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biology aqa a-level > topic 2 - cells > Flashcards

topic 2 - cells Flashcards

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1
Q

what is the main difference between eukaryotic and prokaryotic cells?

A

prokaryotic cells are small and simple, and eukaryotic cells are large and complex.

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2
Q

what is the function of the Golgi body and the Golgi vesicle?

A

the Golgi body processes and packages new lipids, proteins and lysosomes. the Golgi vesicle stores those lipids and proteins.

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3
Q

what do lysosomes contain?

A

enzymes called lysozymes.

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4
Q

what do the enzymes in lysosomes do?

A

they digest invading cells and break down worn out parts of the cell.

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5
Q

what type of cells are vacuoles not found in?

A

animal cells.

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6
Q

what is the function of the vacuole?

A

to keep the cell rigid (stopping it from wilting), and isolating unwanted chemicals within the cell.

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7
Q

what is the function of the rough endoplasmic reticulum?

A

it processes the proteins that ribosomes make.

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8
Q

what is the function of the smooth endoplasmic reticulum?

A

to synthesise and process lipids

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9
Q

what is the cell organisation of specialised cells?

A

cells > tissues > organs > organ systems > organisms.

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10
Q

what can the genes in a prokaryote’s plasmid help with?

A

antibiotic resistance.

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11
Q

what is the process of binary fission?

A

circular DNA and plasmids replicate in the cytoplasm (plasmids can be replicated several times) and the cell increases in size, as the main DNA are pulled to opposite poles of the cell. the cytoplasm divides and new cell walls are formed. there are now two daughter cells with one copy of the DNA loop and a variable number of plasmids.

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12
Q

what are viruses made up of?

A

genetic material surrounded by a protein coat, and attachment proteins.

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13
Q

what is the formula for magnification?

A

magnification = size of image / size of real object.

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14
Q

what is the difference between magnification and resolution?

A

magnification is how much bigger the image is than the specimen, but resolution is how well a microscope can identify two different points that are close.

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15
Q

what are the two types of electron microscopes?

A

transmission electron microscopes and scanning electron microscopes.

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16
Q

what are the advantages to both types of electron microscopes.

A
  • TEM: high resolution images.

* SEM: can be used on thicker specimens, and can be viewed in 3D.

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17
Q

what are the disadvantages for both types of electron microscopes?

A
  • TEM: only used on thin and non-living specimens.

* SEM: lower resolution than TEMs, and only used on non-living specimens.

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18
Q

what are the different stages in mitosis called?

A

interphase, prophase, metaphase, anaphase, and telophase.

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19
Q

what happens in the first stage of mitosis?

A

the organelles are replicated, as is the DNA once it unravels. ATP content is also increased to provide enough energy for the rest of mitosis.

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20
Q

what happens in the second stage of mitosis?

A

a spindle is created when centrioles move to opposite ends of the cell. the nuclear envelope breaks down so that the chromosomes are able to be free in the cytoplasm. the chromosomes also get shorter and fatter.

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21
Q

what happens in the third stage of mitosis?

A

the chromosomes line up in the centre of the cell and get attached to the spindle.

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22
Q

what happens in the fourth stage of mitosis?

A

the chromosomes separate from their pair, creating sister chromatids, which are pulled to opposite poles of the spindle.

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23
Q

what happens in the final stage of mitosis?

A

the chromatids uncoil once they reach the pole they were pulled to, so they become long and thin again (not called chromosomes again). the daughter cells form a nuclear envelope around their chromosomes, making two nuclei. the cytoplasm divides and the daughter cells completely separate.

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24
Q

how are some cancer treatments implementing the cell cycle?

A

they control the rate of cell division by disrupting the cycle; they kill tumour cells and normal cells, but since the tumour cells divide more often, they’re more likely to be killed.

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25
Q

what is the formula for mitotic index?

A

mitotic index = number of cells with visible chromosomes / total number of cells observed.

26
Q

what are membranes composed of?

A

lipids, carbohydrates and proteins.

27
Q

why was the fluid mosaic model suggested in 1972?

A

it was suggested to describe the arrangement of molecules in the membrane.

28
Q

what do channel and carrier proteins allow in the bilayer?

A

they allow large molecules and ions to pass through the membrane.

29
Q

what do receptor molecules allow on cell-surface membranes?

A

they allow the cell to detect chemicals released from other cells.

30
Q

where is cholesterol present?

A

in all cell membranes, but not bacterial cell membranes.

31
Q

what does cholesterol do in the cell membranes?

A

it binds to the hydrophobic tails of phospholipids, restricting their movement and making them more rigid and less fluid. it also makes a barrier for polar molecules.

