B1 CELL BIOLOGY Flashcards
what are the two types of cells?
eukaryotic (plant and animals)
prokaryotic (bacteria)
what are the differences between prokaryotic and eukaryotic cells?
prokaryotic are much smaller then eukaryotes
eukaryotic cells contain their genetic material enclosed by a nucleus whereas prokaryotic don’t.
what is the prokaryotic cell wall composed of?
peptidoglycan
what are plasmids?
small circular loops of DNA found free in the cytoplasm and separate from the main DNA.
what is a centimetre (cm)
1 x 10-2 metres
what is a millimetre (mm)
1x10-3 metres
what is a micrometre (μm)
1x10-6 metres
what is nanometre (nm)
1x10-9 metres
what is the order of magnitude?
a power to the base 10 used to quantify and compare size.
how many order of magnitude is 10x
one zero = 1 order of magnitude
what is the difference in order of magnitude between a human hair (100 μm) and the HIV virus (length = 100 nm)
100μm = 10-4m
100nm = 10-7m
-4-(-7) = -4+7 = 3
list the components of both plant and animals cells (5)
nucleus
cytoplasm
cell membrane
mitochondria
ribosomes
list the additional cell components found in plant cells (3)
chloroplasts
permanent vacuole
cell wall
what is the function of cytoplasm ?
a watery solution where a chemical reaction takes place.
what is the function of mitochondria?
where aerobic respiration takes place
what is the function of chloroplasts?
contains chlorophyll and are the sits of photosynthesis
what is the function of the ribosome?
sites of protein synthesis
what is the function of the cell wall?
made from cellulose, this strength the cell
what is the function of the vacuole?
filled with fluid called cell sap , the vacuole helps give the plant cell its shape.
what is the function of cell membrane?
controls the molecules that can enter and leave the cell.
what is the function of the nucleus?
to enclose the genetic material/controls cellular activities.
describe how nerve cells in animals are adapted to their functions?
axon = carries electrical impulses from one part of the body to another
myelin = insulates the axon and speeds up the transmission of nerve impulses
synapses = junctions which allow the impulses to pass from one nerve cell to another
dendrites = increase surface area so that the other nerve cells can connect more easily.
what is the job of the nerve cell?
to send electrical impulses around the body .
describe how sperm cells in animals are adapted to their functions?
nucleus = contain their genetic material (only half the genetic info a normal adult cell)
tail = allows them to swim to the ovum they are also streamlined to make this easier)
mitochondria = they are packed full of mitochondria , they provide energy for swimming.
enzymes = allows them to digest their way through the outer layer of the ovum.
what is the job of the sperm cell?
join with the ovum (fertillisation)
describe how muscle cells are adapted to their functions?
mitochondria = they are packed with mitochondria to provide energy for muscle contraction
what is the job of the muscle cells?
they can contract (get smaller)
describe how root hair cells in plants are adapted to their function?
large surface area = to absorb nutrients and water from surrounding areas.
what is the job of the root hair cell?
absorb water and dissolved minerals
describe how xylem cells in plants are adapted to their function?
They lose their end walls so the xylem forms a continuous, hollow tube. They become strengthened by a substance called lignin
what is the job of the xylem cells?
they transport water and minerals from the roots to the leaves.
describe how phloem cells in plants are adapted to their function?
sieve plates/phloem vessel cells= dissolved sugar to move through cell interior
companion cells= provide energy to the phloem vessel cells
what is the job of the phloem cells?
carry dissolved sugars up and down the plant.
what is cell differentiation?
the process by which cells become specialised.
why is cell differentiation important?
they are able to perform a specialised function in the body
what changes does a cell go through as it differentiates?
changes in gene expression, the formation of different structures within the cell, and interactions with other cells in the organism.
what is the purpose of cell division in mature animals?
repair and replacement of cells
for how long do plants cells retain the ability to differentiate?
throughout their entire life cycle
at what point in their life cycle do most animal cells differentiate?
early in their life cycle
how can magnification be calculated?
magnification = size of image/size of real object
how does an electron microscope work?
utilises magnets aim a beam of electrons at a cell to produce an image.
how does a light microscope work?
visible light is passed through the specimen and then through glass lenses.
disadvantages of electron microscopes?
expensive , large so less portable , required training to use
advantages of electron microscope?
greater magnification and resolution
disadvantages of light microscope?
limited resolution , limited magnfication
advantages of light microscope?
inexpensive , easy to use , portable
how have electron microscopes enabled scientists to develop their understanding of cells?
allows small sub-cellular structures to be observed in details
enables scientists to develop more accurate explanations about how cell structures relate to its function
why do electrons microscopes have a greater magnification and resolution?
they use a beam of electrons which has a shorter wavelength than protons of light
define resolution?
the smallest distance between two objects that can be distinguished.
define magnification?
the number of times bigger an image appears compared to the size of the real object.
what are chromosomes made up of?
molecules of DNA
what is a gene?
a section of DNA which codes for a protein
how many chromosomes are found in the nucleus of human body cells?
46
how many chromosomes are found in the nucleus of gametes?
23
how are chromosomes arranged in the nucleus of a body cell?
arranged in pairs - 46 chromosomes form 23 pairs
what are the three main stages of the cell cycle?
