Cells

Question 1

List the structures of an animal cell

Answer 1

Nucleus
Nuclear membrane
Cytoplasm
Cell membranes
Mitochondrion

Question 2

List the structures of a plant cell

Answer 2

Chloroplast
Cellulose cell wall
Permanent vacuole
Nucleus
Nuclear membrane
Cytoplasm
Cell membranes
Mitochondrion

Question 3

What is a cell membrane?

Answer 3

A selectively permeable membrane which forms a boundary around cell and controls what goes in and out

Question 4

What is cytoplasm

Answer 4

Where chemical reactions take place

Question 5

What is the nucleus?

Answer 5

Surrounded by the nuclear membrane, it contains the chromosomes. Each chromosome is made of one molecule of DNA. The nucleus is often referred to as the control centre of the cell.

Question 6

What are mitochondria?

Answer 6

Structures within the cytoplasm within which the chemical reactions of respiration take place.

Question 7

What is a cellulose cell wall?

Answer 7

A rigid structure outside the cell membrane that provides support.

Question 8

What is a permanent vacuole?

Answer 8

Contains cell sap and when full pushes the cell membrane against the wall, providing support.

Question 9

What is a chloroplast?

Answer 9

Contains chlorophyll.

Question 10

What is chlorophyll?

Answer 10

A green pigment that traps light for photosynthesis.

Question 11

List the structures of bacterial cells.

Answer 11

Cytoplasm
Non-cellulose cell wall
Plasmid DNA
Bacterial DNA (Chromosomal (DNA))
Flagellum (not always present)

Question 12

What is bacterial DNA?

Answer 12

Bacterial DNA is arranged in a single circular strand in the cytoplasm

Question 13

What is plasmid DNA?

Answer 13

Small rings of DNA

Question 14

What is a flagellum?

Answer 14

A tail-like extension that allows the bacterium to swim.

Question 15

List the parts of a microscope. (Look at a diagram and label the parts if you can.)

Answer 15

Eyepiece
Viewing tube
Arm
Objective lens (low, medium and high power)
Stage
Stage clips
Focusing knob (fine and course)
Diaphragm
Light source
Base

Question 16

What is a slide?

Answer 16

A thin piece of glass used to hold objects under a microscope

Question 17

How do you prepare a slide of plant cells?

Answer 17

1. Peel a thin, transparent layer of epidermal cells, this is a single layer of cells found inside an onion.
2. Place cells on a microscope slide.
3. Add a drop of water or iodine (a chemical stain)
4. Lower a coverslip onto the onion cells using forceps or a mounted needle. This needs to be done gently to prevent trapping air bubbles.

Question 18

How do you prepare a slide of animal cells?

Answer 18

1. Remove cells from the inside of your cheek using a Cotten bud.
2. Smear the Cotten bud onto a microscope slide.
3. Add a drop of methylene blue (a chemical stain)
4. Lower a coverslip onto the cheek cells using forceps or a mounted needle. This needs to be done gently to prevent trapping air bubbles.

Question 19

How do you use a light microscope?

Answer 19

Start with a low power lens, as the field of view will be wider and it’s easier to find what you’re looking for.

Once you have found the cells, ensure they are in the middle of the field of view, then rotate to a higher power lens. Extra care is needed as the the lens can be damaged when it’s this close to the slide.

Question 20

How do you work out total magnification?

Answer 20

Eyepiece magnification x objective lens magnification

Question 21

How should you draw biological thingie magigies?

Answer 21

In pencil (not sketchy)
Large, with the same proportions as the observed cell
Labelled using separate ruled lines
Given a title that includes its magnification or size

Question 22

What is the arrangement of the microscopy triangle?

Answer 22

. Size of image

        ———————— Actual size        X          Magnification

Question 23

What are the units of length used in biology?

Answer 23

Metre (m) 1m=1m
Millimetre (mm) 1m=1000mm
Micrometre (μm) 1m=1000000μm

Question 24

How can you calculate magnification when given a scale bar?

Answer 24

1. Measure the scale bar image (beside drawing) in mm.
2. Convert to μm (multiply by 1000)
3. Magnification = scale bar image divided by actual scale bar length (written on the scale bar)

E.g.

Image length of scale bar = 10mm
= 10 x 1000 = 10000 μm
Actual length of scale bar = 100μm
Magnification = I/A = 10000/100 = 100 times

Question 25

What is an electron microscope?

Answer 25

Powerful microscopes that pass beams of electrons through a specimen, which gives them a much greater resolution than a light microscope.

Question 26

What is resolution?

Answer 26

The ability to show detail. It’s measured in dots per inch (dpi)

Question 27

What is diffusion?

Answer 27

The random movement of substances from a region of high concentration to a region of low concentration. E.g. oxygen moving from a high concentration in the lungs to a low concentration in the blood.

Question 28

What is the rate of diffusion affected by?

Answer 28

Concentration gradient. A larger difference in the high and low concentrations increases the diffusion rate. Temperature. A higher temperature provides particles with more kinetic energy increasing diffusion rate. Surface area. A larger surface area through which diffusion can happen increases the diffusion rate.

Question 29

What is the square cube law?

Answer 29

As an object increases in size, it’s volume increases much faster than its surface area. This means that organisms that rely on diffusion alone for respiration need to stay small, otherwise they wouldn’t be able to absorb enough oxygen to survive.

Question 30

What is the order of complexity in multicellular bodies?

Answer 30

Cells Tissues Organs Organ systems Organism

Question 31

What are stem cells?

Answer 31

Simple unspecialised cells, which can divide to form cells of the same type or differentiate into a variety of specialised cells.

Question 32

What are the 2 types of stem cell?

Answer 32

Embryonic stem cells Can form a full range of cell types Adult stem cells Most have changed permanently, but some can be found in bone marrow. Though these can only become blood cells.

Question 33

Where are stem cells located in plants?

Answer 33

Meristems.

Question 34

What are the benefits to using stem cells in medicine?

Answer 34

Treating leukaemia. Chemotherapy and radiotherapy destroy white blood cells, stopping their bone marrow from producing new cells. A bone marrow transplant containing stem cells allows healthy blood cells to be made in the patient.

Question 35

What are the risks to using stem cells in medicine?

Answer 35

Risk of infection from the environment (and donor) as chemotherapy and radiotherapy leave the patient with no immune system Stem cells may divide in an uncontrolled manner leading to the formation of tumours or the development of unwanted cell types. Transfer of viruses or diseases from other animals.