B1 A - microscopes and cell structure

Question 1

Function of a microscope

Answer 1

Uses lens to magnify an object

Question 2

Magnifcation

Answer 2

How much times bigger the specimen is seen

Question 3

Why should you always use the lowest power objective lens first?

Answer 3

to get a wider field of view

Question 4

resolution

Answer 4

how well you can distinguishe between objects close together

Question 5

light microscope

Answer 5

Light microscopes have a lower resolution and magnification. The specimen can be living, and can be seen in colour.

Question 6

Electron microscope

Answer 6

Have a higher resolution and magnification so can magnify smaller organelles e.g Ribosomes.
The specimen is dead, and cannot be seen in colour.

Question 7

Method for the Microscopy practical?

Answer 7

• Place a tissue sample / specimen on the slide.
• Add a few drops of a suitable stain.
• Lower coverslip onto the tissue.
• Place the slide on the microscope stage and focus on the cells using the low power objective lens.
• Change to higher powered objective lens and refocus.
• Draw any types of cells that can be seen.
• Add a magnification scale to the diagram.

Question 8

Why do you need a stain?

Answer 8

To make certain structures visible

Question 9

Why lower the coverslip and press carefully?

Answer 9

to remove any bubbles

Question 10

Why can you see the nucleus and cell wall but not the mitochondria?

Answer 10

They’re too small.

Question 11

What is the function of the coarse adjustment knob?

Answer 11

Bring the specimen into focus

Question 12

How could we see the smaller structures (e.g. ribosomes)?

Answer 12

You would need to use an electron microscope which has a higher magnification and higher resolution.

Question 13

Actual size =

Answer 13

Image size / magnification

Question 14

How can we now have a greater understanding of subcellular structures?

Answer 14

Smaller subceller structures e.g ribosomes can be seen under an electron microscope

Question 15

1 mm to um?

Answer 15

multiply by 1000

Question 16

1 um to nm?

Answer 16

multiply by 1000

Question 17

What type of cells are plant and animal cells?

Answer 17

Eukaryotic (U)

Question 18

Features of animal cells:

Answer 18

• nucleus (contains the genetic materials, controls the cell’s activities)
• cytoplasm - where the chemical reactions occur
• cell membrane - controls what leaves and enters the cell
• mitochondria - where aerobic respiration occurs
• ribosomes - where protein synthesis occurs

Question 19

Additional features of plant cells:

Answer 19

• have lots of chloroplasts - containing chloropyll, absorbing light for photosynthesis
• Have cell wall - provides strength and structure (containg celll sap)
• permanent vacule - keeps cells turgid

Question 20

What type of cells are bacterial cells?

Answer 20

Prokaryotic cells

Question 21

Differences between prokaryotic and eukaryotic cells?

Answer 21

• Prokaryotic cells do not have a nucleus - they have a single DNA loop, and plasmids.
• They have no membrane-bound organelles.
• Eukaryotic cells are much bigger than Prokaryotics.

Question 22

How the sperm cell adapted to its funtion?

Answer 22

Its function is to swim to the egg and fertilise it.
- It is streamlined so can swim faster
- It is tail which allows movement
- Has lots of mitochondria
- Contains enzymes which help it to digest into an egg cell

Question 23

How is the nerve cell adapted to its funtion?

Answer 23

It passes electrical impulses around the body.
- Lots of denrites to make connections to other nerve cells
- Long axon which carries the electrical impulses
- Contains lots of mitochondria to make the transmitter chemicals that allow the impulses to be transferred to another cell.

Question 24

How are muscle cells adapted for their funtion?

Answer 24

Function - is to contract to allow movement
- there are protein fibres that contract
- lots of mitochondria so more energy is released for the fibres to contract
- store glycogen which is a chemical that is broken down and used by the mitochondria to release energy needed.

Question 25

How are root hair cells adapted for their funtion?

Answer 25

Function - to absorb water and minerals from the soil

• have surface area
• lots of mitochondra to release energy for active transport of mineral ions.
• large permanent vacuole which speeds up omosis of water from the soil

Question 26

How are xylem cells adapted for their function?

Answer 26

function - carry water and mineral ion from the roots to the highest parts of the plant
- has a chemical called lignin which allows a hollow tube to be formed which allows a continuous flow of water and minerals
- spirals of lignin makes the tube strong

Question 27

How are phloem adapted for their function?

Answer 27

function - carries the food made by photosynthesis around the plant
- cell walls between the cells break down and form sieve plates, which allow dissolved food to move from cell to cell.
- companion cells keep them alive. Its mitochondria transfers energy needed to move the dissolved food up and down.

Question 28

Why does a red blood cell burst, but a plant cell does not burst?

Answer 28

Water enters the cell by osmosis.
A plant cell has a cell wall which prevents it from bursting, but a red blood cell doesn’t.