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key definitions > cells > Flashcards

cells Flashcards

1
Q

what makes a cell eukaryotic?

A

it has DNA in a nucleus and has membrane bound organelles

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2
Q

examples of eukaryotes:

A

plants, algae, protozoan, fungi

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3
Q

epithelial cells:

A

adapted for role in absorption and secretion within digestive system

cell membrane of epithelial cell is folded into structures called microvilli which increases surface area for absorption

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4
Q

nucleus:

A
  • largest organelle in the cell;
    contains DNA which codes for protein synthesis;
  • nuclear membrane (double membrane, two phospholipid bilayers);
  • nuclear pores which allow the passage of molecules (mRNA) in and out of nucleus;
  • nucleolus - where ribosomal RNA is made and ribosomes;
  • ribosomal subunits (proteins) synthesised within nucleus;
  • contains chromatin, made from DNA coiled around histone proteins;
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5
Q

how are ribosomes synthesised?

A

ribosomal proteins and ribosomal RNA are synthesised within nucleus but assembled outside of the nucleus

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6
Q

how does chromatin form chromosomes?

A

during cell division, chromatin super condenses and forms thread like structures called chromosomes

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7
Q

mitochondrion:

A
  • site of ATP production by aerobic respiration;
  • hydrolysis of ATP releases the energy for cellular/metabolic reaction or provides phosphate for phosphorylation of molecules to make substances more reactive or lower Ea;
  • double membrane - inner membrane highly folded to form cristae to increase SA for attachment of ATP synthase enzymes;
  • within inner membrane is matrix which contains proteins, lipids, mitochondrial DNA and ribosomes;
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8
Q

cells that require a lot of ATP and have lots of mitochondria:

A

muscle cells for muscle contraction
epithelial cells for active transport of ions

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9
Q

rough endoplasmic reticulum:

A
  • made from highly folded membranes with 80s ribosomes embedded;
  • synthesises and transports proteins hroughout the cell;
  • joined to nucleus - easier for mRNA to get there to make proteins;
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10
Q

cells which make a lot of proteins have a lot of RER:

A

secreting extracellular enzymes - enzyme secreting gland cells;

antibodies producing plasma cells

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11
Q

smooth endoplasmic reticulum:

A
  • SER recombines glycerol and fatty acids to make triglycerides;
  • SER packages triglycerides into vesicles and transports them to the Golgi apparatus;
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12
Q

ribosomes:

A
  • site of protein synthesis from amino acids;
  • eukaryotic cell contains 80s ribosomes;
  • two subunits of a ribosome are made of a combination of long strands of rRNA, dotted with ribosomal proteins;
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13
Q

golgi apparatus:

A
  • sorts, modifies and packages proteins and triglycerides into vesicles;
  • Golgi vesicles may be used to form lysosomes;
  • Golgi apparatus is composed of flattened sacs (cisternae) made of membranes.The sacs are fluid filled and pinch off smaller sacs (called vesicles) at their ends;
  • usually only one Golgi body in each cell, is well-developed in secretory cells; as large molecules must be packaged in vesicles to be transported out of the cell;
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14
Q

cells which have an extensive large golgi, packages lots of molecules for export, mostly large amount of proteins:

A

enzyme secreting gland cells,
antibodies producing plasma cells

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15
Q

lysosomes:

A
  • used to hydrolyse damaged and worn-out organelles;
  • bound by a single membrane and have no internal structure;
  • contain many hydrolytic enzymes which are lysozymes in an acid solution (low pH), which must be kept separate from rest of cell contents to prevent them from digesting organelles;
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16
Q

cells that contain many lysosomes:

A

phagocytes (type of white blood cell)
breakdown invading pathogens

17
Q

cell surface membrane:

A
  • controls the passage of molecules in and out of the cell;
  • made of phosopholipids, transport proteins, carbohydrates, glycoprotein (globular protein w/ a polysaccharide chain of sugars attached, made in Golgi body) has a receptor complementary to molecule that binds;
  • phospholipid bilayer;
18
Q

microvilli:

A
  • finger like projections of the cell membrane,
  • greatly increase the surface area of the cell membrane,
  • this speeds up absorptions of digested food;
  • found on epithelial cells in the small intestine
  • so there may be more carrier proteins for active transport
    eg columnar epithelium lining the small
    intestine
19
Q

centrioles:

A
  • function in mitosis to form a network of spindle fibres across the cell onto which the chromosomes attach;
  • fibres pull the chromosomes / chromatids apart during mitosis;
  • these organelles are not found in plant cells;
  • one centriole = two cylinders at right angles made from microtubules
20
Q

plant cell structure:

A

wax cuticle;
upper epidermis;
palisade mesophyll;
spongy meosphyll:
air spaces;
lower epidermis;
stoma;
guard cells with chloroplasts;
waxy cuticle;

21
Q

animal cell differences to plant cells:

A

no cell wall
no chloroplasts
no large central vacuole
carbohydrates stored as glycogen
has centrioles

22
Q

plant cell differences to animal cell:

