Unit 1

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

Active Site

• The substrate is the molecule changed in the chemical reactions
• …