CELL BIOLOGY CGP Flashcards
what parts do most animal cells have-
what extra parts do plants have
what extra part do plant and algal cells also have-why
nucleus
mitrochondria
ribosomes
cytoplasm
cell membrane
cell wall
-chloroplasts
-permanent vacuole
-cellulose cell wall to strengthen cell + chloroplasts.
what do all eukaryotic cells have- x3what cells are these
compare prokaryotic cell to eukaryotic cell-
What parts are in eukaryotic cell x5
cell membrane, cytoplasm. genetic material enclosed in nucleus- Plant and Animal
pro are smaller
pro dont have mitrochondria
pro circular dna strand floats freely in cytoplasm- no nuclues
pro have plasmids- small rings of DNA
both have cytoplasm,
both have cell membrane,
cell memrane, cytoplasm. nucleus, ribosomes, mitrochondria
describe
nucleus
mitrochondria
cytoplasm
cell membrane
ribosomes
nucleus-has genetic material that controls cell
mitrochondria- site of aerobic respiration, provide energy for cell
cytoplasm-gel like substance- most chemical reactions happen- has enzymes to control the reactions
cell membrane-holds cell tgether, controls what goes IN + OUT
ribosomes-site of protien synthesis
describe
cell wall
permanent vacuole
chloroplasts
cell wall- supports, strengthens cell
permanent vacuole- contains cell sap- sugar + salt solution to keep cell turgid
chloroplasts-site of photosynthesis- chlorophyll absorb light.
do bacteria cells have mitrochondria
do bacteria cells have ribosomes
what are the parts of a bacteria cell x6
no
yes
cell wall
cell membrane
cytoplasm
circular strand
plasmid
ribosomes
how do light microscopes work
how do electron ones work
use light and lenses to form an image of a specimen and magnify it
-use electrons to form an image
measurement names in descending order and symbols
what would you times it by to get number in metre
metre m
centimetre cm 10^-2
millimetre mm 10^-3
micrometre μm 10^-6
nanometre nm 10^-9
pros of electron microscopes - x2
can we see mitrochondria and chloroplasts through electron microscopes
can we see ribosomes and plasmids through electron microscopes
higher magnification and resolving
power than a light microscope.
allow biologists to see and understand more subcellular structures
yes can see their internal structure
yes- tinier than mitrochondria and plasmids
what is resolution
what is magnification
units for magnification
unit for image size is
unit for real size is
how do you convert between these units
ability to distinguish btwn 2 points - higher resolution = sharper image
-how big an object looks
no unit
mm
µm
from µm to mm, divide by 1000,
mm to µm, X by 1000
ribosomes are very small. Can they be seen with an electron microscope, a light microscope, or both
-whats smaller, mitochondria or ribosomes
electron
ribosomes
difference bwn plant and animal cell
plants have a regular shape
(animal cells can change their shape easily)
plant cells packed with chloroplasts, vacuole, cell wall
how has microscopy techniques developed over time
as tech and knowledge has improved
how have electron microscopes increased understanding of subcellular structures
3 points
uses electrons to form an image with much higher magnification AND resolution-
see smaller things in more detail-internal structure of mitochondria + chloroplasts
-see tinier things -ribosomes + plasmids
how do you prepare a slide
6 steps-
-add drop of water to middle of clean slide
-cut up onion, separate into layers. Use tweezers, pull of epidermal tissue from bottom of a layer
-use tweezers- put epidermal tissue into water on slide
-add drop of iodine solution- a stain
-put cover slip on top
-stand slip up, next to water droplet, tilt + lower it so it covers specimen.
important thing to remember when preparing slide
what do stains do
what does iodine stain do
try not get air bubbles when putting cover slip on- obstructs view of specimen.
