B1 cell structure and transport Flashcards
how do light microscopes work
use a beam of light to form an image
how much can light microscopes magnify
x2000
how much can school light microscopes magnify
x400
advantages light microscopes
relatively cheap, can be used anywhere and magnifies live specimens
what did electron microscope allow scientists to see and understand
more about subcellular structure inside cells
how do electron microscopes work
use a beam of electrons to form an image
how much can electron microscopes magnify up to
x 2 000 000
disadvantages of electron microscopes
large, expensive and have to be kept in special temp pressure and humidity
difference between transmission and scanning electron microscope
T - 2d images but high magnification
S- 3d images but low magnification
how to calculate image size
magnification x actual size
how to calculate magnification
image size/ actual size
OR
objective lens x eye piece lens
what does the objective lens do
magnifies object at different intensities
what does the eyepiece do
magnifies image for viewer
what does light do
provides light to view the object
what does the coarse focus do
This moves the stage by a large amount to bring the image into focus
what does the fine focus do
This moves the stage by a small amount to focus the image carefully
what is the resolution
the ability to distinguish between two separate points
what does the resolving power do
affects how much detail an image can show
the lower the resolving power…..
the higher the detail
resolving power for:
light microscope
scanning electron
transmission electron
L - 200nm
S - 10 nm
T - 0.2 nm
how many mm in a micrometre (um)
1000
how many um in a nm (nanometre)
1000
what microscope has a higher resolving power and magnification and what has this enabled scientists to do
An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
when was the light microscope discovered
17th centurary
when was the electron microscope discovered
1930
what does the nucleus do
control all activity in the cell
what does the nucleus contain
genes on the chromosomes
what do chromosomes do
carry out instructions on making proteins to build new cells
diameter of nucleus
10um
what is the nucleus surrounded by
nuclear membrane
what is the cytoplasm and what does it do
- liquid gel where most organelles are suspended and is where most chemical reactions take place
what does the cell membrane do
controls the movement of substances in and out of the cell
what does the mitochondria do
its where aerobic respiration takes place, releasing energy for cells
what to ribosomes do
where protein synthesis takes place, making proteins for the cells that need it
what is the algae apart of
protist kingdom
what are plants and algae cells made out of
cellulose
what does cellulose do
strengthen the cell and gives it support
where is the chloroplast found and what does it contain
in all green parts of the plant, it contain chlorolphyll
what does chlorophyll do
it absorbs light hence its why its used for photosynthesis
what is the permanent vacuole
a space in the cytoplasm filled with sap
why is the permanent vacuole important to plants
its keeps the cell rigid, supporting the plant
what do plant cells contain
mitochondria, cytoplasm, cell wall, nucleus, permanent vacuole, ribosomes, cell membrane and chloroplast
what do animals cells contain
mitochondria, cytoplasm, ribosomes, nucleus, and cell membrane
what do all eukaryotic cells contain
cytoplasm, cell membrane, genetic material and an enclosed nucleus
what is genetic material known as
DNA
what does DNA do
forms chromosomes
what do prokaryotic cells not have
enclosed nucleus
which one is smaller prokaryotic or eukaryotic
prokaryotic
what does Bacteria (prokaryotic) contain
- cytoplasm
- cell membrane surrounded by a cell wall
- does not have an enclosed nucleus but has a single DNA loop in the cytoplasm or/and plasmids
- slime capsule
- flagellum
what are plasmids
extra DNA strands
what is the flagellum and what does it do
its a long protein strand which helps with movement
what is the flagellum and what does it do
its a long protein strand which helps with movement
rules of the order of magnitude
- if the bigger number divided by the smaller number is less than 10 they have the same order of magnitude
- if the bigger number divided by the smaller number is equal to 10 then its 10^1 bigger ( 1 order magnitude)
- if the bigger number divided by the smaller number is equal to 100 then its 10^2 bigger (2 orders of magnitude)
how many micrometres in 1mm
1000
how many nanometres in 1 micrometre
1000
units for micrometers
um
units for nanometers
nm
example of specialised animal cells
- sperm cells
- muscle cells
- nerve cells
what is it called when cells become specialised
differentiation
how are sperm cells specialised
- they are made to join with an ovum (egg cell) through the process of fertilisation
- carry the genetic information of the male parent
adaptations of sperm cells
- long tail which can move side to side to help the sperm move through a females reproductive system or water and are streamlined to make swimming easier
- the middle section is full of mitochondria which transfers energy for the sperms movement
- the acrosome stores digestive enzymes to break the outer sell of the egg
- large nucleus to which its genetic information
how are nerve cells specialised
- they are adapted to send electrical impulses around the body
