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OCR Biology A Level Module 2 Foundations in Biology > Cell Structure > Flashcards

Cell Structure Flashcards

1
Q

What techniques are used to see unstained and live specimens?

A

*Light interference (rather than light absorption. It eliminate halos and extra light. )
*Dark background

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2
Q

What is the structure of the smooth endoplasmic reticulum?

A

System of membranes with cisternae
No ribosomes

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3
Q

What is the structure of the rough endoplasmic reticulum?

A
  • System of membranes containing fluid-filled cavities called cisternae that are continuous with the nuclear membrane.
  • Coated with ribosomes
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4
Q

What is the structure of the nucleus + nuclear envelope + nucleolus?

A

Nucleus surrounded by double-membrane (nuclear envelope)
Nucleolus has no membrane
Nucleus contains Chromatin = genetic material, consisting of DNA wound around histone proteins.
When the cell isnt dividing it’s extended, when about to divide it condenses and coils into chromosomes.

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5
Q

what is the structure of the golgi apparatus?

A

Stack of membrane bound flattened sacs. Secretory vesicles can be pinched off to bring materials to and fro

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6
Q

What is the structure of mitochondria?

A

-spherical, rod shaped or branched.
-surrounded by 2 membranes with fluid filled space in between -> inner membrane folded into cristae
- fluid filled matrix

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7
Q

What is the structure of cilia/undulipodia?

A

protrusions from cell, surrounded by cell surface membrane
made from centrioles + contain microtubules

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8
Q

What is the structure of chloroplasts?

A

large
surrounded by double membrane. Inner = continuous with stacks of flattened sacs called thylakoids which contain chlorophyll. each stack = a granum.
fluid filled matrix = stroma
contain loops of DNA + starch grains

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9
Q

what is the structure and function of the vacuole?

A

contains fluid, surrounded by tonoplast membrane.
filled with water + solutes
maintains cell stability bc when swollen it pushes against cell wall +makes cell turgid which helps to support whole tissues and therefore whole plants.

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10
Q

WHat is the structure and function of the cytoskeleton?

A

rod like microfilaments ( smallest) made of actin: give the cell support + stability, mains cell’s shape. Allows changing of cell’s shape e.g. muscle contraction/ cytokinesis.
intermediate filaments made of a variety of proteins: anchor nucleus, keep organelles held in place, enable cell-cell signalling + stablise tissues.
cylindrical microtubules made of tubulin : form a track along which motor proteins (myosin dynein and kinesin) move organelles e.g vesicles. Also form spindle, which enables chromosomes to be moved. use of cilia/undulipodia to allow cell movement.

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11
Q

what is the structure and function of ribosomes?

A
  • small spherical organelles
  • NO MEMBRANE
  • made of RNA and proteins
  • made in nucleolus as 2 separate sub units, pass through nuclear envelope + combine.
  • protein synthesis
  • some remain free in cytoplasm assemble proteins for IN the cell) and some attach to RER (sythesising proteins exported OUT of the cell)
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12
Q

What is the structure + function of the plant cell wall?

A

made from bundles of cellulose fibres
can prevent plant cells from bursting, provides strength + support
maintains cell shape
permeable and allows solutions to pass through
plasmodesmata form part of a pathway to allow molecules to pass between cells
insoluble, high tensile strength, unreactive, flexible

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13
Q

what is the structure + function of lysosomes?

A

-small bags, each surrounded by single membrane
-contain hydrolytic digestive enzymes (kept -separate from rest of cell) which can digest old cell organelles/foreign object/pathogens and return components for re-use.

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14
Q

what is the structure + function of centrioles?

A
  • 2 bundles of microtubes at 90 degree angle to eachother, made of tubulin subunits arranged to form a cylinder
  • before cell division the spindle forms from them, the chromosomes attach to it + motor proteins walk along the tublin threads, pulling the chromosomes apart.
  • involved in formation of cilia + undulipodia. centrioles multiply + line beneath the plasma membrane + microtubules sprout outwards
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15
Q

What is the function of the smooth endoplasmic reticulum?

A

Contains enzymes that catalyse the metabolism of lipids e.g. cholesterol and steroid hermones. Involved with absorption, transport + synthesis of lipids.

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16
Q

What is the function of the rough endoplasmic reticulum? (2)

A

Intracellular transport system: cisternae form channels for transporting substances
Large SA for ribosomes: translation in protein synthesis occurs.

