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AS UNIT F211: CELLS, EXCHANGE AND TRANSPORT

MODULE 1: CELLS

(a) State the resolution and magnification that can be achieved by a light microscope, a
transmission electron microscope and a scanning electron microscope

Light microscope ­
Resolution ­ 200nm
Magnification ­ x1500

Transmission electron microscope
Resolution ­ 0.1nm
Magnification ­…

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(e) Describe and interpret drawings and photographs of eukaryotic cells as seen under an
electron microscope and be able to recognise the following structures:
(f) outline their functions
Nucleus:

Surrounded by nuclear envelope which contains pores
Inside is nucleolus and chromatin

Chromatin is made from DNA and controls cells activities…

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Small, round, membranebound organelle
Contains digestive enzymes which can be used to digest invading cells e.g in
phagocytosis.
Chloroplast:
Found in plant cells
Stacked up thylakiod membranes to form granum
Linked by llamale (intergranal llamale)

Site of photosynthesis
Cell membrane:
Found on the surface of animal cells and inside the…

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To support the cells organelles by keeping them in place
To strengthen the cell and maintain its shape
Transporting materials eg movement of chromosomes during mitosis
Helps the cell to move ­ e.g flagellum
(i) Compare and contrast, with the aid of diagrams and electron micrographs, the structure of
prokaryotic…

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(a) Outline the roles of membranes within cells and at the surface of cells
Separating contents of the cell from its outside environment
Separating cell components from the cytoplasm
Cell signalling
Cell recognition
Regulating transport of materials into and out of the cell
Plasma membranes: on the surface control what…

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Allow small or charger particles to go across the membrane (molecules that are too large to
diffuse through, or hydrophilic molecules)

Carrier proteins:
Actively transport molecules across the membrane


Glycolipids and Glycoproteins:
Help to stabilise the membrane
Receptor sites for drugs, hormones and antibodies
Act as antigens

(e) Outline the…

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receptor which is complementary to a hormone meaning it can bind to the receptor site to trigger
a response. An example of this is an insulin receptor.

Drugs can also bind to the receptor molecules on the cell's surface. Beta blockers are used to
prevent an increase in heart rate.…

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ACTIVE TRANSPORT
Moves a substance against their concentration gradient by using ATP.

Some carrier proteins can act as pumps...
They have a complementary shape to the shape of a specific molecule or ion
They carry the molecule ONE WAY across the plasma membrane
They use metabolic energy in the form…

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Water potential: the tendency of water molecules to diffuse from a region of high water potential
to a region of low water potential.

When there are substances dissolved in the water, the water potential becomes more
negative, lowering it as there are not as many "free" water molecules.





(j) recognise…

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(a) state that mitosis occupies only a small percentage of the cell cycle and that the remaining
percentage includes the copying and checking of genetic information

Mitosis only occupies a short part of the cell cycle. The remaining part is taken up by
INTERPHASE.
During interphase, the genetic material is…

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