Topic 3- Voice of the Genome

Cells and Organelles

Prokaryotic Cell- Before the nucleus (Bacteria)

• They do not have a nucleus
• They are very small
• And DNA lies free in the cytoplasm

They contain-

• Ribosomes
• Cytoplasm
• Cell wall
• Circular DNA
• Infolding cell membrane - respiration
• Plasmid - small circle of DNA
• Pili - Allow bacteria to stick to surfaces
• Capsule- protection
• Flagellum - Allows bacteria to stick to surfaces

Eukaryotic Cell - After the nucleus

• Nuclei, mitochondria, chloroplasts
• larger
• not all have cell walls

They contain

• Rough ER (ribosomes transported)
• Golgi apparatus (modifies proteins)
• Nucleoulus (ribosomes made)
• Pair of centrioles (transport in cell division)
• Lysosomes (breakdown of unwanted structures)
• Smooth ER ( Makes lipids)
• Mitochondria (site of aerobic respiration)

Protein Trafficking

 Nucleus

1. Transcription of DNA to mRNA

2. mRNA leaves through the nuclear envelope

Ribosome

3.Amino acids made into proteins

Rough ER

4. Proteins travel through rough ER

5. Vesciles pinched off the end of the rough ER contain the proteins

Golgi apparatus

6. Protiens transported to them

7. Proteins are modified here

8.Vesciles are pinched off from the ends containing the modified proteins

Cell surface membrane

9. vesciles fuse here releasing the protein

Cell Organisation

Cells - All cells of multicellular organisms are eukaryotic

Tissue - Is made up of many cells to perform a function (muscle tissue)

Organ - Made up of many tissues to perform a function (heart)

System - made up of many tissues to perform a large function (digestive system)

Cell Cycle

To make the vast number of cells to build individuals new cell contents must be synthesised and then one cell must divide into two.

1. Interphase

New cell organelles are synthesised and DNA replication occurs . This then means one cell contains double the amount of organelles, cytoplasm and DNA to form 2 cells. To do this individual chromosomes are unravelled allowing access to genetic material enabling new proteins to be synthesised. Cells must also produce two copies of DNA. The length differs depending on the role of the cell.

2. Mitosis

• Prophase

Chromosomes condense and two become joined at the centromere. The 2 strands are identical copies of one another. Each chromosome is visible as two strands (chromatids) Microtubles from cytoplasm form spindle. The centrioles are involved in organisation of the spindle

• Metaphase

This phase begins when the nuclear envelope has been broken down. The centromeres attach to the spindle fibres at the equator

• Anaphase

The spindle fibres contract and pull the 2 halves of each centromere towards the poles. The spindle then breaks down

• Telophase

This is the reverse of prophase. Chromosomes unravel and nuclear envelope reforms to that 2 sets of genetic material become inclosed in seperate nuclei.

3. Cytoplasmic Division

Into 2 cells.

Animals: cell surface membrane constricts around the centre by muscle contraction untill the cell is divided into two.

Plants: A new cell plate is synthesised between 2 new cells.

Practical to observe Mitosis

The root tip squash - cut the ends of the root tips from the plant. Add…