CELL BIOLOGY

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Eukaryotic Cells
Plant and animal cells have a cell membrane, cytoplasm and genetic material enclosed in a nucleus making them eukaryotic
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Prokaryotic Cells
Bacteria cells are much smaller in comparison to eukaryotic cells. Have cytoplasm and a cell membrane surround by cell wall. Genetic material not enclosed in nucleus. Single DNA loop, may be one or more small rings of DNA called plasmids.
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What is the equation for magnification?
Size of image/Size of real object
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Orders of magnitude
If 2 numbers have the same order of magnitude, they are about the same size. If 2 numbers differ by one order of magnitude, one is 10x larger. If they differ by 2 orders of magnitude then it is about 100x larger.
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What sub-cellular structures are in an animal cell?
Nucleus, Cytoplasm, Cell membrane, mitochondria, ribosomes.
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What subcellular structures are found in a plant cell that aren't in animal cells
Chloroplasts, Permanent Vacuole, Cell wall (also found in algal cells)
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Function of a nucleus
Contains genetic material and controls what the cell does
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Function of a cytoplasm
Most chemical reactions happen here, controlled by enzymes
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Function of a cell membrane
Controls movement of substances into and out of cell
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Function of a mitochondria
Where respiration happens; energy released
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Function of ribosomes
Protein synthesis happens
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Function of chloroplasts
contains chlorophyll, where light is absorbed for photo synthesis
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Function of permanent vacuole
Filled with cell sap used to make the cell turgid
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Function of a cell wall
Strengthens the cells
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When would a light microscope be used?
Form an image of specimen and magnify it. See individual cells and large subcellular structures like nuclei
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When would an electron microscope be used?
Higher magnification; Internal structure, mitochondria, and chloroplasts. Ribosomes and plasmids
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Microscope required practical
Look at revision note
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How is a sperm cell specialised for it's function?
Long tail and streamlined head to help it swim to the egg. Lot of mitochondria in the cell to provide the energy needed. Also carries enzymes in its head to digest through the egg cell membrane
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How is a nerve cell specialised for it's function?
Carries electrical signals from one part of the body to another. Cells are long (cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body
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How is a muscle cell specialised for it's function?
Needs to contract quickly. These cells are long (space to contract) and contain lots of mitochondria to generate the energy for contraction
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How are root hair cells are specialised for absorbing water and minerals?
On surface of plant roots, grow into long hairs that stick out into the soil . Big surface area for abosrbing water and mineral ions from soil.
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How are phloem and xylem cells specialised for transporting substances?
Form phloem and xylem tubes, transport substances such as food and water around plants. To form the tubes, the cells are long and joined end to end. Xylem cells hollow in centre and phloem cells have very few subcellular structures, stuff can flow.
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What is cell differentiation?
Process by which a cell changes to become specialised for its job
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Why is cell differentiation important?
They develop different subcellular structures and turn into different types of cells. Carry out specific functions.
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When does cell differentiation occur?
As an organism develops, cells differentiate to form different types of cells. Animals cells differentiate at an early stage. Plant cells retain ability to differentiate throughout life.
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Cell division in mature animals
Mainly restricted to repair and replacement. As a cell differentiates it acquires different subcellular structures to enable it to carry out a certain function. Become specialised cell.
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How has electron microscopes helped biologists?
Higher magnification and resolving power has enabled biologists to see and understand many more sub-cellular structures
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Culturing microorganisms- bacteria
Bacteria multiply by simple cell division (Binary fussion) as often as once every 20 minutes if there is enough nutrients and a suitable temperature. Grown in nutrient broth solution or as colonies on an agar gel plate
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What are uncontaminated cultures of microorganisms required for?
Investigating the action of disinfectants and antibiotics.
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Why should a petri dish and culture media be sterilised before use?
To kill any unwanted microogranisms that may be lurking on them.
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Why are inoculating loops sterilised to transfer microorganisms to the media?
to avoid cross contamination
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Why should the lid of the petri dish be secure with adhesive tape and stored upside down?
To avoid microorganisms from the air getting in and to stop drops of condensation falling into agar surface
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Why should cultures be incubated at 25 degrees celsius?
Temperatures close to the body temperature allows the growth of pathogens to be harmful to health
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How to calculate cross-sectional areas of colonies or clear areas around colonies?
