CELL THEORY  All organisms are composed of cells  The cell is the smallest unit of living matter  Cells arise from pre-existing cells  Information is passed on to cells in the form of DNA

PROKARYOTIC v EUKARYOTIC Prokaryotic Cells (Bacteria) Eukaryotic Cells (Plants, Animals, Fungi, Protists) Average diameter 0.5 – 5µm (10 times smaller in diameter) (100 – 1000 times smaller in volume) DNA is circular and lies free in the cytoplasm (circular chromosome in the nucleoid) (rings of accessory DNA called plasmids) Smaller ribosomes NO Endoplasmic Reticulum (ER) NO MEMBRANE BOUND ORGANELLES Cell wall present (made of cross-linked peptidoglycan) No true nucleus present Other structures may include: flagellum, capsule, mesosome, pili) Often up to 40 µm in diameter (size can vary) (10 times larger in diameter) (100 – 1000 times larger in volume) DNA is not circular and is contained in the nucleus (chromosomes) Larger ribosomes Endoplasmic Reticulum present (may contain ribosomes) CONTAINS MEMBRANE BOUND ORGANELLES  single membrane eg: lysosomes, golgi body, vacuoles  double membrane eg: nucleus, mitochondria  no membrane eg: ribosomes May have cell walls eg. Plants NUCLEUS present with nucleus containing DNA The Importance of compartmental organisation o Allows cells to carry out a variety of different functions at the same time o The membranes of the organelles have important roles themselves and often contain many of the necessary proteins

PLANT CELLS v ANIMAL CELLS Plant Cells Animal Cells NO CELL WALL NO CHLOROPLASTS MAY CONTAIN SMALLER TEMPORARY VACUOLES Mitochondria Cell Membrane Nucleus + Nucleolus Golgi Body ER Ribosomes Lysosomes Cytoplasm Centrioles CELLULOSE CELL WALL CHLOROPLASTS (Containing chlorophyll) LARGE PERMANENT VACUOLE Mitochondria Cell membrane Nucleus + Nucleolus Golgi Body ER Ribosomes Lysosomes Cytoplasm Centrioles

PLANT CELL

ANIMAL CELL

ORGANELLES CELL MEMBRANE LOCATION: - surrounding the cell and below the cell wall in plants FUNCTION: - gives the cell shape and Protection from the exterior world. Regulates the movements of substances into and out of the cell. Has fluid type movement due to the PHOSPHOLIPID BILAYER and contains various proteins PLANT CELLS:- Yes ANIMAL CELLS:- Yes LIGHT MICROSCOPE:- Yes

RIBOSOMES (no membranes) LOCATION:- Free in the cytoplasm or attached to rough ER FUNCTION:- Comprise of a complex ribosomal RNA and protein and are the site of polypeptide/protein synthesis PLANT CELLS:- Yes ANIMAL CELLS:- Yes LIGHT MICROSCOPE:- No

Mitochondria LOCATION:- In the cytoplasm enclosed by a double membrane FUNCTION:- Responsible for energy production via ATP. Site of Kreb’s Cycle, Electron Transport Chain. Contain mitochondrial DNA. Matrix and folded cristae are sites for cellular respiration PLANT CELLS:- Yes ANIMAL CELLS:- Yes LIGHT MICROSCOPE:- No (only very high powered light microscope)

Golgi Apparatus (single membrane) LOCATION:- In the cytoplasm, associated with the smooth ER, often close to the nucleus FUNCTION:- Flattened sacs (cisternae) are constantly being formed from one end by vesicles which bud off from the smooth ER and broken down at the other end to form Golgi vesicles. Collects, processes and sorts molecules (esp. Proteins and lipids) ready for transport in the Golgi vesicles. Used to make lysosomes. PLANT CELLS:- Yes ANIMAL CELLS:- Yes LIGHT MICROSCOPE:- No (only very high powered light microscope)

ROUGH ENDOPLASMIC RETICULUM LOCATION:- Throughout the whole cytoplasm often closely associated with the nuclear envelope. FUNCTION:- Rough endoplasmic reticulum houses ribosomes. Membranes form a system of flattened sacs (cisternae) which can go on to form the golgi apparatus. The rough ER transports proteins formed by ribosomes throughout the cell. PLANT CELLS:- Yes ANIMAL CELLS:- Yes LIGHT MICROSCOPE:- No

CHLOROPLASTS (double membrane) LOCATION:-Within the cytoplasm, particularly in the cells at the surface of leaves in plants FUNCTION:- The site of photosynthesis. The light-dependant stage taking place in the thylakoids and involves the absorbtion of blue and red light wavelengths that eventually energise the electron transport system. The light- independant stage occurs in the stroma and produces sugar molecules via the Calvin-Benson cycle. Contains its own DNA. PLANT CELLS:- YES ANIMAL CELLS:- NO LIGHT MICROSCOPE:- YES

CENTRIOLES LOCATION:- Found in the cytoplasm, usually near the nucleus FUNCTION:- Arranged at right angles to each other and comprising of microtubules. The centrioles help organise chromosomes via poles during cell replication. They ARE NOT found in most higher plants. PLANT CELLS:- Variable (not in higher plants) ANIMAL CELLS:- YES LIGHT MICROSCOPE:- NO

CILIA & FLAGELLA LOCATION:- Anchored in the cell membrane and extending outside of the cell FUNCTION:- Flagella are often limited to 1 per cell and cilia may be many. They are structures used in locomotion, particularly in water PLANT CELLS:- NO ANIMAL CELLS:- YES LIGHT MICROSCOPE:- Occasionally (depending on the preparation)

CELLULOSE CELL WALL LOCATION:- Surrounds the plant cell and sits outside the plasma membrane FUNCTION:- Provides rigidity and strength, supports the cell against changes in turgor (water pressure) PLANT CELLS:- YES ANIMAL CELLS:- NO LIGHT MICROSCOPE:- YES

LYSOSOMES (single membrane) LOCATION:- Throughout the cytoplasm FUNCTION:- Contain digestive enzymes which aid in the digestion of foreign matter (eg. Bacteria) as well as the cells own organic material. The digestive enzymes function best at pH 5 (acidic) and therefore cause minor damage if small amounts are leaked. Large amounts may cause cell death via autodigestion PLANT CELLS:- YES (variably, vacuoles have lysosomal function) ANIMAL CELLS:- YES LIGHT MICROSCOPE:- NO

VACUOLE (single membrane) LOCATION:- Free in the cytoplasm FUNCTION:- In plants they are large and permanent and involved in storage and support. In animal cells they are smaller and can be formed via phagocytosis (FOOD VACUOLES) to be then digested by lysosomes. Also used for storage of water, wastes and soluble pigments PLANT CELLS:- YES (large & permanent) ANIMAL CELLS:- YES (smaller & often numerous) LIGHT MICROSCOPE:- YES (plant cell) NO (animal cell)

NUCLEUS (double membrane) LOCATION:- within the cytoplasm, position variable FUNCTION:- The control centre of the cell containing the nuclear material (DNA). Surrounded by a porous envelope, allowing RNA into and out of the nucleus. PLANT CELLS:- YES ANIMAL CELLS:- YES LIGHT MICROSCOPE:- YES