Unit 1 biology
1- the microscope
2- cells are the basic units of living organisms
Light microscope:
D) poor resolution due to the wavelength of the light.
A) coloured images can be obtained and living samples can be examined.
Electron microscope:(high magnification and resolution)
1) transmission: 2D images of internal structure
2) scanning: 3D images of external structure
resolution : the ability to distinguish between two separate points which are very close to each
other.
Magnification : how many times larger is the image than the specimen
Magnification = image / size of specimen
(should be in same unit)
The shorter the wavelength the higher the resolution, the higher the resolution the smaller the
organelles that can be seen.
1.2 cells are the basic unit of living organisms:
Plant cell:1) Cell surface membrane;(control what
molecules enter or exit the cell.)
phospholipid bilayer Molecules embedded within and
attached to the outside.
2) Nucleus;(site of dna replication and transcription
Contains genetic code for each cell and site of ribosome
synthesis)
Nuclear envelope - double membrane
Nuclear pores
Nucleolus : site or rRNA production and makes
ribosomes.
Nucleoplasm : jelly like structure in the nucleus
Chromosomes : protein bound, linear DNA
3) Flagella; ( mobility and sensory organ for chemical stimuli)
“Whip” like structure
4) Cillia; (move substances in sweeping motion and important in sensory organs)
“Hairlike” projections coming out of the cell
5) Microvilli (increase cell surface area for transport across membranes)
Folding in the cell surface membrane to create “finger” like projections.
6) Centrioles or microtubules; (involved in production of spindle fibres and organisation of
chromosomes in cell division. Microtubules aid in the movement of cilia and flagella.
Centriole is made out of microtubules
Unit 1 biology
7) Cytoskeleton; (provides mechanical strength to cells and helps maintain the shape and
stability of a cells
(-microfilaments are responsible for cell movement.)
(-microtubules are responsible for creating a scaffold-like structure.))
A network of fibres formed within the cytoplasm all over a cell, consists of microfilaments,
microtubules and intermediate fibres.
8) Endoplasmic reticulum; (SER synthesizes and stores lipids and carbohydrates and RER
synthesizes protein)
The endoplasmic reticulum have folded membranes called cisternae and the RER has
ribosomes on its surface)
9) Golgi apparatus; (add carbohydrates to proteins to form glycoproteins; produce
secretory enzymes; secretes carbohydrates; transports modifies and stores lipids; forms
lysosomes; molecules are “labelled” with their destination; finished products are
transported to cell surface membrane in golgi vesicles when they fuse with the
membrane and contents are released)
Folded membranes making cisternae.
10) Lysosome; (hydrolyse phagocytes; break down dead cells; exocytosis-release enzymes
to outside of the cell to destroy material)
Bag of digestive enzymes
11) Mitochondria; (site of aerobic respiration; site of ATP production; DNA code for enzyme
needed in respiration)
Double membrane; inner membrane called cristae.
12) Ribosomes (site of protein synthesis)
((80s large ribosomes found in eukaryote cells and 90s small ribosomes found in prokaryotic
cells, mitochondria and chloroplast.))
13) Chloroplast (site of photosynthesis)
Double membrane, contains thylakoids, fluid filled stoma containing enzymes for photosynthesis
14) Cell wall( structural strength to the cell)
In plants its made of microfibrils of the cellulose polymer and in fungi it is made up of chitin a
nitrogen containing polysaccharide.
15) Large permanent vacuole ( regulates osmosis and and has a pigment which gives
flowers its colour)
Single membrane bound sacs
16) plasmodesmata (provides a channel through cells to enable movement of water and
minerals between cells)
Pore like channel in cellwall