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Biology Revision Notes - Unit 1, Module 1

1.1) Microscopes

Magnification: the degree to which the size of an image is larger than the object itself. It is the
image size divided by the actual size of the object.

Resolution: the degree to which it is possible to distinguish between…

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Division of labour: refers to each organelle within the cell having a specific role which contributes to
the cell's survival.

The cytoskeleton: regards the network of protein fibres found within cells that gives structure and
shape to the cell, and also moves organelles around inside.

Plant Cell: Animal Cell:


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1.3) Cell Membranes

The phospholipid bilayer: is the basic structural component of plasma membranes (cell surface
membranes). It consists of two layers of phospholipid molecules. Proteins are embedded in this

Roles of membranes:
separating cell contents from the outside environment
separating cell components from cytoplasm
cell recognition and signalling…

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The fluid mosaic model: refers to the model of cell membrane structure. The lipid molecules give
fluidity and proteins in the membrane give it a mosaic (patchwork) appearance.

Membrane components and their roles:
- gives the membrane mechanical stability
- fits between fatty acid tails to help make the…

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are often protein molecules or modified protein molecules
have specific shapes so only messenger molecules with a complementary shape can
bind to them
the cell with the receptor for the messenger molecule is known as a target cell

1.4) Transport Across Cell Membranes

Diffusion: the movement of molecules from a…

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How carrier proteins in active transport differ from the proteins used in facilitated diffusion:
they carry specific molecules one way across the membrane
in carrying molecules across the membrane, they use metabolic energy in the form of
they carry molecules against the concentration gradient
they can carry molecules at…

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Asexual Reproduction:
some organisms reproduce asexually using mitosis
this produce two new genetically identical organisms
they are genetically identical to the original parent organism
yeast cells reproduce asexually through a process called budding

is a type of cell division that occurs in the reproductive organs to produce gametes

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- contain many lysosomes in their cytoplasm, containing digestive enzymes to
break down the engulfed particles
- have no nucleus so they can contain more haemoglobin
- the biconcave disc shape provides a larger surface area for gas exchange

1.7) Organising the organism

Tissues: a collection of cells that…




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