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biology > section 2: cells > Flashcards

section 2: cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

B lymphocytes

A
  • mature in the bone marrow

- associated with humoral immunity

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2
Q

T lymphocytes

A
  • mature in the thymus gland

- associated with cell-mediated immunity

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3
Q

process of cell-mediated immunity

A
  1. pathogens invade body cells or are taken in by phagocytes
  2. the phagocyte placa antigens from the pathogen on its cell-surface membrane
  3. receptors in a specific helper T cell fit exactly onto these antigens
  4. this attachment activated the T cells to divide rapidly by mitosis and form a clone of genetically identical cells
  5. the cloned T cells:
    • develop into memory cells that enable a rapid response to future infections by the same pathogen
    • stimulate phagocytes to engulf pathogens by phagocytosis
    • stimulate B cells to divide and secrete their antibody
    • activate cytotoxic T cells
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4
Q

how do cytotoxic T cells kill infected cells?

A

produce a protein called perform that makes holes in the cell-surface membrane,
these holes mean the cell membrane becomes freely permeable to all substances and so the cell dies as a result of this

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5
Q

process of humoral immunity

A
  1. the surface antigens in an invading pathogen are taken up by a B cell
  2. the B cell processes the antigens and presents them on its surface
  3. helped T cells attach to the processed antigens on the B cell and activate the B cell
  4. the B cell is now activated to divide by mitosis to make clone plasma cells
  5. the cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogen’s surface
  6. the antibody attaches to antigens on the pathogen and destroys them
  7. some B cells develop into memory cells that respond to future infections from the same pathogen - secondary immune response
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6
Q

Fick’s Law

A

rate of diffusion =
surface area x concentration gradient/
length of diffusion pathway

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7
Q

non-specific defences

A

• stomach - hydrochloric acid that kills pathogens
• blood - platelets form acaba to stop pathogens entering
- white blood cells/phagocytes
• eyes - tears contain salt and lysozyme
- blinking and eyelashes prevent things from entering
• nose - lined with mucus and hairs
• lungs - air passages are clones with 2 types of cells: goblet cells (make mucus) and ciliated cells (have cilia)
• skin - acts as a tough barrier
- hair follicles make sebum (oily substance)

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8
Q

process of phagocytosis

A
  1. the phagocyte is attracted to the chemical products of the pathogen - chemoattractants
  2. phagocyte moves towards the pathogen
  3. phagocyte has receptors on its surface and these attach to the chemicals on the surface of the pathogen
  4. the phagocyte engulfs the pathogen and forms a phagosome
  5. lysosomes inside the phagocyte move towards the phagosome
  6. lysosomes release lysozymes (lytic enzymes) into the phagosome
  7. the lysozymes hydrolyse the pathogen
  8. the products of the hydrolysis are absorbed by the pathogen
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9
Q

what is passive immunity?

A
  • antibodies introduced from an outside source not by the individual making them themselves
  • no memory cells are produced
  • not long lasting
  • examples: anti-venom, immunity passed from mother to fetus
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10
Q

what is active immunity?

A
  • antibodies produced by the individual
  • must be direct contact with the pathogen/antigen
  • immunity takes time to develop
  • generally long lasting
  • 2 types:
    • natural - from an individual being infected by a disease under normal circumstances, body produces its own antibodies
    • artificial - the basis of vaccination (immunisation), involves inducing an immune response in an individual without them suffering symptoms of the disease
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11
Q

what is a vaccination?

A

the introduction of the appropriate disease antigens into the body either by injection or by mouth, to stimulate an immune response against that particular disease so memory cells are produced

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12
Q

features of a successful vaccination programme

A
  • must be economically viable so that it can be available in large enough quantities to immunise most of the vulnerable population
  • must be few and not severe side effects so people aren’t put off
  • the means of producing, storing and transporting the vaccine must be available
  • must be reasonable means of administrating the vaccine, not too difficult, also staff must be trained to do it properly
  • must be possible to vaccinate a large amount of the vulnerable population to produce herd immunity
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13
Q

what is herd immunity?

