Biological Molecules

Question 1

Why do all living things have a similar biochemical basis?

Answer 1

Monomers and polymers of four kinds of organic polymers: lipids, carbs, proteins and nucleic acids.

Question 2

What is a monomer?

Answer 2

Small identical (or similar) molecules joined together to make polymers.

Question 3

What is a polymer?

Answer 3

Large molecules made from joining many identical monomers.

Question 4

Examples of monomers

Answer 4

B-glucose, Nucleotides, a- glucose etc.

Question 5

Examples of polymers?

Answer 5

Polynucleotides, Cellulose, Amylose.

Question 6

Describe a condensation reaction.

Answer 6

Joining two monomers with the removal of one water, forming a bond.

Question 7

Describe Hydrolysis

Answer 7

Adding one water molecule to break the bond between two monomers.

Question 8

Test for reducing and non-reducing sugar.

Answer 8

Reducing: benedicts, heat 95 for 5 mins, blue to brick red.

Non-reducing: negative benedict’s, HCL, boil for 5 mins, NaHCO3, benedict’s test, brick red ppt.

Question 8

Two monomers of glucose and their differences

Answer 8

A and B glucose.
B glucose has the same structure but the H and OH group are inverted on C1

Question 9

Describe how the three disaccharides are formed? (Maltose, Lactose, Sucrose)

Answer 9

Condensation reaction, 1-4 glycosidic bond, producing water.

glucose + glucose –> maltose
glucose + galactose –> lactose
glucose + fructose –> sucrose

Question 9

How are polysaccharides formed?

Answer 9

Polymer formed by joining many monosaccharides together.

Question 10

Describe how larger carbohydrates are formed from monosaccharides.

Answer 10

Condensation reaction between monosaccharides forming a glycosidic (covalent) bond and producing water, catalysed by an enzyme.

Question 11

Structure of Glycogen and Starch?

Answer 11

A glucose
condensation reaction
1-4 and 1-6 glycosidic bonds producing water
Branched + Helical/ highly branched
Large insoluble
compact.

Question 11

Test for starch?

Answer 11

iodine brown/orange to blue/black

Question 12

Formation of Cellulose?

Answer 12

B glucose
Long straight chains
Every other B glucose rotates 180
1-4 glycosidic bonds cond reaction water.
H bonds between chains
Microfibrils
High tensile strength, support and rigidity, resists turgor pressure.

Question 13

Structure to Function of Starch?

Answer 13

Plants
Compact- lot in a small space
Large and Insoluble- no effect on water potential.
Branched allow hydrolysis of terminal glucose for respiration.

Question 14

Structure to Function glycogen

Answer 14

Animals
Compact- lot in a small space
Large and Insoluble- no effect on water potential.
Highly Branched allow hydrolysis of terminal glucose for respiration.

Question 15

Structure to function of cellulose

Answer 15

Long unbranched chains with H bonds in between forming strong microfibrils which resist turgor pressure.

Question 16

What are lipids made from

Answer 16

Glycerol, fatty acids (and phosphate)

Question 17

Roles of lipids

Answer 17

Dense Storage Molecule
Forms membranes
Insulation
Protection

Question 18

How can lipids be fats/oils ?

Answer 18

Saturated/ unsaturated fatty acids R groups:

Double/ No double bonds
(Only single bonds)
H can/cannot be added
Long straight chains/ kinked chains.
Stronger/Weaker IMF
Higher/Lower MP
Solid/Liquid at rtp

Question 19

Test for lipids?

Answer 19

Ethanol + water mix, colourless to positive cloudy white emulsion.

Question 19

Formation of Triglycerides.

Answer 19

One glycerol, three fatty acids, 3 cond reactions, 3 waters, 3 ester bonds.

Question 20

Formation of phospholipids.

Answer 20

One phosphate, oen glycerol, 2 fatty acids. Hydrophobic tails, hydrophilic head, 2 ester bonds.

Question 21

Structure of Triglycerides relate to their properties?

Answer 21

High ratio of C-H bonds to C atoms, better at storing energy. Low Mass- Energy ratio makes for better energy storage. Large and non polar no effect on water potential. High ratio of H- O atoms so good source of H2O.

Question 22

General structure of an Amino acid

Answer 22

Amine and Carboxyl group with C bonded to ONE H and ONE R grp.

Question 22

Structure relates to function for phospholipids.

Answer 22

Phospholipids form a bilayer in water, cell surface membrane. Allows lipid soluble molecules in, polar molecules cant pass through membrane.

Question 23

How can a functional protein contain one or more polypeptides?

Answer 23

Enzymes are made up of one polypeptide chain and only have a tertiary structure. Quaternary proteins have multiple chains and possibly a prosthetic group. e.g haemoglobin has 4 polypeptide chains and iron 2 ion.

