B1 Biological Molecules Flashcards
Define a monomer
Smaller units which can create larger molecules
Define a polymer
Made from lots of monomers bonded together
Examples of monomers
Glucose
Amino acid
Nucleotide
Examples of polymers
Starch
Cellulose
Glycogen
Protein
DNA
RNA
What do carbohydrates contain
C
H
O
What are the 3 types of carbohydrates
Monosaccharides (monomers)
Disaccharides (diners)
Polysaccharides (polymers)
What are 3 examples of monosaccharides
Glucose
Fructose
Galactose
What are 3 examples of disaccharides
Sucrose
Maltose
Lactose
What are 3 examples of polysaccharides
Starch
Cellulose
Glycogen
Define isomer
Same molecular formula but different structure
What’s the molecular formula of glucose
C6H12O6
What are disaccharides made of
2 monosaccharides
What is the Bond in disaccharides
Glycosidic bond joining 2 monosaccharides together
Disaccharides are formed via which reaction
Condensation recation
What are the 3 disaccharides word equations
Glucose + glucose —> maltose + water
Glucose + galactose —> lactose + water
Glucose + fructose —> sucrose + water
Define a condensation reaction
Joining 2 molecules together by removing water
Define a hydrolysis reaction
Splitting apart molecules through addition of water
How are polysaccharides formed
Created by condensation reactions between many glucose monomers
Where is starch found
Plant cells (e.g. in chloroplast)
(Can be found in starch grains inside plant cells)
Where is cellulose found
Plants - cell wall
Where is glycogen found
In animals - mainly in muscle and liver cells
What is the function of starch
insoluble store of glucose
What is the function of cellulose
Provide Structural strength for cell wall
What is the function of glycogen
Insoluble Store of glucose
What are the monomers in starch
Alpha glucose
What are the monomers in cellulose
Beta glucose
What are the Monomers in glycogen
Alpha glucose
What is the bond between monomers in starch
1-4 glycosidic bonds in amylose
1-4 & 1-6 in amylopectin
What is the bond between monomers in cellulose
1-4 glycosidic bonds
What is the bond between monomers in glycogen
1-4 & 1-6 glycosidic bonds
What is the structure of starch
Made of 2 polymers
Amylose - unbranched helix
Amylopectin - branched molecule
What is the structure of cellulose
Polymer forms long, straight chains.
Chains held parallel by many hydrogen bonds to form fibrils
What is the structure of glycogen
Highly branched molecule
1-6 glycosidic bond creates branch, even more 1-6 glycosidic bonds branch of this branch to create highly branched polymer
Explain how structure leads to function in starch
Helix shape of amylose compact to fit lots of glucose in small space.
Amylopectin branched structure - multiple exposed ends of molecule, increases SA - rapid hydrolysis back to glucose.
insoluble - wont affect water potential
Explain how structure leads to function in cellulose
Many hydrogen bonds - collective strength (HBs weak individually but collectively strong)
Insoluble - wont affect water potential
Explain how structure leads to function In glycogen
Branched - increases SA for rapid hydrolysis back to glucose
Insoluble - wont affect water potential
compact easily, store lots of glucose in small space - advantage = animals need to move, movement requires energy, glucose needed in respiration to release that energy, so animals have more branched store of glucose compared to plants.
What is a triglyceride made up of
1 glycerol
3 fatty acids
What is a phospholipid made up of
1 glycerol
2 fatty acids
1 phosphate group
How are triglycerides formed
3 condensation reaction between 1 glycerol and 3 fatty acids
Produces 3H2O as bi products
Forms 3 ester bonds
What is an R group in a triglyceride
Fatty acids
Define a saturated fatty acid
The hydrocarbon chain has only single bonds between carbons
Define an unsaturated fatty acid
The hydrocarbon chain consists of at least 1 double bond between carbons
What are the properties of triglycerides
1) energy storage; large ratio of energy-storing C-HBs:number of Carbons, a lot of energy stored in molecule
2)high ratio of H:O atoms, act as metabolic H2O source. Can release H2O if oxidised. essential for desert animals , e.g. camels
3) don’t affect water potential + osmosis; they’re large + hydrophobic - insoluble to H2O.
4) relatively low mass, therefore a lot can be stored without increasing mass + preventing movement.
