Section 1: Biological molecules Flashcards
what is a condensation reaction
joining 2 molecules together
monomer to polymer
larger molecule is formed
covalent bond
water is released
what is a hydrolysis reaction
polymer to monomer
breaking down larger molecule into a smaller one
water molecule is used
how many carbons are in a alpha glucose
six
what is the ratio of carbon : hydrogen : oxygen in glucose
c : 2h : o
1 : 2 : 1
what is the name of two monosaccharides joined together
disaccharide
glucose x 2 is what disaccharide?
maltose
glucose + galactose is what disaccharide?
lactose
glucose + fructose is what disaccharide?
sucrose
what bond forms between 2 monosaccharides
glycosidic bond when it forms a disaccharide
what does the prefix glyco mean
sugar (carbohydrates)
name function, location and structure of starch (in plants)
polysaccharide storage molecule
long straight chain amylose molecules and branched amylopectin
stored in chloroplasts in membrane bound starch grains
can be broken down into glucose for respiration to release energy
describe function, location and structure of glycogen (in animals)
polysaccharide storage molecules
more branched amylopectin
shorted 1-4 amylose chains
can be broken down into glucose for respiration to release energy
more compact , forms glycogen granules in places like liver and muscle cells
Describe the function, location and structure of cellulose
B-glucose , straight un-branched, parallel Hydrogen bonds with cross linkage makes it strong micro-fibrils form fibres , plant cell walls prevents from bursting
What are lipids made up of? and describe there solubility in water and organic solutions?
Made up of carbon oxygen hydrogen
Insoluble in water
Soluble in organic solutions
What are the roles of lipids
energy source : more energy released than carbs + releases water when oxidised
Waterproofing: waxy lipid cuticle, oily skin secretion
Insulation: slow conductors of heat so retain body temperature well
Protection: around delicate organs
What are the adaptations of lipids that make it good for their roles
High ratio of bonds to carbon atoms make it excellent energy source
Low mass to energy ration excellent storage molecule
Large, non polar and insoluble doesnt effect water potential so wont diffuse or osmosis out of cells
Important water source due to high H:O ratio
What is the reaction forming a triglyceride? state equation and bond
Glycerol + 3 fatty acids —> triglyceride + 3 water
condensation reaction
ester bond formed
What does a phosphate and 2 fatty acids make
Phospholipid
Describe features of phospholipid and their uses
Polar molecule : forms bilayer and barrier due to hydrophilic head and hydrophobic tail
Structure allows them to form glycolipids
How would cellulose give something strength
Straight un branched chain
Many hydrogen bonds and cross linkage
Chains lie side by side (micro) fibrils
Give two feature and explain why starch is a good storage substance
Insoluble : water isnt drawn out or into cells by osmosis/ doesnt effect water potential
Coiled : Very compact lots can be stored
Large : wont diffuse out cells
Branched : multiple ends acted on by enzymes rapidly
What is the difference between a globular and fibrous protein
Globular are spherical and soluble
Fibrous are elongates and not water soluble
What proteins are globular
Enzymes
Hormones
transport
Antibodies
What proteins are fibrous
Keratin
Collagen
Myosin, actin
What are four factors effecting enzyme action
Temperature
PH
Substrate concentration
Enzyme concentration
What are buzz words to use in an enzyme question
Acts as catalyst
Lowers activation energy
Enzymes substrate complex
Induced fit
Describe structure of an amino acid
Amino group (-NH2)
Carboxylate group (-COOH
R group
Hydrogen (-H)
Primary structure description
Polymerisation
Peptide bonds -OH and -H
Long polypeptide chain
Specific order
Secondary structure description
3-D shape
Hydrogen bonds -NH and -COOH
A helix or b pleated sheets
Tertiary structure
Disulphide bridges
Ionic bonds
Hydrogen bonds
Quaternary structure description
Multiple polypeptide chains together for example haemoglobin has 4
What is a prosthetic group and give example
Prosthetic groups are non-peptide (non-protein) compounds that mostly attach to proteins and assist them in different ways.
