cell structure

Question 1

Explain how cellulose molecules are adapted for their function in plant cells.

Answer 1

1. Long and straight chains;
2. Become linked together by many hydrogen bonds to form fibrils;
3. Provide strength (to cell wall).

Question 2

Describe how you could make a temporary mount of a piece of plant tissue to observe the
position of starch grains in the cells when using an optical (light) microscope.

Answer 2

1, Add drop of water to (glass) slide;(prevent air bubbles)

2. Obtain thin section (of plant tissue) and place on slide / float on drop of water
3. Stain with / add iodine in potassium iodide. (you are finding a starch grain)
4. Lower cover slip using mounted needle.

Question 3

what does a chloroplast look like in an electron microscope?

Answer 3

big dark features- chloroplasts
nucleus has a clear membrane and has a black circle in the nucleus.

Question 4

A transmission electron microscope was used to produce the image in the figure
above.
Explain why.

Answer 4

high resolution
Can see internal structure of organelles.

Question 5

why are egg cells used to insert genes

Answer 5

gene gets into all / most of cells of specie

So gets into cells that make specific proteins

Question 6

Describe how the Golgi apparatus is involved in the secretion of enzymes.

Answer 6

-package proteins in vesicles
- transport to cell surface membrane

Question 7

Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope.

Answer 7

ribosome
endoplasmic reticulum

Question 8

what happens to the absorption of a substance via facilitated diffusion as concentration increases for a long period of time

Answer 8

Rate of uptake proportional to concentration;
All channel / carrier proteins in use / saturated / limiting;

Question 9

when testing the permeability of beetroot the student put the same volume of water in each tube why

Answer 9

different volumes of water would change the concentration of pigment, changing the amount of light absorbed.
so same volume allows for comparisons

Question 10

Suggest and explain two ways the cell-surface membranes of the cells for absorption of glucose

Answer 10

• lots of channel proteins and carrier proteins- more co transport
• folded membrane large surface area

Question 11

how does sodium potassium pump cause sodium to and potassium to be moved in and out of cell

Answer 11

2. Uses (hydrolysis of) ATP;
3. Sodium ion and proton bind to the protein;
4. Protein changes shape (to move sodium ion and / or proton across the membrane);- active transport carrier proteins

Question 12

how does sodium in gut increase mass of gut?

Answer 12

-lower water potential
-water moves from high water potential to more negative water potential VIA OSMOSIS
- increasing mass of gut

Question 13

High absorption of salt from the diet can result in a higher than normal
concentration of salt in the blood plasma entering capillaries. This can lead
to a build-up of tissue fluid.

Answer 13

1. (Higher salt) results in lower water potential of tissue fluid;
   2.(So) less water returns to capillary by osmosis (at venule end);

• more salt moves out of capillary
  -lowers water potential of tissue fluid
  -less water moves back into capillary

Question 14

what type of substance can diffuse past the phospholipid membrane

Answer 14

lipid soluble