23 November 2012

#15 Cell functions

Multicelullar plants and animals contain many different types of cell. Each type of cell is design for a particular function. 

Here are examples of cells and their functions in tissues

1. Ciliated cells in respiratory tract

Features: tiny hairs called cilia which can move mucus.
Function:  waft mucus with bacteria and dust away from the lungs. 

2. Muscle cells

Features: cells merge together to form fibres that can contract
Function: cause movement 

3. Red blood cells

Features: have no nucleus, contain hemoglobin
Function: transport oxygen around the body

4. Root hair cell (plants)

Features: the hair gives a large surface area
Function: absorb water and mineral ions; anchor the plant firmly in the soil

5. Xylem cells

Features: long, thin cells arranged end-to-end to form vessels (tubes). The cells lack end wall and cell contents such as cytolplasm and nucleus. The walls become lignified (woody).
Function: conduction (transport water and mineral ions from roots to leaves)        
                  support (Lignin provides strength for the stem).

Common misconceptions

Xylem and phloem tissue are often confused. Xylem carries water and mineral salts, while Phloem transports sugars and amino acids.
In a vascular bundle in a stem, Phloem is on the outside and Xylem is on the inside

Examiner's tips
  1. You need to be able to give examples of tissues, organs and organ systems in both plants and animals. A leaf is an organ made up of a number of tissues, e.g. upper epidermis, palisade, mesophyll. 
  2. If you draw a diagram to support an exam answer, make sure you refer to its in your written answer. Annotation is more likely to help you gain extra mark. 
Example of annotation

Action of phagocyte

1 comment:

  1. Extremely helpful article, thank you! I might however note that there is a typo in section five of this page, where lignin is spelled as "ligmin."