cells
basic structural and functional units
unicellular/multicellular
protoplasm
plasma membrane, cytoplasm, nucleus
cell surface membrane/ plasma membrane
- present in all living cells
- surrounds the cytoplasm
- partially permeable membrane
- made up of lipids and proteins (double phospholid layer)
selective barrier that allows certain substances to pass through, controlling the exchange of substances between the cell and its environment
cytoplasm
- colloidal; found in sol (liquid) or gel (semi-solid) state
- contains enzymes and cell organelles (specialized structures to carry out specific functions)
- most cell activities occur here (endless chemical reactions take place)
site where most cell activities and reaction occur
nucleus
- nuclear envelope: a membrane which separates the contents of nucleus from the rest of the cytoplasm
- nucleoplasm: dense material within nucleus
- nucleolous: plays a part in making of proteins
- chromatin: genetic materials
controls cellular activities such as cell growth and repairing of worn-out parts
essential role in cell division
chromatin
- network of long thread-like structures found within the nucleus
- each chromatin thread is made up of protein and deoxyribonucleic acid (DNA)
hereditary information is stored in DNA
DNA contains instructions a cell needs for carrying out all the chemical reaction within itself
rough endoplasmic reticulum (RER)
- a network of membranes in the shape of flatted sacs/spaces, with ribosomes attached
- outer surface is continuous with the nuclear envelope
transport proteins synthesized by the ribosomes to the Golgi apparatus for secretion out of the cell
smooth endoplasmic reticulum (SER)
- a network of membranes, without ribosomes attached
- more tubular than RER
synthesize fats and steriods (e.g. sex hormones)
involved in detoxification by converting harmful substances into harmless materials
Golgi apparatus
- a stack of flattened spaces surrounded by membranes (disc-shaped)
chemically modifies substances made (mainly proteins) by endoplasmic reticulum
store and replaces substances (mainly proteins) made by endoplasmic reticulum into vesicles for secretion out of the cell
vesicles can be seen fusing with one side of the Golgi apparatus and pinching off from the opposite site
mitochondria
- oval-shaped with highly intricate internal folds
site where aerobic respiration occurs to oxidise glucose to release large amount of energy
these energy are used by cells to perform cellular functions and activities
ribosomes
- small round structures
- either found attached to the surface of RER or exists/ lie freely in the cytoplasm
synthesize proteins in the cell
ribosomes attached to RER synthesize proteins that will be transported out of the cell
- RER transport proteins (made by ribosomes) to the Golgi apparatus for secretion out of the cell
ribosomes lying freely in cytoplasm synthesize proteins to be used within cytoplasm of cell
vacuole
(animal/plant)
- fluid-filed space enclosed by a membrane
(animal)
animal vacuoles contain water and nutrients. animal cells contain many small vacuoles that exist temporarily
(plant)
a large central vacuole that contains cell sap
cell sap in the plat vacuole contains dissolved sugar, mineral salts and amino acids and some water. Plant vacuoles are enclosed by tonoplast (a partially permeable membrane)
cell wall
- on the outermost part of the cell
- made up of cellulose
- fully-permeable membrane
- non-living, not part of the living protoplasm
- rigid structure
protects the cell from from injury
provide mechanical support
chloroplast
- oval structures which contains green pigment known as chlorophyll
chlorophyll is essential for photosynthesis to occur
centrioles
- a pair of small, hollow cylinders near nucleus
- only found in animal cells
plays an important role in cell division
red blood cell
(transport oxygen from lungs to all parts of the body
contains haemoglobin - binds reversibly to oxygen no nucleus (contains more haemoglobin) - enables it to carry more oxygen biconcave in shape (increases surface area to volume ratio) - allows efficient diffusion of oxygen into and out of the cell/ increase the rate of diffusion of oxygen
root hair cell
absorbs water and mineral salts
has long and narrow protrusion/elongated (increases surface area to volume ratio) - efficient absorption of water and mineral salts
xylem vessel
to transport water and mineral salts from roots to leaves
no cross walls/no protoplasm (reduces resistance to water flowing through xylem) - efficient conduction of water and minerals
cell walls are thickened with lignin - provide mechanical support to prevent the vessel from collapsing
organelle
mitochondrion RER Golgi apparatus ribosomes chloroplast
cell
red blood cell
nerve cell
guard cell
tissue
simple tissue: muscle tissue
complex tissue: blood, nerve tissue, phloem tissue
organ
skin
heart
leaf
organ system
circulatory system
root system
organism
human
bird
fish
