cell biology Flashcards
What is a eukaryotic cell? give examples
contains dna enclosed in a nucleus in a nucleus
animal cells and plant cells
what is a prokaryotic cell? give example
Smaller, dna not enclosed in a nucleus, instead in a loop
bacterial cell
What is a eukaryote?
O rganisms made up of eukaryotic cells
What is a prokaryote?
prokaryotic cell (single celled organism)
found in both animal and plant cells vs just plant cells
P + A
nucleus
mitochondria
cytoplasm
cell membrane
ribosomes
P
vacuole
cell wall
chloroplast
found in bacterial cell
loop of dna
plasmids (small rings of dna)
cytoplasm
cell membrane
cell wall
what does it mean if something is one order of magnitude larger than something. how is this different to two orders of magnitude
order of magnitude is 10x than the one before
one: 10x
two: 100x
what is the nucleus do?
Contains genetic material that controls the activities of a cell
What is mitochondria do?
aerobic respiration take place, which transfers energy
What does a cytoplasm do?
Where most of the chemical reactions happen
What does a cell membrane do?
Controls what goes in and out
What do ribosomes do?
protein synthesis (proteins made)
what does a cell wall do?
Made of cellulose. It supports and strengthens the cell.
what does vacuole do?
Contains cell sap, for shape
what does chloroplast do?
what photosynthesis occurs. It contains chlorophyll which absorbs the light needed.
What do light microscopes let us see
individual cells, and large, subcellular structures like nuclei
What would you use an electro microscope to see?
Internal structure of mitochondria and chloroplast
how do you calculate the magnification of an image
Image size/real size
what is a specialised cell
a cell that has differentiated to get certain adaptations to perform a certain funtion
How are sperm cells specialised
Long tail and streamlined head to swim. Lots of mitochondria for energy
Enzymes to digest through egg cell membrane.
how are nerve cells specialised
Long axon to carry electrical impulses around body
myelin insulates axon to speed the transmission of impulses
synapses to allow impulse to pass to other nerve cells
dendrites increase SA so other nerve cells can connect more easily
how are muscle cells specialised
contain protein fibres, which can change length to allow contract and relax
lots of mitochondria of contraction
how are root hair cell specialised?
- grow long hair to increase SA to absorb water & mineral irons from the soil
- no chloroplast (no sunlight)
what are xylem cells and how are theyspecialised
long tubes that carry water and dissolved minerals from roots to leaves
- thick walls of lignin - support
- end walls between cells break down to form tube
- no internal structure: allow water and dissolved minerals to flow
what are phloem cells and how are they specialised
carry dissolved sugars all around plant
- minimal internal structures to allow flow
- structures rather found in companion cells, mitochondria provide energy for phloem vessel
- end walls have pores called sieve plates to allow flow
parts of a microscope
stage
slide held by clips
lamp
objective lenses, 4x 10x 40x eyepiece
eyepiece lens, 10x
coarse adjustment knob
fine adjustment knob
disadvantage of light microscope
- limited magnification, not all subcellular structures can be seen
- limited resolution, no fine detail
light microscope vs electron microscope
- light uses light, electron uses electrons
- electron has greater magnification and resolution
how do bacteria multiply and how often
binary fission - one cell splits into two
every 20 minutes with sufficient nutrients and temperature
how to find out number of bacteria present after given time
2 to the power of (number of rounds of division)
number of rounds = time / 20
how to avoid contamination when culturing microorganisms and why
- petri dish, nutrient broth and agar must be sterilised
- pass inoculating loop through flame to sterilise it
- petri dish lid should be taped on to
- store petri dish upside down
kill or prevent unwanted microorganisms and prevent contamination
what temp are culture mediums kept in
in school - 25 degrees, to prevent harmful pathogens that grow at temperatures abov
in lab - 37 degrees, accurate to human body temp
how to investigate effect of antibiotics on bacterial growth
- sterilise petri dish and culture medium
- pass inoculating loop over flame to sterilise it
- use loop to evenly cover plate with bacteria
- place paper discs soaking in different antibiotics onto plate
- place one control disc, that has been soaked in sterile water to make sure the antibiotic is the only factor affecting bacteria
- incubate upside down for 48 hours at 25 degrees
- observe inhibition zones - larger = more effective antibiotic
how does culturing bacterial growth work
antibiotic soaks into jelly.
