IGCSE Biology 0610

2.1 Cell structure

A plant cell
An animal cell

Comparing Plant and Animal Cell Structures

FeaturePlant CellAnimal Cell
Cell wallPresentAbsent
Cell membranePresent and surrounded by cell wallPresent
NucleusPresentPresent
CytoplasmPresentPresent
ChloroplastsPresent in some cellsAbsent
RibosomesPresentPresent
MitochondriaPresentPresent
VacuolesLarge permanent vacuole in cytoplasm containing cell sapSmall vacuoles in cytoplasm that do not contain cell sap
A bacterial cell

Bacterial Cell Structure

Cell wallPresent
Cell membranePresent
CytoplasmPresent
RibosomesSmaller than those in eukaryotic cells, found in cytoplasm and NOT attached to rough endoplasmic reticulum
Circular DNAFound in cytoplasm
PlasmidsSometimes present, they are small rings of DNA that contain extra genes

Functions of Cell Structures

Cell wall-Stops cells from bursting when filled with water
-Gives shape to cells
-Allows water and dissolved substances to pass through freely
-Fully permeable
Cell membrane-Forms a barrier between cell and surroundings
-Keeps cell contents inside
-Allows simple substances to pass through
-Controls movement of other substances into or out of cell
-Partially permeable
Nucleus-Controls all activities in the cells
-Controls how cells develop
Cytoplasm-Place where many metabolic reactions occur
Chloroplasts-Photosynthesis
-Store starch
Ribosomes-Synthesise proteins
Mitochondria-Sites of aerobic respiration
Vacuoles-Full of water to maintain shape and firmness of cell
-Stores salts and sugars
Circular DNA-Contains essential DNA
Plasmids-Contains non-essential DNA
  • New cells are produced by division of existing ones

Special Cells

Specialised cells have different functions:

  • Ciliated cells -> Movement of mucus in the trachea and bronchi
  • Root hair cells -> Absorption
  • Palisade mesophyll cells – > Photosynthesis
  • Neurons -> Conduction of electrical impulses
  • Red blood cells -> Transport of oxygen
  • Sperm and egg cells (gametes) -> Reproduction

Levels of Organisation

Cell – Small building blocks that make up organisms

Tissue – A group of similar cells working together

Organ – A group of different tissues worting together to perform specific functions

Organ system – Different organs that work together

Organism – All the different organ systems

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