cells Flashcards
1
Q
what makes a cell eukaryotic?
A
it has DNA in a nucleus and has membrane bound organelles
2
Q
examples of eukaryotes:
A
plants, algae, protozoan, fungi
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
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;
5
Q
how are ribosomes synthesised?
A
ribosomal proteins and ribosomal RNA are synthesised within nucleus but assembled outside of the nucleus
6
Q
how does chromatin form chromosomes?
A
during cell division, chromatin super condenses and forms thread like structures called chromosomes
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;
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
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;
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
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;
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;
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;
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
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;
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
cellulose cell wall (in plants and algae):
- 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
bacterial cell (prokaryotic cell):
- 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
prokaryotic cells:
- circular DNA, not associated with histones;
- contains no membrane blund organelles;
- smaller ribosomes 70s;
- mesosomes for ATP synthesis;
- murein or peptidoglycsn cell wall;
28
eukaryotic cells:
- 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
viruses:
- 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
fungi cell walls are made out of
chitin
31
light microscopes:
- 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
how to use eyepiece graticule:
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
eyepiece graticule and state micrometer:
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
transmission electron microscope:
- 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
scanning electron microscope:
- 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
magnification equation:
Image size / actual size
37
cell fractionation and differential centrifugation:
- 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
ice cold, isotonic, pH buffered solution:
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
