Biological Molecules Flashcards
Monomer
Small molecules
Joins to other similar or identical monomers
To form larger complex molecules
Called polymers
Polymers
Large complex units
Consisting of repeating chains of 3 or more similar or identical monomers
Joined together by chemical bonds
Condensation reaction
Anabolic process
Making large molecules from smaller ones
New chemical bond joining molecules as a molecule of water is released
Hydrolysis reaction
Catabolic process
Breaks large molecules into small ones
Chemical bond broken as a molecule of water is added
What is the difference between chitin and other polysaccharides
Chitin is nitrogenous
How does amylose make starch adapted for its function
Carbon 1:4 glycosidic bonds Form long linear chains That coil into a helix Compact So good for storage Can store a lot in a small space
What is starch
A carbohydrate of 2 polysaccharides of alpha glucose called amylose and amylopectin
How does amylopectin make starch adapted for its function
Branched chain Branches caused by carbon 1:4 and 1:6 glycosidic bonds Large surface area Rapid hydrolysis by enzymes To release glucose for respiration
Starch adaptations
Insoluble so doesn’t affect the water potential of cell
Large molecule so doesn’t diffuse out of cell
Helical/compact so stores a lot in a small space
Branched so large surface area and rapid hydrolysis
How do glycogen and starch act as energy stores
Can be hydrolysed to glucose
Glucose using to release energy through respiration
Glycogen adaptations
Highly branched structure for large surface area for rapid hydrolysis by enzymes to release Glucose for respiration
Insoluble so doesn’t affect the water potential of cells
Large so doesn’t diffuse out of cells
What is cellulose
A beta glucose polysaccharide
Formed from condensation reactions to form long unbranched chains of beta glucose
Joined by beta 1:4 glycosidic bonds
Cellulose structure
Long unrbanched chains Joined by beta 1:4 glycosidic bonds Every other molecule inverted 180° To allow weak hydrogen bonds to form between straight chains Making strong macrofibrills Wound together to make cellulose fibres Providing strength and support in plant cell walls Resist turger pressure, osmotic pressure
Why can’t humans digest cellulose
Human digestive system cannot break down the beta 1:4 glycosidic linkage in cellulose
Since it requires a specific enzyme absent in humans
What is a triglyceride
Type of lipid
Made of one molecule of glycerol joined by ester bonds to 3 fatty acids
Not a polymer since not made of similar monomers
Where are triglycerides found
Waxy cuticle of plants and insects (waterproof)
Aquatic organisms (less dense than water so organisms can stay buoyant)
Blubber in whales/seals (thermal insulator conducts heat slowly and reduces heat loss)
Stored around delicate organs (for shock absorption to protect organs from internal damage)
Saturated fatty acid
Fatty acid with no double bonds/only single bonds between carbon atoms of the hydrocarbon chain
Maximum number of hydrogen and so chain lies flat/no kink
Unsaturated fatty acid
One or more double bonds between carbon atoms in the hydrocarbon chain of a fatty acid
Causing a kink in the chain and not the maximum number of hydrogens
Can’t pack together tightly
Saturated vs unsaturated fatty acids
Both have a hydrogen chain
Saturated fatty acids only have single bonds between carbons
Unsaturated have one or more double bonds between carbons
Saturated are fully saturated with hydrogen/have maximum number of hydrogen
Unsaturated not fully saturated with hydrogen and don’t have maximum number of hydrogens
Double bond causes a kink in the chain of unsaturated fatty acids but saturated lies flat
What lipids are solids at r.t.p
Saturated lipids
Single bonds means no kinks in hydrocarbon tail
So lie flat and can pack tightly together as solids
What lipids are liquid at r.t.p
Unsaturated lipids with one or more double bonds in fatty acid tail/hydrocarbon chain
Because the kink causes the chains to be unable to pack tightly together hence liquid
E.g oil
Phospholipid
A type of lipid
Consisting of a molecule of glycerol
Bonded to a phosphate group
And go two molecules of glycerol by ester bonds
Phospholipid function
Main component of cell membranes
Forming the phospholipid bilayer
Explain the structure and interaction of phospholipids
Phosphoglycerol head is hydrophilic because it is polar (-ve) and so attracts water
The fatty acids are hydrophobic and so repel water
In water they form small droplet called micelles
The hydrophobic tails orientate into the middle and the hydrophilic heads outwards towards the water
Test for reducing sugars
Benedicts test
Add 2cm³ benedicts solution to sample
Heat to 95°C
Colour change from blue to green/yellow/orange/red/brick red precipitate indicates presence of reducing sugar
Stronger colour change means more reducing sugar present
No colour change means no reducing sugar but may be a non reducing sugar
Test for non reducing sugars
Modified benedicts test
Add 2cm³ benedicts solution to sample
Heat to 95°C
Colour change from blue to green/yellow/orange/red/brick red precipitate indicates presence of reducing sugar
Stronger colour change means more reducing sugar present
No colour change means no reducing sugar but may be a non reducing sugar
Boil a fresh sample with dilute hydrochloric acid for a few minutes to hydrolyse glycosidic bonds
