Biological Molecules( Biological Molecules ) Flashcards
What are the four elements amino acids are made up from
Carbon , hydrogen ,oxygen and nitrogen
What do amino acids often contain (2 elements )
Sulphur and phosphorus
What test detects proteins
Buiret test detects the prescience of peptide bonds .
What is a dipeptide
Two amino acids
How are dipeptides created
Condensation of two amino acids forms a dipeptide bond held by a peptide bond
What happens when a dipeptide is created
The peptide bond is formed between the CH (carboxyl) group on first amino acid and amino group on second amino acid which also releases water
What is the name for the reaction breaking the disaccharide
Hydrolysis reaction splits apart the disaccharide leaving 2 monosaccharides
What is polymerisation (amino acids)
Dipeptides can become polypeptides in repeated condensation reactions
Example peptide bond question : if you have 383 amino acids , how many peptide bonds do you have?
- (-1 as 3 amino acids only has 2 peptide bonds )
What does the primary structure of a protein determine
It’s shape and function
What is the primary structure protein
It’s a chain of amino acids joined in condensation reactions by peptide bonds , creating a specific sequence of amino acids . Which therefore dictates its bonds and therefore structure and function
What is the secondary structure protein
Either alpha helix or beta pelted sheet , hydrogen bonds form which causes the long polypeptide chain to be twisted into a 3D shape.
What is the tertiary structure of proteins
Can be twisted and folded into more complex 3D shapes which is maintained by a number of different bonds
Hydrogen bonds -between amino and carboxyl to maintain shape
But easily broken
Ionic bonds -are easily broken by changes in ph . Polar interactions of the R groups maintain shape
Disulphide bridges -fairly strong not easily broken .
Why is the 3D shape of a protein so important
It makes each protein distinctive and allows it to recognise and be recognised by other molecules , it can then interact with them in a very specific way.
What is the quaternary structure
Quaternary protein structures are made of 2 or more tertiary proteins joined together by all the same bonding as tertiary
How is haemoglobin a quaternary structure
Haemoglobin consists of 4 tertiary structures bonded together with iron in the middle
what is the structural formula for glucose
CH2OH (C6H12O6)
c o
c h oh h c h oh
h c c c
ho h oh
describe how hydrolysis works with a disaccharide?
when water is added to a disaccharide under suitable conditions it breaks the glycocidic bond releasing the monosaccharides.
what is a monosaccharide
a simple sugar molecule( one unit of carbohydrate)
what elements do all carbohydrates contain?
all carbohydrates contain only carbon , hydrogen and oxygen
give 3 examples of monosaccharides
glucose , galactose , fructose
are monocaccharides soluble or insoluble
soluble
what is the general formula of a monosaccharide
(Ch20)n
what do monosaccharides end in
‘ose’
what is hexose
hexose is a sugar which contains 6 carbon atoms glucose is an example of a hexose
in alpha glucose the OH on carbon 1 is on the bottom how is it in beta glucose?
it is flipped so the OH (carboxyl) group is above
how do disaccharides form?
through condensation reactions which water is removed and a glycocidic bond is formed between c1 and c4
examples of disaccharides
glucose + glucose =
maltose (malt sugar) 2 glucose molecules joined by an alpha 1-4 glycocidic bond
glucose + fructose =
sucrose . joined by an alpha 1-4 glycocidic bond
galactose + glucose =
lactose (milk sugar) . joined by a 1-4 glycocidic bond
what are the 2 main functions of monosaccharides
they are used as a primary energy source for fuelling metabolism and joining together to form ccarbohydrate macromolecules
what are isomers
isomers are compounds with the same chemical formula but different arrangements of atoms so have different properties. for example glucose - alpha and glucose -b are both c6h12o6 but the oh and h are flipped round
give 3 examples of polysaccharides and state if they are in plant or animals
starch (plant) , glycogen (animal) and cellulose(plant)
why are polysaccarides insoluble
because they are very large molecules
what are the two types of starch
amylose and amylopectin
describe amylose
amylose is unbranched and monomers are connected by an alpha 1-4 glycocidic bond and is wound into a tight coil which makes it compact
describe amylopectin
amylopectin is branched with 1-4 and 1-6 bonds
describe glycogen
glycogen is branched 1-4 bonds and 1-6 bonds it is insoluble , compact .
What are the two types of proteins and what they have and an example
Fibrous have structural functions eg collagen and globular have metabolic functions eg enzymes and haemoglobin
Describe fibrous proteins
Fibrous proteins form long chains which run parallel to one another . These chains are linked by cross bridges and so form very stable molecules.