-hold slide/ slip by edges, dont get fingerprints on it - obscure image
highlight objects in a cell by adding colour- make subcellular structures easier to see.
stains the starch in onion cells
what are parts of microscope slide- 6 parts
eye piece
high/low power objective lenses
stage
coarse adjustment knob
fine adjustment knob
light/lamp
what do some light microscopes have instead of a light- what does this do
a mirror- the mirror reflects light through microscope slide
how many objective lenses do most microscopes have- give example of these
what does the eyepiece have
3
4x 10x 40x
the eyepiece lens- 10x magnification
how to use light microscope to look at slide- 6 steps
What would you do if u need greater magnification
-clip prepared slide onto stage
-select lowest powered objective lens
-position lens so almost touches slide
-to do this- use coarse adjustment knob to move stage just below objective lenses
-look down eyepiece. Use coarse adjustment know to move stage downwards till image in rough focus
-adjust focus w/ fine adjustment knob till you get clear image
—swap to higher powered objective lens+ refocus
what is important to remember when adjusting level of objective lens or the power of objective lens
look from the side so u see how close the slide + lens are so u dont damage slide
things to remember when drawing observations x7
p
1/2
c
c
p
t
ll
- use sharp pencil
-should take up minimum 1/2 space available
-draw with clear, unbroken lines
-dont colour/shade
-subcellular structures drawn in proportion
-add title of what you were observing and magnification used
-label important features eg nucleus w/ un-crossed lines
how can you find size of cell w/out using magnification equation
Try find a row with whole cells along diameter
Count how many cells eg 4
get a ruler and use microscope to measure diameter of field of view eg 2 mm
turn mm to um 2mm= 2000 um
2000um divide by 4 cells = 500um per cell
parts of baceria cell- x6
cell membrane
cell wall
circular strand of dna
plasmids
cytoplasm
ribosomes
what is cell differentiation
What happens as an organism develops
when do most animal and when do most plant cells specialise
process by which cell changes to become specialised for its job
-cells differentiate- to form different types of cells
-animal cells- at early stage
-plant cells- retain ability to differentiate throughout life
why is differentiation important
-in mature animals- cell division is restricted…….
what happens to a cell as it differentiates-
-allows cell to carry out specific function
-restricted to repairing and replacing cells
- develops different sub-cellular structures to enable it to carry out certain function
***when using an optical/light microscope on an plant cell, what structures can be seen
cytoplasm
nucleus
cell wall
vacuole
chloroplasts
cell membrane
when is a cell said to be specialised
what are stem cells
when it has differentiated and has different subcellular structures to carry out it specific function
UNdifferentiated cells
3 specialised animal cells
3 specialised plant cells
sperm, nerve, muscle cells
root hair, xylem, phloem cell
SPERM CELL
function-
how are they specialised x4
to join with the egg cell- so genetic information of male and female can combine during fertilisation
1-nucleus has 1/2 the genetic info of a normal adult cell
2-long tail, streamlined head-help swim to egg
3-packed with mitochondria, provide energy to swim
4-enzymes (in head) digest through egg cell membrane
NERVE CELL
function-
how are they specialised x4
-carry electrical impulses around body.