Neutralise by adding small solid pieces of sodium hydrogen carbonate
Repeat benedicts test
Colour change (like a reducing sugar) means non reducing sugar is present
Since the sucrose has been hydrolysed, it can react with the benedicts solution to give a positive result
Reducing sugars
Glucose Fructose Lactose Maltose Galactose
Non reducing sugars
Sucrose
Monosaccarides
Glucose
Lactose
Fructose
Disaccharides
Maltose (Glucose+Glucose)
Sucrose (Glucose+Fructose)
Galactose (Glucose+Galactose)
What elements do amino acids contain
Nitrogen
Carbon
Hydrogen
Oxygen
Some contain Sulphur
List the parts of an amino acid
Amino/amine group (NH2) Carboxylic acid group (COOH) Variable side chain (R) Hydrogen (H) All attached to centre carbon (alpha)
Explain the ends of an amino acid
N terminal ~ Amine group at the end
C terminal ~ Carboxyl group at the opposite end
How do amino acids bond
Via condensation reactions
A molecule of water is released as a peptide bond produced
Between the amine and carboxyl group
The water is from the hydroxyl group of one amino acid and hydrogen from the amine of the other
What makes amino acids different
The different R groups (variable side chains)
Primary structure
Type Number Order Of amino acids in polypeptide chain Held together by peptide bonds (C-N) from condensation reactions
Secondary sturcture
The way the polypeptide chain folds into a beta pleated sheet
Or coils into an alpha helix (H bond every 4th AA)
Held together by weak hydrogen bonds
Tertiary structure
Further folding of peptide chain into a specific complex 3D structure
R groups determine how it folds
Held together by ionic bonds between ionised oppositely charged R grouos
Hydrogen bonds between R groups
Disulphide bridges between cysteine amino acids
Final 3D structure for proteins made of one polypeptide
Quaternary structure
The way multiple polypeptide chains assemble themselves
Held together by ionic, hydrogen and disulphide bonds
Some van der waals
Bonds between different polypeptide polypeptides
Final 3D structure for proteins made of more than 1 polypeptides
Where do hydrogen bonds occur in proteins
Secondary structure
Tertiary structure between H and O atom of different hydroxyl groups
Quaternary between H and O atom of different polypeptides
Where do ionic bonds form in proteins
Tertiary
Between opoisitely charged R groups of different amino acids
Quaternary
Between oppositely charged R groups of different polypeptide chains
Where do disulphide bridges form in proteins
Tertiary
Between sulphur and hydrogen of adjacent variable R groups
Usually cysteine amino acid
Quaternary
Between sulphur and hydrogen of suffering polypeptides amino acids R groups
What are van der waals and where are they found
Hydrophobic interactions
Between R groups that are both water hating
List 3 types of globular proteins
Transport proteins
Enzymes
Hormones
Examples of the globular transport proteins
Haemoglobin
Carrier proteins
Channel proteins
Examples of the globular protein enzymes
Lipase
DNA polymerase
ATP synthase
Examples of the globular protein hormones
Insulin
Oestrogen
Thyroxine
What is a globular protein
A type of protein that is spherical in shape
And soluble in water
3 types of structural protein
Collagen
Keratin
Silk
Explain the 3 types of structural protein
Collagen: Connective tissue e.g tendons/cartilage
Keratin: Hair and nails
Silk: In spiders webs
Structural protein
Type of protein that is strong, tough and insoluble in water
Made of elongated or fibrous polypeptide chains
3 polypeptides
Why are enzymes only specific to one substrate
Enzymes have a specific 3D tertiary structure
Which determines the shape of active site so it is only complementary to one substrate
Therefore it can only form an Enzyme Substrate Complex with the one substrate complementary to its active site
So can only catalyse one type of reaction
Test for proteins
Biuret test for proteins
Detects peptide bonds
Add equal volumes of sample and biuret solution to a test tube
Colour change of blue to purple/violet = protein present
No colour change, stays blue = no protein present
What are enzymes
Globular proteins
That are biological catalysts
Increase the rate of reaction by lowering the activation energy
By stretching/distorting/weakening substrate bonds
Not used up in the reaction and remain unchanged
Explain the lock an key model
Active site is rigid and does not change shape
Substrate enters and binds to enzymes active site
Substrate fits exactly into it - complementary
Products are formed and no longer fit into active site
So released
Enzyme free to take part in another reaction
Explain the induced fit model
Substrate enters enzymes active site and binds to it to form enzyme substrate complex
Binding induces a change in shape of active site
Slight change in shape of 3D specific tertiary structure of active site causes stress/distorts substrates bonds
Lowering the activation energy of reaction
When substrate leaves, active site returns to original shape
Compare and contrast globular and fibrous proteins
Both have peptide, hydrogen and ionic bonds
Same bank of 20 amino acids makes them up
Globular round and spherical/Fibrous elongated
Globular compact and folded/Fibrous strong and tough
Globular soluble in water/Fibrous insoluble in water
Globular involved in metabolic reactions/Fibrous involved in forming structures
How does temperature affect enzyme activity
