Biology - B1

cells + transportation of substances

what are the two different types of cells?

eukaryotic - has a nucleus (animal and plant)

prokaryotic - without a nucleus (bacteria)

what are the function of organelles?- nucleus, cytoplasm, mitochondria, ribosomes, cell membrane, cell wall

nucleus - hold genetic information

cytoplasm - where chemical reactions take place

mitochondria - where aerobic respiration takes place

ribosomes - protein synthesis

cell membrane - allows substances in + out of the cell

cell wall - gives structure

microscopes and their uses

light: for living things, less resolution, cheaper, in colour

electron: not for living things (vacuum), better resolution, used by unis/government, higher magnification

REQUIRED PRACTICAL - microscopes

1. take specimen and place on slide
2. stain specimen
3. place a cover slip on
4. start on lowest magnification then focus
5. repeat on higher magnification

what are the specialised animal cells?

sperm: flagellum for swimming, acrosome containing enzymes, mitochondria for energy to travel to the cells, half the genetic info

muscle cells: many mitochondria to respirate + release energy for movement

nerve cells: heavily insulated, long to speed up electric impulse

what are the specialised plant cells?

xylem - dead cells form a tube that transports water from the roots (one way transportation)

phloem - transport glucose (both directions)

root hair cells - large surface area for active transport of ions, lots of mitochondria for energy to transport

what is cell differentiation?

animal cells - differentiate in the early stages ONLY

plant cells - differentiate throughout life

REQUIRED PRACTICAL - growing micro-organisms

1. petri dish + culture are sterilised
2. spread onto agar plate with inoculating loop (passed through flame)
3. sellotape and store upside down
4. in schools - stored at 25C not body temp

once grown, chemicals can be placed on to see what kills them - zones of inhibition around chemical

larger zone of inhibition = chem works better

what is cell division?

1. every body cell needs same number of chromosomes so cell duplicates all of the organelles before division
2. the chromosomes are pulled to the edge of the cell and the nucleus divides
3. cytoplasm and cell membrane divides

stem cells + their uses (humans)

undifferentiated cells - can turn into any cell

found in embryos (any cell) and bone marrow (blood cell)

stem cells can treat diabetes + paralysis

therapeutic cloning = embryo produces with the patients genes so tissue is not rejected

issues: risk of viral transfer and ethical reasons

stem cells (plant)

found in the meristem tissue

can turn into any cells throughout life

make clones quickly, species can be protected, crop plants with disease can be cloned

what is diffusion?

diffusion is the movement of gas + liquid from a high to low concentration

PASSIVE - no energy required

rate of diffusion is increased by:

* high concentration
* temperature increase
* larger surface area

how is diffusion helped?

in large animals diffusion is increased by:

* areas of large surface area (lungs or small intestine)
* thin membrane to allow shorter pathway
* good blood supply
* being ventilated (gaseous exchange)

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other organisms have gills, roots + leaves which improve diffusion

what is osmosis?

osmosis is the movement of water molecules from a high to low concentration

PASSIVE - no energy required

has to go through a semi-permeable membrane

sugars + salts CANNOT pass through membrane, ONLY WATER

what is active transport?

movement of molecules from low to high concentration

ACTIVE - requires energy from respiration so cells (such as root hair cells) have many mitochondria

REQUIRED PRACTICAL - concentrations + at

1. fill 5 test tubes with different concentrations of solution
2. weigh the 5 pieces of potatoes (or any veg)
3. places pieces into the different solutions
4. leave for a set amount of time
5. take potato out, blot with paper and reweigh