Levels of organization
Organisms are made from organizations of smaller structures. You need to know the following hierarchy of structures.
Organelles – intracellular structures that carry out specific functions within a cell
Cells – the basic structural and functional unit from which all biological organisms are made
Tissues – a group of specialized cells, which are adapted to carry out a specific function.
Organs – a collection of two or more tissues, which carries out a specific function or functions
Organ Systems – a group of two or more organs
Differences between plant and animal cells
You need to know the differences between plant and animal cells, the functions of the organelles and be able to recognize them in a microscope picture or drawing in I/GCSE Biology.
Organelle | Animal Cell | Plant Cell |
Chloroplast | X | ✔️ |
Cell Wall | X | ✔️ |
Sap Vacuole | X | ✔️
|
Chlorophyll | X | Found in chloroplast |
Size | Roughly 50чm long | Roughly 150чm long |
Shape | No fixed shape | Rectangular |
The cells are measured in чm (micrometers). One micrometer is 1/1000th of a millimetre.
Functions of the Organelles
Cytoplasm – site of chemical reactions in the cell
Cell Membrane – controls what enters / leaves the cell (selectively permeable)
Nucleus – contains nucleic acids, which code for the synthesis of specific proteins. These proteins control all activity in the cell
Mitochondrion – site of respiration
Chloroplast – site of photosynthesis
Cell Wall – made from cellulose. Strengthens the cell and allows it to be turgid
Sap Vacuole – contains the cell sap. Acts as a store of water, or of sugars or, in some cases, of waste products the cell needs to excrete.
That's the end of the topic!
Drafted by Joey (Biology)