1-long axon-carries electrical impulses from+to part of body
2-myelin sheath insulates axon- speed up transmission of nerve impulses
3-end of axon has synapses-allow impulse to pass to another nerve cell
4-cell body has dendrites-increase s.a so other nerve cells can more easily connect
MUSCLE CELLS
function-
how are they specialised x2
contract for movement
1- contain protein fibres which can change length(when cell contracts, fibres shorten= length of cell decreases)
2- contain lots of mitochondria-provide energy for contraction
3–long so they have space to contract-
ROOT HAIR CELL
function
where are they-
how are they specialised x3
-absorb water + minerals
- on surface of plant roots
1-large s.a -have long projection-the root hairs stick out into soil
(2-X contain chloroplasts- underground)
2- thin walls
3-lots of mitrochondria
XYLEM CELL
function
where are they found
how are they specialisedx3
-form long tubes- carry water + minerals from roots to leaves
-in plant stem
1-thick walls contain lignin-provides support for plant
2-end walls btwn cell broken down-form long tube for water,minerals to flow
3-X internal structures(nucleus, cytoplasm, vacuole,chloroplasts-) easier for water,minerals to flow
PHLOEM CELL
function
where is it found
how are they specialised x3
-form tubes -carry dissolved sugars up+down plant
1-phloem vessel cell has X nucleus, limited cytoplasm
2-end walls of vessel cells have pores-sieve plates
BOTH ALLOW DISSOLVED SUGARS TO MOVE THROUGH CELL
3-companion cell connected by pores- have mitochondria to provide energy to phloem vessel cell
define stem cell
where are they found-
undifferentiated capable of giving rise to many more cells of same type, and from which certain other cells can arise from differentiation
-early human embryos
-adult bone marrow
-Meristem tissue in plants
what can stem cells in adult bone marrow do
what can stem cells from human embryos be used for
what can Meristem tissue in plants do
differentiate to form many types of cells inc. blood cells
-cloned and made to differentiate into most different types of human cells
-differentiate into any type of plant cell, throughout life of plant
what are stem cells from embryos and bone marrow used in- how
-medicine and research
-stem cells grown in lab, to produce clones and made to differentiate (depending on the instructions given) into specialised cells which are used
eg of how does medicine currently use adult stem cells
stem cells from bonemarrow of healthy person can replace faulty blood cells in person who receives them
how is an adult made- 4 steps
-sperm cell fertilises egg cell
-fertilised egg undergoes mitosis- forms ball of cells-embryo
-cell in embryo continue to undergo mitosis and differentiate to specialised cells
-these cell eventually form adult
how would someone with bone marrow cancer be treated using stem cells - 3 points
-existing bone marrow destroyed w/ radiation
-patient recieves transplant of bone marrow from healthy donor
-stem cells in bone marrow divide and form new bone marrow + differentiate to form blood cells
problems with bone marrow stem cell transplants x2
donor must be compatible w/ patient or the stem cells may be rejected or wbcells produced by donated bone marrow could attack patient’s body
-risk of viruses passed from donor to patient
how could stem cells help diabetes/ paralysis-3 steps
-embryonic stem cells could replace faults cells
-could make insulin producing cells for ppl w/ diabetes
-or nerve cells for paralysed ppl
what happens in therapeutic cloning- 3 steps
a risk
embryo produced w/ same genes as patient
-stem cells produced from embryo can be transplanted w/out being rejected by patients immune system
-stem cells can differentiate inside patient to replace faulty cells
* stem cell grown in lab could become contaminated w/ virus - pass to patient- make sicker
argument for x2 and against x3 stem cell research
F-curing suffering ppl who already exist> important than rights of embryos
F- embryos used usually unwanted from fertility clinics- would just be destroyed
A- human embryos should’t be used for research- a potential human life
A-scientists should find and develop other sources of stem cells to help ppl w/out using embryos
A-stem cell research banned in some countries. In Uk- must follow strict guidelines
where is meristem tissue found
-what can mersitem tissue stem cells be used for
- pros of using mersistem tissue for this x2
roots and buds of plants (parts where growth happens)
-quickly + cheaply produce clones of whole plants
PROS
-clone rare plant to stop extinction
-clone large numbers of crop plants with special features eg disease resistance for farmers
what is therapeutic cloning-
embryo produced w/ same genes as patient- stem cells from embryo not rejected by patients body so can be used for medical treatment
what does nucleus contain - 3 points
what do genes do
chromosomes - coiled up lengths of dna molecules.
Chromosomes contain many genes
and are found in pairs
-genes control development of characteristics
explain what is meant by chromosomes being found in pairs
-how many pairs of chromosomes do human cells have
body cells have 2 copies of each chromosomes, 1 from mum, other from dad
-23 pairs
what is the cell cycle-
what are the two parts of the cell cycle
series of stages through which cells (of multicellular organisms) divide to produce new cells
1-growth and DNA replication
2-Mitosis-cell divides
cell division by mitosis is important for
-the end of the cell cycle results in….
growth and development of multicellular organisms and repair / replacement of damaged cells
-2 cells identical to og cell, w/ same no. of chromosomes
before a cell can divide it needs to….
grow and increase no. of sub-cellular structures such as ribosomes and mitrochondria
which human cells contain unpaired chromosomes
how many genes do most human chromosomes contain ( approx)
2 ways cells can divide by
gametes
hundreds
mitosis, meiosis
1st stage of cell cycle
4 points
-cell grows
-number of sub cellular structures increases
-DNA replicates
-2 copies of each chromosome formed- they form x shaped chromosomes (each arm of the chromosome is a copy of the other)
stage 2 of cell cycle- 3 points
mitosis-
1 set of chromosomes pulled
to each end of cell
nucleus divides
stage 3 of cell cycle-
cell membrane and cytoplasm divide to form 2 identical daughter cells
process of mitosis
46 pairs of chromosomes - paired duplicates line up and are pulled apart by cell fibres
1 set of each chromosome go to opposite ends of cell
23 pairs on each side
membranes form around the sets of chromosomes- they become the nuclei of new cells- nucleus has divided
how would you know if a cell is undergoing mitosis
SEE ANY OF THE STAGES OF MITOSIS
-could see chromosomes lined up at centre of cell
-could see arms of each chromosome at opposite ends of cell
-could see membranes forming around sets of chromosomes
-could see that nucleus has divided
what is binary fission
How often does it happen
simple cell division- the way bacteria mutliply
-as often as once evry 20 mins IF they have enough nutrients and suitable temp
process of binary fission- 4 steps
-circular DNA and Plasmids replicate
-cell grows, dna strands move to opposite ends of cell
-cytoplasm starts dividing,new cell walls start forming
-cytoplasm divides, 2 daughter cells produced. Each has 1 copy of circular DNA but VARIED no. of plasmid copies
a bacterial cell has a mean division time of 30 mins. How many cells will it have produced after 2.5 hours?
-2.5 hours x 60 = 150 minutes
-150 minutes divided by 30 = 5 divisions
-2⁵ = 32 cells
what are ideal conditions for binary fission
-what happens if conditions aren’t ideal
warm, lots of nutrients
-bacterial cells stop dividing, eventually begin to die
how to work out the number of bacteria cells produced in certain amount of time - you know mean division time
-make both times in same units eg minutes
-find out how many divisions will happen- total time/ mean division time
-do 2 to power of however many divisions will happen
how can stem cells be used to preserve rare plant species
copies of the plant can be made by taking stem cells from the meristem
and growing them into new, genetically identical plants
-where can bacteria be grown
-what does ‘culture medium’ contain- what is it
-what will happen to bacteria on agar plates
in nutrient broth solution/ colonies on agar gel plate
-carbs, minerals, protiens, vitamins, bacteria need to grow- nutrient broth solution/ agar jelly
-form visible colonies/ spread out to give even covering
-what temp should cultures be incubated at schools-why
-what are they incubated at in industrial conditions-why
25*C - harmful pathogens more likely to grow above this temperature
-alot higher so they grow faster
why are uncontaminated cultures required when investigating action of disinfectants/antibiotics-x2
using a culture of microorganisms contaminated by other microorganisms naturally in the environment
-will affect you results
-may cause growth of harmful pathogens
how to prepare uncontaminated bacterial culture using aseptic technique
-4 things inc. why
-sterilise petri dishes, nutrient broth/ agar (culture medium) to kill unwanted microorganisms
-sterilise inoculating loop- pass through bunsen burner flame
-lid of petri dish (lightly) taped on-stop lid falling + microorganisms eg in air entering
-agar plate placed upside down in incubator, stop condensation dripping onto bacteria and disrupting colonies
how is an agar plate made
- how can bacteria be transferred onto agar gel plate x2
hot agar jelly poured into petri dish and sets.
-use inoculating loop
-use sterile dropping pipette and a spreader to get even covering of bacteria
RP- the effect of antibiotics on bacterial growth-
8 steps
-clean bench w/disinfectant
-sterilise innoculating loop
-open sterile agar plate near bunsen flame
-use loop to evenly spread bacteria over plate
-put sterile filter paper discs soaked w/ different types/conc. of antibiotic on agar plate
-use a control-disk soaked in STERILE water
-leave some space btwn discs
-incubate at 25*c for 2 days
RP- antibiotics on bacteria growth
why is a control disk used-
-the area where no bacteria grew is called-
make sure difference btwn bacteria growth around control disk and an antibiotic disk is due to effect of antibiotic alone (eg not something wierd w/ the paper)
-zone of inhibition
why might there be no zone of inhibition formed around one of the antibiotic discs
the strain of bacteria used may be resistant to that antibiotic.
what is diffusion
what increases rate of diffusion-
spreading out of particles(of any substance in solution or particle of gas) resulting in net movement from an area of high concentration to an area of low concentration
- bigger concentration gradient
-higher temperature- particles have more kinetic energy, move faster
-s.a of membrane- larger s.a= more particles can pass through at once
examples of substances transported in and out of cells by diffusion x2
oxygen and carbon dioxide in gas exchange
waste product urea from cells into blood plasma for excretion in kidney
what do cell membranes do
-dissolved substances move in/out of cells by-
-what type of molecules can diffuse through membranes
-hold cell together AND let particles in and out
-diffusion
-small molecules- O2, glucose, amino acids, water, not big molecules like starch + protiens
a student adds drop of ink to a glass of cold water
-what will student observe, why
-what if ink was added to warm water-
- the ink will diffuse through the water, ink particles will move from where ther is a high concentration of them (ink droplet) to where there’s a low concentration of them (surrounding water)
-faster rate of diffusion of ink particles
define osmosis
diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
what is a partially permeable membrane
-why do water molecules pass both ways through the membranes
- if there are more water molecules on one side of the membrane what happens
membrane with super small holes, only tiny molecules like watr can pass, bigger molecules (like sucrose) cant
-bcse water molecules move randomly
-theres a net/overall flow of water to the more concentrated side
describe the concentration of cytoplasm
-what happens if animal cell placed in water
-what happens if animal cell placed in concentrated solution-
-what happens if plant cell placed in water
-what happens if plant cell placed in concentrated solution-
cytoplasm is a highly concentrated solution- low concentration of water.
-osmosis takes place, water will move in and cause cell to expand- maybe even burst
-water moves out of cell by osmosis, cell shrinks
-water moves in by osmosis, cell expands. cell wall prevents cell from bursting- cell becomes turgid
-water moves out by osmosis, cell shrinks-becomes flaccid
- are cells surrounded by high/low conc. of O2-why
-describe the whole process of diffusion of gases in/out cells -4 points
-cells are surrounded by high coc. of O2 bcse it’s transported in bloodstream
-O2 diffuses into cell
-Used in respiration to produce energy and carbon dioxide
-higher concentration of carbon dioxide in cell than outside
-moves out of cell by diffusion
things to remeber in RP-effect of sugar solution on plant tissue. x3
-why should u not cut potato less than 3cm
-why is DISTILLED water used
-why should u be careful when drying the cylinders
-use same potato
-use high resolution balance
