The Cell and Homeostasis

Question 1

what is the plasma membrane?

Answer 1

outer surface of the cell.

selective barrier that regulates flow of material in and out of the cell

Question 2

explain the structure of the cell membrane.

Answer 2

the cell membrane is primarily composed of a lipid bilayer; two back-to-back layers made up of phospholipids, cholesterol and glycolipids

Question 3

what are membranes

Answer 3

fluid structures, most membrane proteins and lipids move easily in their half of the bilayer

Question 4

describe the permeability of membranes.

Answer 4

membranes are semi-permeable.

• highly permeable to non polar molecules such as oxygen and carbon dioxide
• moderately permeable to small, uncharged molecules such as water
• impermeable to large uncharged polar molecules e.g. glucose

Question 5

what is the cytoplasm?

Answer 5

jelly-like substance that keeps the organelles in place

Question 6

what is the nucleus?

Answer 6

cell’s DNA.

controls what happens inside the cell

Question 7

what is the mitochondria?

Answer 7

bean-shaped organelle that produces ATP
- cells that are inactive have few mitochondria because no high energy demand. numerous found in liver, kidney, skeletal muscles etc.

Question 8

what is the rough endoplasmic reticulum?

Answer 8

produces various substances used within the cell and throughout the body, such as protein
- manufacture all proteins secreted by cells

Question 9

what is the role of the sooth endoplasmic reticulum?

Answer 9

involved in lipid and steroid synthesis, metabolism of carbs, drug detoxification etc.

Question 10

what is the golgi apparatus?

Answer 10

modifies, sorts and packages macromolecules for cell secretion

Question 11

what is cell respiration?

Answer 11

cells break up sugars and produce energy (requires sugar (glucose) and oxygen to make ATP)

Question 12

what is the concentration gradient?

Answer 12

molecules move from high to low concentration

Question 13

what is simple diffusion?

Answer 13

a type of passive transport.

- moves with the concentration gradient

Question 14

what is facilitated diffusion ?

Answer 14

a type of passive transport.

- transport proteins (carrier) help molecules that may be too big to cross the membrane on their own

Question 15

what is active transport?

Answer 15

movement of molecules from low to high, will take energy (ATP)

Question 16

what is endocytosis?

Answer 16

a form of active transport.
cell fuses with the molecules it’s taking in, in order to bring it inside
e.g. phagocytosis - cell surrounds molecule and engulfs it

Question 17

what is exocytosis?

Answer 17

can be used to get rid of cell waste, and also important for getting valuable materials that the cell has produced, out.

Question 18

what is homeostasis?

Answer 18

the maintenance of a stable internal environment despite changes in the external environment
- the foundation of health - state of equilibrium or balance

Question 19

what is a positive feedback loop? (provide example)

Answer 19

where the response enhances the condition
e.g. during childbirth. release of oxytocin to intensify and speed up contractions. increased contraction = increased oxytocin

Question 20

what is a negative feedback loop? (provide example)

Answer 20

where the response counteracts or antagonises the condition.

e. g. human body temperature
- high body temp = hypothalamus detection, body will sweat, vasodilator, temp decreases