B1-Cell Structure and Transport

Question 1

How do you work out total magnification on a light microscope?

Answer 1

Eyepiece lens (often x10) times by objective lens

Question 2

How do you work out the real size of an object?

Answer 2

Image size divided by total magnification

Rearrange for either part

Question 3

What is resolution?

Answer 3

Ability to distinguish between two points

Question 4

Animal cell structures and function

Answer 4

Nucleus- Controls cell activity and contains chromosomes with genes to help build new cell or organisms. Around 10 micrometers in diameter.
Cytoplasm- Gel in which organelles are suspended and where most chemical reactions for life take place.
Cell membrane- Controls what enters and leave cell
Mitochondria - Place respiration occurs for energy. Around 0.4 micrometers in diameter.
Ribosomes- Where protein synthesis takes place.

Question 5

What are the extra features of a plant cell and functions?

Answer 5

Chloroplasts- Contain chlorophyll which absorbs light so that photosynthesis can take place.
Cellulose cell wall- Helps keep the cell rigid.
Permanent vacuole- Filled with cell sap to help support the plant.

Question 6

What are eukaryotes?

Answer 6

More complicated cells (e.g plant and animal cells).

Question 7

What are prokaryotes?

Answer 7

Single celled living organisms that have strands of genetic material and sometimes plasmids for extra DNA

Question 8

How big are prokaryotes?

Answer 8

0.2 - 2.0 micrometers.

Question 9

How big are eukaryotes?

Answer 9

10-100 micrometers.

Question 10

Three specialised animal cells.

Answer 10

Nerve cells, Muscle cells, Sperm cells.

Question 11

How are nerve cells specialised?

Answer 11

• Lots of dendrites (branches) to make connections to other nerve cells.
• Very long axons.
• Synapses (nerve endings) are able to pass impulses with special chemicals so have lots of mitochondria.

Question 12

How are muscle cells specialised?

Answer 12

• Work in pairs to contract and relax.

- More mitochondria as more energy is needed.

Question 13

How are sperm cells specialised?

Answer 13

• Have a long tail to help movement.
• Lots of mitochondria for the tail to work.
• Large nucleus containing the genetic information to be passed on.

Question 14

Four specialised plant cells.

Answer 14

Root hair cells, Photosynthetic cells, Xylem cells and Phloem cells

Question 15

How are root hair cells specialised?

Answer 15

• Large surface area to take in more water.
• Large permanent vacuole to speed up water take in by osmosis.
• Lots of mitochondria for energy for active transport.

Question 16

How are photosynthetic cells specialised?

Answer 16

• Lots of chloroplasts.
• Positioned on outer layers to take in more light.
• Large permanent vacuole helps spread leaf out to absorb more light.

Question 17

How are xylem and phloem cells specialised?

Answer 17

• Xylem cells are hollow so more water can transport through and string to withstand the pressure from the water.
• Phloem cells can absorb food from other cells as it has no space to create own food.

Question 18

How do dissolved substances and gases move into and out of cells?

Answer 18

They diffuse across the cell membrane.

Question 20

What is diffusion?

Answer 20

The spreading out of gas or solute particles from an area of higher concentration to an area of lower concentration.

Question 21

What is net movement?

Answer 21

As particles are free to move about, some will go back to areas of higher concentration however the majority of particles (the net movement) will be towards an area of lower concentration

Question 22

Where does diffusion occur in the body?

Answer 22

• Air from your lungs diffuse into red blood cells.

- Air from red blood cells diffuse into the cells of the body.

Question 23

What is osmosis?

Answer 23

The movement of water across partially permeable cell membranes. Often in plant cells and sometimes in animals.

Question 24

What does ‘the solution is isotonic to the cell’ mean?

Answer 24

That the concentration of solutes outside the cell is the same as the internal concentration.

Question 25

What does ‘the solution is hypotonic to the cell’ mean?

Answer 25

The concentration of solutes outside the cell is lower than the internal concentration (more water outside).

Question 26

What does ‘the solution is hypertonic to the cell’ mean?

Answer 26

The concentration of solutes outside the cell is higher than the internal concentration (less water outside).

Question 27

What is active transport?

Answer 27

Sometimes substances need to move across a partially permeable membrane against a concentration gradient (to where there is more of it).

Question 28

What does active transport do?

Answer 28

Allows cells to absorb mineral ions from very dilute solutions

Question 29

Why do cells with a higher rate of active transport also have a higher rate of respiration?

Answer 29

Energy is required for active transport to take place.

Question 30

What will speed up diffusion?

Answer 30

• The steeper the concentration gradient (difference in concentration) then diffusion will be faster.
• If the temperature is higher then diffusion will be quicker.

Question 31

What is the importance of the surface area to volume ratio?

Answer 31

As an organism gets bigger the surface are to volume ratio falls. As the distance between the centre of the organism and the surface gets bigger, it becomes more difficult for diffusion to take place.