32
Q

what required practical investigates permeability of cell membranes?

A

the beetroot practical. it investigates the effect of temperature and solvents.

33
Q

what is the definition of diffusion?

A

the net movement of particles from an area of high concentration to an area of low concentration.

34
Q

is diffusion an active or passive process?

A

passive: it requires no response energy for it to occur.

35
Q

what factors can affect diffusion?

A
  • concentration gradient: the higher, the faster the rate.
  • thickness of exchange surface: the thinner, the faster the rate.
  • surface area: the larger, the faster the rate.
36
Q

what is facilitated diffusion?

A

the net movement of particles from an area of high concentration to an area of low concentration, involving carrier and channel proteins to assist larger molecules.

37
Q

is facilitated diffusion an active or passive process?

A

passive: it requires no response energy for it to occur.

38
Q

what is the function of carrier proteins?

A

they move large molecules across the cell membrane.

39
Q

how do carrier proteins facilitate diffusion?

A

a large molecule attaches, and the protein changes shape to release it on the other side of the membrane.

40
Q

what is the function of channel proteins?

A

they form pores in the cell membrane for charged particles to diffuse through.

41
Q

what factors can affect facilitated diffusion?

A
  • concentration gradient: the higher, the faster the rate (until equilibrium).
  • number of transport proteins: is they’re all being used, the process can’t happen, regardless of concentration gradient.
42
Q

what is osmosis?

A

the diffusion of water water molecules across a partially permeable membrane, from a area of high water potential to an area of low water potential.

43
Q

what is water potential?

A

the potential (likelihood) of water molecules to diffuse in or out of a solution.

44
Q

how does adding solutes to pure water affect the water potential?

A

it lowers it, making any solution negative (other than pure water).

45
Q

what is the word that describes 2 solutions with the same water potential?

A

isotonic.

46
Q

what would happen to a cell that is placed in a hypotonic solution?

A

the cell would swell; water moves into it since the water potential in the solution is higher than the cell.

47
Q

what would happen to a cell that is placed in a hypertonic solution?

A

the cell would shrink; water moves out of it since the water potential in the cell is higher than the solution.

48
Q

what factors can affect osmosis?

A
  • water potential gradient: the higher, the faster the rate.
  • the thickness of exchange surface: the thinner, the faster the rate.
  • the surface area of exchange surface: the larger, the faster the rate.
49
Q

what is active transport?

A

the use of energy to move molecules and ions across a plasma membrane against the concentration gradient. it involves carrier proteins and co-transporters.

50
Q

how do carrier proteins assist in active transport?

A

a molecule attaches to the carrier protein and it releases it on the other side after changing shape. active transport requires energy and transports from a low to high concentration.

51
Q

how do co-transporters assist in active transport?

A

they’re types of carrier proteins. they bring 2 molecules together and transport them to the other side of the membrane. one molecule travels against the concentration gradient while the other molecule travels down the concentration gradient.

52
Q

what factors can affect active transport?

A
  • the speed of carrier proteins: the faster they work, the faster the rate.
  • the number of carrier proteins:the more, the faster the rate.
  • the rate of respiration/ATP availability: if respiration is inhibited, active transport can’t occur.
53
Q

how does phagocytosis occur in an immune response?

A

a phagocyte occurs the antigens on a pathogen and engulfs it. it is inside a phagocytic vacuole in the cytoplasm and lysosomes bind with it and release lysozymes.

54
Q

how do helper T-cells help in an immune response?

A

they release chemical signals that activate phagocytes. they also activate B-cells.

55
Q

how do cytotoxic T-cells help in an immune response?

A

they kill abnormal/foreign cells.

56
Q

how do B-cells help in an immune response?

A

they’re covered in antibodies that form antigen-antibody complexes.

57
Q

what happens in the primary response in an immune response?

A

there aren’t many B-cells that can make the antibodies needed. once there are enough antibodies produced, the body will start showing symptoms. after this, memory cells are made that remain for a long time, with memory T-cells remembering the antigen type and memory B-cells recording the quantity of antibodies needed.

58
Q

what happens in the secondary response in an immune response?

A

if the same pathogen enters the body, memory B-cells activate and divide into plasma cells that will produce lots of antibodies that are right. memory T-cells are activated and divide into the right T-cells. you don’t usually show symptoms.

59
Q

what are the types of immunity?

A

active and passive immunity.

60
Q

what is antigenic variation?

A

when some pathogens have the ability to change their surface antigens.

61
Q

how can you see if a patient has antibodies to an antigen?

A

ELISA test.

biology aqa a-level (8 decks)

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