A

cellulose cell wall
chloroplasts present
large central vacuole
carbohydrates stored as starch
has no centrioles

23
Q

chloroplasts (found in plants and algae)
function:

A
  • absorbs light energy and converts it to chemical energy;
  • chemical energy used to make carbohydrates from CO2 and H2O;
  • these then used for respiration to make other organic molecules in cell, which enables plant to grow;
24
Q

chloroplasts structure:

A
  • double membrane
  • granum = stack of thylakoid membranes;
  • thylakoid membrane = contains chlorophyll for photosynthesis & ATP synthase enzymes to produce ATP;
  • stroma = fluid filled part, some of the photosynthetic reactions occur here, colourless;
  • starch grains = energy storage molecules in plants;
  • DNA and ribosomes = chloroplasts have their own DNA and 70S ribosomes to make enzymes needed for photosynthesis;
25
Q

cellulose cell wall (in plants and algae):

A
  • very strong (many WEAK hydrogen bonds between cellulose fibrils), limits the volume of water that can move into the cell and stops osmotic lysis;
  • wall is permeable to most molecules, unlike the membrane (micro fibrils arranged in a matrix);
  • cell walls of adjacent cells separated by middle lamella (thin layer), acts to stick the walls together with pectin;
  • plasmodesmata = gaps in the cell walls that connect cell cytoplasm’s together, to allow the easy movement of water-soluble molecules;
26
Q

bacterial cell (prokaryotic cell):

A
  • prokaryotes do not have nuclei or other membrane bound organelles.
  • circular DNA, found free the cytoplasm, and it is not associated with histones.
  • cell membrane, cell wall, plasmid, 70s ribosomes, flagellum, capsule
27
Q

prokaryotic cells:

A
  • circular DNA, not associated with histones;
  • contains no membrane blund organelles;
  • smaller ribosomes 70s;
  • mesosomes for ATP synthesis;
  • murein or peptidoglycsn cell wall;
28
Q

eukaryotic cells:

A
  • linear DNA;
  • contains membrane bound organelles (mitochondria, RER, SER, Golgi body, lysosomes);
  • larger ribosomes 80s
  • no capsule
  • plant cells have cell wall made of cellulose
29
Q

viruses:

A
  • not cells, not alive
  • small
  • require a living cell to replicate inside
  • contains DNA or RNA, which can be single or double standed
  • protein coat = capsid
  • attachment proteins enable it to bind to host cells
  • enzymes used to replicate genetic information and insert into host cell DNA
  • no organelles
30
Q

fungi cell walls are made out of

A

chitin

31
Q

light microscopes:

A
  • specimens illuminated with light
  • focussed using glass lens;
  • specimens can be dead or living;
  • organelles need to be stained with colours dye to make them visible;
  • dye binds to a specific protein due to charge/bond;
  • magnification is limited;
  • low resolution, longer wavelength of light
32
Q

how to use eyepiece graticule:

A

measure each stomata using an eyepiece graticule
calibrate the eyepiece graticule against a state micrometer
take at least 5 measurements and calculate a mean = more acc, more rep

33
Q

eyepiece graticule and state micrometer:

A

eyepiece graticule fits into eyepiece lens, transparent rule with numbers but no units

stage micrometer is a microscope slide, acc scale, placed on stage, used to work out value of each division on eyepiece graticule when using a certain magnification

allows you to take stage micrometerr away and replace it with slides with a tissue specimen to measure size of cells

34
Q

transmission electron microscope:

A
  • produces 2D images;
  • higher resolution, electrons have smaller wavelength;
  • focussed using electromagnets;
  • electrons pass through specimen;
    allows you to view internal structures/organelles;
  • specimens fixed in resin and sliced extremely thin = must be dead;
  • stained using heavy metals = complex, lengthy process and can create artefacts
  • electrons fired through specimen,
  • less dense (cytoplasm) absorb less electrons so appear lighter
  • denser areas (nucleolus) absorb more electrons and so appear darker,
  • specimens must be in a vaccum so specimen must be dead
35
Q

scanning electron microscope:

A
  • produces 3D images;
  • higher resolution, electrons have smaller wavelength;
  • focussed using electromagnets;
  • specimens are not sliced, and the electrons bounce off the surface of the specimen;
36
Q

magnification equation:

A

Image size / actual size

37
Q

cell fractionation and differential centrifugation:

A
  • tissue is homogenised in blender, in ice cold, isotonic, pH buffered solution to break open the cells releasing the organelles
  • mixture is then filtered to remove any large pieces of tissues/ cells (cellular debris)
  • differential centrifugation at high speeds, densest organalles go to bottom as a pellet
  • pellet is removed and supernatant is spun again at higher speeds for the next dense organelle
38
Q

ice cold, isotonic, pH buffered solution:

A

ice cold: reduce the action of enzymes that would digest organelles
isotonic: prevents osmosis of water in or out of organelles so organelles don’t burst or shrivel
pH buffered: to stop pH changes which could denature proteins

key definitions (9 decks)

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