B1 - Cell Biology Part 2 Flashcards
Magnification equation and units
Magnification = image size/real size
Magnification = mm/mm
How to prepare slide for microscopy (normal microscope)
(6 marks)
Add drop of water to the middle of a clean slide
Cut onion, separate into layers
Use tweezers to peel off epidermal tissue from the bottom of one of the layers
Using tweezers, place the epidermal tissue into water on the slide
Add a drop of iodine solution - to stain the epidermal tissue
Place a cover slip on top,
How do you use a light microscope to look at your slide
(6 marks)
Clip the slide prepared on the stage
Select the lowest-powered objective lens
Use coarse adjustment knob to move stage up to just below the objective lens
Look down eyepiece, use coarse adjustment knob to move stage downwards until the image is in focus
Adjust focus with the fine adjustment knob until a clear image is shown on the slide
Swap to a higher-powered objective lens and refocus in case greater magnification is needed
What is the equation for total magnification
Total magnification = eyepiece lens x objective lens
What type of cell are cheek cells
Epithelial cells
What is a specialised cell
What is differentiation
What are stem cells
A cell that is adapted to its function by having special shape and features.
When a cell changes to become specialised for its job
Undifferentiated cellsq
What is the purpose of a sperm cell and how is it specialised to do this
To get male DNA to female DNA
Has a long tail and streamlined head to help it swim to the egg
Lots of mitochondria to transfer energy needed
Carries enzymes in its head to digest through the egg cell membrane
Purpose of nerve cell
How is it specialised to do this
Carry electrical signals from one part of the body to another.
They are long to cover more distance
Have branched connections at their ends to connect to other nerve cells and form a network throughout the body
Purpose of muscle cell
How is it specialised to do this
Contract quickly
They are long to have space to contract
Contains lots of mitochondria to transfer energy needed for contraction
Purpose of root hair cell
How is it specialised to do this
Absorbing water and minerals
Long hairs to stick into soil
Large surface area for absorbing water and mineral ions from soil
Purpose of Phloem and Xylem
How is it specialised to do this
Transporting substances
Xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them
What does the nucleus of a cell contain
What do each chromosome carry
The nucleus of a cell contains chromosomes made of DNA
molecules. Each chromosome carries a large number of gene
What is the purpose of mitosis?
To grow or replace cells that have been damaged
Repair damaged tissues
Describe the process of growth and dna replication ( 6 marks)
Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria.
The DNA replicates to form two copies of each chromosome ( X shaped)
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Finally the cytoplasm and cell membranes divide to form two
identical cells.
Stem cells in the early human embryo (embryonic stem cells) can turn into..
any kind of cell at all
Stem cells from embryos and bone marrow can be grown in a lab to produce..
clones and to differentiate into specialised cell for medicine
Give examples of real life use of adult stem cells and embryonic stem cells
Adult: replace faulty blood cells
Embryonic: replace faulty cells
Meristem tissue in plants can differentiate into..
any type of plant cell
In therapeutic cloning an embryo could be made to have the same.. so the stem cells produced would not be
an embryo could be made to have the same genes as the patient, so the stem cells produced from it would not be rejected by patients body
Why are people against stem cell research
(3 marks)
Because each human embryo is a potential human life
Others think that curing existing patients who are suffering is more important than the rights of embryos
Unwanted embryos from fertility clinics are usually destroyed
What are the risks of using stem cells in medicine
Stem cells grown in the lab may become contaminated with a virus and could pass onto the patient
Describe the benefits of using meristem (stem cells)
( 3 marks)
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
Rare species can be cloned to protect from extinction.
Grows crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers
3 factors that affect diffusion
difference in concentrations
temperature
surface area of the membrane
How does surface area of the membrane affect the rate of diffusion (2 mark)
The larger the S.A of the membrane, the faster the diffusion rate because more particles can pass through at once
Explain the need for exchange surfaces
and a transport system in multicellular organisms
(4 marks)
Multicellular organisms have a smaller surface area compared to their volume
Not enough substances can diffuse from their outside surface to supply their entire volume
They need some sort of exchange surface for efficient diffusion
Exchange surface allows enough of necessary substances to pass through
How are exchange surfaces adapted to maximise effectiveness (4 marks)
thin membrane, substances only have a short distance to diffuse
large surface area, lots of a substance can diffuse at once
Exchange surfaces in animals have lots of blood vessels to get stuff into and out of the blood quickly
Gas exchange surfaces in animals are often ventilated, air moves in and out
How is a single celled organism adapted for sufficient transport of molecules ( 2 marks)
single-celled organism has a relatively large surface area to volume ratio.
Allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.
How is active transport used in the guts
when there is a lower concentration of nutrients in the gut, but higher concentration of nutrients in the blood
How are alveoli’s specialised to maximise diffusion
(4 marks)
An enormous surface area
Moist lining for dissolving gases
Very thin walls
Good blood supply
Where is villi found and what is its purpose
How are villi adapted
S.I
Lots of microvilli to increase surface area so digested food is absorbed much quickly into the blood
Single layer of surface cells
Good blood supply to assist quick absorption
Cells have many mito - release energy needed for active transport
Describe the potato osmosis investigation ( 6 marks)
Cut potato into identical cylinders
Get two beakers one should be pure water and other should be a very concentrated sugar solution with same volume of 25cm^3
Measure the mass of cylinders then leave one cylinder in each beaker for 24 hours
After 24 hours take them out and dry them with a paper towel and measure their masses
Cylinder has drawn in water by osmosis - increased in mass
Water has been drawn out - decreased in mass
What problems may arise during/after the experiment
How can this be reduced
(Potato)
If potato’s were not fully dried - excess water would give higher mass
If water evaporate from the beakers - concentrations of sugar solutions would change
Repeating experiment and calculating a mean
What is active transport - 3 marks
Minerals absorbed from a dilute solution, against a concentration gradient requires energy to do so
How are exchange surfaces adapted to maximise effectiveness ( 4 marks)
They have a thin membrane, so substances only have a short distance to diffuse
Large surface area so lots of substances can diffuse at once
Exchange surfaces in animals have lots of blood vessel to get substances into and out of blood quickly
Gas exchange surfaces in animals are often ventilated too
Two ways electron microscopes are better than light microscopes
Much higher magnification
Much higher resolution
Can see smaller things in more detail
Convert 1mm to micrometers
1000 μm
Convert 1μm to nanometer
1000 nanometers
Convert 1μm to mm
1/1000
Convert 1 nanometer to μm
1/1000
How are gills adapted for gas exchange ( 6 marks)
Each gill is made of lots of thin plates called gill filaments
- increases surface area for exchanging gases
Gill filaments are covered in lots of lamellae - increases surface area even more
Lamellae have lots of blood capillaries to speed up diffusion
Thin surface layer of cells to minimise the distance that the gases have to diffuse
Blood flows through lamellae in one direction and water flows over in the opposite direction - maintains a large concentration gradient
Concentration of oxygen in the water always higher than that in the blood so as much oxygen as possible diffuses from the water into the blood
