Biology CH 2 -- Organisation of the organism

Cells

smallest units from which all organisms are made and contains organelles

Cell membrane

• thin layer of protein and fat that controls what goes in and out of the cell

• Partially permeable

• separates the content of the cell from the surroundings

organelle

smaller specialized part of the cell with its own function

cell wall

• thick rigid layer covering cell membrane

• found in plant (cellulose), bacterial (peptidoglycan) and fungal cells (chitin)

• fully permeable

• provides protection and support

cytoplasm

• jelly-like substance

• many substances dissolve in it esp protein

• metabolic reactions takes place

• provides a medium for diffusion of substances

vacuole in plant

• large, permanent central

• contain a solution of sugars and other substances called cell sap

• when fully filled, becomes turgid and provides support

vacuole in animal

• fluid filled space surrounded by its own membrane

• contains water and dissolved substances

• only. a few vesicles present

nucleus

• contains genetic material DNA enclosed in chromosomes

• DNA controls what proteins are synthesized in the cell

• controls all activities of the cell

• double membrane bound organelle

chloroplasts

• contains chlorophyll for photosynthesis

• never found in animal cells

• chloroplasts contain starch grains

• double membrane bound

mitochondria

• aerobic respiration takes place to release energy

• double membrane bound

ribosomes

• where protein are synthesized

unicellular cells

made up of one cell eg bacteria

divided into prokaryotes and eukaryotes

multicellular cells

many cells eg humans

• cells = smallest unit at which all organisms are made

• tissue= group of similar cells working to perform a certain function

• organ = consists of diff tissues to perform functions

• system = composed of several organs and tissues to perform a process

bacterial cell structure

• cell wall made of peptidoglycan

• supports the cell

• stops bursting if water is taken by the cell

• flagellum to help it move

• partially permeable cell membrane— controls movement in and out of the cell

• have cytoplasm and ribosomes

• no double membrane bound like mitochondria, chloroplasts and nucleus (prokaryotic)

DNA of bacterial cell

• have circle of DNA

• sometimes call bacterial chromosomes

• also have one or more circles of DNA — Plasmids

ciliated epithelial cell

• lining of trachea and bronchi

• mucus transport trapped dust and microbes when pushed

adaptation: layer of tiny hair cilia which can move and push the mucus upwards

neurones

• conducts nerve impulses

Adaptations: - long fibre made of cytoplasm called axon for impulses to travel

-branched extensions known as dendrites to recieve eletrical impulses form other cells

-fatty layer myelin sheath to give electrical insulation

red blood cell

• transport oxygen from the lungs to the tissues where aerobic transportation occurs

Adaptation: - cytoplasm filled with haemoglobin—carries oxygen

- no nucleus more space for haemoglobin

-flexible can move in narrow vessels

sperm cell

• head hold nucleus

• nucleus holds DNA

• responsible in sexual reproduction

Adaptation: - mid-piece many mitochondria provide energy

-the flagellum tail allows it to swim

- acrosomes in the head for fusion with the egg

root hair cell

• absorbs minerals and water from the soil water

Adaptation: - long extension to increase surface area for the absorption of material

- thin cell for easier absorption

- more mitochondria to generate energy for nutrient absorption

palisade mesophyll cell

• tall thin cells arranged in columns separated by very narrow air spaces

• photosynthesis

adaptation: - many chloroplast and densely packed to allow maximum absorption of light energy

magnification

size of image/actual size of object

cm to m

x 10²

mm to m

x 10³

micrometer to meter

x 10^6

nanometer to meter

x 10^9