cell structure Flashcards
1
Q
explain what is meant by the endosymbiotic theory
A
- large prokaryotic cells engulfed smaller photosynthetic bacteria + smaller ones that make ATP using oxygen —> evolved to mitochondria
- facts that support:
- both have own DNA like prokaryotes
- DNA arranged like prokaryotes (loop)
- divide on their own - bacteria
2
Q
what is the structure of eukaryotic cells?
A
- complex
- can be multi or unicellular
- larger
- membrane bound organelles
- large ribosomes - 80s
- DNA:
—> in a membrane bound nucleus
—> wrapped tightly around histone proteins to form chromatin
—> chromatin coiled into chromosomes
—> linear DNA molecules
3
Q
describe the structure of the nucleus
A
- double membrane
- nuclear envelope with nuclear pores
- nucleolus
- chromosomes - made from protein-bound linear DNA
4
Q
describe the function of the nucleus
A
- controls activities of cell by controlling transcription of DNA.
- site of DNA replication + transcription to produce mRNA
- instructions to make proteins
- contains the genetic material for each cell
- pores allow transfer of substance (RNA)
- nucleolus makes mRNA and where ribosomes subunits assemble
5
Q
describe the structure of the cell surface membrane
A
- phospholipid bilayer with molecules embedded
- surrounds animal cells and is inside cell walls of other cells
6
Q
describe the function of the cell surface membrane
A
- regulates movement of substances into and out of the cell
- has receptor molecules to respond to chemicals like hormones
7
Q
briefly explain the structure of RER and SER
A
- system/sheets of membranes enclosing a fluid filled space
- forms flattened sacs called cisternae
- RER covered in ribosomes on surface
8
Q
describe the functions of rough endoplasmic reticulum and smooth endoplasmic reticulum
A
RER
—> protein synthesis on ribosomes
—> proteins into lumen of RER + folds into tertiary structure
—> polypeptide packed into vesicles to travel to Golgi apparatus
SER
—> synthesis and stores lipids and carbohydrates
9
Q
describe the structure of the Golgi apparatus
A
- system of membranes enclosing a fluid filled space
- folded to form cisternae
10
Q
explain the function of the Golgi apparatus
A
- processes + modifies proteins/polypeptide chain
-packs into vesicles - makes vesicles + lysosomes
11
Q
describe the structure of the Golgi vesicles
A
- small, fluid filled, membrane bound sac
- found at edges of apparatus
12
Q
explain the function of Golgi vesicles
A
- transports liquids and proteins made by the Golgi apparatus
- to the cell surface membrane where it fuses with membrane
- releases contents out of cell by exocytosis
13
Q
describe the structure of lysosomes
A
- bags of powerful digestive lysosomal enzymes
- membrane bound sac with no clear internal structure which is acid filled
14
Q
explain the function of lysosomes
A
- digest large molecules into smaller molecules
- key role in phagocytosis
- digest old organelles in the cell
- digest invading cells
- transfer enzymes out of the cell - exocytosis
15
Q
describe the structure of ribosomes
A
- made up of 2 subunits
- made of proteins and RNA
- either floats free in cytoplasm or attached to surface of rough ER
16
Q
explain the function of ribosomes
A
- site of protein synthesis - translation
- proteins made by ribosomes in cytoplasm remain in cytoplasm
-ones made on RER secreted from cell by exocytosis
17
Q
describe the structure of mitochondria
A
- double membrane with intermembrane space
- inner membrane folded to form crista
- matrix inside the inner membrane with enzymes
18
Q
explain the function of mitochondria
A
- site of aerobic respiration to produce ATP
- cristae provides larger surface area for oxidative phosphorylation
19
Q
describe the structure of the chloroplast
A
- small, flat organelle in photosynthesising cells
- double membrane
- thylakoids are flat discs with pigments in and enzymes
- grana - stacked thylakoids
- lamellae - flattened membranes which connect grana to transport chemicals
- strong - fluid with starch granules in
20
Q
explain the function of chloroplast
A
- site of photosynthesis
- light dependent on thylakoids and lamellae
- light independent in storms which contains enzymes for it
- grana absorb light efficiently
21
Q
describe the structure of the cell wall
A
- plants and algae —> cellulose
- fungi —> chitin
- bacteria —> peptidoglycan, murein, glycoprotein
22
Q
explain the function of the cell wall
A
- keeps shape of cell + prevents change of shape
- supports and strengthens
- osmosis —> cell wall mechanically strong enough to resist hydrostatic pressure
- permeable to water molecules
23
Q
describe the structure of the vacuole
A
- permanent in plant cells
- membrane sac, larger than vesicles
- fluid filled - tonoplast
- contains cell sap —> weak solution of salts + sugars
24
Q
explain the function of the vacuole
A
- maintains pressure inside cell
- keeps cell rigid
- stops plants wilting
- isolation of unwanted chemicals
- water in —> hydrostatic pressure outwards, vacuole becomes turgid
25
explain the adaptations of cel specialisation
- cells adapt for their specific function to make function efficient
- every cell has every gene to be able to become any cell, but only some gene switched on and rest switched off
- examples:
- muscles cells —> lots of mitochondria, release ATP - help contraction
- sperm cells —> lots of mitochondria and tail —> help them to swim to egg
- white blood cells —> lots of lysosomes - phagocytosis + digestion
26
explain what the function of cells
- smallest unit that can live on its own and that makes up all living organisms and the tissues of body
27
explain what is the function of tissues?
