Specialised Cells, Tissues, Organs and Systems

Differentiation: It is the process by which a cell becomes specialised for a specific function.

How is cell structure related to cell function?

Red blood cell

• contains haemoglobin which binds reversibly to oxygen and transportoxygen from lungs to rest of body
• circular and biconcave shape to increase surface area to volumeratio to increase rate of diffusion of oxygen in andout of cell
• Absence of nucleus which enables the cell to carry morehaemoglobin for more oxygen to be transported

Xylem vessels

• Absence of cross walls andprotoplasm so that water and mineral salts moves easily (NOTfaster!!) through the lumen
• Lignin deposited on its walls to strengthen the walls to prevent vessel fromcollapsing

Root hair cells

• Has a long and narrow protrusion to increase surface area to volume ratio for root cell to absorb water and mineralsalts at a faster rate.
• Large no. of mitochondria which allows for large amount of energy to bereleased through aerobic respiration, for activetransport of mineral salts
• Large central vacuole which allows for large amount of mineral saltsand sugar for storage in the root hair cell to allowcell sap to have lower water potential than soil solution so that water molecule can move into root hair cell byosmosis

Organ System

Cells are specialised for a particular function. A tissue is a group of cells with similar structures that work together to perform a specific function. An organ is different tissues working together to carry out a specific function. Several related organs working together to carry out a particular function form an organ system.

­Plants

The upper epidermal cells on the leaves form the covering tissues called the epidermis. Together with the palisade tissue, spongy mesophyll tissue, xylem tissue and phloem tissue, it forms an organ – leaf. Parts of a plant – leaf, stem, roots, flowers – forms an entire organ system.

Animals

The epithelial cells on the villi of the small intestine form an epithelial tissue. Together with muscular tissue, connective tissue, blood tissue etc, it forms the small intestine. Stomach, small intestine, oesophagus are organs which are parts of an organ system.

Using a named animal structure as an example, describe the relationship between cells, tissues and organs. [4]

The stomach is an organ in Man that is made up of different tissues performing the specific function of digestion. Examples of tissues in the stomach are muscle tissue, connective tissue and glandular tissue. Each tissue is a group of same cells performing a specific function. Example is the muscle cells of muscle tissue which has the ability to contract to cause the stomach to churn its contents well with the digestive juice.