-maybe put bung on test tube to prevent evaporation
-shorter than 3 cm may struggle to measure effect of osmosis
distilled water contains X dissolved substances- could affect rate of osmosis
be careful not to not press cylinders, u want to remove surface moisture- not force water out of cells
RP-effect of sugar solution on plant tissue
8 steps
-remove potato skin- skin can affect osmosis
-use cork borer- cut potatoes into cyclinder w/ same diameter
-cut to same length -3 cm
-measure mass using a balance and length of each cylinder
-put into tubes w/ different concentration sugar solutions and one w/ pure water (eg 10cm³ 0,25 molar, 0.5 molar, distilled water)
-leave for 24 h, take out, dry w/ paper towel
-remeasure length and mass
-calculate % change of mass and length of each cylinder
Graph of percentage change of mass/ length against concentration of sugar solution,
-what does it look like-why
-what does the point where the line crosses the x axis tell us
negative gradient-
in water, potato gains mass
in sugar solution potato loses mass-higher conc. sugar solution means more osmosis out of cells
-thats where there was no change in mass-conc. of sugar inside + outside cell is same- tells us sugar conc. inside potato cell
what is the dependant variable
what is the independant variable
what are control the variables x4
errors that could happen x2
-how can you reduce effect of errors
chip mass/ length
concentration of sugar solution
volume of solution, temp, time, type of sugar used
-not dried fully/water pushed out when drying-excess or too little water gives higher/lower mass
-water evaporates from beakers, concentration of sugar solution changes
-repeat and take a mean-
what is active transport
example of when active transport is used in plants-why
movement of substances from a more dilute solution to more concentrated solution against concentration gradient- requires energy from respiration
absorption of mineral ions into root hairs from dilute solutions in soil -lower conc. than in root hairs
-plants need ions for healthy growth
example of when active transport is used in animals-why
another example- not in spec
sugar molecules absorbed from lower concentrations in gut (and kidney tubules) into blood w/ higher sugar concentration
sugar molecules needed for cell respiration
describe how sugar molecules absorbed from lower concentrations in gut into blood and then sent around body - 3 steps
-where does the energy for this come from
lumen (in sm. intestine where food is digested) has lower conc. of molecules produced when food is digested eg sugar than in the blood
-active transport carries sugars from lumen into cells lining small intestine, then into blood
-glucose transported to cells to be used in respiration
the cells lining the small intestine have many mitrochondria, provide energy for active transport
describe how mineral ions are absorbed into root hairs from dilute solutions in soil to leaf
where does energy for this come from
active transport used to move ions into cell
ions then transported to xylem vessel and moved to leaf
root hair cells have many mitochondria to provide energy for active transport
how easy it is for an organism/ thing to exchange substances with its environment depends on
its s.a to vol ratio
describe the s.a to vol ratio of single celled organism
who would have a bigger s.a to vol ration- mouse or hippo
relatively large s.a to vol ratio
-mouse
single celled organisms have large s.a to vol ratios- this allows….
sufficient transport of molecules in and out of cells
why do single celled organisms not need exchange surfaces
gases and dissolved substances can diffuse directly into / out of the cell across the cell membrane. Bcse they have large S.A to VOL ratio- enough substances can be exchanged across the membrane to meet the needs of the organism(supply the volume of the cell).