- they provide a rapid communication system to different body parts
how are nerve cells adapted
- have a long axon which carries the electrical impulses from one part of the body to another, which contains myelin which insulates the axon and speeds up the transmission of nerve impulses
- lots of dendrites which increase the surface area to make connections to other nerve cells easily
- contain synapses which are adapted to send impulses to another cell or muscle using a special transmitter chemical and contain a lot of mitochondria which release energy to make the special transmitter chemical
how are muscle cells specialised
- to contract and relax
how are muscle cells adapted
- they contain proteins that slide over each other making the fibres contract
- they contain mitochondria to send energy to the muscles that need to contract and relax
- they store glycerol which is a chemical that can be broken down by respiration and transfer energy to contract and relax
examples of specialised plant cells
root hair cells
xylem cells
phloem cells
how are root hair cells specialised
- they increase their surface area of the root so it can absorb water and dissolved mineral efficiently-
- they are located close to the xylem
adaptions of roots hair cells
- they increase their surface area for water to move into the cell
- they have a large permanent vacuole that speeds up the movements of water by osmosis from the soil to the cell
- they have lots of mitochondria to transfer the energy needed for active transport of mineral ions
how are xylem cells specialised
they transport mineral ions and water from the roots to the leaves
adaptions of xylem cells
- they are alive when they are formed but when a special chemical builds up in spirals in the cell wall they die and form long hollow tubes which allow water and mineral ions to flow through easily
- they have thick walls containing lignin which provides support to the plant and withstand the pressure of the water
- they have no internal structures making it easier for water an minerals to flow
how are phloem cells specialised
- they carry dissolved sugars made by photosynthesis around the plant
how are phloem cells adapted
- the vessel cells contain sieve plates which allow dissolved sugars to move up and down the cell
- they have phloem vessel cells that have no nucleus and only a limited cytoplasm
- they have companion cells which help keep the phloem cell alive as they lose a lot of their internal structure and contain mitochondria that transfers energy to the phloem vessel cell
REQUIRED PRACTICAL - how to use a microscope to view a prepared slide
1) place the microscope onto a stage and use the clips to hold the slide in place
2) select the lowest power objective lens and position the objective lens so it almost touches the microscope slide, by slowly turning the coarse focusing dial
3) when the objective lens almost touches the slide, we stop turning the dial its important to do this whilst looking at the side of the microscope as if we do this whilst looking through the eyepiece there is a risk of damaging the slide
4) then we look down through the eyepiece and slowly turn the coarse focusing dial until the cells come into focus
5) then use the fine focusing dial to bring the cells into a clear focus
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 does oxygen move in and out of cells by diffusion
- cells are surrounded by a high conc of oxygen, so the oxygen molecules move into the cell by diffusion from an area of high conc to an area of low conc
how does co2 move in and out of cells by diffusion
as oxygen is used to generate respiration, this produces the waste gas CO2, meaning that we have a higher conc of CO2 inside the cell than outside the cell, so the carbon dioxide moves out of the cell by diffusion
how does urea move in and out of cells by diffusion
urea is a waste product that is produced inside cells and diffuses out of the cells into the blood plasma and is excreted by the kidneys
what factors effect the rate of diffusion
- the difference in concentrations
- temperature
- surface area of molecules
how does the difference in concentrations affect the rate of diffusion
- the greater the concentration gradient (difference in concentration) the faster the rate of diffusion as many particles would move randomly to the area of low concentration
how does the temperature affect the rate of diffusion
the higher the temperature the greater the rate of diffusion as the particles have more kinetic energy and are moving faster
how does the surface area of the membrane affect the rate of diffusion
the greater the surface area the faster the rate of diffusion
how to calculate the SA:V ratio of a cube
surface area - multiply the length by the height the times it by 6
volume - l x w x h
what happens to the SA:V as organisms get larger
the ratio decreases, this means that the diffusion distance gets bigger and simple diffusion is less efficient for exchanging materials
why is SA:V a problem for multicellular organisms
as they have a small SA:V as their surface area is not large enough for their volume, this means that not enough oxygen diffuses into cells in the centre of the organism as they are too far away from the surface
how does fish transport gases around its body
1) the oxygen rich water passes into the mouth
2) it then flows over gills where the oxygen is transported into the blood stream
