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BIOLOGY: CELL BIOLOGY, cell wall, cell membrane, ribosome, nucleus, sap…
BIOLOGY: CELL BIOLOGY
cell structure
eukaryotic cells - cells that contain a nucleus
cellular structures:
Prokaryotic cells
they have no nucleus or mitochondria and are commonly bacteria
cell differentiation
when 2 sex cells become fertilised, they produce a ball of undifferentiated cells which are blank cells with no function, these can become differentiated to become a differentiated cell e.g nerve cell, xylem, sperm etc
in animals, cell division is for repair and replacement of old weakened cells and one a cell is differentiated they cannot differentiate again whilst plants cells can keep the ability to differentiate.
Nerve cells - have insulation that can speed up electrical impulses. dendrites connect to other nerve cells, Long axon projection allows for impulses to travel long distances around the body
Sperm cell - have lots of mitochondria to provide energy for movement (of the tail), tail for swimming towards the egg, acrosome that contains enzymes that can penetrate the cell membrane of the egg. nucleus with 23 chromosomes for jokes
Muscle cell - the fibres can shorten for muscle contraction, has lots of mitochondria for respiration and the release of energy for muscle contraction, contains glycogen for stored energy.
Xylem - has no end plates to allow for water to move through, no cytoplasm to allow for water to move through and rings of lignin for support, elongated cells that form tubes to transport - xylem is a dead tissue
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Phloem - elongated cells to form tubes to allow for transport, very little cytoplasm to allow more solution through, end plates with pores to allows more dissolved substances through, companion cells which provides energy for the transport of sugars
Root hair cell - has lots of mitochondria to provide energy for active transport, large surface area of maximum absorption of water and mineral ions
microscopy
Light - low resolution, in colour, uses light beams, lower cost, smaller in size, can only see large cellular structures, can use living/dead samples, 5 - 15X magnification, low resolving power
Electron - high resolution, no colour, uses beam of electrons with shorter wavelength, large in size, expensive, can see very small cellular structures, can only use dead samples, 1500X magnification, hight resolving power
3 units of measurements are used millimetres (mm), Micrometers (um) and nanometers (nm). to convert to a unit below times by 1000 and to go up a unit divide by 1000
Magnification = size of image / actual size of object
Mitosis and cell cycle
cells divide to repair and replace damaged or weakened tissue other than for growth and development of an organism
cells go through a 3 stage cell cycle
stage 1 - interphase: the cell grows and increases the amount of sub cellular structures and the DNA replicated to form 2 copies of each chromosome.
Stage 2 - mitosis: the chromosomes line up along the centre and are pulled to each end of the cell and the nucleus divides
stage 3 - Cytokinesis: finally the cytoplasm and the membrane divides to form 2 identically identical daughter cells
Stem cells
stem call are undifferentiated cells that can differentiate into specialised cells
3 types
embryonic stem cells - found in the embryo and can differentiate into many different cells such as nerve, muscle, heart, liver, and blood cells
adult stem cells - these cane be found in the bone marrow and can differentiate into red/white blood cells
meristem tissue - this can be found in the meristem of a plant and can differentiate into many different cells throughout a plants life time
these meristem cells can be used to clone a plant quickly and protect rare and endangered species from extinction. plants with special uses or features can be clones in large numbers.
Therapeutic cloning - this involves taking a patients body cell and removing the nucleus and taking a human egg cell and discarding the nucleus and replacing it with the patient's nucleus.
this allows for the cell to be cloned in mass and for it to differentiate into a cell that the patient needs.
pros of this is that the cells and tissue made cannot be rejected by the body and will have a high chance of being successful however this can lead to the transfer of viral infections. many people have strong religious and moral objections to this
Diffusion and Active Transport
diffusion is the movement of particles in a solution or a gas that moves from an area of high concentration to low concentration
diffusion can be seen in the capillaries when oxygen diffuses into cells from the blood and carbon dioxide form respiration will diffuse out of the cells into the blood
diffusion is net movement and an equilibrium Is when there is no net movement
factors that effect this
concentration difference - the greater the difference of concentration will give a faster rate of diffusion.
