2.6.8 The Organisation Of Cells

Question 1

The Organisation of Cells

Answer 1

In complex multicellular organisms, eukaryotic cells become specialised for specific functions
For example:
- epithelial cells in the small intestine are specialised to absorb food efficiently
- red blood cells are specialised to transport oxygen
In multicellular organisms, specialised cells of the same type group together to from tissues
A tissue is a group of cells that work together to perform a particular function
For example:
- epithelial cells group together to form epithelial tissue (the function of which, in the small intestine, is to absorb food)
- muscle cells group together to form muscle tissue (the function of which is to contract in order to move parts of the body)
Different tissues work together to from organs
For example:
- the heart is made up of many different tissues (including cardiac muscles tissue, blood vessel tissues and connective tissue, as well as many others)
- different organs work together to form organ systems

Question 2

Xylem Vessel Cells

Answer 2

Function: - transport tissue for water and dissolved ions
Adaptions: - no top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
- cells are essentially dead, without organelles or cytoplasm, to allow free movement of water
- outer walls are thickened with lignin, strengthening the tubes, which helps support then plant

Question 3

Phloem Vessel Cells

Answer 3

Function: - transport of dissolved sugars and amino acids
Adaptions: - made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells
- cells are joined end-to end and contain holes in the cell walls (sieve plates) forming tubes which allows sugars and amino acids to flow easily (by translocation)
- cells also have very few subcellular structure to aid the flow of materials

Question 4

Muscle Cells

Answer 4

Function: - contraction for movement
Adaptions: - there are three different types of muscle in animals: skeletal, smooth, cardiac (heart)
- all muscle cells have layers of protein filaments in them, these layers can slide over each other causing muscle contraction
- muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
- skeletal muscle cells fused together during development to form multinucleated cells that contract in unison

Question 5

Ciliated Epithelium

Question 6

Squamous Epithelium

Question 7

Cartilage

Answer 7

Function: - to provide support
- cartilage isn a strong and flexible tissue found in various places around the body
- one place is in rings along the trachea, called Tracheal rings
- these rings help to support the trachea and ensure it stays open while allowing it to move and flex while we breathe

Question 8

Specialised cells organised into tissues, organs and organ systems

Answer 8

Epithelial Cell - epithelial tissue (made up of epithelial cells) - stomach (made up of epithelial tissue, muscular tissue and glandular tissue) - digestive system (made up of all the organs involved in the digestion and absorption of food, including the stomach, small intestine, large intestine and liver, as well as many others)
Muscle Cell - muscle tissue (made up of muscle cells) - bladder (made up of muscle tissue, epithelial tissue, connective tissue and fatty tissue) - urinary system (made up of the kidneys, ureters, bladder and urethra)
Neurones (nerve cells) - nervous (neural) tissue (made up of neurones) - brain (made up of gray matter tissue, white matter tissue and the tissue that make up the blood vessels in the brain) - central nervous system (made up of the brain and the spinal cord)
Rod cells and cone cells - retina (made up of rods and cones) - eye (made up of many tissues, including the retina, cornea, sclera and choroid) - visual system (made up of the eyes, optic nerves and the visual cortex in the brain)