Use Pi x radius squared
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Mean division time
Average amount of time it takes for one bacterial cell to divide into 2. Make sure both times are in same units, divide total time by mean division time. Gives you number of divisions. Multiply 2 by itself for the number of divisions to find number.
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Required practical- Effect of antiseptics or antibiots on bacterial growht
look at revision notes.
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Where are chromosomes found?
In the nucleus of a cell made of DNA molecules.
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What does each chromosome carry?
large number of genes
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How are the chromosomes in the body found?
In pairs
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What is the series of stages that cells divide in called?
Cell cycle
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3 stages of cell cycle
Genetic material doubled and then divided into 2 identical cells. Before cell can divide it needs to grow and increase number of sub-cellular structures such as ribosomes and mitochondria. DNA replicates- form 2 copies of each chromosome.
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3rd stage of cell cycle
In mitosis one set of chromosomes are pulled to each end of cell and nucleus divided
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Why is cell division by mitosis important?
For growth and development of multicellular organisms
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What are stem cells?
An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, form which certain other cells arise from differentiation
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Function of stem cells in embryos
Potential to turn into any kind of cell
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Function of adult animals?
Found in bone marrow, can't turn into any cell; blood cell.
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Function of meristems in plants
Differentiate into any type of plant cell. Produce clones of whole plants quick and cheap. Grow more rare species. Helpful for farmers
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What can treatment of stem cells help?
Diabetes and paralysis
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Therapeutic cloning.
Embryo produced with same genes as patient. Stem cells from embryo are not rejected by patients's body so may be used for medical treatment.
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Risks of stem cells
Transfer viral infections, some people have ethical and religious objections
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Definition of diffusion
Spreading out of particles of any substance in solution, or particles of a gas, net movement from an area of higher concentration to an area of lower concentration.
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Examples of substances transported by diffusion
Oxygen and carbon dioxide in gas exchange, and waste product urea from cells into blood plasma from excretion in the kidney.
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Factors which affect the rate of diffusion are:
Difference in concentrations (concentration gradient). Temperature. Surface area of membrane
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What do single-celled organisms have that allows sufficient transport of molecules into and out of the cell to meet the ends of the organism.
Relatively large surface area to volume ratio.
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Why do multi-cellular organisms need exchange surfaces?
Because they have a smaller surface area compared to their volume- so not enough substances can diffuse from their outside surface to supply their entire volume. Exchange surfaces allow enough necessary substances to pass through
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How are the lungs adapted for gas exchange?
They need to transfer oxygen to the blood and remove waste carbon dioxide. They have millions of air sacs called alveoli where gas exchange takes place. They have enormous surface area, moist lining, very thin walls and good blood supplu
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How are the small intestine adapted for gas exchange?
Covered in millions of villi. Increase surface area in big way so digested food is absorbed quicker into blood. Single layer of surface cells, very good blood supply to assist quick absorption
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How are gills adapted for gas exchange?
Gill filaments for a big surface area- gas exchange. Lamallae- increase surface area. Have capillaries to speed up diffusion. Thin surface layer of cells to minimise distance that gases have to diffuse.
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Leaves for gas exchange
Stomata CO2 diffuses in through. Oxygen and water vapour diffuse out, Controlled by guard cells, Close if losing water faster. Flattened shape of leaf increase area. Walls have air spaces- increase area.
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How is effectiveness of an exchange surface increased?
Large surface area, membrane is thin, efficient blood supply, being ventilated
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What is osmosis?
Diffusion of water from dilute solution to a concentrated colution through a partially permeable membrane
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Required practical- osmosis
look at revision notes
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What is active transport?
Move substances from more dilute solution to a more concentrated solution (against concentration gradient). Energy from respiration. Allows mineral ions absorbed into plant root hairs from very dilute solution in soil. Plant requires ions for healthy
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What does active transport allow?
Sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules used for cell respiration.
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Bacteria cells are much smaller in comparison to eukaryotic cells. Have cytoplasm and a cell membrane surround by cell wall. Genetic material not enclosed in nucleus. Single DNA loop, may be one or more small rings of DNA called plasmids.

Card 3

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What is the equation for magnification?

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Card 4

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Orders of magnitude

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