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17
Q

What is the function of the nucleus/ nuclear envelope/ nucleolus? (5)

A

Nuclear envelope separates contents of nucleus from cell
In some regions outer + inner nuclear membranes fuse to allow some dissolved substances + ribosomes to pass.
Nuclear pores allow movement of molecules in/out of the nucleus.
Nucleolus contains RNA and is where ribosomes are synthesised.
Chromosomes contain the organism’s genes

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18
Q

What is the function of the golgi apparatus?

A

proteins modified, processed by adding sugars or lipids or by being folded into their 3D shape.
packaged into vesicles + stored in cell or moved to plasma membrane/ secreted out.
lysosomes are made here

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19
Q

what is the function of mitochondria?

A
  • site of ATP production during aerobic respiration
  • self replicating = can accomodate for energy needs
    -abundant in cells where much metabolic activity happens e.g at synapses or in muscle cells.
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20
Q

what is the function of cilia/undulipodia?

A

epithelial cells lining airways have cilia that move mucus by beating
cells have 1 cilium usually that contains receptors + allow it to detect signals about its immediate environment
only animal cell to have undulipodium is sperm so it can move

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21
Q

what is the function of chloroplasts?

A

site of photosynthesis

22
Q

What is the endosymbiont theory?

A

Indicates that eukaryotic cells evolved from prokaryotes.
Prokaryotic cells with infolded membranes were thought to include those that could release their own energy(ATP), + those that contained chlorophyll

Many prokaryotic cells were engulfed ( but not digested ) by other larger ones

this produced the double membrane of what are now mitochondria and chloroplasts.

23
Q

What evidence is there for endosymbiont theory?

A

Have small ribosomes
Have loops of DNA
Are of a similar size to bacteria
Can divide by binary fission

24
Q

what is the definition of resolution?

A
  • the ability to see more detail; the ability to distinguish between two separate points/objects
25
Q

what is the definition of magnification?

A
  • the number of times larger an image appears compared with the size of the object
26
Q

what is sudan red stain?

A

stains lipids red

27
Q

what is methylene blue used for?

A

*All purpose staining
*Highlights certain cell parts of animal, bacteria, and blood tissue specimens

28
Q

what is iodine stain?

A

-Potassium iodide will stain cellulose yellow
-and starch granules blue/black

29
Q

what is eosin stain?

A

stains basic alkaline structures ( such as the cytoplasm) red/pink.

30
Q

What is an eyepiece graticule? What is a stage micrometer?

A
  • Eyepiece graticule fitted into a microscope eyepiece, with 100 divisions and no scale = eyepiece units. It represents diff
    lengths at diff mags and so has to be calibrated for each objective lens.
  • a microscopic ruler is etched onto a slide = stage micrometer/stage graticule. each tiny unit is 10 micrometres, and the whole ruler is 1mm.
  • you line up the eyepiece graticule and stage micrometer as best as you can, see what equals what and then calculate what one eyepiece unit is worth
    in micrometres.
  • measure how many eyepiece units the specimen is in width/length, and x by the micrometre amount.
31
Q

what is acetic orcein stain?

A
  • binds to DNA + stains chromosomes dark red
32
Q

What is a logarithmic scale?

A
  • A scale of measurement in which an increase of one unit represents a tenfold increase in the quantity measured. used to compare relative sizes of biological structures since it enables plotting of very large sizes on graph paper
33
Q

What features do plant cells have that animal cells don’t?

A

cell wall
chloroplasts
large/permanent vacuole

plasmodesmata

34
Q

What features do animal cells have that plant cells don’t?

A

cilia
flagella
centriole

35
Q

What features do all eukaryotic cells have?

A
  • Nucleus, nuclear envelope with DNA
  • Nucleolus with RNA
  • Plasma membrane
  • Cytoplasm in which organelles are suspended
  • A cytoskeleton = network of protein filaments
  • Membrane bound organelles (mitcochondria, golgi)
  • ribosomes
  • small vesicles
36
Q

What are the steps involved in making and secreting a protein?

A

Gene that has the coding instructions for a protein is transcribed into mRNA in the nucleus
mRNA transported out of nucleus through pores in the nuclear envelope
mRNA attaches to a ribosome on the RER
at the ribosome the instructions are translated (tRNA brings specific, complementary amino acids) and peptide bonds form between adjacent amino acids, protein molecules are assembled
protein molecules pass into cisternae + along hollow sacs
molecules “pinched off” in transport vesicles and pass via microtubules + motor proteins to the Golgi apparatus
vesicles fuse with the Golgi, and it processes, modifies/folds, and packages proteins in secretory vesicles ready for release
they move towards plasma membrane, where they fuse with it.
plasma membrane opens to secrete the protein outside of the cell ( exocytosis)

37
Q

What are the similarities between eukaroytic and prokaryotic cells?

