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A Level - Biology > Cells > Flashcards

Cells Flashcards

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1
Q

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

A

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.

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2
Q

What are the steps of cell fractionation?

A

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.

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3
Q

In what order do organelles come out of the centrifuge?

A

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

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4
Q

Where are ribosomes made?

A

In the nucleolus in the nucleus.

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5
Q

What is the function of rough endoplasmic reticulum?

A

To fold and process proteins made on the ribosomes.

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6
Q

What is the function of smooth endoplasmic reticulum?

A

To produce and process lips.

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7
Q

What is the function of a golgi apparatus?

A

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

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8
Q

What is the function of mitochondria?

A

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

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9
Q

What is the function of a centriole?

A

To produce spindle fibres for cell division.

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10
Q

What is the function of a ribosome?

A

To make proteins.

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11
Q

What is the function of a lysosome?

A

To hold and release digestive enzymes.

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12
Q

What is the function of a capsule?

A

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

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13
Q

What is a plasmid?

A

A circular piece of DNA.

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14
Q

What is the function of a flagellum?

A

To allow the cell to move.

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15
Q

What is the function of pili?

A

To attach to other cells.

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16
Q

What is the function of mesosomes?

A

To contain the enzymes for respiration and ATP for energy.

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17
Q

What does mitosis produce?

A

2 Identical daughter cells that are genetically identical.

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18
Q

Why is mitosis important?

A

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

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19
Q

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

A

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.

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20
Q

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

A

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.

21
Q

What are the phases within interphase?

A

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.

22
Q

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

A

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.

23
Q

What is the function of a cell’s membrane?

A

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

24
Q

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

A

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.

25
Q

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

A

Running through the membrane.

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

26
Q

Where are extrinsic proteins found? What is their function?

A

On the surface of the membrane.

To act as receptors.

27
Q

What is the function of cholesterol?

A

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

28
Q

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

A

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

29
Q

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

A

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.

30
Q

What is the definition of diffusion?

A

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

31
Q

What is the definition of facilitated diffusion?

A

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.

32
Q

What is the definition of osmosis?

A

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

33
Q

What is the definition of active transport?

A

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.

34
Q

What is the definition of co-transport?

A

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

35
Q

What increases the rate of gas exchange?

A

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

36
Q

Where is the genetic information of a bacteria stored?

A

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

37
Q

Where is the genetic information of a virus stored?

A

It is just nucleic acid encased in a protein coat.

38
Q

What are the physical barriers to infection within the body?

A

The skin.
Stomach acid.
Gut and skin bacteria.

39
Q

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

A

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.

40
Q

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

A

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.

41
Q

What is the definition of active immunity?

A

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

42
Q

What is the definition of natural active immunity?

A

Being exposed to the antigen/getting the disease.

43
Q

What is the definition of artificial active immunity?

A

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

44
Q

What is the definition of passive immunity?

A

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

45
Q

What is the definition of natural passive immunity?

A

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

46
Q

What is the definition of artificial passive immunity?

A

Getting a vaccine that contains the antibodies.

47
Q

What is the definition of a vaccine?

A

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

48
Q

What is the definition of herd immunity?

A

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

49
Q

What are the uses of monoclonal antibodies?

A

They are used within pregnancy tests.

A Level - Biology (9 decks)

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