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biology paper 1 > topic 2 - cells > Flashcards

topic 2 - cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the appearance and behaviour of chromosomes during mitosis

A

prophase - chromosomes condense and 2 sister chromatids join at centromere
metaphase - chromosomes line up at centre of cell and are attached to spindle fibres by their centromere
anaphase - centromere splits and sister chromatids are pulled to opposite poles of the cell
telophase - chromatids uncoil

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2
Q

how can you tell a cell is in anaphase

A

chromatids at opposite poles of cell

v shape shows sister chromatids have been pulled apart at their centromeres

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3
Q

what is the cell cycle

A

gap phase 1 - cell grows and new organelles and proteins are made
synthesis - cell replicates its DNA
gap phase 2- cell keeps growing and proteins needed for cell division are made
mitosis

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4
Q

what happens during interphase

A

cell prepares to divide, DNA is unravelled and replicated to double its genetic content. the organelles are replicates so it has spare ones and its ATP content is increased

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5
Q

what happens during prophase

A

the chromosomes condense getting shorter and fatter. tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle. the nuclear envelope breaks down and chromosomes lie free in the cytoplasm

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6
Q

what happens during metaphase

A

chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere

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7
Q

what happens during anaphase

A

the centromeres divide, seperating each pair of sister chromatids. the spindles contract pulling chromatids to opposite poles of the spindle, centromere first. this makes the chromatids appear v shaped

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8
Q

what happens during telophase

A

the chromatids reach the opposite poles on the spindle and uncoil, becoming long and thin. a nuclear envelope forms around each group of chromosomes, so there are now two nuclei. division of the cytoplasm finishes in telophase, producing two identical daughter cells

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9
Q

what is the division of the cytoplasm called and when does it start

A

cytokinesis (starts in anaphase ends in telophase)

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10
Q

describe binary fission in bacteria

A

1) circular DNA and plasmids replicate
(DNA loop only replicated once)
2) cell gets bigger and DNA loops move to opposite poles of cell
3) cytoplasm divides and new cell wall forms

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11
Q

how are algal cells different to plant cells

A

chloroplast structure is different, could only have 1 large chloroplast

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12
Q

what are the differences between fungal and plant cells

A

fungal’s cell walls made of chitin not cellulose
they dont have chloroplasts as they don’t photosynthesise

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13
Q

function of cell surface membrane

A

d- mainly made of lipids and protein

regulates movement of substances into and out of the cell, it has receptor molecules on it which allow it to respond to hormones

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14
Q

function of nucleus

A

controls cells activities and transcription of DNA as DNA contains instructions to make proteins. the pores allow substances to move between nucleus and cytoplasm

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15
Q

function of nucleolus

A

makes ribosomes

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16
Q

description of mitochondria’s components

A

oval shaped and double membraned, inner membrane folds to form cristae
inside is the matrix which contains enzymes involved in respiration

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17
Q

what are antigens

A

foreign proteins that can generate an immune response when detected by the body, found on surface of cells

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18
Q

what are pathogens

A

organisms that cause disease (bacteria,viruses,fungi) and have antigens on their surface

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19
Q

what are abnormal body cells

A

cancerous or pathogen infected cells that have abnormal antigens on their surface

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20
Q

what are toxins

A

poisons produced by pathogens

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21
Q

why do bodys reject organ transplants

A

the cells will have antigens that are different to your own so the foreign antigens trigger an immune response, leading to rejection of the organ

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22
Q

what are the main stages of immune response

A

1) phagocytosis
2) t cells
3) b cells

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23
Q

steps of phagocytosis

A

1) phagocyte recognises foreign antigens on a pathogen
2) cytoplasm of phagocyte moves round the pathogen, engulfing it
3) pathogen now contained in PHAGOCYTIC VACUOLE in cytoplasm of phagocyte
4) lysosome fuses with phagocytic vacuole and lysozymes break down the pathogen
5) phagocyte presents the pathogens antigens to activate other immune system cells

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24
Q

describe the function of T cells

A

they are white blood cells with receptor proteins on its surface that bind to complementary antigens presented by phagocytes, activating T cell.
helper T cells - release chemical signals that activate and stimulate cytotoxic T cells which kill abnormal cells

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25
Q

describe the function of B cells

A

coveried with antibodies (proteins that bind with antigens to form an antigen-antibody complex) and when they bind it activates the B cell to divide into plasma cells

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26
Q

describe antibody production and destruction of pathogens

A

plasma cells secrete antibodies specific to antigen (monoclonal) which bind to the antigen on the surface of the pathogen.
antibody has 2 binding sites so can clump pathogen together by agglutination
phagocytes bind to antibodies and phagocytose many pathogens at once

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27
Q

describe primary immune response

A

primary response is slow as there aren’t many B cells that can make the antibody needed to bind to it, eventually the body will produce enough of the right antibody to overcome the infection. infected person shows symptoms of disease

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28
Q

describe secondary immune response

A

-both T and B cells produce memory cells once exposed to antigen
-memory T cells remember specific antigen and will recognise it a second time round
-memory B cells record specific antibodies needed to bind to antigen
-person now immune and pathogen is gone before they show symptoms