Such as Haemgroup (Fe containing) in Haemglobin
What are nucleotides made up of
Phosphate group, pentose sugar and nitrogen base
How would heat effect the tertiary structure
Will damage the ionic H or disulphide bonds and break the shape
How may a change in the primary structure of a globular protein result in a change of three-dimensional structure
Sequence of amino acid changes
Different places where bonds are
different folding into tertiary
How does temperature effect enzyme action
temp falls = less kinetic energy = less frequent collisions = rate of reaction decreased
How does ph effect enzyme action
Alters shape
Bonds break
Active site deformed
cant form e-s complex
Rate of reaction decrease
Describe 5 features of DNA
Double helix provides strength
Phosphodiester backbone protects from chemicals
THe Higher the C-G pairings more stable the DNA because C-G has 3 hydrogen bonds
Very stable and can be passed on generation to generation
Base pairings ensure this
Large and carry’s lots of information
When does DNA replication happen?
Interphase
Describe DNA replication briefly
Semi-conservative
DNA helicase break H bonds linking bases
Double helix separates
Both strands act as templates
Free nucleotides attach to bases
DNA polymerase join agacent nucleotides together
What bonds do DNA helicase and polymerase break and form
DNA helicase hydrolyse hydrogen bonds
DNA polymerase form phosphodiester bonds
What is ATP made up of
Nitrogen base (Adenine)
Ribose
3 phosphates
What are the uses of ATP
Metabolic processes - making starch from glucose
Movement - muscle contraction
Active transport - changes shape of carrier proteins
Secretion - needed to form lysosomes
Activation of molecules - addition of phosphate to glucose at start of glycolysis
Why is ATP a good energy source
Manageable quantities: releases less energy than glucose
Immediate energy source: only requires one reaction ( hydrolysis of ATP) unlike glucose
Regenerate/Reversible reaction
What are the 5 features of water and the mnemonic
Metabolite (hydrolysis)
Solvent (dissolves gasses, enzymes, wastes)
High heat capacity (due to hydrogen bonds)
Large latent heat of vaporisation (evaporation of sweat very effective)
Cohesion (tendency of molecules sticking together ex. xylem tube)
My sofa has large cushions
Does water have a charge
No however is dipolar as Oxygen has slight negative change and hydrogen has a slight positive charge so 2 water molecules are often attracted to each other hydrogen bonds between water molecules and covalent bonds betweeen 2 hydrogen atoms and one oxygen atom.
What is a monomer (1mark)
small repeating unit molecule from which larger molecules/polymers are made
Describe a biochemical test to show that a solution contains non-reducing sugar (3marks)
Heat with acid and neutralise
Heeat with Benedict’s solution
Red precipitate colour
Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and a glycogen molecule.
Cellulose is made up of β-glucose (monomers) and glycogen is
made up of α-glucose (monomers);
Cellulose molecule has straight chain and glycogen is
branched;
Cellulose molecule has straight chain and glycogen is coiled;
glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has
only 1,4- glycosidic bonds;
Ignore ref. to H bonds / microfibrils
2 max
Describe the structure of glycogen (2marks)
Polysaccharide of alpha glucose
Joint by glycosidic bonds or branched structure
Suggest how glycogen acts as a source of energy
Hydrolysed to glucose
Glucose used in respiration
Describe how you would test for the presence of a lipid in a liquid sample of food
Add ethanol then add water and shake and mix
white milky emulsion if positive
Describe how a triglyceride molecule is formed (3 marks)
One glycerol and three fatty acids
Condensation reactions and removal of three molecules of water
Ester bond is formed
Describe how an ester bond is formed in a phospholipid molecule. 2 marks
Condensation reaction
loss of water
between glycerol and fatty acids
Explain five properties that make water important for organisms
A metabolite in condensation/hydrolysis/ photosynthesis/respiration;
A solvent so allowing transport of substances;
High (specific) heat capacity so buffers changes in temperature;
Large latent heat of vaporisation so provides a cooling effect (through
evaporation);
Cohesion (between water molecules) so supports columns of water
(in plants);
Cohesion (between water molecules) so produces surface tension
supporting (small) organisms;
State and explain the property of water that helps to prevent temperature increase in a cell.
