the degree to which the size of an image is larger than the actual size of the object.
the dregree to which you can distinguish between 2 objects very close to each other.
- uses lenses to produce an image that can be viewed directly at the eye piece
- light passes from a bulb under the stage through a condenser lens and then through the eye piece
- the light beam is focused through the objective lens and then through the eyepiece
- objective lens can be rotated to give different magnifications
- high magnification
- can image a wide range of specimen
- maximum resolving power is 200 nm
- cant give detailed information about the internal structure
More about microscopes
chemicals which bind to chemicals within the specimen. they are specific to different cell structures
specimens are embedded in wax and thin sections are cut. it if good for making sections of soft tissue
Scanning Electron Microscope- an electron beam is directed onto a sample. They dont pass through the sample and are bounced off producing a 3D image.
Transmittion Electron Microscope-electron beam passed through a thin sample. it passes through denser parts less easily. Produces a 2D image.
Advantages of EM
- high resolution
- detailed image of organelles
Disadvantages Of EM
- electrons are deflected by molecules in the airso sample has to be in a vacuum
- high level of skill needed to opperate them
keeps the shape of the cell by providing an internal framework
size is 25nm. they are made of tubulin
Undulipodia and cillia are made up of microtubules (in eukaryotes)
flagella are made up of a spiral of protein (in prokaryotes)
membrane bound sacs used to carry differnt substances
surrounded by a nuclear envelope
the nucleus contains all the genetic material. consists of DNA and proteins
The Nucleolous makes RNA and ribosomes
- it has 2 membranes with fluid between them
- nuclear pores
- dense inner sphere called the nucleolous
series of fleatterend membrane bound sacs called cisternae
they are contimuous with the nuclear membrane
Rough endoplamic reticulum is studded with ribosomes it transports proteins which are made by the ribosomes
smooth ER makes the lipids needed for metabolim in the cell
more cell stuff
stack of flatterend membrane bound sacs, it recieves proteins from the rough ER and modifies them. It then packages them into vesicles
2 membranes separated by a fluid-filled space.
the inner membrane is folded into cristae
the central part is the matrix.
2 membranes separated by a fluid filled space
continous inner membrane with a network of thylakoids.
a stack of thylakoids which are rich in chlorophyll molecules. they make energy by photosynthesising
Spherical sacs surrounded by a single membrane. They contain digestive enzymes
tiny organelles, they are the site of protein synthesis
small tubes made from microtubules. They take part in cell division by forming spindle fibres.
Division of Labour
1) mRNA for a protein is made in the cells nucleus
2) mRNA travels through the nucleus pore
3) mRNA attaches to ribosomes on the rough endoplasmic reticulum.
they read the instructions and assemble the protein
4) protein is pinched off into vesicles and travels to the golgi apparatus
5) vesicles fuse with the golgi which modifies and packages protein into vesicles
6) the packaged protein are pinched off in the vesicle and move towards the cell surface membrane.
7)vesicle fuses with the cell membrane wich open to release the protein
- they have a cell wall made from murein
- no mitocondria
- no chloroplasts
- smaller ribosomes
- single loop of DNA
- no membrane surrounding the DNA (nucleiod)
- ATP made is mesomes
prokaryotes can become resistant to drugs because the gene for resistance is coded in plasmid DNA. Bacteria share plasmid with one another and therefor share the resistancy gene
the basic structural component of the plasma membrane. it consists of 2 layers of phosopholipid molecules. Proteins are embedded within it.
Roles of the Plasma Membrane
- separating cell contents from the outside environment
- cell signalling
- separating cell contents from the cytoplasm
- holding components of metabolic pathways in place
- regulation transport of materials in and out of the cell
when phospholipids are completely surrounded by water a bilayer can for. It is 7nm think.
fluid mosaic model
THE FLUID MOSAIC MODEL
model of cell membrane structure. Lipid give it fluidity and proteins give the mosaic appearance.
gives mechanical stability and maintains fluidity. It fits between the hydrophobic tails making a more complete barrier.
carry ions. They are pores in the membrane which are shaped to allow only one type of ion through. They can be gated.
FLUID MOSAIC MODEL 2
carry larger molecules through the membrane. They are specific to the molecule. When the molecule fits the protein changes shape tp allow the molecule through.
the energy used in pumping molecules across the membrane by active transport causes the the protein to change shape. this shape change means that the specific molecule to be pumped fits into the carrier on one side of the membrane only.
As the molecule is carried energy is used changing the shape so the molecules leaves the carrier protein.
CARRIER PROTEIN- large molecule
CHANNEL PROTEINS- ions
the fluid mosaic model
GLYCOLIPIDS AND GLYCOPROTEINS
cell signalling. they allow recognition by the immune system and the can also bind cells together in tissues.
they bond membranes together such as folded cristae and thylakoids.
Increasing the temperature of an organisms increase the kinetic energy of a membrane causing it to be more fluididy and therefor more leaky.
CELL SIGNALLING- cells communicating with one another by signals
TARGET CELL- any cell with receptors for hormone molecules
insulin is released from beta-cells in the pancreas in response to increased blood sugar. Insulin attaches to insulin receptors on the plasma membrane triggering an internal response causing more glucose channels being present
have a complimentary shape to the receptor molecule blocking them. They stop the heart muscle from increasing its heart rate.
viruses enter the cells by binding with receptors EG HIV
when one parent cell divides to produce 2 new daughter cells
M-nuclear division G1- biosynthesis S-DNA synthesis G2-growth
The material of which the chromosomes of eukaryotes are composed.
HISTONE -Any of a group of basic proteins found in chromatin
CENTROMERE- The point on a chromosome by which it is attached to a spindle fiber during cell division.
CHROMATIDS- Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
nuclear division where 2 genetically identical nuclei are formed from one parent cell
chromosomes shorten and thicken. The nuclear envelope breaksdown and disappears.
chromosomes move to the equator and become attached to a spindle fibre at its centromere.
replicated sister chromatids are separated from each other and the centromere splits. Spindle fibres shorten pulling chromatids to the poles.
sister chromatids reach the poles and a new nuclear envelope forms. Spindle fibres breakdown and dissappear.
whole cell splits to form 2 new identical cells. The cell membrane forms a cleavage furrow.
2 gametes fusing form a zygote
changes in cells of a multicellular organism so that different type of cells become speciallised to perform a specific function.
collection of cells that are similar to each other to perform a specific function
tissues working together to perform a paticular function
an number of organs working together to perform and overal life function
made up of flattened cells forming a smooth flat surface which lines tubes such as blood vessels. it is made from collagen and glygoproteins.
collumn shaped cells found in the inner surface of tubes.
TRANSPARENT UPPER LAYER- lets light through
PALLISADE LAYER- many chloroplasts tightly packed together
SPONGY MESOPHYLL- air spaces allowing the circulation of gases
LOWER EPIDRERMIS- contains stomata
LEAF VEIN- supports the leaf and transports water.
STOMATA- guard cells appear in pairs, they contain chloroplasts. When water moves into the cells they become turgid causing the outer cell wall to stretch. Guard cells buldge so the stomata closes