• Cell structure and organisation

• All living organisms are made of cells

• Cell: The basic structural unit of life

• Although cells carry out different functions, animal and plant cells both have common features:

  • Cell membrane

  • Cytoplasm

  • Nucleus

  • Endoplasmic reticulum

  • Mitochondria

  • Ribosomes

  • Golgi Body

  • Lysosomes

Functions of Cellular structures

• Cell wall: Outer most sstructure in the plant cell, made of cellulose and is dead

  → Fully permeable; allows substances in and out of the cell

  →Gives the cell its shape and structure

• Cell membrane: Located inner to the cell wall in a plant cell and the outermost structure in an animal cell

  →Semi-permeable; allows some/specific substances in and out of the cell

• Cytoplasm: Jelly like fluid inside the cell made of water and dissolved substances eg. glucose & salt

  →Site of all metabolic (chemical) reactions

• Nucleus: Contains genertic material of the cell in chromosomes which controls cell functions

  →Controlling centre of the cell

  →Determines quality and quantity of proteins made by the cell

• Chloroplasts: Site of photosynthesis

  →Contains a green pigment (chlorophyl)

  →Chlorophyl absorbs light energy and converts it into chemical energy by photosynthesis

  6H2O + 6CO2 → C6H12O6 + O6

• Mitochondria: Made up of a doublr membrane: inner and outer

  → Inner has many foldings to increase the surface area for enzyme reactions

  →Site of aerobic respiration and release energy

  → ‘Powerhouse’ of the cell

• Rough of Endoplasmic Reteculum: Membranous outgrowth of outer nuclear membranes and has ribosomes attached to its surface

  →Site of synthesis and transport of protein

• Ribosome: The smallest cell of organelles present in the cytopplasm

  →Either free or attached to rough ER

  →Site of protein synthesis

• Vacoule: Large, permanent, cenraly located in a plant cell but small and temporary in animal cells. Contain cell sap which is a solution of nutrients and salts

  → Provides turgor pressure to the plant cell and helps maintain its shape

• Vesicle: Sac like structures containing secretory substances eg. enzymes in the cytoplasm

Specialised Cells

Large organisms are multicellular

Different types of cells have particular structures to help them carry out specific functions, and so they become specialised

Specialised Cells in Plants

Root hair cells:

• Absorb nutrients from soil by osmosis

• Absorb minerals by active uptake/transport

• Fix the plant in the soil

→Adaptations:

• Have finger like outgrowth to increase the surface area for more absorption

• Have extended vacoule and cytoplasm for easier absorption

• Have more mitochondria to privude energy for active uptake/transport

Xylem vessels:

Found in vascular bundles

• Transport water and minerals from the roots to the stem and leaves

• Provide mechanical support to the stem and leaves

→Adaptations

• Do not have a nucleus or cytoplasm to make space for bulk transport of water and minerals

• Cells are dead and hollow and connected from end to end to form a long continous tube

• Cell wall is strengthened with lignin (hard substance) which gives mechanical support

  

Specialised Animal Cells

Red Blood cells:

• Transport oxygen from lungs to the rest of the body

• Transport CO2 from the body to the lungs

→Adaptation

• Red pigment (haemoglobin) which binds with oxygen to allow transport

• Dont have a nucleus; increase the surface area to carry more oxygen; biconcave shape

• Spongy/ flexible to squeeze into cappilaries

Ciliated Epithelial cells:

• Goblet cells secrete mucus which traps the dust particles from the inhaled air

• Cillia of the cells beat and push the trapped dust and air towards the throat (outside)

Muscle cell:

• Contracts and relaxes and brings about movement

• Contracts and relaxes so that structures can be brought closer

  →Adaptation

• Made of myofibres which have the ability to contract and relax

• Have protein fibre; can shorten the cell when energy is present

Nerve cells:

Sensory nerve cell: Conducts message from sense organ to the central nervous system

Motor nerve cell: Carries message from central nervous system to the effector

→Adaptation

• Has extensions and branches so that it communicates with other nerve cells and glands

• The Axon (extension of the cytoplasm away from cell body to carry impulse long distances) is covered with fatty sheath which insulates the cell and speeds up the nerve impulse

Egg cell:

Female gamete (responsible for reproduction in females)

→Adaptations

• Alot of cytoplasm that contains alot of nutrients for the growth of the early embryo

• Haploid nucleus containing genetic material for fertilisation

• Cell membrane that modifies after fertilisation so that only one sperm cell can penetrate

Sperm cell:

Male gamete (responsible for reproduction in males)

→Adaptation

• Head contains haploid nucleaus

• Acrosome in head contains digestive enzymes to breakdown jelly coat around egg cell so sperm can penetrate egg cell

• Many mitochondria to provide energy so sperm can travel long distances

• Flagellum allows sperm to travel

Levels of Organisation

Cell: Basic structural and functional unit of life

Tissue: A group of identical cells which work together to perform a specific function

Organ: Many tissues which work together to perform a specific function

Organism: A group of organ systems which coordinate with each other to create an effective functioning of the body

Cell →Tissue→Organ→Organ System→Organism

Size of specimens

Size of a structure or an organism

Magnification = Measured lenght / Actual length

Magnification has no units so is represented as eg. x100

The image size is usually given in centimetres or millimetres so make sure to convert both the actual size and image size units to be the same to get thr correct magnification

1cm = 10mm

1mm = 1000μm (micrometer)