat for pond skaters due to surface tension
Ice is more dense than water so it forms insulating layer above water, means organisms don’t freeze to death
What are polymers
Long-chain molecules made up by linking multiple individual molecules, monomers, in a repeating pattern
What is a condensation reaction
Joining of 2 molecules with formation of a chemical bond and production of a water molecule
Example of condensation reaction
Joining of 2 alpha glucose molecules, 1-4 glycosidic bond formed, forms maltose
What is a hydrolysis reaction
Addition of water to a molecule that breaks chemical bonds to form 2 smaller molecules
Example of a hydrolysis reaction
Releasing glucose for respiration, starch or glycogen undergo a hydrolysis reaction
What elements are present in carbohydrates
C H O
What elements are present in lipids
C H O
What elements are present in proteins
C H O N S
What elements are present in nucleic acids
C H O N P
Structure of glucose
C6H12O6
Hexose monosaccharide
Polar, soluble in water due to H bonds formed between water and glucose
Structure of alpha glucose
OH on carbon 1 us facing down
Structure of beta glucose
OH on carbon 2 is facing up
Structure of ribose
Pentose monosaccharide
Structure of sucrose
Glucose and fructose
Structure of lactose
Galactose and glucose
Structure of maltose
2 alpha glucose
Amylose structure
Alpha glucose molecules joined by 1-4 glycosidic bonds
Helix is formed, stabilised by H bonding
Compact and less soluble
Polysaccharide
Amylopectin structure
1-4 and 1-6 glycosidic bonds between alpha glucose molecules
Branched structure
Polysaccharide
Structure of glycogen
Very branched, more compact, less space needed to be stored
Why are amylose, amylopectin and glycogen suited to their function
Coiling or branching makes them compact and good for storage
Branching means free ends for glucose to be added/removed which speeds up process of storing and releasing glucose molecules
Insoluble
Structure of cellulose
Alternate beta glucose molecules are turned upside down and joined together
Straight chain formed
Cellulose in the body
Molecules form H bonds with eachother, forming microfibrils, microfibrils join to form microfibrils which combine to form fibres
Fibres are strong and insoluble, used for cell walls
Hard to break down into monomers, forms roughage necessary for healthy digestive system
Structure of triglyceride
One glycerol molecules, three fatty acids
Hydroxyl groups of glycerol and fatty acids interact and 3 water molecules form, ester bond formed, esterification reaction (condensation)
Macromolecule
CHO
Structure of phospholipid
CHOP
Phosphate group, glycerol, 2 fatty acids
Non-polar tail, hydrophobic
Charged head, hydrophilic
Surfactants
How does unsaturation effect fatty acids
Causes molecule to kink/bend
Can’t pack closely together
Liquid at room temp
Oils, not fats
Roles of lipids
Membrane formation
Hormone production
Electrical insulation
Waterproofing
Thermal insulation
Cushioning
Buoyancy
Energy storage
Structure of sterols and an example
Hydroxyl group at one end, hydrophilic and hydrophobic regions
Cholesterol: important in cell membranes which stabilises and regulates fluidity
General structure of amino acids
Amine group
C
H
R group
Carboxyl group
How are peptides synthesised
Amino acids join when amine and carboxyl groups join
Peptide bond forms and water is produced (condensation)
Dipeptide forms
Many join, forms polypeptide
What’s primary protein structure
Sequence that amino acids are joined
Directed by information in DNA
Only involved peptide bonds
What’s secondary protein structure
H bonds, forms along long protein molecules depending on AA sequence
O H N from repeating structure of amino acids interact
Hydrogen bonds can form and create coil shape, alpha helix
Chains can lie parallel to eachother joined by H bonds, forms beta pleated sheets
What’s tertiary protein structure
Folding of protein into final shape
R groups brought closer together by secondary structure
R groups interact
- hydrophobic/hydrophilic interactions
- H bonds
- ionic bonds
- disulfide bridges (covalent bonds between R groups w sulfur atoms)
What’s quaternary protein structure
Association of 2 or more individual proteins (subunits)
Same as interactions in tertiary structure
Enzymes have 2 identical subunits
Insulin has 2 different subunits
Haemoglobin four subunits, 2 pairs of identical subunits
How do peptides breakdown
Proteases can catalyse it
Water molecules used to break peptide bond
Structure of globular proteins and how they form
Compact, water soluble, spherical
Form when proteins fold in tertiary structure so that hydrophobic R groups are kept away from aqueous environment
Hydrophilic R groups on outside
Function of globular proteins
