IGCSE Biology Theory Unit 2 Full Class Notes

BIOLOGY THEORY

LIGHT AND ELECTRON MICROSCOPE

1. Light microscope can show (natural colour)
a. Cell membrane
b. Cytoplasm
c. Nucleus
2. Electron microscope can show (black and white)
a. everything

PARTS OF A CELL

Cell Membrane




 Made of:
1. phospholipids
2. proteins
3. carbohydrates
4. cholesterol
 selectively permeable
o freely permeable to lipids
o partially permeable to water and water-soluble substances
o waste products can leave the cell
 acts as boundary
 gives shape to cell
 encloses cytoplasm

Cytoplasm

 Jelly-like substance (matrix)
 Site of chemical reactions
 Supports to embed organelles

Nucleus

,  Double membraned
 Contains chromosomes w genetic info
 Nuclear pores = gaps in membrane that allow exchange of substances
 Controls:
o Chemical reactions
o Cell division
o Protein synthesis
o Pattern of inheritance

Protoplasm = Cytoplasm + Nucleus

Mitochondria




 Double membraned
 Inner membrane folded to form cristae
 Sight of aerobic respiration
 Energy released from food stored as ATP

Endoplasmic Reticulum

RER

 Ribosomes attached to outer membrane
 Transports proteins produced by ribosomes

SER

 No ribosomes
 Involved in lipid synthesis
 Transports lipids and carbs

Cell Wall

,  Outer layer of plant cell
 Composed of cellulose – rigid molecule
 Gives shape and structural support
 Freely permeable to water and water-soluble substances
 Protects against damage

Vacuole

 Located usually in center of cell
 Surrounded by elastic membrane called tonoplast – single membrane
 Contains cell sap, is a permanent feature of cell
 Stores waste material
 Maintains turgidity of cell

Chloroplast




 Site of photosynthesis
 Contains chlorophyll to absorb light energy to convert to chemical energy
 Double membraned
 Stroma has enzymes for photosynthesis

SPECIALISED CELLS

Red Blood Cell




1. No organelles or nucleus – for more space to absorb oxygen
2. Biconcave disc shape – large surface area and flexible to push through narrow blood vessels
3. Contains hemoglobin – transport oxygen

, Ciliated Epithelial Cell




1. Cilia, fine hair like structures – beats in rhythm to move mucus along w bacteria and dust
particles
2. Goblet cells – secrete mucus

Nerve Cell




1. Very long – to carry electrical impulses to and from brain and spinal cord
2. Axon covered in myelin sheath – protect from electric impulses

Sperm Cell




1. Head contains lots of enzymes – help penetrate egg cell membrane
2. Body contains many mitochondria – helps give more energy
3. Long tail – helps cell swim to egg cell

Muscle Cell