3- cell specialisation

The order of levels

• The cell is he basic unit of life

• Organisms are made from millions of cells

• Different cells within the organism are specialised for different roles

• Specialised cell-tissue-organ-organ system- organism

Specialisation of cells

• Stem cells are undifferentiated cells

• These cells undergo mitosis and then differentiate Into a specialised cell for a specific function

Erythrocyte- red blood cell

• Biconcave shape which increases the surface area

• No nucleus or organelles

• Increases space for haemoglobin

• Small ands flexible to squeeze through capillaries

Neutrophils- cells

• White blood cell with an essential role in the immune system

• Multilobed nucelus to allow it to squeeze through small gaps to get to infection sites

• Granular cytoplasm containers many lysosomes that contain enzymes

Sperm cell

• Male gametes

• Have a tail for movement

• A mid piece which contains many mitochondria to supply ATP for movement

• Acrosome on the head of the sperm contains digestive enzymes to penetrate the egg

Squamous epithelial cell

• Sometimes known as pavement epithelial cell

• Flattened cells

• Layer of single flattened cells sit on basement membrane

• Forms lining of blood vessels and alveoli

Ciliated epithelium cell

• Hair like cilia on cells

• Move in rhythmic manner

• Lines the trachea

• Moves mucus out of lungs

• Many mitochondria to supply ATP for movement of the cilia

Palisade cell

• Present in the mesophyll

• Large numbers of chloroplasts containing chlorophyll for photosynthesis

• Thin cell walls to increase rate of diffusion

• Large vacuole maintains turgidity

• Chloroplasts can move to light source

Root hair cell

• Water enters by osmosis

• Present at surface of roots near growing tips

• Long extensions increase surface area for uptake of water and internal ions

Guard cell

• Pairs of guard cells form openings called stomata

• When guard cells lose water they change shape and the stomata close, this conserves water

• The cell wall of a guard cells is thicker one side which gives rise to the opening

Tissues

Collection of differentiated cells that have specialised functions

4 main tissue types:

• Epithelial- forms linings

• Connective- holds structures together

• Muscle

• Nervous

Phloem tissue

• Vascular tissue used for transport of organic nutrients

• Columns of sieve tube cells separated by sieve plates

Ciliated epithelial tissue

• Ciliated epithelial cells and goblet cells

• Lines trachea

• Goblet cells produce mucus which traps dirt and pathogens

• Ciliated cells move mucus out of lungs

Cartilage tissue

• Connective tissue found in outer ear, nose and end of bones

• Contains collagen and elastin

• Firm, flexible connective tissue

• Chondocyte cells embedded in an extracellular matrix

• Prevents bones rubbing together

• Some fish have whole skeletons made of cartilage

Muscle tissue

• Shortens in length to move bones

• Skeletal muscle fibres contain microfibrils

• Muscle fibres are separated by connective tissue

Plant epidermal tissue

• Single layer of closely packed cells

• Waxy waterproof cuticle to reduce water loss

Xylem tissue

• Transport water and minerals

• Vessel elements as re elonged dead cells

• Strengthened with lignin which gives structural support

Organs

• Collection of tissue that are adapted to perform a particular function in an organism

• E.g

  • Heart- made up of muscle tissue and connective tissue, adapted for pumping blood around the body

Organ systems

• Number of organs working together to perform a function

• Skeletal system: provides structure to body, protects internal organs

• Muscular systems: supports body and allows it to move

• Digestive system: breaks down food and absorbs its nutrients

• Respiratory system: takes in oxygen and releases water gases