Question 23

How many different types of Amino Acids are there and how are they different?

Answer 23

Around 20 Amino Acids. Differ in R groups.

Question 24

How does a polypeptide form.

Answer 24

Amino acids join together in condensation reactions to form a polypeptide chain and water with peptide bonds.

Question 25

Primary to Quaternary structures of proteins?

Answer 25

Primary: Number and Sequence of Amino Acids. Folds and H bonds between Amine and Carboxyl Groups Secondary: A helix or B pleated sheets. Folds and Bonds form between R groups, H, Ionic, disulphide bridges, hydrophilic hydrophobic interactions. Tertiary: Unique specific 3d shape. Folds, may join with other polypeptide chains, addition of prosthetic group. Quaternary: Functional Protein such as haemoglobin.

Question 26

Explain how all proteins have a variety of function within all living organisms.

Answer 26

Their roles depend on their molecular shape, either fibrous proteins, or globular proteins.

Question 27

Can you relate the structure of proteins to a variety of proteins? Globular and fibrous proteins.

Answer 27

Globular: Coiled/Spherical, hydrophilic out phobic in, soluble Roles in Metabolic reactions (enzymes) Fibrous: long/unbranched, philic in phobic out insoluble Structural roles (keratin/collagen)

Question 28

Can you describe the role of hydrogen bonds, ionic bonds, and disulfide bridges in the structure of proteins?

Answer 28

Disulfide bridges: ~ Fairly strong and therefore not easily broken. - Ionic bonds: ~ Formed between any carboxyl and amino groups that are not involved in forming peptide bonds. ~ They're weaker than disulfide bridges and are easily broken by changes in pH. - Hydrogen bonds: ~Numerous but easily broken. Forms tertiary structure, affects active site of enzymes, changes in these bonds can denature enzymes

Question 29

Test for Proteins.

Answer 29

Biuret reagent, shake vigorously, blue to lilac and foam

Question 30

Can you explain how each enzyme lowers the activation energy of the reaction it catalyses?

Answer 30

stressing/ bending bonds in substrate during formation of ES complex.

Question 31

Describe how you would measure the rate of an enzyme-catalysed reaction and explain the results you would expect?

Answer 31

Conc of products, Conc of reactants High initial rate of reaction, rate decreases until graph plateaus.

Question 31

How does an enzyme's structure relate to its function?

Answer 31

Specific tertiary structure due to specific order of amino acids. active site complementary to their specific substrate.

Question 32

Can you describe the induced-fit model of enzyme action?

Answer 32

Active site not initially complementary Substrate causes a change in shape of the active site as it binds forming ES complex. Substrate released as products, leaving the enzyme to revert back to its original shape.

Question 33

Can you describe how models of enzyme action have changed over time?

Answer 33

Lock and Key: active site always complementary. Induced fit: active site changes shape to become complementary and reverts back after catalysis complete.

Question 34

How does the temperature affect the rate of an enzyme-controlled reaction?

Answer 34

As Temp increases, rate increases up to optimum. more frequent successful collisions. After optimum, R group Bonds break change shape of active site. Denaturation.

Question 35

How does the pH affect the rate of an enzyme-controlled reaction?

Answer 35

rate increases closer towards optimum ph. away from optimum increased conc of H+/OH- ions cause charges of AA to become altered, breaking ionic bonds and altering the shape of the active site or repelling the substrates.

Question 36

How does the substrate concentration affect the rate of an enzyme-controlled reaction?

Answer 36

As conc increases, rate increases until it becomes constant. All active sites become occupied (V max) and conc of enzyme becomes the limiting factor

Question 37

How does the enzyme concentration affect the rate of an enzyme-controlled reaction?

Answer 37

Increase enzyme conc increases rate until reactants are no longer in excess, then no further effect.

Question 38

How does the concentration of competitive inhibitor affect the rate of an enzyme-controlled reaction?

Answer 38

inhibitor has similar shape to substrate, compete for enzymes active site. If substrate conc increases, inhibitor effect reduced. Inhibitor only temporarily binds to active site, temporarily reducing rate of reaction. Time until rate returns to original is dependent on conc of inhibitor.

Question 39

How does the concentration of non-competitive inhibitor affect the rate of an enzyme-controlled reaction?

Answer 39

Attach to allosteric site, changing shape and denaturing active site/enzyme. Permanently reducing rate of reaction by reducing number of available active sites. Enzyme can no longer function properly and increase in substrate has no effect on the inhibitor.

Question 40

what is End product inhibition

Answer 40

Chain of Enzyme catalysed reactions produce the final desired product which is an inhibitor of the initial enzyme that began the chain, halting the reaction chain.