Transport

Question 1

Vesicles

Answer 1

Vesicles are compartments formed by a lipid bilayer separating its contents from the cytoplasm or a fluid-based extracellular environment. They have a wide range of functions in cells across the living world from regulating buoyancy to secreting hormones.

Question 2

Endocytosis

Answer 2

The process of actively transporting molecules into the cell by engulfing it with its membrane.

Question 3

Vesicle movement in cells

Answer 3

Transport vesicles can move molecules between locations inside the cell.
Example proteins from the rough endoplasmic reticulum to the Golgi apparatus.

Question 4

Growing cell requirements

Answer 4

Cells can only be formed by division of pre-existing cells
The first cells must have arisen from non-living material
The origin of eukaryotic cells can be explained by the endosymbiotic theory

Question 5

Secretion vs Excretion

Answer 5

Secretion: a process by which substances are produced and discharged from a cell, gland, or organ for a particular function in the organism or for excretion.

Excretion: the process of eliminating or expelling waste matter.

Question 6

Simple diffusion

Answer 6

Diffusion is the net movement of molecules from a region of high concentration to a region of low concentration

This directional movement along a gradient is passive and will continue until molecules become evenly dispersed, reaching an isotonic solution

Question 7

Significance of the
hydrophobic area
of membrane

Answer 7

it is this strongly hydrophobic layer of material that gives the cell membrane its waterproof nature and allows it to act as a container for the cell and its contents.

Question 8

Osmosis

Answer 8

is the net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration

Question 9

Active transport

Answer 9

Active transport involves the movement of materials against a concentration gradient (low concentration ⇒ high concentration)

Because materials are moving against the gradient, it requires the expenditure of energy (e.g. ATP hydrolysis)

Question 10

Active transport of
sodium and
potassium in
axons (structure and function)

Answer 10

Three sodium ions bind to intracellular sites on the sodium-potassium pump
A phosphate group is transferred to the pump via the hydrolysis of ATP
The pump undergoes a conformational change, translocating sodium across the membrane
The conformational change exposes two potassium binding sites on the extracellular surface of the pump
The phosphate group is released which causes the pump to return to its original conformation
This translocates the potassium across the membrane, completing the ion exchange

Question 11

Cell division and the origin of cells

Answer 11

Cells can only be formed by division of pre-existing cells
The first cells must have arisen from non-living material
The origin of eukaryotic cells can be explained by the endosymbiotic theory

Question 12

Zygote

Answer 12

diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

Question 13

Endosymbiotic theory

Answer 13

An endosymbiont is a cell which lives inside another cell with mutual benefit

Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis

The engulfed prokaryotic cell remained undigested as it contributed new functionality to the engulfing cell

Question 14

Mutualistic relationships

Answer 14

When two organisms of different species work together each benefitting from the relationship

Question 15

Features that
mitochondria and
chloroplasts evolved
from independent
prokaryotes

Answer 15

an enclosed double membrane, circular DNA, and bacteria-like ribosomes. Mitochondria and chloroplast both conduct prokaryotic activities. Mitochondria performs respiration while chloroplast performs photosynthesis.

Question 16

Hypotheses of different stages of cell evolution

Answer 16

1. Both use RNA and DNA are the genetic material
2. Both use the same 20 amino acids
3. Both have ribosomes and DNA and RNA
4. Both have a lipid bilayer cell membrane.
5. Both use L amino acids and D sugars

Question 17

Pasteurs Experiment and spontaneous generation

Answer 17

All cells come from pre existing cells, according to the broth experiment

Question 18

Exocytosis

Answer 18

Exocytosis is an energy-consuming process that expels secretory vesicles containing nanoparticles (or other chemicals) out of the cell membranes into the extracellular space.

Question 19

Facilitated diffusion

Answer 19

a form of facilitated transport involving the passive movement of molecules along their concentration gradient, guided by the presence of another molecule – usually an integral membrane protein forming a pore or channel.