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29
Q

suggest investigations that should be done before a drug is tested on patients

A

-healthy human volunteers
-other mammals
-investigate different conc of drug to find a safe dosage

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30
Q

what is active immunity

A

where your immune system makes its own antibodies after being stimulated by an antigen
natural- becoming immune from catching a disease
artificial- becoming immune after you’ve been given a vaccination exposing you to antigen

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31
Q

what is passive immunity

A

where you are given antibodies made by a different organism
natural- babies becoming immune due to the antibodies it recieves from its mother in placenta and breast milk
artificial- becoming immune after being injected with antibodies from someone else (blood donations)

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32
Q

4 differences between active and passive immunity

A

active requires exposure to antigen, passive doesn’t
active takes a while for protection to develop, passive is immediate
active memory cells are produced, passive they aren’t
active protection is long term as antibody is produced, passive is short term as antibodies given are broken down

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33
Q

what is a vaccine

A

a small sample of attenuated pathogen

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34
Q

ethical issues surrounding use of vaccines

A

-tested on animals
-volunteers may put themselves at unnecessary risk of contracting a disease because they think theyre protected from testing the vaccine
-some people don’t want to take the vaccine due to risk of side effects but are still protected from HI- others think this is unfair

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35
Q

what is antigenic variation

A

different antigens are formed on the surface of pathogens due to changes in the genes of it

36
Q

what are monoclonal antibodies

A

antibodies produced from a single group of genetically identical B cells (plasma cells)

37
Q

how do cancer drugs not affect normal cells

A

cancer cells have antigens called tumour markers which are not on normal cells so monoclonal antibodies can be made to attach to these specifically and can carry drugs to only cancer cells

38
Q

describe how a pregnancy test works

A

1) application area contains antibodies that are complementary to HCG protein bound to a coloured bead
2) when urine is applied to application area any HCG will bind to antibodies and urine moves up stick to test strip
3) test strip contains antibodies to HCG that are immobilised and if there is HCG present the test strip turns blue because the immobilised antibodies bind to any HCG, concentraing the HCG antibody complex
4) no HCG present, beads will not bind and pass through

39
Q

describe an Elisa test

A

1) apply sample containing antigen to well and leave to stick
2) wash well to remove any antigens that didnt stick
3) add an antibody which is specific for the antigen and wait for the antibodies to stick to antigens, wash to remove excess antibodies
4) add a second antibody which will stick to first antibody and is attached to an enzyme molecule, wash to remove excess 2nd antibodies
5) add substrate (colourless) which enzyme will turn into a coloured molecule
intensity of colour= how many antigens present

40
Q

why is an Elisa test repeated at different dilutions

A

all of the antigens may not stick to the well and therefore antigen quantity cannot be accurately measured

41
Q

ethical issues surrounding use of monoclonal antibodies

A

animals are used to produce cells from which the monoclonal antibodies are produced, some people disagree with this

42
Q

what is AIDS and why does HIV lead to AIDS

A

AIDS is a condition where the immune system deteriorates and eventually fails
HIV infects and eventually kills helpers T cells (these send chemical signals that activate phagocytes, cytotoxic T cells and helper B cells) so they’re hugely important for the immune response

43
Q

symptoms of HIV and AIDS

A

HIV - flu like symptoms
latency period: no symptoms

AIDS - minor infections of mucuous membranes
-chronic diarrhoea and severe bacterial infections
-candidiasis of respiratory system

44
Q

describe HIV structure

A

core - reverse transcriptase and RNA
surrounded by capsid protein
surrounded by envelope, made of membrane stolen from cell membrane of a previous host cell
attachment proteins stick out of envelope

45
Q

describe how HIV replicates

A

1) attachment protein attaches to receptor molecule on the cell membrane of host T cell
2) capsid released into cell where it uncoats and releases RNA into cytoplasm
3) reverse transcriptase is used to make complementary strand of DNA from viral RNA template
4) double stranded DNA is made and inserted into human DNA
5) host cell enzymes make viral proteins from the viral DNA found within the human DNA
6) viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells

46
Q

how do antibiotics work

A

kill bacteria by interfering with metabolic reactions by targeting the bacterial enzymes and ribosomes

viruses dont have their own enzymes or ribosomes, they use the ones in host cells, so antibiotics cannot inhibit them
most antiviral drugs are designed to target the few viral specific enzymes

47
Q

what is the cell membrane mainly made of

A

phospholipids, proteins and carbohydrates

48
Q

what does the Fluid Mosaic Model show

A

-phospholipid molecules form a continuous bilayer which is fluid as they are constantly moving
-channel and carrier proteins scattered through bilayer which allow large molecules and ions to pass through membrane
-receptor proteins on the membrane surface allow membrane to detect chemicals released from other cells and act on it (eg absorb more glucose)

49
Q

describe phospholipids

A

head- hydrophilic
tail- hydrophobic

centre of bilayer is hydrophobic so water soluble substances cannot diffuse through it (eg ions)

50
Q

describe cholesterols role

A

-gives membrane stability as it binds to hydrophobic tails so they pack together and make membrane rigid