A
  • Both have ribosomes
  • Both have DNA
  • Both have a cytoplasm and a plasma membrane
38
Q

What are the guidelines for a low power plan?

A
  • Draw all identified tissues and completely enclose each tissue by lines
  • Don’t draw individual cells
  • Accuracy is important – the specimen will not necessarily look like a textbook drawing.
39
Q

what are the guidelines for a high power drawing?

A

Draw only a few representative adjacent cells (assessment questions will usually give specific instructions about what exactly is required.)

If all the cells are similar, then three cells is often sufficient. In such a case, detail of only one cell may be needed, with outlines only of adjacent cells just to show their relative positions.
* Don’t shade in nuclei – just draw the outline.

40
Q

what are the features of an SEM?

A
  • electrons reflect off SURFACE
  • x15 - x200,000 mag
  • resolution between 0.2nm and 10nm usually. Lower than TEM
  • 3D image black and white ( colour can be added)
  • specimen in vacuum with fine coat of metal
  • large, training needed, expensive
41
Q

What are the differences between eukaryotic and prokaryotic cells?

A

Ribosomes small (70s)
Ribosomes large (80s)
Small cell
Larger cells
Always unicellular
Often multicellular
No true nucleus
True nucleus with nuclear envelope
No membrane bound organelles
Has membrane bound organelles
Cell division by binary fission (no linear chromosomes and no spindle fibre)
Cell division by mitosis/meiosis
DNA is in circular plasmids + chromosomal DNA, without proteins
DNA = linear + associated with proteins
No/very simple cytoskeleton
Always has cytoskeleton
Cell wall containing peptidoglycan
Cell wall (if present) of cellulose or chitin
Reproduction = asexual
Reproduction = sexual/asexual

42
Q

What are stains? What are the types of staining in microscopy? Why are they used?

A
  • coloured chemicals that bind to molecules on the specimen
  • create higher contrast -
  • a clearer image can be obtained since they make more structures visible
  • specific staining: some stains bind to specific structures (use of 1 dye) - named organelle/cell component visible
  • differential staining: uses more than one chemical stain to differentiate between different microorganisms, cell types and cellular components
43
Q

What are features of the TEM?

A
  • electrons go THROUGH specimen.
  • around x500,000 mag, can even be between 2 million and 50 million
  • 0.2nm resolution ( in some exam Q it says 1nm) HIGHER THAN SEM
  • 2D black and white image
  • large, needs training, expensive, specimen has to be dead.
44
Q

What are features of the laser scanning microscope?

A
  • laser scans across object + image is built pixel
    by pixel on a screen
  • x2000 magnification
  • high resolution but not as high as TEM
  • sharp 3D images - colour via computer
  • can be used to see live specimens
  • depth selectivity- observe whole specimens or cells
45
Q

What 2 types of mounts can be done?

A
  • usually done for optical microscope
  • wet mount: adding a drop of water to the specimen before placiing coverslip- esp used for mobile organisms.Prevents distortion and flattens the sample.
    -dry mount: no water, placing coverslip straight away - used for hairs, pollen etc.
46
Q

How do you calculate magnification?

A

image size / actual size

47
Q

How are slides prepared in a lab, ready to be seen under an electron microscope? (6)

A
  • tissue fixation + processing in formaldehyde
  • dehydration of specimens to remove water
  • embedding in wax to avoid distortion
  • section-cutting using special instrument to make very small, THIN slices (to maximise light that can penetrate)
  • staining (add stain at the edge of the slide)
  • add coverslip - try to avoid air bubbles.
48
Q

What are some key features of a bacterial cell?

A
  • capsule - for protection
  • mesosome also aids the cell in cellular respiration due to increased surface area
  • cell wall made of peptidoglycan
  • nuclear material = chromosomal DNA
  • pilli allows bacteria to adhere to host cell and allows passage of plasmid DNA
  • flagellum for movement
49
Q

What are some features of the light microscope? ( what it uses, magnification, resolution, type of image)

A
  • Uses visible light
  • x1500
  • 200nm resolution
  • produce 2D colour images of whole cells and tissues
  • cheap, easy to use, portable, specimen can be living
    magnification quite low, same with resolution, can’t see small organelles such as ribosomes.
50
Q
A

OCR Biology A Level Module 2 Foundations in Biology (6 decks)

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