temperature - higher the temperature the faster the rate as particles have more kinetic energy for movement
surface area - the bigger the surface area the faster the rate of diffusion.
active transport - the movement of particles from a low area of concentration to a high area of concentration against the concentration gradient, requiring energy from respiration.
this can be seen in sugar absorption in the small intestine. there is a low concentration of sugars in digested food and a high concentration of sugar in the blood so sugar is actively transported into the blood from the food
this can also be seen in the root hair cell and there is allow concentration of mineral ions in the soil and higher concentration in the root hair cell so mineral ions form the soil will be actively transported form the soil to the root hair cell
Surface area to volume ratio
single cell organisms have a high surface area to volume ratio and this allows for sufficient transport of molecules into/out of the cell
larger organisms have a lower surface area to volume ratio and they cannot transport a sufficient amount of molecules into/out of the body across their surface so an exchange/transport system is needed
calculating surface area to volume ratio - Volume = w X h X l and Surface area = w X h X num of sides. from this you get SA:V and you then do SA/V to get your answer
adaptations for exchange examples
small intestine - Villi and Micro villa increase the surface area for more absorption of food molecules, they have very thin wall to provide a short diffusion distance, microvilli have many mitochondria to provide energy for active transport, they have a good blood supply to maintain a hight concentration gradient
lungs - many alveoli to provide a large surface area for gas exchange, good blood supply and many capillaries maintain a concentration gradient of o2 and co2, alveoli wall are thin/one cell thick to provide a short diffusion distance, lungs are ventilated to bring fresh oxygen to maintain a concentration gradient
leaves - leaves are flat and wide to provide a large surface area, leaves are thin to provided a short diffusion pathway, air spaces between the calls increase the rate of diffusion, stomata that can open and close to increase/decrease gas exchange
gills - many gill filament provide a large surface area for gas exchange, good blood supply to maintain a concentration gradient of o2 and co2, capillary walls are very thin/one cell thin to provide a short diffusion pathway, fresh water flows over filaments to maintain a concentration gradient.
Osmosis
osmosis is the diffusion of water from a dilute solution (high concentration) to a concentrated solution (low concentration) through a partial permeable membrane
when water moves into a plant cell its becomes turgid and turgid cells help support a plant am deep it upright
plant cell does not burst because it has a cell wall
e.g root hair cells absorb water by osmosis as water moves into the root hair cells as it has a low concentration of water and enters through osmosis
REQUIRED PRACTICAL: Osmosis in a potato `
control variables - temperature, type of potato, age of potato, size of potatoes, solution volume, time all potatoes are left in solution,
independent variable -concentration of the solution
dependant variable - percentage change in mass
add 30cm3 of 0.8 mol/dm-3 sugar solution into a boiling tube
repeat step 1 with concentrations 0.6,.0.4, 0.2 of equal volumes
use water to give a concentration of 0.0 mol/dm-3
cut 5 cylinder of potato of equal size and volume using a cork borer and dry them with a paper towel
weight each potato cylinder and record it and place them into each tube
remove potato cylinders from the solutions after 24 hours
dry each potato cylinder with paper towel
reweigh potato cylinders and record them and find out the percentage change in mass
mass gain - has increased as the solution inside the potato is more concentrated than the outside of the potato so water moves in by osmosis
mass loss - mass has decreased as the outside of the potato is more concentrated than the inside of the potato so water moves out by osmosis
cell wall
cell membrane
ribosome
nucleus
sap vacuole
cytoplasm
mitochondria
chloroplast
cell membrane
ribosome
nucleus
cytoplasm
mitochondria
cell membrane - where chemical reactions take place
cytoplasm - controls what enters/exits cell
ribosomes - performs protein synthesis form amino acids
mitochondria - performs respiration and releases energy
nucleus - controls cell activities and contains DNA
cell wall - strengthens and supports the cell, made from cellulose
sap vacuole - contains cell sap
chloroplast - contain chlorophyll to absorb sunlight for energy for photosynthesis
10 micrometers
50 micrometers
plasmid
ribosome
cell wall
cell membrane
tail/flagellum
loop of DNA
cytoplasm
tail - helps the cell with movement
plasmid - small ring of DNA
5 micrometers