High heat capacity
Acts as a buffer for temperature change / needs a large amount of energy to heat water up
State and explain the property of water that can help to buffer changes in
temperature.
- water has a relatively) high (specific) heat capacity;
Ignore numbers relating to heat capacity - Can gain / lose a lot of heat / energy without changing temperature;
OR
Takes a lot of heat / energy to change temperature;
Accept due to H bonding between water molecules
Give two properties of water that are important in the cytoplasm of cells.
For each property of water, explain its importance in the cytoplasm.
- Polar molecule;
- Acts as a (universal) solvent;
OR - (Universal) solvent;
- (Metabolic) reactions occur faster in solution;
OR - Reactive;
- Takes place in hydrolysis / condensation / named reaction;
How can i test wether a sample contains reducing or non-reducing sugars?
First add benedict’s reagent to the sample and heat in a water bath
If it turns brick-red reducing sugar is present
If it stays blue no reducing sugar is present and you can test further
Boil the sample with dilute HCL then neutralise and add Benedict’s reagent again and heat
If it now turns brick-red a non reducing sugar was originally present
Why Don’t Non-Reducing Sugars React with Benedict’s Reagent?
They can’t donate electrons to Benedict’s reagent, so the solution stays blue instead of turning brick-red.
While reducing sugars do have free electron to donate so do turn solution brick-red.
Why Does Breaking Down a Non-Reducing Sugar Give a Positive Result to Benedict’s reagent?
The acid breaks it into smaller sugars that can donate electrons to Benedict’s. These sugars are reducing sugars, so the solution turns brick-red after heating.
Describe structure and function of the nucleus. 4 marks
Nuclear envelope, double membrane and nuclear pores
Chromosomes or DNA with hi stones
Nucleolus
Holds genetic information for polypeptides
DNA replication occurs
Production of mRNA/tRNA or transcription occurs
Production of rRNA/ribosomes
Give two types of molecules that make up a ribosome.
RNA/nucleotides
Protein/ amino acids
Describe the role of the ribosome in the formation of a polypeptide. 3 marks
mRNA binds to ribosome;
Idea of two codons/binding sites;
(Allows) tRNA with anticodons to bind/associate;
(Catalyses) formation of peptide bond between
amino acids (held by tRNA molecules);
Moves along (mRNA to the next
codon)/translocation described;
Suggest and explain two ways the cell-surface membranes of the cell lining the uterus may be adapted to allow rapid transport of nutrients. 2 marks
Membrane folded so increased/large surface area;
OR
Membrane has increased/large surface area for (fast) diffusion/facilitated diffusion/active transport/co-transport;
Large number of protein channels/carriers (in membrane) for facilitated diffusion;
Large number of protein carriers (in membrane) for active transport;
Large number of protein (channels/carriers in membrane) for co-transport
In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA. Explain why. 2 marks
- Introns (in pre-mRNA);
- Removal of sections of (pre-mRNA)/splicing
How many binding sites/ codons do the ribosomes act on during translation?
Two codons/ binding sites
Describe how bacteria divide.
- Binary fission;
- Replication of (circular) DNA;
- Division of cytoplasm to produce 2 daughter cells;
- Each with single copy of (circular)
High absorption of salt from the diet can result in a higher than normal concentration for salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid. Explain how.
(Higher salt) results in lower water potential of tissue fluid;
(So) less water returns to capillary by osmosis (at venule end);
OR
(Higher salt) results in higher blood pressure/volume;
(So) more fluid pushed/forced out (at arteriole end) of capillar
