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Question 1

Give the definition of an enzyme.

Answer 1

• An enzyme is a biological catalyst, typically a protein, that speeds up chemical reactions in living organisms by lowering the activation energy required for the reaction to occur.
• Enzymes are highly specific to their substrates and do not get consumed in the reaction, meaning they can be reused.

Question 2

What is the Michaelis Menten equation?

Answer 2

Question 3

How do you calculate the reaction velocity (v) at a given substrate concentration [S]?

Answer 3

1) Measure the reaction rate (v): find the rate of product formation or substrate consumption by measuring the change of its concentration over time.
2) Plot the graph: reaction rate (v) vs. Substrate concentration [S]
3) Determine vmax: At high substrate concentrations, the enzyme is saturated, and the reaction rate reaches its maximum velocity (Vmax). Identify the point on the graph where the reaction rate
plateaus, indicating saturation.
4) Find Km: the substrate concentration which the reaction rate is half vmax - find the substrate concentration at which the reaction rate is half the maximum velocity
5) Substitute the values into the equation

Question 4

How is enzyme activity regulated?

Answer 4

Allosteric regulation – molecules bind to sites other than the active site to activate or inhibit the enzyme.

Covalent modification – chemical groups (like phosphate) are added or removed to alter activity.

Feedback inhibition – the end product of a pathway inhibits an earlier enzyme to prevent overproduction.

Proteolytic activation – inactive enzyme precursors (zymogens) are activated by cleavage.

Gene expression control – enzyme levels are regulated by increasing or decreasing their synthesis.

Question 5

What is animal plasma membrane?

Answer 5

The plasma membrane (also called the cell membrane), is the membrane found in all cells that separates the interior of the cell from the outside environment. In bacterial and plant cells, a cell wall is
attached to the plasma membrane on its outside surface.

Question 6

Plasma membrane: how is it interlinked with proteins?

Answer 6

The plasma membrane consists of a phospholipid bilayer which has embedded proteins for performing functions like transport and signalling

Question 7

What is the structure phospholipid bilayer?

Answer 7

• Membranes have a phospholipid bilayer structure, with hydrophobic fatty acid tails facing inward and hydrophilic phosphate heads facing outward.
• This arrangement creates a barrier that separates the internal and external environments.
• The lipid bilayer is fluid, allowing for dynamic movement of molecules within the membrane. -Proteins are embedded in or associated with the lipid bilayer and contribute to the membrane’s structure and function.

Question 8

What are crucial functions of the plasma membrane?

Answer 8

1) Barrier and compartmentalisation
2) Selective permeability
3) Cell signalling
4) Transport
5) Cell adhesion
6) Energy Production

Question 9

Function of plasma membrane: explain barrier and compartmentalisation

Answer 9

Membranes create barriers that separate different cellular
compartments, allowing for the establishment of distinct environments and specialized functions within cells. They regulate the entry and exit of molecules, ions, and signals, controlling the flow of
materials between compartments

Question 10

Function of plasma membrane: explain selective permeability

Answer 10

Membranes are selectively permeable, meaning they allow certain
molecules or ions to cross while restricting others. This property is vital for maintaining the internal
environment of cells and organelles and regulating ion gradients necessary for cellular processes
such as nutrient uptake, waste elimination, and energy production.

Question 11

Function of plasma membrane: explain cell signalling

Answer 11

Membranes contain receptors that recognize and bind specific signaling molecules,
initiating intracellular signaling cascades. These signals play crucial roles in cellular communication,
regulation of gene expression, and response to external stimuli.

Question 12

Function of plasma membrane: explain transport

Answer 12

Membranes facilitate the transport of molecules across cellular compartments. Integral
membrane proteins, such as channels, transporters, and pumps, mediate the movement of ions,
nutrients, and waste products across the membrane, maintaining homeostasis and allowing cells to
acquire necessary resources.

Question 13

Function of plasma membrane: explain cell adhesion

Answer 13

Membranes participate in cell adhesion and cell-cell interactions. Proteins, such as
cadherins and integrins, mediate adhesion between cells, contributing to tissue organization,
development, and immune response.

Question 14

Function of plasma membrane: explain energy production

Answer 14

Mitochondrial membranes play a crucial role in energy production through
oxidative phosphorylation. The inner mitochondrial membrane contains electron transport chain
complexes and ATP synthase, allowing for ATP generation.

Question 15

Name all the proteins that are involved in the plasma membrane!

Answer 15

1) Transport Protein (Channel)
2) Globular protein
3) Peripheral protein
4) Glycoprotein
5) Integral protein
6) Surface protein
7) Alpha helix protein

Question 16

Name all the proteins that are involved in the plasma membrane!

Answer 16

1) Transport Protein (Channel)
2) Globular protein
3) Peripheral protein
4) Glycoprotein
5) Integral protein
6) Surface protein
7) Alpha helix protein

Question 17

Name the functions of all proteins involved in the phospholipid bilayer

Answer 17

1. Transport Protein (Channel)
   – Facilitates the passive movement of specific ions or molecules across the membrane via channels or pores.
   
   2. Globular Protein
      – Often function as enzymes, transporters, or signaling molecules; their soluble and compact shape suits interaction with both the membrane and aqueous environments.
   3. Peripheral Protein
      – Attach to the membrane surface or to integral proteins; play roles in signaling, cell recognition, or structural support.
   4. Glycoprotein
      – Proteins with carbohydrate chains; involved in cell recognition, immune response, and communication.
   5. Integral Protein
      – Span the bilayer or are deeply embedded; function in transport, signal transduction, and anchoring the cytoskeleton.
   6. Surface Protein
      – Loosely attached to the membrane exterior; involved in cell signaling, interaction, or structural support.
   7. Alpha Helix Protein
      – Common structural motif in transmembrane proteins; forms helical segments that span the bilayer, contributing to transport or receptor functions.

Question 18

Calculation of Vmax

Answer 18

See calculation notes