Unit 1

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Cell Structures

Eukaryotic - complex; incl. plant and animal cells

Prokaryotes -  simpler; incl. bacteria cells

Animal Cell:

  • Nucleus - contains genetic material that controls activities of the cell. Arranged into chromosomes
  • Cell membrane - holds cell together and controls what goes in and out
  • Mitochondria - aerobic respiration takes place; transfers energy that the cell needs to work
  • Ribosomes - involved in the translation of genetic material in the synthesis of proteins
  • Cytoplasm - where most of the chemical reactions take place; contains enzymes that control these chemical reactions

Plant Cell: (same as animal cell with a few additions)

  • Cell wall - made of cellulose; supports the cell & strengthens it
  • Large permenant vacuole - contains cell sap and maintains internal pressure to support cell
  • Chloroplasts - where photosynthesis occurs; contain chlorophyll

Bacteria Cell:

  • Chromosonal DNA - one long circular chromosome; controls cell's activities and replication. Floats free in the cytoplasm
  • Plasmid DNA - small loops of extra DNA that aren't part of the chromosome. Contains genes for things like drug resistance & can be passed btwn bacteria
  • Flagellum - long, hair like structure that rotates to make the bacteria move

(also contains ribosomes, cell wall and cell membranes)

Specialised Cells

Egg Cell: 

  • Contains nutrients in the cytoplasm to feed the embryo
  • Haploid nucleus
  • After fertilisation, it's membrane changes structure to stop any more sperm getting in = offspring end up with the right amt. of DNA 

Sperm Cell:

  • Long tail to swim to egg
  • Lots of mitochondria in midpiece to provide energy to help it to swim
  • Acrosome in head which stores enzymes which are needed to digest their way through the membrane of the egg cell
  • Haploid nucleus


In sexual repro. the nucleus of egg fuses with sperm's nucleus = fertilises egg = embryo. Important that both haploid, because when they fuse the embryo contains the right amount of chromosomes (diploid)


Ciliated Epithelial Cells:

  • Epithelial cells line the surfaces of organs
  • Some have cilia on the top of the cell
  • Function of the ciliated epithelial cells is to move subtances; the cilia beat to move substances in one direction along the surface of the tissue

e.g cilia in lungs - move mucus up to throat to be swallowed and doesn't reach the lungs.



Microscopes use lenses to magnify images. They also increase the resolution of an image.

  • Light microscopes invented in 1590s - work by passing light through the specimen
  • Electron microscopes invented in 1930s - use electrons rather than light; much higher magnification and resolution = more detail


total magnification = eyepiece lens magnification x objective lens magnification 


magnification = image / real

Enzymes are biological catalysts.

  • They control chemical reactions
  • Being a biological catalyst means that they speed up chemical reactions, without the need of raising temperatures which can be unhelpful because can make other reactions speed up too

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  • The substrate is the molecule changed in the chemical reactions


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