Biology AS Module 1 of Module 2

MAGNIFICATION

the degree to which the size of an image is larger than the actual size of the object.

RESOLUTION

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

Advantages                                                                                    

•  high magnification                                    
• can image a wide range of specimen

Disadvantages

• maximum resolving power is 200 nm
• cant give detailed information about the internal structure

Stains

chemicals which bind to chemicals within the specimen.  they are specific to  different cell structures

Sectioning

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
• expensive
• high level of skill needed to opperate them

CYTOSKELETON

keeps the shape of the cell by providing an internal framework

MICROTUBULES

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)

VESICLES

membrane bound sacs used to carry differnt substances

THE NUCLEUS

surrounded by a nuclear envelope

the nucleus contains all the genetic material. consists of DNA and proteins

The Nucleolous makes RNA and ribosomes

Structure

• it has 2 membranes with fluid between them
• nuclear pores
• dense inner sphere called the nucleolous

Structure

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 

Golgi Apparatus

stack of flatterend membrane bound sacs, it recieves proteins from the rough ER and modifies them. It then packages them into vesicles

Mitochondria

2 membranes separated by a fluid-filled space.

the inner membrane is folded into cristae                     

the central part is the matrix.

CHLOROPLASTS

2 membranes separated by a fluid filled space

continous inner membrane with a network of thylakoids.

GRANUM

a stack of thylakoids which are rich in chlorophyll molecules.  they make energy by photosynthesising

LYSOSOMES

Spherical sacs surrounded by a single membrane.  They contain digestive enzymes

RIBOSOMES

tiny organelles, they are the site of protein synthesis

CENTRIOLES

small tubes made from microtubules. They take part in cell division by forming spindle fibres.

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
• Flagella
• 

RESISTANCY

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

phospholipid bilayer

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.

THE FLUID MOSAIC MODEL

model of cell membrane structure. Lipid give it fluidity and proteins give the mosaic appearance.

CHOLESTEROL

gives mechanical stability and maintains fluidity.  It fits between the hydrophobic tails making a more complete barrier.

CHANNEL PROTEINS

carry ions. They are pores in the membrane which are shaped to allow only one type of ion through.  They can be gated.

CARRIER PROTEINS

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

GLYCOLIPIDS AND GLYCOPROTEINS

cell signalling.  they allow recognition by the immune system and the can also bind cells together in tissues.

ENZYMES

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 RECEPTORS

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

BETA-BLOCKERS

have a complimentary shape to the receptor molecule blocking them. They stop the heart muscle from increasing its heart rate.

HIJACKING RECEPTORS

viruses enter the cells by binding with receptors EG HIV

CELL CYCLE

when one parent cell divides to produce 2 new daughter cells

M-nuclear division  G1- biosynthesis S-DNA synthesis G2-growth

CHROMATIN

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.

MITOSIS

nuclear division where 2 genetically identical nuclei are formed from one parent cell

PMAT

PROPHASE

chromosomes shorten and thicken. The nuclear envelope breaksdown and disappears.

METAPHASE

chromosomes move to the equator and become attached to a spindle fibre at its centromere.

ANAPHASE

replicated sister chromatids are separated from each other and the centromere splits. Spindle fibres shorten pulling chromatids to the poles.

TELPHASE

sister chromatids reach the poles and a new nuclear envelope forms. Spindle fibres breakdown and dissappear.

CYTOKINESIS

whole cell splits to form 2 new identical cells. The cell membrane forms a cleavage furrow.

2 gametes fusing form a zygote

DIFFERETIATION

changes in cells of a multicellular organism so that different type of cells become speciallised to perform a specific function.

TISSUES

collection of cells that are similar to each other to perform a specific function

ORGAN

tissues working together to perform a paticular function

ORGAN SYSTEM

an number of organs working together to perform and overal life function

SQUATAMOUS EPITHELIUM

made up of flattened cells forming a smooth flat surface which lines tubes such as blood vessels.  it is made from collagen and glygoproteins.

CILLIATED EPITHELIUM

collumn shaped cells found in the inner surface of tubes.

LEAF STRUCTURE

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