- epithelial tissue lines surfaces of organs + protective and secretory function, xylem tissue transports water and mineral ions + mechanical support
28
explain what the function of organs are
- combination of tissues, stomach has muscle to chum, epithelium to protect and secrete, connective tissue to hold tissues together, lead has palisade mesophyll for photo
- spongy mesophyll for gas diffusion, upper epidermis to protect and let light through
- lower epidermis for protection and allow diffusion, xylem for transport of water and minerals
29
what is the function of the organ system
- organs work together as single unit, digestive, respiratory, circulatory
30
explain the structure of prokaryotic cells
- less complex than eukaryotic
- single celled organisms
- smaller
- no membrane bound organelles
- more organelles
- cell wall made of murein/peptidoglycan
- smaller ribosomes - 70s
- DNA -
free in cytoplasm
circular loop, coiled strand not linear
plasmids - single loops which contain gene for antibiotic resistance
31
- less complex than eukaryotic
- single celled organisms
- smaller
- no membrane bound organelles
- more organelles
- cell wall made of murein/peptidoglycan
- smaller ribosomes - 70s
- DNA -
free in cytoplasm
circular loop, coiled strand not linear
plasmids - single loops which contain gene for antibiotic resistance
32
what is the main function of the nucleoid in a prokaryotic cell
- not membrane bound region within bacteria, contains most bacterial DNA, some RNA and proteins, seen under TEM
33
describe the genophore in a prokaryotic cell
- long, double strand of DNA, usually circle, within nucleoid
34
describe what ribosomes are in terms of a prokaryotic cell
- 70s bacterial inclusion, site of protein synthesis were mRNA read + assemble amino acids to complete protein chain based on RNA sequence
35
describe the function of the cytoplasm in a prokaryotic cell
- gel-like matrix of mainly water, bounded on outside by envelope, contains bacterial inclusions
36
what are the storage granules in a prokaryotic cell
- stores nutrients/resevers in cytoplasmic inclusions in form of glycogen, lipids and sometimes sulfur/nitrogen
37
what’s the role of the cell envelope in a prokaryotic cell
- includes the cell membrane and cell wall
38
what’s the role of the capsule in a prokaryotic cell
- layer of polysaccharide/protein that protects the bacterial cell from attack of WBCs/phagocytosis, made of secreted slime
39
what’s the role of the pili in a prokaryotic cell
- hollow/hair-like structures made of proteins, - allow bacteria attach to other cells, specialised pilus allow transfer of plasmid DNA between cells
40
what’s the role of the flagella in a prokaryotic cell
- long appendages which rotate by a motor in cell envelope, purpose is for motility
41
what is the role of the endospore in terms of a prokaryotic cell
- simplified form of bacteria, bundle of genetic information in tough internal structure to withstand hostile environment
42
describe the structure of a virus
- acellular - not cells
- nucleic acids surrounded by proteins
- not alive, smaller than bacteria
- no cell surface membrane, no cytoplasm, no ribosomes
- capsid —> protein coat
- attachment proteins sticking out to attach to host cells
- genetic information in core
- can look different to each other
43
define the term ‘magnification.’
- how much bigger the image is than the specimen
44
define the term, ‘resolution’
- the ability to distinguish between two points on an image I.e - how detailed the image is
- resolution of optical microscopy is low as wavelength of light too long
45
Light/optical microscope. How does this work? What are the advantages and disadvantages?
- uses light to form an image
- advantage: living specimen, colour image, cheap, easy to use
- disadvantage: 2d image, low resolution, low magnification, thin specimen, can’t see ribosomes and ER
46
SEM. How does it work? What are the advantages/disadvantages?
- scans a beam of electrons over surface, knocks electrons off specimen, collect in cathode ray tube
- advantage: colour image, surface of specimen, topography, 3D, thick specimen
- disadvantage: non-living, lower resolution than TEM.
47
TEM. How does it work? What are the advantages/disadvantages?
- focuses a beam of electrons on the specimen, denser parts absorb more electrons so are darker.
- advantages: higher magnification, highest resolution, internal organelles
- disadvantages: non-living. Black and white image, 2D, thin specimen
48
What is the maximum magnification and resolution of optical/light microscopy.
- max mag: x1500.
- max resolution: 0.2 micrometers
49
What is the maximum magnification and resolution of electron microscope?
- max mag: x1,500,000
- max resolution: 0.0002 micrometers
50
Describe the homogenisation stage of cell fractionation
- break up cells by vibrating or grinding in blender
- breaks plasma membrane, releasing organelles into solution.
51
Describe the filtration stage of cell fractionation
- pass the solution through a gauze.
- removes large cell debris, organelles are small and pass through.
52
Describe the ultracentrifugation stage in cell fractionation
- solution into test tube then into centrifuge and spun at low speed.
- heaviest organelles go bottom of tube and form a pellet.
- lighter organelles remain in solution, the supernatant which drained
- respun at higher speed, with next heaviest organelles form pellet —> repeat to separate rest organelles.
- separate in order of mass —> nucleus, chloroplasts, mitochondria, lysosomes, ER, ribosomes