A

when large enough proportion of the population has been vaccinated to make it difficult for the pathogen to spread within that population

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14
Q

why does a vaccination rarely eliminate a disease?

A
  • vaccines don’t work for everyone
  • people could get infected by the vaccine and harbour it and pass the disease on to others
  • pathogens mutate frequently
  • there are too many varieties of disease
  • some people object to getting vaccines
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15
Q

ELISA test for HIV/AIDS

A
  • stands for enzyme linked immunosorbant assay
  • it uses antibodies to detect the presence of a protein in a sample but also the quantity of it
  • works by the antibodies attaching to the specific antigens and then using an antibody with an enzyme (that will bind to the original antibody) and then add these together and the more intense the colour produced then the more of those antigens there is present
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16
Q

antigen

A

a foreign protein on the cell surface that triggers an immune response

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17
Q

antibody

A

a protein produced by B cells that have a specific binding site to a specific antigen

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18
Q

nucleus

A
  • surrounded by a double membrane called the nuclear envelope
  • nuclear pores allow passage of large molecules (such as RNA)
  • nucleoplasm jelly making up nucleus
  • nucleolus within the nucleoplasm manufactures RNA
  • controls the cell and holds genetic material
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19
Q

mitochondria

A
  • made of two membrane: the outer membrane is for the external shape and structure, the inner membrane has many folds called cristae
  • main job is to perform cellular respiration which provides energy for the cell
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20
Q

golgi apparatus

A
  • stack of membranes (flattened sacs) and membranes contain small hollow structures called vesicles
  • transport, modify and store proteins and lipids produced by the ER, molecules are transported to and from the golgi by vesicles
  • produce lysosomes and secretory enzymes
  • cell post office
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21
Q

lysosomes

A
  • surrounded by a membrane, can contain up to 50 enzymes
  • garbage disposal of the cell, remove useless or dangerous material
  • formed when vesicles produced by the golgi contain useful enzymes, contain digestive enzymes to break down waste
22
Q

ribosomes

A
  • 80S in eukaryotic cells, 25nm in diameter
  • 70S in prokaryotic cells, mitochondria and chloroplasts, slightly smaller than 80S
  • have 2 sub units, one small unit and one large, each contain ribosomal RNA and protein
  • site of protein synthesis
  • found in cytoplasm or associated with RER
23
Q

rough endoplasmic reticulum

A
  • ribosomes present, connected to outer nuclear membrane
  • protein synthesis, pathway for the transport of materials
  • motorway of the cell
24
Q

smooth endoplasmic reticulum

A
  • does not contain any ribosomes

- synthesise, store and transport lipids and carbohydrates

25
Q

chloroplasts

A
  • contain two fluid separated membranes, the inner membrane is folded into a network of flattened sacs called thylakoids that are stacked into grana
  • responsible for photosynthesis
26
Q

cell wall

A
  • is rigid and semi-permeable protective layer, is positioned right next to the cell membrane of many cells
  • helps to prevent over expansion and keep structure, also to withstand turgor pressure and regulate growth and diffusion
27
Q

cell vacuole

A
  • formed by the joining of many vesicles, they have no specific shape and contain water with a number of different compounds within it
  • their function can vary greatly e.g. in a plant cell they are important for maintaining turgor pressure
28
Q

cell differentiation

A

the process by which cells become specialised for different functions

+ cells can perform their functions more effectively so the organism can process more efficiently

29
Q

parts of the structure of a virus

A
  • genetic material (RNA)
  • reverse transcriptase (enzyme)
  • capsid
  • matrix
  • lipid envelope
  • attachment proteins
30
Q

magnification

A

magnification of an object is how many times bigger the image is when compared to the actual size

31
Q

resolution

A

the minimum distance apart that two objects can be in order for them to appear as separate items

