Topic 2 - Cells, Viruses And Reproduction Of Living Things

Question 1

Why are Viruses considered to be ‘non-living’ ?

Answer 1

Viruses are non-living because they don’t reproduce on their own (need a host cell).

Question 2

What is a virus?

Answer 2

A virus is a type of pathogen.

Question 3

What is a pathogen?

Answer 3

A pathogen is a harmful agent which can cause disease.

Question 4

How does a virus reproduce when it’s in a host cell?

Answer 4

It hijacks the host cell’s protein production machinery (such as ribosomes) to make copies of it’s DNA/RNA.

Question 5

Define Magnification.

Answer 5

Magnification is a measure of how much bigger the image you see is than the real object.

Question 6

Define Resolution/resolving power.

Answer 6

• The Resolution of a microscope is defined as the smallest distance at which 2 small objects can still be seen as separate.
• (In other words, the microscope’s ability to distinguish details of a small specimen).

Question 7

How do you calculate the total magnification?

Answer 7

Eyepiece lens x Objective lens = Total magnification.

Question 8

How you calculate Image size?

Answer 8

Image size = Actual size x Magnification.

Question 9

What are ‘Artefacts’ In Microscopy?

Answer 9

• When looking at a prepared sample, there may be things visible that aren’t part of the specimen, such as bubbles or dust.
• These variables are known as Artefacts.

Question 10

What are Transmission Electron Micrographs (TEMs) ?

Answer 10

TEMs are two-dimensional (2D) images, like those from a light microscope, but with better magnification and resolution.

Question 11

What are Scanning Electron Micrographs (SEMs) ?

Answer 11

SEMs are three-dimensional (3D) images, with the cost of slightly lower magnification.

Question 12

What are the advantages of using Electron Microscopes?

Answer 12

Great magnification and resolution.

Question 13

What are the disadvantages of using Electron Microscopes?

Answer 13

• It is impossible to look at living material using an electron microscope as the specimens have to be examined in a vacuum.
• Specimens undergo severe treatment which may result in artefacts.
• Very expensive
• Very large & high maintenance.

Question 14

What is a Eukaryote?

Answer 14

A Eukaryote is an organism consisting of cells in which the genetic material (DNA) is stored in the form of Chromosomes in a Nucleus.

Question 15

What is a Prokaryote?

Answer 15

A Prokaryote is a single-celled organism which has neither a nucleus or other membrane-bound organelles.

Question 16

What is the main role of the cell surface membrane?

Answer 16

The cell surface membrane regulates what substances move into and out of the cell.

Question 17

What 2 molecules are membranes mainly made up of?

Answer 17

Lipids & Proteins.

Question 18

How are Phospholipids arranged in the membrane?

Answer 18

• Phospholipids form a bilayer .
• The Hydrophilic heads point towards the water
• The hydrophobic tails point away from the water

Question 19

What model gives an insight to the structure and function of a cell membrane?

Answer 19

Fluid Mosaic Model.

Question 20

What are gated channels?

Answer 20

• Gated channels are protein channels in the cell membrane which can be open or shut depending on the conditions in the cell.

Question 21

What are Glycoproteins?

Answer 21

Glycoproteins are proteins with a carbohydrate part added to the molecule.

Question 22

What is Protoplasm?

Answer 22

The Cytoplasm and Nucleus together is collectively known as Protoplasm.

Question 23

What is chromatin?

Answer 23

Chromatin is a complex consisting of DNA molecules wrapped around Histone proteins.

Question 24

What is Chromatin made up of?

Answer 24

Chromatin consists of DNA molecules wrapped around Histone proteins.

Question 25

When is Chromatin used to store DNA?

Answer 25

When the cell is not actively dividing.

Question 26

What is the Nucleolus?

Answer 26

An extra dense area (found in the nucleus) consisting of almost pure DNA and protein.

Question 27

What is the primary role of the Nucleolus?

Answer 27

The production of the cell's ribosomes.

Question 28

What can the quantity of mitochondria found in a cell tell us about the cell?

Answer 28

Whether the cell requires a lot or little energy to function.

Question 29

What does the endosymbiotic theory state?

Answer 29

The endosymbiotic theory states that some organelles (Mitochondria & chloroplasts) were once individual prokaryotic cells.

