Cells

Question 1

What are the 3 types of microscope? How do they work?

Answer 1

Light: 2 convex glass lenses that can see images that are 0.2um apart, as this is the wavelength of light and therefore can only see up to the mitochondria, but not in detail. Worse resolution than the other 2 types.
SEM: (Scanning Electron Microscope) uses a beam of electrons that passes over the surface of the sample and scatters, and the patter of the scattering makes a 3D image. Greater resolution than the light microscope, but a worse one than TEM.
TEM: (Transmission Electron Microscope) uses a beam of electrons that passes through a thin section of a sample, and it absorbs electrons to look dark on the micrograph, the more electrons absorbed the darker it appears. Greater resolution than the other 2 types.

Question 2

What are the steps of cell fractionation?

Answer 2

Homogenisation: Blending the cells, breaking the membrane and releasing all of the organelles to make a homogenate.
Ultracentrifugation: The homogenate is spun in a centrifuge at a low speed until the first supernatant is formed at the top and the pellet is formed at the bottom. The supernatant is removed to be spun again, but this time faster to reveal the next heaviest organelle.

Question 3

In what order do organelles come out of the centrifuge?

Answer 3

Nucleus, (Chloroplast), Mitochondria, Lysosome, Endoplasmic Reticulum, Ribosome.

Question 4

Where are ribosomes made?

Answer 4

In the nucleolus in the nucleus.

Question 5

What is the function of rough endoplasmic reticulum?

Answer 5

To fold and process proteins made on the ribosomes.

Question 6

What is the function of smooth endoplasmic reticulum?

Answer 6

To produce and process lips.

Question 7

What is the function of a golgi apparatus?

Answer 7

To process and package proteins and lipids, and to also produce lysosomes.

Question 8

What is the function of mitochondria?

Answer 8

They contain the enzymes needed for respiration and ATP for energy.

Question 9

What is the function of a centriole?

Answer 9

To produce spindle fibres for cell division.

Question 10

What is the function of a ribosome?

Answer 10

To make proteins.

Question 11

What is the function of a lysosome?

Answer 11

To hold and release digestive enzymes.

Question 12

What is the function of a capsule?

Answer 12

To protect the bacterium, provide moisture and adhere to surfaces.

Question 13

What is a plasmid?

Answer 13

A circular piece of DNA.

Question 14

What is the function of a flagellum?

Answer 14

To allow the cell to move.

Question 15

What is the function of pili?

Answer 15

To attach to other cells.

Question 16

What is the function of mesosomes?

Answer 16

To contain the enzymes for respiration and ATP for energy.

Question 17

What does mitosis produce?

Answer 17

2 Identical daughter cells that are genetically identical.

Question 18

Why is mitosis important?

Answer 18

Used for growth, repair and (in the cases of single celled organisms) reproduction.

Question 19

What are the stages of the cell cycle, and what happens in them?

Answer 19

Mitosis: cell divides.
Interphase: cell grows and readies itself for division, chromosomes begin to condense.
Cytokinesis: the division of the cytoplasm occurs to produce the 2 cells.

Question 20

What are the phases within mitosis? What happens within them?

Answer 20

Prophase: Spindle fibres appear, chromosomes become condensed and the nuclear envelope is broken down.
Metaphase: The chromosomes are aligned down the middle of the cell.
Anaphase: The centromeres divide and the sister chromatids move to opposite poles.
Telophase: The nuclear membrane reforms, spindle fibres disappear and the chromosomes decondense.

Question 21

What are the phases within interphase?

Answer 21

G1: Cellular contents are duplicated, except the chromosomes.
S: Each of the 46 chromosomes are duplicated.
G2: The cell checks over the duplicated chromosomes for damage and repairs them where they can.

Question 22

By what process do prokaryotic cells replicate? What are the steps?

Answer 22

Binary fission.
Circular DNA replicates, and they attach to the cell membrane. (Plasmids replicate themselves too)
Cell membrane grows between the DNA molecules and pinches inwards to divide the cytoplasm in 2.
A new cell wall is formed to divide the cells, each with one copy of the circular DNA but a differing number of plasmids.

Question 23

What is the function of a cell’s membrane?

Answer 23

To control the movement of substances in and out of cells/ organelles, and to allow hormones and other cells to attach to them.

Question 24

What is the structure of phospholipids? What does this mean for the membrane?

