B1.1 - Cell Structures

Question 1

What is a Eukaryotic Cell?

Answer 1

Cells where the genetic material is contained within a nucleus.

Question 2

What is a Prokaryotic Cell?

Answer 2

Cell where the genetic material floats in the cytoplasm.

Question 3

Around 10 μm - 100 μm in size.

Answer 3

Eukaryotic Cells.

Question 4

Around 1 μm - 10 μm in size.

Answer 4

Prokaryotic Cells.

Question 5

What subcellular structures do you find in all basic Eukaryotic cell?

Answer 5

• Nucleus
• Mitochondria
• Cell Membrane
• Cytoplasm

Question 6

What extra subcellular structures can be found in plat cells?

Answer 6

• Chloroplast
• Cell Wall
• Vacuole

Question 7

What is the function of the Nucleus?

Answer 7

• Controls the activities of the cell
• Contains genetic material (arranged as chromosomes)
• Determines the cells appearance and function

Question 8

What are mitochondria?

Answer 8

Mitochondria are membrane bound organelles that are the site of aerobic respiration.

Question 9

What is the cell membrane?

Answer 9

• Selective semi-permeable ‘barrier’
• made of two layers of phospholipid molecules
• Holds the cell together
• Contains receptor molecules for cell communication

Question 10

What is the cytoplasm?

Answer 10

• ‘jelly-like’ substance
• site of all chemical reactions which make up metabolism

Question 11

Which English inventor and scientist where discovered cells using his self-designed microscope in 1665?

Answer 11

Robert Hooke

Question 12

MRS GREN

Answer 12

M = ovement

R = espiration

S = ensitivity

G = rowth

R = eproduction

E = xcretion

N = utrition

Question 13

What are ribosomes?

Answer 13

• Small organelles present in all cells
• site of protein synthesis

Question 14

What are chloroplasts?

Answer 14

• The organelle that is responsible for photosynthesis
• Contains ‘chlorophyll’ - green pigment which absorbs light energy.

Question 15

What is a a vacuole and what is its function?

Answer 15

• A large cavity filled with a watery solution of salts and sugars (cell sap).
• It keeps the cell rigid, pushing outwards.

Question 16

What is the cell wall?

Answer 16

• Surrounds the cell
• Thick wall made of cellulose ( tough rubbery fibre)
• Gives the cell rigidity and support.

Question 17

Explain why leaf cells contain chloroplasts but roots do not.

Answer 17

Leaf cells are able to photosynthesise because they have access to sunlight. Root cells do not so cannot photosynthesise, so do not need chloroplasts.

Question 18

Name a few examples of Bacteria and what they do.

Answer 18

• Escherichia Coli (E.coli) – food poisoning
• Streptococcus bacteria – sore throats
• Streptomyces bacteria – found in soil & Antibiotic streptomycin comes from it.

Question 19

Name extra subcellular structures bacteria can have.

Answer 19

• Plasmids
• Slime Capsule
• Pilli
• Flagella

Question 20

What is a plasmid and how can it be advantageous?

Answer 20

• A circular piece of DNA found in bacteria cells
• Not needed for day-to-day survival but can give the bacterium advantages such as antibiotic resistance

Question 21

What are pilli?

Answer 21

• Tiny ‘hair-like’ structures that allow the cell to attach to structures (e.g. cells in your digestive tract).
• They are also used to transfer genetic material between bacteria cells.

Question 22

What is the function of a slime capsule?

Answer 22

• Protects bacteria from drying out and from poisonous substances.
• Helps bacteria to stick to smooth surfaces.

Question 23

What are flagella?

Answer 23

Tail-like structures that allow bacteria cells to move through liquids.

Question 24

What is the equation for magnification?

Answer 24

Image size = Actual size x Total Magnification

I = A x M

Question 25

Define Resolution.

Answer 25

The degree to which it is possible to distinguish between two objects that are very close together, rather than them look merged into one object.

Question 26

Name the two types of electron microscopes.

Answer 26

- Transmission electron microscope (TEM) - Scanning electron microscope (SEM)

Question 27

Describe the key features and how TEM microscopes work.

Answer 27

- Used to examine an extremely thin slice or section of cells or tissues. - A beam of electrons passes through a thin slice of the sample; the beam is focused to produce an image. - Has revealed subcellular structures in cells not visible with a light microscope such as mitochondria and chloroplasts.

Question 28

Describe the key features and how SEM microscopes work.

Answer 28

- SEM has a large depth of field so can be used to examine the surface structure of specimens. - A beam of electrons is sent across the surface of a specimen; the reflected electrons are collected and produce a 3D image.

Question 29

What are the advantages and disadvantages of light microscope and electron microscopes?

Answer 29

Light microscope - Cheap to buy and operate - Small and portable - Simple to prepare sample - Natural colour of sample is seen unless staining is used. - Specimens living or dead - Resolution up to 0.2 µm (2 x 10-7 m) Electron Microscope - Expensive to buy and operate - Large and difficult to move - Sample preparation is complex - Black and white images produced; false colour can be added to images - Specimens are dead - Resolution up to 0.1 nm (1 x 10-10 m)

Question 30

Name three common stains used.

Answer 30

methylene blue - makes it easier to see the nucleus of an animal cell iodine - makes it easier to see plant cell nuclei crystal violet - stains bacterial cell walls

Question 31

How do you use a microscope?

Answer 31

To observe cells under the microscope, follow the steps below: 1) Move the stage to its lowest position 2) Select the objective lens with the lowest magnification. 3) Place the slide, which has cells on it, on the stage. 4) Raise the stage to its highest position, taking care that the slide does not touch the lens. 5) Lower the stage slowly using the coarse focus knob until you see your object (it will normally be blurred). 6) Turn the fine focus knob slowly until your object comes into clear focus. 7) To see the cells in greater detail, switch to a higher magnification objective lens without moving the stage, Use the fine focus knob to bring the object into clear focus again.

Question 32

How do you apply a stain?./

Answer 32

This is how to apply a stain: 1) Place the cells on a glass slide. 2) Add one drop of stain. 3) Place a coverslip on top. 4) Tap the coverslip gently with a pencil to remove air bubbles.