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Cells, Exchange and Transport

Cell Structure
Light microscope
Use glass lenses to refract light rays to create an image
Most biological specimens are colourless, so we stain them to they are easier to see
- Different cell parts absorb more stain than others so we can distinguish them…

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Cells, Exchange and Transport
Golgi Structure Stack of curved membranes enclosing flattened sacs, sacs constantly change
when Lysosomes fuse to it
Apparatus Function To process and package proteins
Lysosomes Structure Bags of digestive enzymes
Function To fuse with another vesicles containing something that needs to be broken
down, destroy unwanted…

Page 3

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Cells, Exchange and Transport

Cell Membranes
Roles of membranes
Within cells On cell surface
Separates cell components from cytoplasm Cell recognition and signalling
Holds components of some metabolic Regulates transport in and out of cells
pathways in place Separates cell components from the outside

Structure of cell membranes

Page 4

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Cells, Exchange and Transport
Protein and glycoprotein
Transport substances
- Channel proteins: for large molecules, very hydrophilic molecules
- Carrier proteins: for ions, active movement
Recognition and communication
- Receptor sites bind with hormones (and drugs)
- Glycoproteins and glycolipids allow self-recognition to the immune system
- Glycoproteins can bind…

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Cells, Exchange and Transport
Insulin receptor
Insulin released from beta-cells in islets of langerhans in the pancreas
Insulin attaches to receptors in many cells
Triggers more glucose channels to be present in membrane
Medicinal drugs
Drugs developed to have complimentary shape to a receptor
Some drugs block receptors e.g. beta…

Page 6

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Cells, Exchange and Transport
Endocytosis: bulk transport of materials into cell
Exocytosis: bulk transport of materials out of cell
- Possible as membranes can fuse, separate and pinch
off, in form of vesicles
- Requires ATP

e.g. Hormones ­ insulin is produces in large quantities in the
pancreatic cells,…

Page 7

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Cells, Exchange and Transport

Cell Division and Cellular Organisation
Cell Cycle
95% of cell cycle in embryo
Normal cell functions still carried out
G1 phase:
Cellular contents (not DNA) duplicated
S phase:
DNA duplicated
Each chromosome now consists of two sister chromatids attached by a centromere
G2 phase:…

Page 8

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Cells, Exchange and Transport
Cytoplasm divides
Cell membrane forms a
cleavage furrow and a
contractile ring pulls
membrane together
Plant cells: cell plate

Significance of mitosis
In humans
Used for growth of an embryo and human being
Needed for replacement of damaged or dead cells
e.g. lining of…

Page 9

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Cells, Exchange and Transport
Stem cells
Embryonic stem cells
After the fusion of the gametes, a zygote is formed, which divides into a tiny ball of cells called a
The blastocyst is made up of stem cells
Stem cell: An undifferentiated cell with no hayflick limit that can…

Page 10

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Cells, Exchange and Transport
Specialised plant cells
Xylem vessels and phloem sieve tubes
Most plant cells are able to differentiate into other kinds of cells throughout their lives
In the meristem, cells are able to divide at a high rate
- Found just behind the root tip, cells are in…




This is an amazingly good resource! So much detail, great!

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