Sem 1 Human Bio

Question 1

What is the immediate environment of a cell?

Answer 1

Fluids, tissue fluid or extracellular fluid. All cells have a thin layer of fluid between them

Question 2

What does extracellular fluid allow?

Answer 2

Continual exchange of materials into and out of cells

Question 3

Which process ensures a constant temperature and environment for a cell?

Answer 3

Homeostasis (maintains constant temperature and extracellular fluid is always kept at same concentration)

Question 4

What do cells require to carry out activities and what do cells produce?

Answer 4

Cells require glucose and oxygen, which produces water and carbon dioxide alongside energy. The water and carbon dioxide must be removed.

Question 5

What separates the intracellular and extracellular?

Answer 5

Cell membrane

Question 6

Current accepted model of Cell Membrane?

Answer 6

Fluid Mosaic Model

Question 7

What is the fluid mosaic model and why is it called that?

Answer 7

It’s a model of the cell membrane, as the cell membrane molecules are constantly changing position hence the word fluid while the membrane is made of a number of different molecules, a bit like a mosaic.

Question 8

What is the structure of the cell membrane? (not too in depth)

Answer 8

Cell membrane is comprised of phospholipids, lipids with a phosphate group attached, which are arranged in a bilayer (two sets of phospholipids)

Question 9

What is meant when we say phospholipid bilayer?

Answer 9

Cell membrane formed from two layers of phospholipids, with hydrophilic heads on the outside and hydrophobic tails on the inside. These molecules bunch together and drift from place to place, causing the membrane to be fluid.

Question 10

What is the function of the phospholipids inside the cell membrane?

Answer 10

To provide integrity and stability to the cell membrane

Question 11

Describe the permeability of cell membranes (3 types of permeability)

Answer 11

Cell membranes are either differentially permeable (allows the passage of small molecules, but not large molecules), semi-permeable (only solvent, not solute of a solution can pass through) and selectively permeable (only certain things can pass through, but size is not a factor as large molecules can pass through

Question 12

Main functions of the cell membrane

Answer 12

1. Acting as a physical barrier, separating extracellular fluid from cytoplasm. This is important as the composition are very different.
2. Regulates the passage of materials (inside and outside, removal of waste and entry of nutrients)
3. Support of the cell structure, which provides support to entire tissue structure

Question 13

Two types of transfer processes

Answer 13

Passive (do not use energy)

Active (use cells energy in the form of ATP or adenosine, triphosphate)

Question 14

3 processes for transport of materials

Answer 14

1. Simple diffusion, passive process, resulting from random movement of ions and molecules (note, osmosis is a special case where water moves across a selective membrane)
2. Facilitated transport, a passive or active process that requires special proteins in the cell membranes, either by channel proteins or carrier proteins.
3. Vesicular transport, an active process in which materials move in membrane-bound sacs.

Question 15

What is a key concept of cellular transport?

Answer 15

Transport of materials is controlled

Question 16

What is a concentration gradient?

Answer 16

Difference in concentration that brings about diffusion

The greater the difference in concentration, the steeper the concentration gradient and the faster the rate of diffusion

Question 17

What are some molecules that cannot cross the cell membrane directly?

Answer 17

Large polar molecules such as sodium ions are they are repelled by hydrophobic tails in bilayer

Question 18

What are some molecules that can cross the cell membrane directly?

Answer 18

Water molecules via facilitated transport and if they are small enough, they can pass between the lipid tails

Question 19

What is vesicular transport?

Answer 19

Movement of substances across the cell membrane in membrane bound sacs called vesicles

Question 20

Definition of endocytosis

Answer 20

Taking solids or liquids into cell via vesicular transport