- replication of DNA
- mitosis
- division of cell
what do chromosomes carry?
a large number of genes which determines many of our features
describe the first stage of the cell cycle?
the DNA replicates to form two copies of each chromosomes , the cell grows and copies its internal structure.
describe the second stage of the cell cycle?
mitosis takes place , one set of chromosomes is pulled to each end of the cell , the nucleus also divides.
describe the third stage of the cell cycle?
the cytoplasm and cell membrane divide to form two identical daughter cells to form
why is mitosis important?
growth , repair , reproduction
what is a stem cell?
an undifferentiated cell which can give rise to more cells of the same type and can differentiate to form other types of cells.
what is the function of stem cells in embryos
they can replicate themselves and differentiate into many other types of cells.
they may be able to treat conditions e.g diabetes , paralysis by dividing to replace damaged cells
what is the function of stem cells in adult bone marrow?
adult stem cells can differentiate into several cell types to replace dead or damaged tissues.
e.g bone marrow stem cells can form may different types of blood cells
what is the function of stem cells in meristems in plants
these stem cells can differentiate into any type of plant tissues at any type of plant tissue at any point in the life of a plant
what is therapeutic cloning?
an embryos is produced with the same genes as the patient. stem cells from the embryos are not rejected by the patient’s body so they may be used for medical treatment.
The technique involves the transfer of the nucleus from a cell of the patient, to an egg cell whose nucleus has been removed
what are the advantages of cloning plants using meristem stem cells?
clone a rare plant to stop it from going extinct
can produce cloned crop plants for farmers.
what are issues are associated with the use of embryonic stem cells?
the doner has to be compatible with the patient otherwise the white bool cells produced by the donated bone marrow could attack the patient body
there is a risk that viruses can be passed from the doner to the patient.
some people have ethical/religious objection
what are issues are associated with the use of embryonic stem cells?
the doner has to be compatible with the patient otherwise the white blood cells produced by the donated bone marrow could attack the patient body
there is a risk that viruses can be passed from the doner to the patient.
some people have ethical/religious objection
what are three main factors affect the rate of diffusion?
concentration gradient - larger gradient , faster diffusion
temperature - higher temp , faster diffusion
surface area - larger surface area , fast diffusion
give examples of substances transported by diffusion in the lungs and the kidney
lungs: oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood, both down their concentration gradient.
kidney: urea diffuses from cells into blood plasma so it can be excreted in urine.
what is diffusion?
the spreading out of particles in a net movement from an area of higher concentration to an area of lower concentration.
how are single-celled organisms adapted for diffusion?
they have a large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organisms needs
how is surface area to volume ratio calculated?
surface area = number of sides x (side x length x side width)
volume = length x width x depth
ratio = surface area : volume
what four factors increase the effectiveness of a gas exchange surface?
large surface area
thin membrane (short diffusion path)
efficient blood supply (animals)
ventilation (animals)
what is osmosis?
the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
what is meant when a solution is isotonic to a cell?
the concentration of the external and internal (inside cell) solutions are the same
what is meant when a solution is hypertonic to a cell?
the concentration of the external solution is higher than that of internal solution (inside cell)
what is meant when a solution is hypotonic to a cell?
the concentration of the external solution is lower than that of the internal solution (inside cell)
what may happen when an animal cell is placed in a very hypotonic solution?
water moves into the cell causing it to burst.
what may happen when an animal cell is placed in a very hypertonic solution?
water moves out of the cell causing it to shrivel up .
how do plants leaves and stems remain rigid?
turgor pressure = water moves in by osmosis causing the vacuole to swell and the cytoplasm to press against the cell wall
what may happen when a plant cell is placed in a very hypertonic solution?
water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size. the cell membrane may pull away from the cell wall causing the cell to become plasmolysed.
how is active transport used to absorb the products of digestion?
active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. glucose is then transported to the tissues where it can be used in respiration
how do plant root hair cells use active transport?
take up minerals ions from a more dilute solution in soils
ions such as magnesium and nitrates are required for healthy growth.
what is active transport?
moves substances from a dilute solution to more a concentrated solution (this requires energy from respiration)
how do bacteria multiply?
binary fission (simple cell division)
how often do bacteria multiply?
once every 20 minutes if enough nutrients are available and the temperature is suitable.
REQUIRED PRACTICAL MICROSCOPES METHOD
place the slide onto the stage (use clips to hold them in place)
select the lowest power objective lens (usually 4x)
need to position the objective lens so it almost touches the microscope slide (we turn the coarse focussing dial).
we look at the microscope from the side while we adjust the position of the objective lens.
when the objective lens almost touches the slide , we stop turning the dial.
look down through the eyepiece , we need to slowly turn the coarse focusing dial (increases the distance between the objective lens and the slide) we do this until the cell comes to focus. (use the fine focusing dial to bring the cells into a clear focus)
what are the risks of MICROSCOPES PRACTICAL
if we look through the eyepiece while positioning the objective lens there is a risk that we damage the slide.
Care must be taken when looking down the microscope if the illumination is too bright.
Care must be taken when using microscope stains.
describe how to investigate the effects of osmosis on a plant tissue
- peel the potato (because the potato skin can affect osmosis)
- use a cork borer to produce three cylinders of potato (using one makes all the cylinders the same diameter)
-use scapel to trim the cylinders the same length (around 3cm)
-measure the length of each cylinder (using a ruler) and the mass of each cylinder (using a balance) - place each cylinder into a test tube, add 10cm cubed of 0.5 molar sugar solution to the first test tube ,
- repeat the process but with 0.25 molar and distilled water
- leave it overnight to allow osmosis to take place
-roll them on paper towel to remove any surface moisture - measure length and mass again.
percentage change equation?
change/original x 100
