IGCSE BIO 2. cells

organelles in animal cells (&plant cells)

partially permeable cell membrane, cytoplasm, nucleus, mitochondria, ribosomes

organelles in plant cells only

cell wall, vacuole, chloroplasts

role of cell membrane

controls the entry and exit of substances into and out of a cell

role of cytoplasm

contains all the organelles, site of metabolic reactions

role of nucleus

stores genetic information in form of DNA, on chromosomes, controls cell actions

role of mitochondria

site of aerobic respiration

role of ribosomes

site of protein synthesis

role of cell wall

provides protection and support, maintains shape of cell, prevent cell from bursting

role of vacuole

contains cell sap, having water and dissolved salts & nutrients, helps maintaining the shape of the cell

role of chloroplasts

contains chlorophyll which absorbs light energy for photosynthesis

organelles in bacterial cell

cell wall, cell membrane, cytoplasm, circular loop of DNA, ribosomes, plasmids, flagellum

plasmid

small circular extra-chromosomal genetic structure that can replicate independently of the main chromosome, containing non-essential genes

role of plasmid

contain many antibiotic resistance genes, can transfer genes from one cell to another, useful in genetic engineering because it can produce large amount of DNA quickly

ciliated epithelial cells

found in the inner lining of respiratory tract, has motile cilia

cilia

microscopic cytoplasmic projections on ciliated epithelial cells which help to move the mucus away from lungs to mouth and nose

role of mucus

traps germs and dirt

RBCs (red blood cells)

transport oxygen to all parts of body, no nucleus to give more space to haemoglobin, biconcave shape for larger surface area

neuron

conduct nerve impulses, longest cell in body, branched endings to pick up impulses from multiple cells and faster transmission of impulses

sperm cell

has acrosome containing enzymes to penetrate through layer of jelly surrounding the egg cell, middle piece contains mitochondria to provide energy for swimming, flagellum allows swimming movement

egg cell

large cell, cytoplasm provides nutrition to growing zygote, jelly coat which hardens after ferilization to prevent entry of other sperms

palisade mesophyll cells

main photosynthetic cell, elongated & closely packed, to have maximum exposure to sunlight, many chloroplasts to trap maximum possible solar energy for photosynthesis

root hair cells

for absorption of water and mineral ions from soil, has root hairs, microscopic cytoplasmic projections which increases surface area for absorption, vacuole extends to here

cell

smallest unit from which all organisms are made

tissue

group of similar cells that work together to perform a particular function

organ

group of tissues that work together to perform a particular function

organ system

several organs that work together to perform a particular function

organism

a complete living thing