antibiotic resistant bacteria can continue to grow around the discs, whereas non resistants will die. clear area left where bacteria dies: inhibition zone
what is a stem cell
an undifferentiated cell that can:
- divide to produce more undifferentiated cells
- differentiate into other types of cell
where are Stem
cells found in humans
Human embryos and bone marrow
stem cell from embryo vs stem cell from bone marrow
embryonic: cells have not differentiated, can differentiate into any body cell
bone marrow: can only differentiate to form cells found in blood
uses of bone marrow stem cells
transplants for leukaemia patients (cancer of bone marrow)
- existing marrow destroyed using radiation
- then receives transplant of bone marrow from donor
- stem cells in bone marrow now divide to form new bone marrow, and differentiate to form blood cells
disadvantage of bone marrow transplant
- donor must be compatible with patient blood type otherwise WBCs from donor marrow could attack patients body
- risk of viruses from donor to patient
uses of embryonic stem cells
therapeutic cloning - producing an embryo with same genes as patient
- stem cells from embryo transplanted into patient without being rejected by patients immune system
- once inside, stem cells can differentiate to replace cells that stopped working correctly
advantages disadvantages of therapeutic cloning
- useful for range of medical conditions eg diabetes, paralysis
- ethical/religious objections as embryos are “potential human life”
what are stem cells like in plants and where are they found
can differentiate into any plant cell at any time
meristem tissue in roots and buds
how can stem cells be used in plants
to produce clones quickly and cheaply
- clone rare plants to stop it going extinct
- produce cloned crop plants with desired features for farmers eg disease resistant
What are chromosomes?
carry many genes
made up of dna molecules
How many pairs of chromosomes do we have in a cell
23
what is mitosis?
the stage of a cell cycle where cell divides
explain the steps of mitosis
- dna replicates to form two copies of each chromosome (attatched)
- cell grows and other internal structures replicate
- one set of chromosomes pulled to each end of cell
- nucleus divides
- cytoplasm and membrane divide to form two identical cells
what is diffusion
net movement of particles from an area of high conc to an area of low conc
describe the diffusion that occurs in cells
- oxygen diffuses in as blood is oxygenated by lungs so has a higher conc outside of cell
- co2 diffuses out as respiration produces co2 in cell so has a higher con inside cell
- urea diffuses out as it is produces inside cell so has a higher conc inside cell
what affects fate of diffusion
- conc gradient
- temp (particles have more energy)
- SA of membrane
why might a multicellular organism struggle to get enough oxygen for cells
they have a larger surface area to volume ratio, meaning cells in the centre are too far away
how do multicellular organisms get enough oxygen despite SA:Vol ratio
- special structures with high SA for gas exchange eg lungs
- transport system to carry gas around body
how are gases exchanged and transported in fish
gills
- covered in lots of fine filaments
- deoxygenated blood passes into filaments
- oxygens diffuses from water to blood
- oxygenated blood returns to body
how are filaments adapted to increase diffusion
- provide large SA
- thin membrane, shorter distance
- efficient blood supply to maintain high conc gradient
why is mitosis needed
- growth and development of multicellular organisms (eg plants and animals)
- when an organism repairs itself (eg broken bones)
- asexual reproduction
what is osmosis?
diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
how does osmosis affect animal cells
- cytoplasm has low water conc
- in water, water will move inside
- cell expands and bursts
- in concentrated solution, water will move out
- cell shrinks (flaccid)
how does osmosis affect plant cells
same as animal, however cell wall prevents bursting. cell becomes swollen (turgid)
how to investigate affect of osmosis
- peel a potato and use a cork borer to get 3 cylinders on equal diameter
- use scalpel and ruler to cut each cylinder to 3cm
- record mass of each cylinder
- place each into test tubes of different concentrations, one being pure distilled water
- leave overnight
- remove cylinders and pat dry to remove excess water
- remeasure masses, calculate percentage change, plot graph
what is active transport
movement of particles from low conc to high conc (against gradient) - requires energy
how is active transport used in humans
small intestine
- area where food is digested (lumen) may have lower conc than cell
- travel into cell via active transport where they can be transported into blood
how is active transport used in plants
root hair calls
- conc of mineral ions is lower in soil than cell
- ions move into cell via active transport, where they can be transported into xylem and leaf