Essential for regulating processes for life, chemical reactions, immunity, muscle contraction
Example of globular protein and how its structure relates to function
Insulin
Hormone involved in regulation of blood glucose concentration
Hormones transported in bloodstream, need to be soluble
Need precise shapes to fit into specific receptors on cell-surface membranes
Conjugated protein structure
Globular proteins with prosthetic group (non-protein component)
Types of prosthetic groups: lipids/carbohydrates/ haem groups
Metal ions ( cofactors when essential for function)
2 examples of conjugated proteins and structure of them
Haemoglobin: each subunit contains prosthetic haem group, iron ions present combine reversibly with oxygen molecule
Catalase: contains 4 haem prosthetic groups, iron ions present allow catalyse to speed up and interact with H2O2
Structure of fibrous proteins
Formed from long, insoluble molecules
Only contain amino acids with hydrophobic R groups
Usually repetitive sequence
Strong
3 examples of fibrous proteins, structures and functions
Keratin: lots of cysteine, results in lots of disulfide bridges, strong inflexible and insoluble materials, present in skin hair and nails
Elastin: in elastic fibres, walls of blood vessels and alveoli, provide flexibility to expand and recoil, quaternary protein
Collagen: connective tissue found in skin ligaments tendons and nervous system, made up of 3 polypeptides wound together in long strong rope-like structure, flexible
Uses of calcium ions
Nerve impulse transmission
Muscle contraction
Uses of sodium ions
Nerve impulse transmission
Kidney function
Uses of potassium ions
Nerve impulse transmission
Stomatal opening
Uses of hydrogen ions
Catalysis of reactions
PH determination
Uses of ammonium ions
Production of nitrate ions by bacteria
Uses of nitrate ions
Nitrogen supply to plants for amino acid and protein formation
Uses of hydrogen carbonate ions
Maintenance of blood ph
Uses of chloride ions
Balance positive charge of sodium and potassium ions in cells
Uses of phosphate ions
Cell membrane formation
Nucleic acid and ATP formation
Bone formation
Uses of hydroxide ions
Catalysis of reactions
Ph determination
Describe how to test for reducing sugars
Place sample in boiling tube
Add equal volume of Benedict’s reactant
Heat mixture gently in boiling water bath for 5 minute
Brick red precipitate will form if the sample is a reducing sugar (qualitative test)
Blue = none
Green = very low
Yellow = low
Orange = medium
Red = high
Examples of reducing sugars
All monosaccharides
Maltose
Lactose
What is a reducing sugar
Sugar can donate electrons or reduce another molecule or chemical
How to test for non-reducing sugar
Place sample in boiling tube
Add equal volume of Benedict’s reagent
Heat mixture gently in boiling water bath for 5 minutes
Will remain blue precipitate if its a non-reducing sugar
Example of non-reducing sugar
Sucrose
How to test for starch
Add a few drops of iodine dissolved in potassium iodide solution to a sample
If the solution changes colour from brown to blue-black, starch is present
How to use reagent strips
Test for presence of reducing sugars (glucose)
Use a colour coded chart to determine concentration of sugar
How to test for protein
Add a few drops of sodium hydroxide solution to sample
Add copper (II) sulfate solution
Goes purple if protein is present
Stays blue if no protein is present
How to test for lipids
Shake sample with ethanol for a minute
Pour solution into water
Solution will turn milky if lipid is present
Will stay clear if no lipid is present
How to determine concentration of a solution
Create 5 serial dilutions with solution factor of 2
Do Benedict’s test on each solution, and a control of water
Remove any precipitate by centrifuging
Use colorimeter with red filter to measure absorbance of Benedict’s solution in each tube
Use results to create calibration curve, plot absorbance against glucose concentration
Then test unknown solution and use calibration to find concentration
How does chromatography work
Mobile phase: where molecules can move (solvent)
Stationary phase: molecules can’t move (chromatography paper or thin layer of solid)
Mobile phase moves over or through stationary phase
Components in mixture spend different amounts of time in each phase
Components that spend more time in mobile phase travel faster/ further
How to carry out paper chromatography
Draw pencil line near bottom of chromatography paper
Put concentrated spot of mixture on it
Add small amount of solvent to a beaker and dip bottom of paper into it
As solvent spreads up paper, mixture will separate and move up at different speeds
When solvent has nearly reached the top, mark where it reached and take it out
How to calculate Rf value
Rf = distance travelled by spot ÷ distance travelled by solvent
