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Flashcards in Biology: Cells Deck (35)
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1
Q

how do electron microscopes work and what are the conditions they have to be in?

A
  • electrons fire through the sample, the reflected electrons are observed.
  • it must be in a vacuum
  • TEM microscope: sample is sliced and stained with a heavy metal
  • SEM microscope: specimen is coated with a thin layer of gold.
2
Q

how does centrifugation happen in order to obtain a small organelle?

A
  • cell is homogenated (broken up)
  • it’s filtered to remove whole cells and membrane debris.
  • it’s put in a supernatant, it’s isotonic, ice cold and buffered to prevent pH or temp. change.
  • it’s spun at a slow speed, a pellet containing large organelle forms at the bottom.
  • it’s spun at a faster speed for a longer time and smaller organelle collect at the bottom.
3
Q

what is an eyepiece graticule?

A
  • it’s a glass disc that rests on the rim of the eyepiece.

- the stage micrometer is used alongside the graticule to measure the size of the sample.

4
Q

how do you find image size?

A

actual size x magnification

5
Q

what is the structure of the mitochondria?

A
  • the inner membrane is folded into cristae.

- this maximises surface area so there’s more transport over the organelle.

6
Q

what is the structure of the chloroplast?

A

-the thylakoid membranes are stacked to increase surface area for maximum light absorption.

7
Q

what do the RER and SER do?

A

RER:

  • it’s rough due to ribosomes on its surface.
  • it’s used to sythensise proteins

SER

  • lacks ribosomes so it’s smooth
  • lipid synthesis.
8
Q

what is cell differentiation?

A
  • the cells of an embryo at an early stage are all the same.
  • cells become different from each other.
  • differentiated cells are specialised so they carry out specific functions.
9
Q

what is a tissue?

A

a group of cells of the same type.

10
Q

what are the uses of tissues?

A
  • protection of internal organs from damage
  • diffusion of substances across the surface of the epithelium
  • absorption of materials, such as the products of digestion.
  • secretion of substances onto the surface of the epithelium.
11
Q

what are prokaryotic cells?

A
  • cells with no membrane bound organelle.
  • no true nucleus.
  • DNA is in a strand which is freely floating inside the cell
12
Q

how does the virus invade cells and replicate?

A
  • attachment proteins bind to receptors on the cell.
  • it releases a capsid into the cell.
  • this releases its RNA into the cell, which changes the DNA of the cell.
  • it replicates viruses
  • the cell bursts due to overcrowding.
13
Q

describe the process of mitosis

A

interphase: DNA replicates so there’s 2 chromatid per chromosome.
prophase: the chromosomes ondense and become more visible, the nuclear membrane breaks down.
metaphase: the chromosomes line up along the middle of the cell and attach to spindle fibres at the poles.
anaphase: the spindle fibres shorten, pulling the chromosomes apart to each of the poles.
telophase: it begins so constrict down the middle and new nuclear membrane forms around both groups of chromosomes. chromosomes decondense and become less visible

14
Q

what is the fluid mosaic model?

A
  • it shows the structure of the phospholipid bilayer

- it’s fluid mosaic as it’s flexible and consists of many parts, each of different shapes and sizes.

15
Q

what is the purpose of the phospholipid bilayer?

A
  • the hydrophilic head and hydrophobic tail doesn’t let water in.
  • intrinsic proteins allow the passage of certain molecules through
16
Q

what is the purpose of the channel and carrier proteins?

A

CHANNEL:
-water filled tubes to allow the passage of water-soluble molecules into the cell.

CARRIER:

  • used in active transport
  • change shape to let larger molecules enter the cell.
17
Q

what is the purpose of cholesterol in the phospholipid bilayer?

A
  • increases resistance to temp. change

- keeps the membrane structurally strong

18
Q

what is diffusion and what factors can affect it?

A

the movement of a substance from high to low concentration down a concentration gradient until it reaches equilibrium. it’s a passive process as it doesn’t require energy.

factors:

  • conc. of substance
  • length of diffusion pathway
19
Q

what is facilitated diffusion?

A

diffusion using the channel proteins. it’s still passive etc.

20
Q

what is osmosis?

A

the net movement of water molecules through a partially permeable membrane until equilibrium is reached. high to low concentration

21
Q

what is water potential?

A

the pressure exerted by water molecules. measured in kPa.

22
Q

what is the water potential of pure water?

A

0

23
Q

what does fick’s law state?

A

rate of diffusion proportional to:

(surface area x gradient) / length of diffusion pathway

24
Q

how does active transport work?

A
  • molecules go into carrier protein
  • a phosphate from ATP phosphorylates the protein and it changes shape.
  • this releases the molecules out of the other end of the membrane and into the cell
25
Q

how does the sodium-potassium pump work?

A

3 sodium out, 2 potassium in

  • 3 sodium ions bind using ATP
  • phosphate binds, changing the tertiary structure
  • 3 sodium released from cell
  • higher affinity for potassium
  • 2 potassium bind
  • phosphate dissocated
  • 2 potassium carried into the cell as well as glucose and amino acids etc.
26
Q

what does hypertonic mean?

A

concentration of solute in a solution surrounding the cell is greater than that inside the cell

27
Q

what does isotonic mean?

A

solutes in solution = solutes in cell

28
Q

what does hypotonic mean?

A

conc. of solute in solution surrounding the cell is less than that inside the cell.

29
Q

what happens to a cell in a:

hypertonic solution
hypotonic solution
isotonic solution

A

hypertonic:
cell deflates as water potential outside the cell is lower so water leaves the cell

hypotonic:
cell lysis as water enters the cell

isotonic:
nothing happens

30
Q

how do barriers prevent us against pathogens?

A

-prevent pathogens from entering the body

  • eyes: tears, eyelashes, blinking
  • skin: oily substance called sebum
31
Q

describe the process of phagocytosis

A
  • phagocyte attracted to pathogen by chemoattractants
  • it engulfs the pathogen and puts it in a vesicle called a phagosome
  • lysosomes line up around the vesicle
  • they release lysozyme, a digestive enzyme, into the vesicle
  • it hydrolyses the pathogen
  • it leaves the phagocyte by exocytosis.
32
Q

what to cytotoxic t-cells do?

A
  • they use an enzyme to break down the membrane of a cell

- water enters the cell, causing cell lysis

33
Q

what do b-cells do in response to phagocytosis?

A
  • divide and produce clones of cells.
  • most of these cells are plasma cells and produce monoclonal antibodies
  • monoclonal antibodies are complementary to a certain antigen
34
Q

how do antibodies destroy antigens?

A

agglutination: easier for phagocytes to engulf them
precipitation: facilitates phagocytosis
markers: signal phagocytes

neutralisation of toxins

lysis: breaks down bacteria

35
Q

what’s the difference between artificial and natural immunity?

A

natural: the body’s response to the antigen
artificial: brought about by vaccinations