Question 30

What is the evidence for the endosymbiotic theory?

Answer 30

- Mitochondria & Chloroplasts have their own circular DNA (like prokaryotic cells) - Mitochondria & chloroplasts divide by binary fission (like prokaryotic cells) - Mitochondria & Chloroplasts are approximately the same siize as prokaryotic cells.

Question 31

What are Centrioles made up of?

Answer 31

Each centriole is made up of a bundle of 9 tubules.

Question 32

What is the Cytoskeleton?

Answer 32

The cytoskeleton is a 3D web-like structure that fills the cytoplasm.

Question 33

What is the Cytoskeleton made up of?

Answer 33

The cytoskeleton is made up of microfilaments (protein fibres) and microtubules.

Question 34

What is the role of the Cytoskeleton?

Answer 34

The Cytoskeleton gives the cytoplasm structure, keeping the organelles in place.

Question 35

What type of ribosomes do Eukaryotes contain?

Answer 35

- 80S and 70S Ribosomes - (70S ribosomes found in Chloroplasts & Mitochondria)

Question 36

What type of ribosomes do Prokaryotes contain?

Answer 36

- 70S Ribosomes.

Question 37

What is the role of the Rough Endoplasmic Reticulum?

Answer 37

- RER has 80S Ribosomes imbedded in its membrane which synthesise proteins. - The RER transports these proteins within the cell or outside the cell (exocytosis)

Question 38

What is the role of the Smooth Endoplasmic Reticulum?

Answer 38

- The SER is involved in the synthesis and transport of Steroids and Lipids.

Question 39

How do Proteins get from the Rough Endoplasmic Reticulum to the Golgi Apparatus?

Answer 39

- A vesicle forms around the Protein being transported. - The Vesicle is pinched off the RER - The Vesicle travels and fuses with the Cisternae of the Golgi Apparatus, releasing the Protein.

Question 40

What is the Golgi Apparatus made up of?

Answer 40

Flattened stacks of membrane called Cisternae.

Question 41

What is the Role of Lysosomes?

Answer 41

- Lysosomes break down dead organelles in to molecules that can be re used. - Lysosomes can also break down food content in single-celled organisms. - Lysosomes also destroy bacteria.

Question 42

Describe the structure of Lysosomes.

Answer 42

- Lysosomes are membrane bound organelles - They are vesicles containing Digestive Enzymes.

Question 43

How is a dead organelle broken down by a Lysosome?

Answer 43

- A membrane vacuole forms around the dead organelle - The Lysosome fuses with this vacuole, releasing the Digestive Enzymes which break down the dead organelle.

Question 44

What is the Tonoplast?

Answer 44

The Tonoplast is the membrane that surrounds the Vacuole in a Plant Cell.

Question 45

What are Plasmodesmata?

Answer 45

Plasmodesmata are microscopic channels in the Plant Cell Wall.

Question 46

What is the role of Plasmodesmata?

Answer 46

Plasmodesmata allow communication and transport between plant cells.

Question 47

In plant cells, what is the Vacuole filled with?

Answer 47

The Vacuole is filled with Cell Sap.

Question 48

What is the role of the Cell Sap in the Plant Vacuole?

Answer 48

- Cell Sap is a solution which allows water to move in to it via osmosis. - This causes the Vacuole to expand and the cytoplasm around it to be pushed against the Cell Wall under high pressure - This results in the Plant Cell becoming turgid.

Question 49

What are Chloroplasts?

Answer 49

Chloroplasts are organelles which are the site of Photosynthesis in Plant Cells.

Question 50

What is the role of Amyloplasts?

Answer 50

Amyloplasts store Starch.

Question 51

What is the role of the Cell Wall in Bacteria?

Answer 51

The Cell Wall in Bacteria prevents the cell from swelling and bursting.

Question 52

What do all Bacterial Cell Walls contain a layer of?

Answer 52

All Bacterial Cell Walls contain a layer of Peptidoglycan.

Question 53

What is the role of the Capsule/Slime layer which surrounds SOME bacterial cells?

Answer 53

- Capsules/Slime layers protect the bacterium from Phagocytosis by White blood cells - The Capsule also covers cell markers on the cell membrane of the bacterium, making it harder for the immune system to identify the bacterium.