32
Q

magnification equation

A

magnification = image size / actual size

33
Q

describe the process of cell fractionation and ultracentrifugation

A
  1. tissue is cut up and kept in a cold, buffered solution
  2. cut up tissue is further broken up in a homogeniser or using a high frequency sound
  3. homogenised tissue is spun in an ultracentrifuge at a low speed for 10 minutes
  4. after being spun at a low speed the supernatant is transferred to another tube and spun at a higher speed
  5. the speed is increased and the process repeated until everything has separated
34
Q

supernatant

A

the clear liquid that lies above the solid residue after centrifugation
(still contains cell components so is spun again at higher speed)

35
Q

describe how a light microscope works

A
  • use a pair of convex glass lenses to direct a beam of light onto the specimen
36
Q

describe how scanning electron microscopes work

A
  • electron beam is passed back and forth across a section of the specimen
  • builds up a 3D colour image as the scattering of electrons depends on the contours of the specimen
37
Q

describe how a transmission electron microscope works

A
  • it consists of an electron gun that produces a beam of electrons that is focused into the specimen
  • the beam passes through a thin section of the specimen
  • parts of the specimen absorb electrons so they appear dark and parts that allow electrons to pass through, appear light
38
Q

why is mitosis important?

A
  • growth - all daughter cells are produced to be identical so organisms can grow
  • repair - organisms can replace dead tissue using identical cells produced in mitosis
  • reproduction - some organisms reproduce by mitosis
39
Q

3 stages of the cell cycle

A

interphase - G1: protein synthesis, S: DNA replication, G2: organelle synthesis
mitosis - form of nuclear division that produces 2 daughter cells, has 4 stages: prophase, metaphase, anaphase and telophase
cytokinesis - the cytoplasm divides producing the daughter cells

40
Q

binary fission

A
  • the circular DNA molecule replicates and both copies attach to the cell membranes and plasmids replicate
  • the cell membrane grows between the DNA molecules and begins to pinch inwards, dividing the cytoplasm in 2
  • new cell wall forms, dividing the original cell into 2 identical cells
41
Q

purpose of cholesterol in cell membranes

A
  • to reduce lateral movement of other molecules including phospholipids and make it more rigid
  • prevent leakage of water and dissolved ions
  • make the membrane less fluid at high temperatures
42
Q

purpose of phospholipids in the membrane

A
  • allow lipid-soluble substances to enter and leave the cell
  • to prevent water soluble substances entering and leaving the cell
  • make the membrane flexible and self-sealing
  • makes up the overall structure
43
Q

why are glycoproteins in the cell membrane?

A
  • to act as recognition sites
  • helps cells to attach to each other to form tissues
  • allows cells to recognise one another
44
Q

purpose of proteins in the cell membrane

A
  • provide structural support
  • act as channels to help water soluble molecules cross the membrane
  • allow active transport across the membrane through carrier proteins
  • act as receptors
  • help cells to adhere together
45
Q

purpose of glycolipids in the cell membranes

A
  • act as recognition sites
  • help maintain the stability of the membrane
  • help cells to attach to one another to form tissues
46
Q

solute

A

any substance that dissolved in a solvent to form a solution

47
Q

water potential

A

the pressure created by water molecules the greater the number of water molecules, the higher the water potential (less negative)

48
Q

solution

A

a mixture of solvent and solute molecules

49
Q

active transport

A

the movement of substances from an area of low concentration to an area of high concentration against a concentration gradient, using ATP and carrier proteins

50
Q

how are glucose and amino acids absorbed?

A
  1. sodium ions are actively transported out of the epithelial cells by the sodium-potassium pump
  2. this maintains a higher concentration of sodium ions in the lumen of the intestine than in the epithelial cells
  3. sodium ions diffuse down the concentration gradient into epithelial cells, as the sodium ions diffuse through they carry amino acids or glucose molecules with them
  4. the glucose/ amino acids pass into the blood by facilitated diffusion
51
Q

ethical issues of vaccines

A
  • can involve use of animals
  • may have side effects with can be serious or long term
  • who should they be tested on?
  • can be very expensive

biology (10 decks)

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