-not present in bacterial cell membranes

-helps maintain shape of animal cells eg red blood cells

-has hydrophobic regions to further prevent polar substances from passing through

51
Q

describe membrane permeability at below 0 degrees

A

-rigid as phospholipids don’t have much energy so cannot move
-channel and carrier proteins denature so permeability increases
-ice crystals may form and pierce the membrane, increasing permeability when it thaws

52
Q

describe membrane permeability between 0 and 45 degrees

A

-partially permeable as phospholipids can move around and aren’t tightly packed together
-as temp increases so does permeability as phospholipids gain energy

53
Q

describe membrane permeability above 45 degrees

A

-bilayer starts to melt and the membrane becomes more permeable
-water inside cell expands putting pressure on membrane
-carrier and channel proteins denature further increasing permeability

54
Q

define diffusion

A

net movement of particles (molecules/ions) from a region where they are more highly concentrated to one where their concentration is lower until evenly distributed

55
Q

does diffusion require energy

A

no its passive

56
Q

factors that affect diffusion rate

A

surface area: bigger = faster
thickness of exchange surface: thinner = faster
conc gradient: higher = faster

57
Q

what is faciliated diffusion and its conditions

A

diffusion of larger/charged molecules
-passive
-requires channel or carrier proteins

58
Q

describe how carrier proteins carry out faciliated diffusion

A

1) large molecule attaches to carrier protein in membrane
2) protein changes shape
3) releases molecule on other side of membrane

59
Q

describe how channel proteins carry out faciliated diffusion

A

form pores in the membrane for charged particles to diffuse through

60
Q

two differences between channel and carrier proteins in facilitated diffusion

A

channel-only involved in facilitated diffusion and osmosis
carrier-also involved in active transport
channel- substances pass straight through a water filled pore
carrier- substances bind to carrier protein then it changes shape

61
Q

factors affecting rate of facilitated diffusion

A

conc gradient: higher=faster
amount of proteins: less proteins=slower rate

62
Q

define osmosis

A

the net movement of water from a high water potential to a low water potential through a partially permeable membrane

63
Q

define water potential

A

potential of water molecules to diffuse out of/into a solution

64
Q

what is pure waters water potential and how can it be affected

A

0
adding solute reduces water potential e.g squash

65
Q

what are two solutions with the same water potential called

A

isotonic

66
Q

describe movement of water in isotonic conditions

A

no net movement of water

67
Q

describe movement of water in hypotonic conditions

A

solution has higher water potential than cell
cell swells as water moves into cell

68
Q

describe movement of water in hypertonic conditions

A

water potential higher in cell than in solution
cell shrinks as water moves out of cell

69
Q

factors that affect rate of osmosis

A

water potential gradient: higher = faster
thickness of exchange surface
surface area of exchange surface

70
Q

describe active transport and its conditions

A

-uses energy to move molecules and ions across plasma membranes
-usually against conc gradient
-involves carrier proteins or co transporters

71
Q

how do carrier proteins carry out active transport and what are the 2 main differences between this and facilitated diffusion

A

molecule attaches to it
protein changes shape
released on other side of membrane

active transport goes against conc gradient usually, facilitated diffusion goes down
active transport requires energy, facilitated diffusion is passive

72
Q

what source of energy does active transport use

A

ATP -> ADP + P
creates energy

73
Q

how do co transporters work

A

binds 2 molecules at a time as the concentration gradient of 1 of the molecules can help the other to move against its concentration gradient

74
Q

describe co transport of glucose

A

1) sodium ions are actively transported out of epithelial cells in the ileum into the blood by the sodium potassium pump, this creates a conc gradient as there is now more sodium ions in the lumen than in the cell
2) sodium ions diffuse from lumen into epithelial cell down conc gradient, taking glucose molecules with it against its conc gradient. conc of glucose increases in cell
3) glucose diffuses out of cell into blood down its conc gradient through a protein channel by facilitated diffusion

75
Q

what factors affect rate of active transport

A

speed of carrier proteins
amount of carrier proteins available
availability of ATP depending on rate of respiration

76
Q

what is an antibody

A

a protein specific to an antigen produced by B cells

77
Q

difference of light microscope and electron

A

electron- higher resolution and use beam of electrons focused by electromagnets inside vacuum environment

78
Q

how does TEM work

A

beam of electrons passes through a specimen and areas that absorb electrons appear darker

79
Q

how does SEM work

A

beam of electrons passes across surface and scatters, building a 3d image

80
Q

limitations of electron microscopes

A

living specimens can’t be observed in a vacuum
complex staining process required which may introduce artifacts into the image
specimens have to be very thin so electrons can pass through
SEM has lower resolving power

81
Q

describe cell fractionation

A

1) homogenisation - blend cells to break them open, place in centrifuge and spin at slow speed
2)heaviest organelles form a pellet at bottom
3) supernatant removed

82
Q

why should homogenate be ice cold

A

to inactivate any enzymes from breaking down organelles

83
Q

why should homogenate be isotonic

A

to prevent organelles from bursting

84
Q

why should homogenate be buffered

A

so pH doesnt fluctuate

85
Q

t

A

biology paper 1 (4 decks)

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