Chapter 7

Question 1

What is the meaning of amphipathic.

Answer 1

Amphipathic refers to substances that possess both hydrophilic and hydrophobic properties.

Question 2

Define selective permeability

Answer 2

Selective permeability refers to the permissive passage of particular molecules/substances across a membrane.

Question 3

What is a phospholipid bilayer? State its function.

Answer 3

Phospholipids are made up of glycerol, two fatty acid chains and a phosphate group. They contain hydrophobic tails and hydrophilic heads which arrange themselves to form a bilayer, where the tails are within and interacting, and the heads are exposed to the outer aqueous solution.

Question 4

What is the fluid mosaic model?

Answer 4

The phospholipid bilayer is referred to as a fluid mosaic model as the bilayer is ‘fluid’ and the various structures within the membrane can be compared to that of a mosaic.

Question 5

Define/Explain passive transport. Give examples.

Answer 5

Passive transport refers to the transport of cellular materials/contents without the use/requirement of ATP/energy. The substances are moved across their concentration gradient. eg. Facilitated diffusion, Osmosis

Question 6

Define equilibrium.

Answer 6

Equilibrium refers to the equal spread of a particular molecule/substance across an expansive area.

Question 7

What is a concentration gradient?

Answer 7

The concentration gradient refers to the ‘region along which the density of a substance increases/decreases’

Question 8

Define the terms hypotonic, hypertonic and isotonic.

Answer 8

Isotonic: refers to a balance of concentration and therefore net movement in and out of the cell/membrane is equal. (preferred for animal cells)
Hypertonic: refers to a higher concentration of solute. a cell in such solution will have water leaving itself, becoming flaccid or shriveled (plasmolyzed).
Hypotonic: refers to a lesser concentration of solute whereby water will enter the cell, which will either burst(animal) or become turgid(plant). (preferred for plant cells).

Question 9

What are aquaporins?

Answer 9

Aquaporins are protein channels that allow for the rapid movement of water across the phospholipid membranes.

Question 10

What is active transport? Give examples.

Answer 10

Active transport refers to the movement of substances against their concentration gradient, therefore requiring energy/ATP.

Question 11

Explain the concept of Bulk Transport.

Answer 11

Bulk transport generally occurs with larger macromolecules, whereby they are transported across plasma membranes by exocytosis or endocytosis.

Question 12

Explain the concept of Pinocytosis.

Answer 12

Pinocytosis is a form of endocytosis whereby substances are taken into the cell in small ‘gulps’ or groups of vesicles. It is referred to as cell drinking.

Question 13

Explain the concept of Phagocytosis.

Answer 13

Phagocytosis/ Cell eating is a form of endocytosis where the substance/particle is engulfed by pseudopodia and digested into the cell.

Question 14

Explain the concept of Exocytosis.

Answer 14

Exocytosis refers to the transport of substances outside of the cell through the plasma membrane.

Question 15

Explain the concept of Receptor Mediated Endocytosis.

Answer 15

Receptor Mediated Endocytosis refers to the process of specified endocytosis. Particular substances/particles coagulate in an area around a cell receptor and is ingested through vesicles into the cell. The receptors then return to the extracellular membrane and the cycle continues.

Question 16

What are the functions of Biological membranes?

Answer 16

Biological membranes aid in the net traffic of cells and allow for osmoregulation of substances within the cells. This is important as cell contents require certain environments to function best.

Question 17

What are the different parts of a phospholipid bilayer?

Answer 17

The 2 fatty acid chains ( hydrophobic tails), phosphate (hydrophilic head), channel and carrier proteins, cholesterol, glycoproteins and glycolipids, outer proteins.

Question 18

What influences a membrane’s fluidity?

Answer 18

The composition/number of double bonds(increased-more fluid due to less packing), length of the fatty acid chains, cholesterol (high temp-less fluid)

Question 19

What is Diffusion?

Answer 19

Diffusion is the movement of particles over an expansive area across the concentration gradient until equally spread.

Question 20

What is Osmosis?

Answer 20

The movement of water particles across a semipermeable membrane across its concentration gradient.

Question 21

What is facilitated diffusion? Is it considered active or passive transport?

Answer 21

Facilitated diffusion is considered passive transport as it does not require energy due to movement being across the concentration gradient. It simply utilizes a transport protein channel due to the difference of polarity of substances and the bilayer tails.

Question 22

What is the difference between channel and carrier proteins?

Answer 22

Channel proteins allow for passage of polar substances across the membranes. Carrier proteins also do this, but are more specified to particular substances, and they change their shape/orientation in order to transport these substances across the membrane.

Question 23

What is the difference between primary and secondary active transport?

Answer 23

Primary active transport directly uses ATP to power the transport against the concentration gradient. Secondary active transport indirectly uses ATP to drive the transport as it uses the energy from another concentration gradient.

Question 24

What is secondary active transport?

Answer 24

Secondary active transport

Question 25

Explain the Na+/K+ pump.

Answer 25

The sodium/potassium pump is a carrier protein that pumps sodium and potassium against their concentration gradients. For every 3 Na ions pumped out of the cell, three K ions are pumped into the cell.