Solved: Outline the control of metabolism by end-product inhibition. Outline the... [IB Biology (Old)]

Question

HLPaper 2

Outline the control of metabolism by end-product inhibition.

[3]

Verified

Solution

a. end-product of a metabolic pathway inhibits an enzyme earlier in the pathway ✔

b. end-product binds to allosteric site of enzyme ✔

c. changes shape of active site of enzyme ✔

d. enzyme activity reduced/stopped when end-product binds ✔

e. production of end-product reduced/stopped when enzyme inhibited ✔

f. production resumes when end-product used up/concentration of end-product falls ✔

g. example of end-product inhibition ✔

Outline the functions of rough endoplasmic reticulum and Golgi apparatus.

[3]

Verified

Solution

Rough Endoplasmic Reticulum (RER)

Synthesis of proteins/polypeptides 1 mark
Ribosomes on surface/attached to RER 1 mark
Proteins for secretion/export/use outside cell OR proteins for use in lysosomes/cell membrane 1 mark
Modification/processing/folding of proteins 1 mark
Synthesis/processing of lipids/phospholipids 1 mark
Storage of calcium ions 1 mark

Golgi Apparatus

Further modification/processing of proteins 1 mark
Packaging/vesicle formation of proteins for secretion/export 1 mark
Formation of lysosomes 1 mark
Synthesis/processing of carbohydrates/glycoproteins/glycolipids 1 mark

Explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane.

[7]

Verified

Solution

a. Hydrophilic is attracted to/soluble in water and hydrophobic not attracted/insoluble ✔

b. Hydrophilic phosphate/head and hydrophobic hydrocarbon/tail in phospholipids ✔

c. Phospholipid bilayer in water/in membranes ✔

\begin{array}{ccc} \text{Hydrophilic} & \text{Hydrophobic} & \text{Hydrophilic}\\ \text{head} & \text{tail} & \text{head} \end{array}

d. Hydrophilic heads of phospholipids face outwards/are on surface ✔

e. Hydrophobic tails of phospholipids face inwards/are inside/are in core ✔

f. Cholesterol is mainly hydrophobic/amphipathic so is located among phospholipids/in hydrophobic region of membrane ✔

g. Some amino acids are hydrophilic and some are hydrophobic ✔

h. Hydrophobic amino acids/regions of proteins in phospholipid bilayer core ✔

i. Hydrophilic amino acids/regions of proteins are on the membrane surface ✔

j. Integral proteins are embedded in membranes due to hydrophobic properties/region OR transmembrane proteins have a hydrophobic middle region and hydrophilic ends ✔

k. Peripheral proteins on are on the membrane surface/among phosphate heads due to being entirely hydrophilic OR carbohydrate part of glycoproteins is hydrophilic so is outside the membrane ✔

l. Pore of channel proteins is hydrophilic ✔

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