T^ to optimum, so does rate
Increases kinetic energy of substrates molecules
More likely to successfully collide and react
More ESC/second
Beyond optimum
Atoms within amino acids vibrate faster because more kinetic energy
Causes weak hydrogen bonds and ionic bonds between neighbouring amino acids to break
3D tertiary structure changes and coukd alter active site
No longer complementary to substrate
No ESC
Denatured and no longer catalyses any chemical reactions
How does denaturation occur
Beyond optimum
Atoms within amino acids vibrate faster because more kinetic energy
Causes weak hydrogen bonds and ionic bonds between neighbouring amino acids to break
3D tertiary structure changes and coukd alter active site
No longer complementary to substrate
No ESC
Denatured and no longer catalyses any chemical reactions
How does pH affect enzyme activity
pH is a measure of hydrogen ion concentration
If pH is changed from optimum (more acidic or more basic)
The charge on the R groups of amino acids are altered
Ionic bonds and weak hydrogen bonds are broken in tertiary structure
Active site changes shape
Substrate no longer complementary
Less/no ESC formed
Rate decreases
Enzyme denatured
What is pH
Measure of hydrogen ion concentration
2 types of inhibitors
Competitive
Non competitive
What are inhibitors
Substances that decrease the rate of reaction by binding to enzyme at active site or allosteric site
What is a competitive inhibitor
Similar structure to substrate
Binds to active site
Prevents substrate from binding
Fewer ESC/second
Reduced rate
Some product still formed if not all enzymes occupied
Takes longer for all substrate to form products as opposed to no inhibition
What is a non competitive inhibitor
Binds to enzyme away from active site at allosteric site
Causes a change in shape to enzyme and active site
Substrate no longer complementary to active site
Fewer ESC/second
Fewer products
How does substrate concentration affect the rate of reaction
When substrate concentration is low so is the rate of reaction because there are few collisions
So few ESC/second
Substrate is the limiting factor
As concentration increases, more active sites filled and more ESC/second (substrate still a limiting factor)
Plateaus when all enzymes active sites are saturated and enzyme is new limiting factor
Rate falls to 0 when all substrate converted into product
What 4 things can R groups be
Hydrophobic (repels water)
Hydrophilic (attracts water)
Negatively charged
Positively charged
What is the optimum temperature
Temperature at which enzymes perform best at (fastest rate)
Maximum kinetic energy that can be applied to molecules before the hydrogen and ionic bonds start to break
Why can a protein be a substrate for 2 different enzymes
Different parts of protein have different amino acid sequence and different shapes
Each enzymes active site has a specific shape
And 2 different enzymes can be completely to different parts of the same protein
2 types of amino acids
Essential
Non essential
What are essential amino acids
Obtained from food and diet
What are non essential amino acids
Can be synthesised by the body
Example of essential amino acids
Valine
Leucine
Tryptophan
Examples of non essential amino acids
Glycine
Tyrosine
Serine
Where does the condensation reaction between 2 monosaccharides occur
Between the OH hydroxyl groups on C4 of one monosaccharide
And the OH hydroxyl groups on the C1 of another
Isomer
Same chemical formula
Different atom arrangement
Sources of glucose
Fruit and veg
Honey
Dairy
Sources of galactose
Fruit and veg
Dairy
Sources of fructose
Fruit and veg
Honey
Sources of maltose
Fermentation
Found in germinating seeds
Lactose sources
Found in milk of lactating female mammals
Sources of sucrose
Transported in the phloem of plants
Why are hydrogen bonds important in cellulose
Holds chain/molecules together to form cross links between chains called microfibrills
Providing strength and rigidity to cellulose cell wall
Weak hydrogen bonds provide strength in large numbers
Hydrolysis of disaccharide equation
C12H22O11 + H2O»_space;> C6H12O6 + C6H12O6
Condensation reaction for a disaccharide
C6H12O6 + C6H12O6»_space;> C12H22O11 + H2O
Features of sugars and features of polysaccharides
Sugars: sweet, soluble, white crystalline
Polysaccharides: Not sweet, insoluble
What is a precipitate
A solid suspended in a lipid
2 different reducing sugars of same concentration both produce red precipitates
After 10 minutes one had twice as much precipitate
Why
One solution was a disaccharide that was at the same concentration as the monosaccharide
The enzyme hydrolysed the glycosidic bond in the disaccharide
Releasing two monosaccharides
The two monosaccharides are both reducing sugars
So there is double the amount of reducing sugars
Meaning double the precipitate in benedicts test
How would you determine the concentration or an unknown solution
Make up different known concentrations of ‘x’
Carry out the correct test on each sample
Take readings of absorbance/transmission
Using a colorimeter
Plot readings to produce a graph called a calibration curve
With concentration on x and absorbance on y
Draw a line of best fit
Read unknown sample absorbance/transmission from the calibration curve
Read off corresponding concentration of solution
How can an acidic pH make proteib active
Change in ionic and hydrogen bonds/breaks them
So changes the tertiary structure