3) deoxygenated blood passes into the filament, oxygen diffuses from the water into the blood and the oxygenated blood returns to the body
how are fish gills adapted for gas exchange
- they are covered in fine filaments each with a rich blood supply to take the oxygenated blood away, this ensures that the gradiant is always high concentration
- the filaments give the gills a massive surface area
- the filaments have a thin membrane to provide a short diffusion pathway
what is osmosis
the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
what is a partially permeable membrane
a membrane that do not let all types particles through
what is a dilute solution
a solution that always has a high concertation of water and a low concentration of solvent
what is a concentrated solution
a solution that has a low concentration of water and a high concentration of solvent
what is the concentration of a cytoplasm
it is a concentrated solution as it contains a low concentration of water
what happens if we place an animal cell in water
the water will move by osmosis from outside the cell to inside the cell
what happens if we place a cell in a hypotonic solution
the water would move in the cell by osmosis causing the cell to swell and bursts
what is a hypotonic solution
there is more water outside of the cell than inside of the cell
what is a hypertonic solution
when there is more water inside the cell than outside
what is an isotonic solution
when the concertation inside and outside the cell is the same
what happens when we place an animal cell in a hypertonic solution
the water will move out the cell causing it to shrivel and shrink
what happens when we place a plant cell in water
the water will move into the plant by osmosis causing it to expand
why don’t plant cells bursts when placed in water
the cell wall prevents it from bursting so it becomes turgid instead
why does the fluid around the plant need to be hypotonic from the cytoplasm
as it keeps the water moving in the right direction and the cells turgid, which helps keep the leaves and stems rigid and firm
what would happen if you place a plant in a hypertonic solution
the water would move out the plant by osmosis causing the cell to shrink and the cells to become flaccid as there is no pressure on the plant walls, so the plant would wilt as turgor no longer supports the plants tissue
what happens if to much water moves out the plant cell
the vacuole and cytoplasm would shrink and the cell membrane would pull away from the cell wall this is known as plasmolysis
REQUIRED PRACTICAL - osmosis in plants
1) peel the potato as the potato skin can affect osmosis
2) use a cork borer to produce 3 cylinders of potato, the borer ensures that the cylinders are the same diameter
3) use a scalpel to trim the cylinders to the same length
4) measure the length of each cylinder using a ruler and record the mass of each cylinder using a balance
5) now place each cylinder into a test tube, add 10 cm3 of a 0.5 molar sugar solution to test tube 1, add 10cm3 of 0.25 molar sugar solution to test tube 2 and 10cm3 of distilled water to test tube 3 (we use distilled water as tap water contains dissolved substances which could affect our results)
6) leave the potato cylinders overnight to allow osmosis to take place
7) remove the potato cylinders and roll them on a paper towel to remove any surface moisture
8) measure the length and mass of cylinder again the calculate the percentage change
how to calculate percentage change
change in value/ original value x 100
how to calculate net movement
particles in - particles out
how to calculate net movement
particles in - particles out
what is active transport
when substances moves from a more dilute solution to a concentrated solution (high to low conc)
differences between diffusion and active transport
diffusion
- does not require energy from respiration
- moves down the conc gradient
active transport
- requires energy from respiration
- moves against the conc gradient
how does active transport work in the small intestine
- the sugars are carried from the lumen of the small intestine into the cells by active transport once inside the cells the sugars can be transported into the blood and carried around the body, the cells also contain lots of mitochondria providing the energy needed for active transport
how does active transport work in root hair cells
- active transport is used to move the ions in the soil into the root hair cells, these ions are then transported into the xylem vessel then to the leaf, root hair cells contain lots of mitochondria to provide the energy needed for active transport
Name two pieces of laboratory equipment the student could have used to prepare
cells to view using a microscope.
- (microscope) slide
- scalpel
The student tried to look at the cells using the microscope.
Suggest one reason why the student could not see any cells when looking through the eyepiece
- (the microscope is) not
focussed
Red blood cells are specialised animal cells.
Compare the structure of a red blood cell with the structure of a plant cell (6 MARKS)
- red blood cell has no nucleus or plant cell has a nucleus
- red blood cell has no cell wall or plant cell has a cell wall
- red blood cell contains haemoglobin or plant cells do not contain
haemoglobin - red blood cells do not contain chlorophyll or plant cells (may)
contain chlorophyll
both have: - cytoplasm
- cell membrane
