From ZuluNotes - Free Leaving Cert Notes
Structure:The cell membrane is the very thin (7nm) outer layer of the cell. It's a thin unit membrane, the structure is layed out in the fluid-mosaic model. Functions include;
- Provides shape and support for the cell
- Acts as a selectively permeable barrier
- Regulates the internal environment for optimal metabolism
The cell wall is a non-living structure found only in plants. It is made of cellulose and is fully permeable. It's Primary Function is strength and support.
- Function:Cements cells together
- Contains Pectin
The nucleus is the control centre of the cell
It is a sac like structure surrounded by nuclear membrane which contains pores to allow material exchange with the cytoplasm
- Maintains Cell activities
- Cell division (mitosis and meiosis)
- Contains genetic information in the form of DNA
Makes RNA (ribonucleic acid)
The watery gel in which the organelles are suspended, such as those listed below;
- The powerhouse of the cell
- A large number of mitochondria are found in cells with high energy demand, such as the liver and muscle in animals and the shoot and root tips in plants
- Function: Protein Synthesis
- Ribosomes are made of RNA, and are present in large numbers in cells involved in protein synthesis, eg. the liver and pancreas
This is the transport system for the cell. There are two types, the rough endoplasmic eticulum and smooth endoplasmic reticulum, The rough endoplasmic reticulum has ribosomes attached to it, whereas the smooth one does not.
- Functions of the rough endoplasmic reticulum:
Plastids are found only in plant cells only. They are divided into 3 types:
- Luceoplasts - Used in starch storage
- Chromoplasts - Provide pigment colouring
- Chloroplasts - Used in photosynthesis
The structure of the chloroplast is often examined in the leaving cert and it's important to know how to label it.
Lysosomes are saclike structures bound by a single membrane. They contain powerfull enzymes capable of digesting other organelles. Their functions include;
- The breakdown of complex chemicals, eg. Protein and Nucleci acid
- Distruction of worn out ogranelles, eg. Mitochondria
- Helps disintegration of dead cells, eg. In a tadpole's growth to a frog
These are mostly in animal cells, but also in some plant cells. They are absent in the flowering plant It lies close to the nucleus. There are two in each animal cell. Their main function is the formation of spindle fibres in cell division
The centrosome is the area of the cytoplasm containing the centrioles, i.e. close to the nucleus. It is only present only in animal cells and primitive plant cells.
This is a stack of very flattened membrane sacs called cisternae. Mainly in secretion cells, such as goblet cells. The main functions are: