6.4 Specialised cells and tissues- animal and plant

Function of neutrophil

to destroy pathogens by phagocytosis and the secretion of enzymes

Adaptations of neutrophil

• very flexible shape that allows them to squeeze through cell junction in the capillary wall

• Their flexibility also enables them to form pseudopodia that engulf microorganism

• Granular cytoplasm contains large number of lysosomes present in the cell. These digestive enzymes help to digest and destroy invading cells

• A flexible nuclear membrane further helps the cell to penetrate cell junctions. Though it causes lobed nucleus

Function of erythrocytes

to transport oxygen around the body and CO2 to the lungs

Adaptations of erythrocytes

• flattened and biconcave in shape which increases the SA over which O2 can be absorbed

• cytoplasm contains high amounts of haemoglobin which can readily bind to O2

• no nucleus is present which makes more space inside the cell for haemoglobin molecules for maximum O2-carrying capacity

• elastic membrane allows the cell to be flexible and change shape as it squeezes through narrow capillaries

function of epithelial cells

act as a protective shield, control permeability allow for absorption and enable secretions of substances like mucus or hormones

Adaptations of epithelial cell

• numerous microvilli increases the SA for diffusion/ active transport - absorption

• high concentration of mitochondria to produce ATP for moving substances e.g. sodium-glucose co-transport- active transport

• Goblet cells secrete mucus- protection/ secretion

function of sperm cell

reproduction- they fuse with an egg which initiates the development of an embryo and pass on fathers genes

Adaptations of sperm cell

• head contains a nucleus that contains half the normal number of chromosomes

• the acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus

• mid-piece is packed with mitochondria to release energy via respiration for the tail movement

• tail rotates propelling the sperm cell forwards and allowing it to move towards the egg

• sperm cells are motile- their tail helps propel them forward in search of an egg to fertilise

function of cartilage

prevents the ends of bones from rubbing together and causing damage

adaptations of cartilage

• contains fibres of the proteins elastin and collagen

• firm, flexible connective tissue composed of chondrocyte cells embedded in extracellular matrix

Function of cambium cells

Undifferentiated meristematic cells located between the xylem and phloem plant stems and root, acting as a lateral meristem

Responsible for secondary growth, which increases the girth/ thickness of plant stems and roots

Adaptations of cambium cells

• high metabolic activity and rapid continuous division

• Undifferentiated which allows them to divide continuously and differentiate into either xylem or phloem tissues which is essential for secondary growth

• Thin cell walls facilitate rapid division and enable quick differentiation into specialised transport cells

• They contain dense cytoplasm and are highly active metabolically providing the energy and resources needed for frequent mitosis

• Situated between the xylem and phloem in vascular bundles this position allows them to efficiently add new, functional transport tissues to both sides, increasing the diameter of woody plants

• phytohormone response- cambium cells are highly responsive to chemical messenger that regulate their activity and division, enabling adaptation to environmental conditions

Function of root hair cells

Absorption of water and mineral ions from soil

Adaptations of root hair cells

• root hair to increase SA so the rate of water uptake by osmosis is greater which means more water and ions can be absorbed

• Thinner walls than other plant cells so that the water can move through easily due to shorter diffusion distance

• Permanent vacuole contains cell sap which is more concentrate than soil water, maintaining water potential gradient

• Mitochondria for active transport of mineral ions

• No chloroplasts as no need for photosynthesis

• The root hair is an extension of the cytoplasm, increasing the SA of the cell in contact with the soil to maximise absorption of water and minerals

Function of palisade cells

Carry out photosynthesis to produce glucose and oxygen

Adaptations of palisade cells

• a large number of chloroplasts are present in the cytoplasm to maximise the absorption of light for photosynthesis

• The tall and thin shape of the cells allows light to penetrate deeper before encountering another cell wall- cell walls absorb/ reflect light

• The tall and thin palisade cells are densely packed together for the maximum absorption of light

Function of guard cell

Control the opening of the stomata to regulate water loss and gas exchange.

Adaptations of guard cell

• inner cell walls are thicker while the outer cell walls are thinner. The difference in the thickness of the cell walls allows the cell to bend when turgid

• The cytoplasm has a high density of chloroplasts and mitochondria- organelles may play a role in the opening of the stomata

Function of the epidermis

Single layer of closely packed cells covering the surfaces of plants

Adaptations of the epidermis

• usually covered by a waxy, waterproof cuticle to reduce the loss of water

• Stomata formed by a pair of guard cells that can open and close are present in the epidermis

• They allow CO2 in and out and H2O vapour and O2 in and out

Function of xylem tissue

A type of vascular tissue in plants, responsible for the transport of water and minerals throughout plants

Adaptations of xylem tissue

• the tissue is composed of vessel elements which are elongate dead cells

• The wall of these cells are strengthened with a waterproof material called lignin which provide structural support for plants

Function of phloem tissue

another type of vascular tissue in plants responsible for the transport of organic nutrients, particularly sucrose from leaves and stems where it made by photosynthesis to all parts of the plant where it is needed

adaptations of phloem tissues

• it is composed of sieve tube cells separated by perforated wall called sieve plates

Squamous Epithelium

Single layer of flat cells, ideal for fast diffusion. Made of specialised squamous epithelial cells. It is very thin due to the squat or flat cells that make it up and also because it is only one cell thick. It is rapid diffusion across a surface is essential. It forms the lining of the lungs and allows rapid diffusion of O2 into the blood

Ciliated Epithelium

Columnar cells with cilia that sweep mucus/ substance found in the trachea and bronchi. Goblet cells are also present, releasing mucus to trap any unwanted particles present in the air. This prevents the particles, which may be bacteria from reaching the alveoli once inside the lungs.

Cuboidal/ Columnar epithelium

Often found in intestines for absorption