what do multicellular organisms have to supply body with oxygen- x2
-why do they need these - 4 points
exchange surfaces (special structures for gas exchange w/ vry high s.a) and transport systems
-multicellular organisms have smaller SA to VOL ratio
- not enough oxygen can diffuse from their outside surface to supply their entire volume/ to supply the cells in the centre of the organism (only cells on the surface can get enough O2 by diffusion)
-need exchange surfaces for efficient diffusion
- need transport system to carry gases around body
how are exchange surfaces adapted x4
-thin membrane- so substances only have short distance to diffuse
-large s.a so lots of substances can diffuse at once
-exchange surfaces have lots of blood vessels - efficient blood supply to get molecules in and out of blood quickly
-ventilated -air moves in and out
what do the lungs do-
how are they adapted -
what happens at alveoli
How are they adapted for gas exchange x4
-transfer O2 to blood and remove waste CO2 from it
-have millions of alveoli-large s.a
-gases diffuse in/out of bloodstream-sites of gas exchange
-very thin walls- short diffusion path
-good blood supply, once O2 diffuses into blood, rapidly removed- steep concentration gradient
-large s.a- alot of gas diffuse at once
-moist lining- to dissolve gases so they diffuse quickly
what does the small intestine do-
how is the small intestine adapted-x2
-how are villi adapted-x3
-absorbs products of digestion
-covered w/ millions of villi-increase s.a for absorption
-very long- large s.a
-have microvilli- further increase.sa
-good blood supply- quickly removes the products of digestion- increases conc. gradient
-thin membrane- short diffusion path
***edit
how are leaves in plants adapted to gas exchange - 5 points
-thin -gives a short diffusion distance
-flat - large s.a to vol ratio
-many stomata -allow movement of gases in/ out of the air spaces in leaf - steep concentration gradient
-Many stomata in the lower epidermis open in sunlight to allow gas movement in and out of the leaf
-Thin cell walls is another exchange surface- gases move into the cells easily
-close contact between the cells and air spaces -efficient gas exchange
-Air spaces to allow gas movement around the loosely packed mesophyll cells
-Moist air which gases can dissolve into for easier diffusion
why would damaged villi cause low levels of iron in blood
would reduce s.a for absorption so less iron can be absorbed from the digested food in small intestine into the blood.
what are gas the gas exchange surface in fish
gills
describe process of gas exchange in fishes - 5 points
-water containing oxygen enters fish through its mouth and passes over gills
-deoxygenated blood passes into the filament
-oxygen diffuses from water into the blood in the gills(into the bloodstream)
-carbon dioxide diffuses out from the blood into the water
-oxygenated blood returns to the body
how are fish gills adapted for gas exchange x4
-each gill covered in many fine gill filaments where gases pass in and out-
-gill filaments increase s.a for gas exchange
-filaments have thin membrane for short diffusion pathway
-filaments have efficient blood supply to take O2 blood away- increase concentration gradient
how are gill filaments adapted for gas exchange
x4
-gill filaments covered in lamellae-further increases s.a
-lammellae-hav many blood capillaries-speeds up diffusion(the more capillaries there are, the more s.a there is for oxygen to diffuse in and CO2 to diffuse out of capillaries)
-lamellae- have thin surface layer of cells-short diffusion pathway
-blood flows through lamellae one way and water in opposite direction- maintains large concentration gradient (of O2 as theres more in water than blood)
4 general adaptations exchange surfaces have
-thin membrane
-concentration gradient
-large sa. to vol ratio
-permeable to the substance it wants.
-ventilated(for gas exchange)
meiosis
-the 2 daughter cells from mitosis split again to make 4 daughter cells in total
there is no duplication of chromosomes
-2 cells- 23 chromosome pairs in each
-each cell split into two
-so left with 4 cells, 23 SINGLE chromosomes in each
-these cells are called gametes
-each have a specific set of chromosomes for specific characteristics
-this only happens in sexual reproduction
pros of stem cells from embryos-
cons-
pros of stem cells from bone marrow
cons
embryo stem cells
pros
* can treat a wide variety og problems
* many available
* using them better than wasting them
* painless
cons
* (possible) harm / death to embryo
* (relatively) untested / unreliable / may
not work
* embryo can’t be ‘asked’ / ‘embryo rights’
idea
adult bone marrow stem cells –
examples of
pros
* no ethical issues
* quick recovery
* (relatively) safe
* well tried / tested / know they work
cons
* operation hazards eg infection
* few types of cell / tissue produced or few
diseases / problems treated
* painful so may deter donors
Explain why bone marrow can be called is tissue.
group / collection of cells
which work together to produce blood cells
bone marrow is made of stem cells
what subcellular structures can’t be seen under light microscope
Ribosomes and mitochondria
what subcellular structures can’t be seen under light microscope
Ribosomes and mitochondria