Emulsion test for lipids
Dissolve sample in ethanol
Add distilled water
White emulsion appears
How are phospholipids formed
2 fatty acids bond to glycerol via 2 condensation reactions
Form 2 ester bonds
What are the properties of a phospholipid
Hydrophilic head - attract water its charged - phosphate group charged, repels other fats.
Hydrophobic tail - Fatty acid chains not charged, repel water, mix with fats.
Properties of phospholipids (bilayer)
2 charged regions, they’re polar.
In H2O, positioned so heads exposed to water and tails aren’t.
Forms phospholipid bilayer membrane, which makes up plasma membrane around cells.
How many different types of amino acids are there
20 different amino acids
What are proteins made up of
Amino acids
Describe how the amino acids are joined together to form a dipeptide
Via condensation reaction
H2O removed
Peptide bond forms between OH of carboxyl and H of amine group
What is the name of bond in proteins
Peptide bond
What are proteins
Polymers made up of monomer amino acids
How are the 4 structures of a protein
Primary
Secondary
Tertiary
Quaternary
Describe primary structure of a protein
The order (sequence) of amino acids in polypeptide chain - this is a polymer
What are the 2 types of secondary protein structure
Alpha-helix
B-pleated sheet
Describe the secondary protein structure
sequence of amino acids causes parts of protein molecule to bend into a-helix shapes or fold into B-pleated sheets
HBs hold secondary structure
Where are the HBs located in the secondary structure of a protein
HBs form between the C=O groups of carboxyl group of 1 amino acids and H in amine group of another amino acid
Describe tertiary structure of protein
Further folding of secondary structure
form unique 3d shape
Held in place by ionic, hydrogen and disulphide bonds
Describe location of bonds in tertiary structure of protein
Ionic & disulphide bonds form between R groups of diff AAs.
Disulphide bonds only sometimes occur, as there must be sulfur in R groups for this bond to occur.
(S- - -S)
Describe quaternary structure of protein
protein made up of more than one polypeptide chain
E.g. haemoglobin is made of 4 polypeptide chains
What happens to the protein structure when a protein is denatured
Protein denatured
bonds holding tertiary & secondary structure in shape break (ionic and hydrogen bonds break)
Unique 3d shape lost
(e.g. enzymes lose their unique active site shape)
Conditions that denature protein
Too high temp (too much kinetic energy)
Too high/low pH (too many H+ or -OH)
Describe the importance of primary structure
AA in sequence is diff then it cause ionic/hydrogen/disulfide bonds to form in diff location
results in diff 3d shape
impact of change in protein structure on enzymes
have a diff shaped active site (will be non-functioning)
Carrier proteins will have diff shaped binding site (molecules no longer complementary and cannot be transported across membranes)
What might cause a change in AA sequence
Mutations
If there’s a change in DNA sequence, it might then code for diff AA & therefore primary structure changes
Test for starch
Add iodine
orange —> blue/black
Test for reducing sugar
Add Benedict’s reagent + heat
blue —> green, yellow, orange or brick red
(more red, higher conc of reducing sugar)
Why does the colour change occur at the top of the solution first in the reducing sugar test?
Convection currents
Hotter particles in solution rising
hottest point in solution at top
molecules have most kinetic energy, more successful collisions + faster reaction rate
So colour change 1st occurs at the top
Test for non-reducing sugars
Following neg Benedict’s test (reagent remains blue)
Add acid + boil (acid hydrolysis)
Cool solution + then add alkali to neutralise
Add Benedict’s reagent + heat
blue —> green, yellow, orange or brick red
What are 3 types of carbohydrates
Starch
Reducing sugars
Non-reducing sugars
Examples of reducing sugars
Glucose
Fructose
Galactose
Lactose
Maltose
Example of non-reducing sugar
Sucrose
What are reducing sugars
Sugars that can reduce copper sulphate (blue) in Benedict’s reagent to copper oxide (brick red)
What are non-reducing sugars
Reducing group involved in glycosidic bond in sucrose, and therefore sucrose cannot reduce copper sulphate to copper oxide
What happens to sucrose when its hydrolysed
When sucrose hydrolysed (boiling with acid)
Glycosidic bond is broken so reducing group becomes exposed
Pos results achieved with Benedict’s reagent following hydrolysis
Test for proteins
Add Biuret
blue —> purple
What are enzymes
Tertiary structure proteins
Catalyse reactions
What part of enzyme attaches to substrate
Enzymes are large molecules
Only small part of enzyme attaches to substrate to catalyse reaction
known as ‘active site’
Why can enzymes only attach to substrates that are complementary in shape
Active site is specific & unique in shape due to specific folding and bonding in tertiary structure of protein.
