Cell theory and cell membrane

Question 1

What are the 5 points of the cell theory, which is true for both prokaryotic and eukaryotic cells ?

Answer 1

1. A cell is the basic structural and functional unit of all living things
2. Cells have plasma membranes
3. Cells arise from other pre-existing cells
4. Cells pass on their characteristics to their offspring
5. The proteins within the cell are produced by ribosomes

Question 2

Of what is made the plasma or cell membrane ?

Answer 2

It is mostly made of a phospholipid bilayer.

Question 3

What is a phospholipid ?

Answer 3

An amphipatic molecule that has an hydrophobic tail and a hydrophilic head.

Question 4

How can phospholipids move ?

Answer 4

They can move either laterally (side-to-side) or accross the membrane (flip-flopping).

Question 5

What are factors that can increase the fluidity of a cell membrane ?

Answer 5

The presence of unsaturated fatty acids
High temperature
The presence of cholesterol at lower temperatures

Question 6

What are factors that can decrease the fluidity of a cell membrane ?

Answer 6

The presence of saturated fatty acids
Low temperature
The presence of cholesterol at higher temperatures

Question 7

What is the cytosol ?

Answer 7

The aqueous environment inside the cell

Question 8

What are integral membrane proteins ?

Answer 8

proteins that are embedded into the cell membrane that have both a hydrophobic region and two hydrophilic regions

Question 9

What are the functions of the integral membrane proteins ?

Answer 9

transportation of compounds across the membrane
receptors for intercellular messages
help catalyse reactions near the cell membrane
anchors for the peripheral membrane proteins

Question 10

What are peripheral membrane proteins ?

Answer 10

Proteins that are only on the inside or the outside the cell.

Question 11

What are the functions of the peripheral membrane proteins ?

Answer 11

enzymatic activity

contribute to intercellular interactions

Question 12

What are glycolipids ?

Answer 12

lipids with carbonhydrates attached at the top, thus making them amphipatic. They are found exclusively on the extracellular side of a cell membrane

Question 13

What are glycoproteins ?

Answer 13

proteins (often integral membrane proteins) that have carbonhydrates attached to them in the extracellular side of the cell membrane

Question 14

What is a lipid raft ?

Answer 14

The grouping of many of the non-phospholipid components of a cell membrane (such as cholesterol, glycolipids, glycoproteins and integral membrane proteins) to glide across the cell membrane

Question 15

What is simple diffusion ?

Answer 15

When a molecule can directly pass through a membrane

Question 16

When is an environment called hypertonic ?

Answer 16

When the external concentration of a cell is higher in concentration for a certain solute than the cytosol

Question 17

When is an environment called hypotonic ?

Answer 17

When the external concentration of a cell is lower in concentration for a certain solute than the cytosol

Question 18

What is osmosis ?

Answer 18

When water moves to try to balance the concentration of a specific solute

Question 19

What is there passive transport ?

Answer 19

When a solute is going from a higher to a lower concentration. No energy is needed to move the solute. Simple diffusion and facilitated diffusion are examples of passive transport.

Question 20

What is facilitated diffusion ?

Answer 20

Transport proteins that don’t use energy such as a channel or a carrier are needed to move the molecule to a site of lower concentration.

Question 21

What is active transport ?

Answer 21

Involves proteins that use energy ( ATP) to move a solute to a site og higher concentration.

Question 22

What happens when a cell needs to move large amounts of substance ?

Answer 22

A cell uptakes (endocytosis) or sends out (exocytosis) particles.

Question 23

Why are the cells limited in their size ?

Answer 23

Because as the volume increases, the surface area of the cell increases way less.

Question 24

What are the cell wall functions ?

Answer 24

It provides structural stability and support

It can provide protection

Question 25

What is the cytoplasm ?

Answer 25

It contains both the cytosol and the organelles present in the cytosol.