Cell membranes and transport

Question 1

What is the fluid mosaic model?

Answer 1

A model that describes the structure of the plasma membrane as a mosaic of components.

Question 2

What is meant by “fluid mosaic model”?

Answer 2

Fluid describes how particles move freely and mosaic describes the shape of the model when you look from above.

Question 3

What does the fluid mosaic model contain?

Answer 3

Phospholipids, cholesterol, proteins and carbohydrates.

Question 4

Roles of phospholipids

Answer 4

Provide barriers in cellular membranes to protect the cell, and they make barriers for the organelles within those cells.

Question 5

Roles of cholesterol

Answer 5

Reduces permeability of lipid membranes.

Question 6

Roles of glycolipids

Answer 6

To maintain the stability of thecell membraneand to facilitatecellular recognition.

Question 7

Roles of proteins

Answer 7

Help the cell interact with its environment.

Question 8

Roles of glycoproteins

Answer 8

They act incell-to-cellrecognition and binding of other molecules.

Question 9

Roles of cell membranes

Answer 9

Prodiving protection to cell, providing a fixed environment inside the cell, regulating the transport of substances in and out of the cell, receiving chemical messengers from other cell and absorbing substances.

Question 10

Process of cell signalling

Answer 10

First, reception, whereby thesignalmolecule binds the receptor. Then,signaltransduction, which is where the chemicalsignalresults in a series of enzyme activations. Finally, the response, which is the resultingcellularresponses.

Question 11

Process of diffusion

Answer 11

Diffusionis the movement of a substance from an area of high concentration to an area of low concentration.Diffusionhappens in liquids and gases because their particles move randomly from place to place.Diffusionis an importantprocessfor living things; it is how substances move in and out of cells.

Question 12

Facilitated diffusion

Answer 12

The process of spontaneous passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins.

Question 13

Osmosis

Answer 13

The movement of a solvent across a semipermeable membrane from low to high concentration.

Question 14

Active transport

Answer 14

The movement of ions or molecules across a cell membrane into a region of higher concentration

Question 15

Endocytosis

Answer 15

Cellular process in which substances are brought into the cell.

Question 16

Exocytosis

Answer 16

A form of active transport and bulk transport in which a cell transports molecules out of the cell.

Question 17

Effect of changing surface area to volume ratio on diffusion

Answer 17

When the cell increases in size, thevolumeincreases faster than thesurface area, becausevolumeis cubed wheresurface areais squared. When there is morevolumeand lesssurface area,diffusiontakes longer and is less effective.

Question 18

Effects of immersing plant tissues in solutions of different water potentials

Answer 18

When you immerse plant tissues in a solution oflower water potentialthan the cell contains, water leaves by osmosis to its surroundings. The cytoplasm pulls away from the cell wall and cell becomes flaccid (plasmolysis).
When a cell is in a solution ofhigher water potential,water enters by osmosis. Cytoplasm pushes hard against the cell wall and cell becomes turgid (turgor pressure).