Cells structure and organisation

Eukaryotes
1. Plants and animals
  1. Nucleus
    1. 10-20um.
    2. Controls cells activities. Contains DNA/chromosomes.
    3. Nuclear envelope - continues onto ER. Double membrane. Has nuclear pores.
    4. Nucleoplasm and chromatin
    5. Nucleolus makes RNA
  2. Mitochondria
    1. 1-10um.
    2. Double membran edd folded into cristae.inntmembrane space. Inner membrane.
    3. Matrix in the middle with chemical compounds and ribosomes and DNA.
    4. Site of aerobic respiration. Produces ATP. Lots in active cells.
      1. Liver, sperm, muscle.
  3. Endoplasmic reticulum
    1. Parallel double membranes, folded into cristernae.
    2. conected to nuclear membane and maybe golgi body
    3. Rough ER transports the proteins that are made in the ribosomes surrounding.
    4. Smooth ER is involved in synthesis and transport of lipids
  4. Ribosomes
    1. large and a small subunits. They come together around mRNA which fits into the mRNA grove
    2. Ribosomes are important for protein synthesis.
    3. they are made in the nucleus from rRNA and protein.
  5. Golgi body
    1. stack of flattened membranous sacs.
    2. functions: modification and packaging of proteins, formation of glycoproteins, lysosomes, producing sectetorary enzymes.
    3. 1-vesicles containing proteins from RER fuse at one end.
    4. 2-protein modified
    5. 3-modified protein is budded of at other end
    6. 4-vesicle containing protein travles to plasma membrane where the protein is released by exocytosis
2. Just animals
  1. lysosomes
    1. vesicles containing digestive enzymes.
    2. They can be used to break down worn out organelles and material from phagocytosis
    3. 1-material taken into cell by endocytosis and trapped in a vacuole
    4. 2-lysosomes fuse with vacuole and release digestive enzymes
    5. 3-enzymes break down material
  2. centrioles
    1. form spindle fibres during cell division
3. Just plants
  1. chloroplasts
    1. double plasma membrane.
    2. where photosynthesis occurs. sugars/organic compounds are formed from co2 + water and sunlight
    3. the stroma is fluid-filed and contains ribosomes, lipids, circular DNA, and other structures such as starch.
    4. within the stroma are many flattened sacs called thylakoids. A stack of thylakoids is calleda granum. each consits of 2-100 thylakoids
    5. photosynthetic pigments such as chlorophyll are found within the thylakoids.
    6. a large surface area is produced
  2. cellulose wall-keeps cell ridged and prevents bursting. adds mechanical strength
  3. plasmodesmata - pores in cell wall between cells. allows cytoplasm connect and allow exchange of material
  4. large permanent vacuole - contains cell sap. acts as storage of sugars etc and water.
    1. surrounded by tonoplast
4. They are internally divided by membranes
  1. Potentially harmful chemicals and enzymes can be isolated to stop them damaging cell structures
  2. Provide a surface for enzymes to attach to for rections
  3. Act as a transport system
Prokaryotes
1. no membrane bound organelles
2. no enclosed nucleus - DNA free in cytoplasm
3. smaller than eukaryotes (1-10um rather than 10-100um)
4. E.g. bacteria
5. Features
  1. capsule/slime layer - outer layer
  2. murein cell wall (not cellulose) - stops cell from bursting
  3. DNA - free in cytoplasm in an area known as a nucleoid. It is found in a single circular chromosome.
    1. prokaryotes can also have small pieces DNA called plasmids
  4. mesosome - an infolding of the prokaryotes' plasma membrane. it increases the surface area for respiration and other chemical reactions to occur.
  5. ribosomes - smaller than eukaryotes'
  6. flagellum - sometimes they have one, it allows them to move
viruses
1. features
  1. no cytoplasm
  2. nucleic acid (RNA or DNA)
  3. protein layer
  4. no organelles
  5. no chromosomes
2. not alive
3. when they invade a cell they take over the cells metamolism and multiply within the hosts cell.
level of organisation
1. multicellular organisms need specialised cells, forming tissues and organs, to carry out particular functions.
  1. change shape - nerve cells become long and thin
  2. number of a particular organelle - more chloroplasts or mitrochondrion
  3. the contents-e.g. haemoglobin
2. not all cells specialised, some remain unspecialised.
3. tissues
  1. cells that differentiate in the same way can group together to form tissues
  2. a tissue consists of a collection of specialised cells of the same type, working together to carry out a particular function.
  3. epithelial tissue
    1. cuboidal and ciliated epithelial tissue
    2. lines spaces such as digestive system and respiratory system.
  4. muscle
    1. striated and smooth
    2. contracts and relaxes to move parts of animals
  5. connective tissue
    1. colagen
    2. structural tissue in animals
4. organs - an organ is a part of the body which forms a structural or frunctional unit and is made up of more than one tissue
  1. heart, eye, lungs
5. organ system - this is a collection of organs which work together to perform a particular function
  1. digestive system
6. organism - all systems in the body work together to make an organism

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Cells structure and organisation

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