Why are fibrous proteins generally insoluble in water
Fibrous proteins have a large proportion of amino acids with hydrophobic r groups , this means unlike globular proteins , fibrous proteins are insoluble in water
What is the shape of fibrous proteins
Long and narrow
What is the shape of globular proteins
Round / spherical
What is the acid sequence of fibrous proteins
Repetitive amino acid sequence
What is the acid sequence of globular proteins
Irregular amino acid sequence
How durable are fibrous proteins
They are less sensitive to changes in PH, TEMP etc than globular
How durable are globular proteins
More sensitive to changes in PH , temp etc than fibrous
Give 6 examples of fibrous proteins
Collagen , myosin , fibrin , actin , keratin , elastin
Give 4 examples of globular proteins
Enzymes , haemoglobin , insulin , immunoglobulin
Are globular proteins soluble or insoluble in water
Generally soluble in water
What are enzymes structure
A chain of amino acids in a globular tertiary structure
How do enzymes speed up a reaction
Reduces the activation energy
What is the word for bond breakage
Catabolic
What is the word for bond formation
Anabolic
What is the word for inside cell reactions
Intracellular
What is the word for outside cell reactions ( eg tissue fluid , blood )
Extracellular
What is the induced fit theory
Active site does not fit substrate so The active site can be partially flexible enzyme active site changes shape slightly so they are complementary , and therefore enzyme-substrate complex forms and so a substrate can bind even when it’s not a perfect fit .
Therefore bending bonds in substrate leading to a reaction
What is the lock and key theory
Random movement causes the enzyme and substrate to collide , and the substrate enters the active site . Enzyme - substrate complex forms . Charged groups attract distorting the substrate and aiding catabolic or anabolic . Then products are released from the active site leaving the enzyme unchanged and ready to accept another substrate molecule
What does it mean when an enzyme is denatured
The active site of an enzyme changes shape and can no longer fit the substrate
How are enzyme reactions affected
Temperature , ph , enzyme concentration , substrate concentration and the presence of inhibitors
Define a catalyst
A substance that alters the rate of a chemical reaction without undergoing permanent change
what is an inhibitor
they are subtances that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity
define a competitive inhibitor
a substance which binds to the active site of an enzyme
define a non competitive inhibitor
a substance which binds to an enzyme at a postition other than the active site
What is a reducing sugar
One which can donate an electron to another molecule
What’s the test for a reducing sugar
Add 2cm^3 sample to a test tube , if not already liquid grind add water and filter , add 2cm^3 Benedict’s reagent 3. Ensure the solutions are mixed by gently tilting , heat the mixture in a water bath for 5 min
Test for non reducing sugars
Add 2 cm^3 sample to a test tube then add 2cm^3 of dilute hydrochloric acid and heat for 5 min in a water bath to hydrolyse the glycosidic bonds then add sodium hydrogen carbonate solution drop by drop to neutralise the acid (it will fizz) , test with universal indicator paper to ensure it has neutralised if not keep adding solution . Then add 2cm^3 Benedict’s reagent and heat in a water bath
what are the two types of lipids
triglycerides and phospholipids
how are triglycerides made
made up of 2 different molecules , glycerol and 3 fatty acids . 3 condensation reactions (releasing h20) forming ester bonds
where are the ester bonds in a triglyceride
between the carbons and oxygen from fatty acids and glycerol
what are the functions of lipids
buoyancy in marine mammals , cell membranes , energy storage , insulation , metabolic water and protection of organs
how can lipids be a source of energy
when oxidised lipids provide more than twice the energy as the same mass of carbohydrate and release valuble water
how do triglycerides provide metabollic water for eg camels
as they have a high ratio of hydrogen to oxygen atoms triglycerides release water when oxidised and therefore provide an important source of water
how are lipids good at waterproofing
lipids are insoluble in water and therefore useful as a waterproofing
what is ther r group on the fatty acids
the straight chain of carbon atoms
what does it mean if the lipid is saturated
The fatty acid hydrocarbon chain has only single bonds between carbons . they tend to be solid at normal temps because they can be tightly packed
what does it mean if the lipid is unsaturated
The fatty acid hydrocarbon chain consists of at least one double bond between carbons . doesnt have enough hydrogens . normally liquid
what is a phospholipid made of
phosphate , glycerol and fatty acids
why is phospholipids polar
They have two charged regions .they have a hydrophillic head and a hydrophobic tail therefore they can position themselves so that the hydrophillic heads are as close to the water as possible and hydrophobic as far away as possible
what is the bond between fatty acids and glycerol called
ester bond
what is the test for lipids
emulsion test .
