All Notes Needed For OCR As Biology (F211 exam)

Cells

Magnification – the degree to which the size of an image is larger than the object itself.

Resolution - the degree to which it is possible to distinguish between two objects that are close together. The higher the resolution, the greater the detail that can be seen.

Light Microscope 

• x1500 magnification
• 200nm resolution

Scanning Electron

• x100 000 magnification
• 0.1nm resolution

Transmission Electron

• x500 000 magnification
• 0.1nm resolution

Staining- stains bind to specific structures increasing contrast and making different structures more visible.

Magnification = Image Size / Actual Size

Organelles

Nucleus - controls activity of the cell.

Nucleolus – RNA synthesis.

Nuclear Envelope – controls movement of mRNA out of the nucleus.

Rough ER – transports proteins.

Smooth ER – makes and transports lipids.

Golgi Apparatus – modifies and packages proteins.

Ribosomes – protein synthesis.

Mitochondria – aerobic respiration.

Lysosomes – contain powerful digestive enzymes.

Chloroplasts – photosynthesis.

Plasma Membrane – controls entry and exit of molecules from the cell.

Centrioles – form the spindle (only in animal cells and some protoctists).

Flagella – spin using ATP to allow movement of bacterial cells.

Cilia – waft rhythmically, e.g. to move mucus form the lungs.

Protein Synthesis

Nucleus – hold the DNA for the protein.

Nucleolus – make an mRNA copy of the gene

Nuclear Envelope – mRNA moves out of the nucleus through one of the pores.

Rough ER – mRNA attaches to a ribosome on the rough ER.

Ribosomes – 'read' the code on the gene and uses the code to make the protein.

Golgi Apparatus – processes and packages protein into vesicles, these pinch off and move through the cytoplasm.

Cell Membrane – vesicle moves along the cytoskeleton and attaches to the cell membrane, releasing the protein outside the cell.

Cytoskeleton

Actin Filaments – able to move against each other.

Microtubules – made from the protein tubulin.

• used to move a micro-organism through a liquid or to waft a liquid past a cell.

Microtubule Motors – move organelles and other cell content along the fibres. e.g. vesicles.

- use ATP to drive the movement.

Eukaryotic Cells

• Plasma membrane
• DNA wrapped around Histone Proteins
• Larger Ribosomes
• Mitochondria

Prokaryotic Cells

• No plasma membrane
• Naked DNA
• Smaller Ribosomes
• Mesosomes

Animal Cells

• Nucleus
• Centrioles
• Cell Membrane
• Lysosomes

Plant Cells

• Nucleus
• Chloroplasts
• Cell membrane and cell wall

Cell Membranes

Within Cells – control exchange of materials between organelles and cytoplasm.

• provide separate areas for reactions (aerobic respiration in mitochondria).

• isolate enzyme (lysosomes).

• provide an internal transport system.

• provide surfaces for reactions (chloroplasts & mitochondria).

Outside Cells – partially permeable barrier.

• controls exchange of materials between the cell and its environment.

• communicate by cell signalling.

• receptor bind to specific hormones.

Phospholipids – forms the basic structure, acting as a barrier to lipid and protein molecules.

Cholesterol – gives the membrane mechanical stability.

Glycolipids – cell recognition and cell adhesion.

Proteins – act as receptors for cell signalling; transport specific molecules.

Glycoproteins –…