What are the 2 models of enzyme action
Lock & key model
Induced fit model
Define activation energy
All reactions require certain amount of energy before they occur
How do enzymes speed up a reaction
Enzymes attach to substrate
Can lower activation energy needed for reaction to occur
so speed up reaction
Describe the lock and key model
Enzyme = lock and substrate = key that fits into it due to being complementary in shape
Model suggests : active site is fixed shape + due to random collisions substrate can collide & attach to enzyme - forms an enzyme-substrate complex (E-SC)
When E-SC formed, charged groups in active site are thought to distort the substrate & so lower Ea
Products then released & active site is empty and ready to be reused
Describe induced fit model (accepted model for how enzymes function)
Enzyme = glove and substrate = hand
Empty glove isn’t exactly complementary in shape to a hand, but when hand enters it enables glove to mould around hand and become completely complementary.
Induced fit is where active site’s induced/slightly changes shape to mould around substrate.
When E-SC occurs, due to enzyme moulding around substrate - puts strain on bonds + so lowers Ea. Products are then removed, active sire returns to original shape.
Factors that affect rate of enzyme controlled reactions
Temp
pH
Substrate conc
Enzyme conc
Inhibitors
Temp affect on enzymes
Temp too low, not enough Ek for successful collisions between enzymes and substrate
Temp too high, enzymes denature, active site changes shape, E-SC cannot form
pH effect on enzymes
Too high/too low pH, it’ll interfere with charges in AAs in active site.
This can break bonds holding tertiary structure in place & so active site changes shape.
So enzyme denatures & fewer E-SC form
Diff enzymes have a diff optimal pH
Substrate & enzyme conc effect on enzymes
Insufficient substrate, reaction will be slower as there’ll be fewer collisions between enzymes & substrate.
Insufficient enzymes, active site will become saturated with substrate & unable to work any faster.
Competitive inhibitor
Same shape as substrate & bind to active site,
prevents substrate binding & reaction occurring.
add more substrate it will out-compete inhibitor, knocking them out of active site.
Non-competitive inhibitors
Bind to enzyme away from active site, allosteric site
causes active site change shape, substrate no longer bind, regardless of how much substrate added.
Describe structure and function of globular proteins
Spherical & compact
Hydrophilic R groups face outwards & hydrophobic
R groups face inwards = usually water-soluble
Involved in metabolic processes e.g. enzymes & haemoglobin.
Describe the structure and function of fibrous proteins.
Can form long chains or fibres
insoluble in water
Useful for structure and support e.g. collagen in skin.
Outline how chromatography could be used to identify the amino acids in a mixture.
Use capillary tube to spot mixture onto pencil origin line & place chromatography paper in solvent.
Allow solvent to run until it almost touches other end of paper. Amino acids move different distances based on relative attraction to paper & solubility in solvent.
Use revealing agent or UV light to see spots.
Calculate R, values & match to database.
Contrast competitive and non-competitive inhibitors.
Competitive inhibitors
- similar shape to substrate = bind to active site
- don’t stop reaction; E-SC forms when inhibitor is released
- increasing substrate conc decreases their effect
Non-competitive inhibitor
- bind at allosteric binding site
- may permanently stop reaction; triggers active site to change shape
- increasing substrate conc has no impact on their effect
Outline how to calculate rate of reaction from a graph.
gradient of line or tangent to a point.
initial rate: draw tangent at t = 0.
Outline how to calculate reaction rate from raw data
Change in conc of product or reactant/time
Why is it advantageous to calculate initial rate?
Represents maximum rate of reaction before concentration of reactants decreases & ‘end product inhibition’.
Similarities of phospholipids and triglycerides.
Both have:
glycerol backbone
may be attached to mixture of saturated, monounsaturated & polyunsaturated fatty acids
contain elements C, Н, О
formed by condensation reactions
Contrast phospholipids and triglycerides.
Phospholipids
- 2 fatty acids & 1 phosphate group attached
- Hydrophilic head & hydrophobic tail
- Used primarily in membrane formation
triglycerides:
- 3 fatty acids attached
- Entire molecule is hydrophobic
- Used primarily as a storage molecule (oxidation releases energy)
Are phospholipids and triglycerides polymers?
No; they are not made from a small repeating unit. They are macromolecules.