Answer 24

A hydrophilic head and 2 hydrophobic tails, allowing for the lipid soluble molecules to pass through the membrane, but not water soluble molecules. This also means that the membrane is flexible and self-sealing.

Question 25

Where are intrinsic proteins found? What is an example of one?

Answer 25

Running through the membrane. | Channel proteins, and they aid the movement of molecules across the membrane.

Question 26

Where are extrinsic proteins found? What is their function?

Answer 26

On the surface of the membrane. | To act as receptors.

Question 27

What is the function of cholesterol?

Answer 27

To make the membrane more rigid, to reduce the movement of the membrane and to prevent the leakage of water and water soluble ions.

Question 28

What is the function of a glycolipid? What are they made of?

Answer 28

To act as receptors and to attach to other cells to from tissues. Made of carbohydrates that are bound to lipids.

Question 29

What is the function of a glycoprotein? What are they made of?

Answer 29

To act as receptors and neurotransmitters, allowing cells to recognise each other while also being able to form tissues. Made of carbohydrates attached to extrinsic proteins.

Question 30

What is the definition of diffusion?

Answer 30

The passive movement of molecules from an area of high concentration to an area of low concentration, moving directly through the bilayer.

Question 31

What is the definition of facilitated diffusion?

Answer 31

The passive movement of polar, charged and water soluble molecules from an area of high concentration to an area of low concentration, with the use of a channel protein.

Question 32

What is the definition of osmosis?

Answer 32

The diffusion of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane.

Question 33

What is the definition of active transport?

Answer 33

The movement of molecules from an area of low concentration to an area of high concentration through the use of a carrier protein and ATP.

Question 34

What is the definition of co-transport?

Answer 34

The movement of molecules using ions, for example, a sodium-potassium pump.

Question 35

What increases the rate of gas exchange?

Answer 35

An increase in surface area. A steep diffusion gradient. A short diffusion pathway. An increase in temperature.

Question 36

Where is the genetic information of a bacteria stored?

Answer 36

Because bacteria are procaryotic, they store their genetic material in circular DNA and plasmids.

Question 37

Where is the genetic information of a virus stored?

Answer 37

It is just nucleic acid encased in a protein coat.

Question 38

What are the physical barriers to infection within the body?

Answer 38

The skin. Stomach acid. Gut and skin bacteria.

Question 39

What are the non-specific immune responses? What do they do?

Answer 39

Inflammation: Blood flow caused by the release of histamines, increasing the permeability of blood vessels and allowing for antibodies and white blood cells to leak into infected tissue. Lysozyme action: Lysosomes release the enzyme lysozyme to break down the cell walls of bacteria cells. Interferon: They prevent viruses from spreading by stopping their protein synthesis. Phagocytosis: White blood cells engulf pathogens by enclosing them into a phagocytic vacuole and allowing their lysosomes to release lysozyme.

Question 40

What are the elements in the specific immune response? What do they do?

Answer 40

B cells: Have antibodies on their surface to make antigen-antibody complexes, to then clone themselves to make plasma cells, which secrete loads of monoclonal antibodies. T cells: Have receptor proteins on their surface so that phagocytes can activate them. T h cells release chemicals to activate phagocytes, B cells, and T c cells. T c cells kill abnormal and foreign cells.

Question 41

What is the definition of active immunity?

Answer 41

The production of antibodies by the immune system after being exposed to an antigen.

Question 42

What is the definition of natural active immunity?

Answer 42

Being exposed to the antigen/getting the disease.

Question 43

What is the definition of artificial active immunity?

Answer 43

Getting a vaccine which stimulates the immune system to produce antibodies.

Question 44

What is the definition of passive immunity?

Answer 44

The production of antibodies by the immune system after being given the antibodies by another person or animal.

Question 45

What is the definition of natural passive immunity?

Answer 45

The crossing of the mother's antibodies through breast milk or the placenta.

Question 46

What is the definition of artificial passive immunity?

Answer 46

Getting a vaccine that contains the antibodies.

Question 47

What is the definition of a vaccine?

Answer 47

Introducing a dead or inactive pathogen to the body, to produce an immune response.

Question 48

What is the definition of herd immunity?

Answer 48

To vaccinate many people so that the pathogen cannot be spread to those who are unable to be vaccinated.

Question 49

What are the uses of monoclonal antibodies?

Answer 49

They are used within pregnancy tests.