- take a completely dry and grease free test tube
- if sample is sold break up into very small peices . if liquid just add 2 cm 3 of sample . then add 5cm3 ethanol
- shake the tube thoroughly to dissolve any lipid in the sample
4.add 5cm3 of water and shake gently add distilled water - a milky white emulsion indicates the prescence of a lipid if its clear none prescent
6.as a control repeat proceedures using water instead of the sample and this should stay clear
why is there a cloudy colour
the cloudy colour is due to any lipid in the sample being finely dispersed in the water. to form a emulsion light passing through the emulsion is refracted as it passes from oil to water droplets making it appear cloudy
What kind are animal lipids and what do they occur as
Animal lipids are saturated and occur as fats eg butter
What kind are plant lipids and what do they occur as
Plant lipids are unsaturated and occur as oils eg olive oil
What is the initial rate of a reaction
The instantaneous rate at the start of the reaction
Why is rate initially high
Lots of substance , rate slows down over time as amount of substance decreases
what is collagen an example of
a fibrous protein
what is the primary structure of collagen
an unbranched polypeptide chain
what is the secondary structure of collagen
very tightly wound polypeptidechain
how does collagen pack closely
it has lots of the amino acid glycine
what is the tertiary structure of collagen
the chain is twisted into a second helix
what is the quaternary structure of collagen
three polypeptide chains would together to form a triple helix. these make microfibrils and fibrils and these are staggerd so there are no weak spots and furtheer strengthened by cross links between triple helical molecules
state two properties of collagen which make it suitable for ligaments (bones to bones)
strong and insoluble (also flexible but does not stretch)
what is it called when a graph levels off
reaches plateau
What’s the location of starch
Plants as starch grains
What’s the location of starch
Plants as starch grains
How does the structure of starch relate to its function
Helix shape can compact to fit a lot of glucose into a small space. Branched structure increases surface area for rapid hydrolysis from starch to glucose . Additionally it’s insoluble so won’t affect water potential so water is not drawn into cells by osmosis and it itself cannot diffuse out of cells
What is the structure of cellulose
Long straight chains , which run parallel with hydrogen bonds in between to form fibrils. monomers of beta glucose . cellulose molecules alternate .
How does cellulose structure relate to its function
Many hydrogen bonds collectively provides strength to cell wall as many hydrogen bonds is difficult to break. cellulose can resist turgor pressure
How does glycogen structure relate to its function
It’s very highly branched and therefore a lot of free ends and faster hydrolysis back to glucose , this is important because animals have a high metabolic rate and therefore need glucose for respiration and this can be rapidly converted to glucose as it’s highly branched additionally insoluble so won’t affect water protein tusk
Where is glycogen found
Muscle and liver cells
Describe two differences between the structure of a cellulose molecule and a glycogen molecule.
1.Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
2. Cellulose molecule has straight chain and glycogen is branched;
Describe and explain two features of starch that make it a good storage molecule.
Insoluble (in water), so doesn’t affect water potential;
2. Branched / coiled / (α-)helix, so makes molecule compact;
OR
Branched / coiled / (α-)helix so can fit many (molecules) in
small area;
3. Polymer of (α-)glucose so provides glucose for respiration;
4. Branched / more ends for fast breakdown / enzyme action;
5. Large (molecule), so can’t cross the cell membrane
What’s the tips for polysaccharide questions
Say about glucose being used for respiration and say they are polysaccharides
What are the reducing sugars
Glucose , fructose , galactose , lactose and maltose
What are the non reducing sugars
Sucrose
Why would an animal use lipids instead of carbohydrates as an energy store
Lipids provide more than twice as much energy than carbohydrates when oxidised as they have a low mass to energy ratio making them good storage molecules as more energy can be stored in a smaller volume
In the secondary structure protein how do the hydrogen bonds form
They form between the NH group and C=O group ( as water has been removed )
Two proteins have the same number and type of amino acid but different tertiary structures, explain why
Different sequence of amino acids , so different primary structure and therefore hydrogen bonds , ionic and disulphide Bridges form in different places
What is one difference between competitive and non competitive inhibitors
Non competitive , increase in substrate concentration does not change enzyme activity / high substrate conc does not overcome inhibition / maximum rate not retained
Why does an unsaturated fatty acid increase the fluidity of the membrane
Increase in fluidity caused by increased unsaturated fatty acids as contain double bonds which cause kinks in fatty acid tail therefore phospholipids further apart
Why does an unsaturated fatty acid increase the fluidity of the membrane
Increase in fluidity caused by increased unsaturated fatty acids as contain double bonds which cause kinks in fatty acid tail therefore phospholipids further apart
What must you remember with the induced fit model
Active site changes shape not the substrate
State how enzymes help reactions to proceed quickly at lower temps
Lower the activation energy
why does maltose lower water potential
because it is soluble in water
