2.1.6 h-i - specialised cells

Outline the levels of organisation of a multicellular organism.

Organelle

Cell

Tissue

Organ

Organ system

Organism

Define the term ‘specialised’.

Having a specific structure to suit a specific function

Define the term ‘differentiated’.

The process of a cell become differentiated involves the selective expression of genes in a cells genome

Define the term ‘cell’.

the basic unit of life, it consists of cellular contents surrounded by a plasma membrane

Define the term ‘tissue’.

a collection of differentiated cells that work together to perform a specialised function or functions

Define the term ‘organ’.

a collection of tissues that work together to perform a particular function in an organism

Define the term ‘organ system’.

a number of organs working together together to carry out major function in the body

Why do multicellular organisms have specialised cells.

cells do not have to compromise as they divide the labour and can be very efficient at a single job rather than stretched across many roles

Draw, label and annotate a diagram to show how erthrocytes are specialised for their function.

Transport oxygen around the body.

• flattened biconcave shape increases SA:V ration, optimising diffusion of oxygen into cell

• no nucleus or many other organelles, increasing space for haemoglobin

• flexible so can squeeze through narrow capilaries

Draw, label and annotate a diagram to show how neutrophils are specialised for their function.

phagocytes

• multi-lobed nucleus to squeeze through small gaps and get to site of infection

• granular cytoplasm containing many lysosome containing enzymes to attack pathogens and hydrolyse the pathogen’s molecules

Draw, label and annotate a diagram to show how sperm cells are specialised for their function.

• a tail/ flagellum for movement

• many mitochondria to supply energy needed

• acrosome on the head of the cell contains digestive enzymes which are released to digest the protective layers around the ovum

• contain a haploid nucleus in order to restore the diploid number of chromosomes at fertilisation

Draw, label and annotate a diagram to show how palisade cells are specialised for their function.

• contains chloroplasts to absorb large amounts of light for photosynthesis

• rectangular boxed shape so that they can be closely packed to form a continuous layer

• long cells so more opportunity for light to hit a chloroplast

• thin cell walls increasing rate of diffusion of Co2 for photosynthesis

• large vacuole to maintain turgor pressure

• chloroplasts can move within cytoplasm to absorb more light

Draw, label and annotate a diagram to show how root hair cells are specialised for their function.

• long extensions increase the surface area of the cell

• maximises the uptake of water and minerals from the soil

Draw, label and annotate a diagram to show how guard cells are specialised for their function.

• pairs on surface of leaves from small openings called stomata

• openings are necessary for Co2 to enter plants for photosynthesis

• stoma closes to prevent further water loss from the plant when cells lose water and become less turgid

• cell wall on guard cells are thicker on one side so the cell does not change shape symmetrically as its volume changes

State the 4 main categories of tissues in animals.

• epithelial tissue

• connective tissue

• muscle tissue

• nervous tissue

Draw, label and annotate a diagram to show how squamous epithelium are specialised for their function.

• very thin due to flat cells that make it up, one cell thick

Present when rapid diffusion across a surface is essential, e.g. forms the lining of the lungs and allows rapid diffusion of oxygen into the blood

Draw, label and annotate a diagram to show how ciliated epithelium are specialised for their function.

• made of cells with hair like structures called cilia on one surface that move in a rhythmic manner

• lines the trachea, causing mucus to be swept away from the lungs

• goblet cells are also present, releasing mucus to trap any unwanted particles present in the air, this prevents particles which may be bacteria from reaching the alveoli inside the lungs

Draw, label and annotate a diagram to show how cartilage are specialised for their function.

• connective tissue found in the outer ear, nose and at the ends of and between bones

• contains fibres of the proteins elastin and collagen

• firm and flexible connective tissue composed of chondocyte cells embedded in an extracellular matrix, this tissue prevents the ends of bones from rubbing together and causing damage

Draw, label and annotate a diagram to show how muscle are specialised for their function.

• can contract to move bones or perform other contractile functions

• has long, multinucleate cells with contractile elements called myofibrils

• contain many mitochondria to supply the energy for contraction

• cells appear striped due to the arrangement of the proteins, actin and myosin making up the myofibrils

Draw, label and annotate a diagram to show how the epidermis of plants are specialised for their function.

• single layer of closely packed cells covering the surface of plants

• covered in waxy, waterproof cuticle to reduce water loss

• stomata formed by guard cells are present in this tissue, allows Co2 in and water vapour & oxygen out

Draw, label and annotate a diagram to show how xylem tissue are specialised for their function.

• vascular tissue responsible for the transport of water and minerals through plants

• composed of vessel elements which are elongated, hollow, dead cells

• joining walls of these elements have broken down to leave continuous tubes

• side walls are thickened with cellulose and strengthened with lignin to provide structural support for plants

• contains tracheids - separate, dead cells connected by small holes called pits rather than combining to form true vessels

Draw, label and annotate a diagram to show how phloem tissue are specialised for their function.

• vascular tissue responsible for the transport of organic nutrients, particularly sucrose

• transport occurs from where the sucrose is made (either from the products of photosynthesis or from stores of carbohydrates) to where it is needed

• composed of sieve tubes cells (sieve tube elements) which only have cytoplasm around their edges and are joined by highly perforated sieve plates into relatively hollow columns

• have companion cells which perform all of the cellular functions of sieve tubes cells

State 3 examples of organ systems in animals and describe each function.

• digestive

• nervous

• gas exchange

• endocrine

• reproductive

• circulatory

• skeletal muscular