Biology chapter 1

2 types

Light microscope

-very thin samples, often need staining*
Light->condenser lense->glass slide->objective lense->eyepiece

*Stains

Methylene blue-stains living cells~dark blue nucleus, light blue cytoplasum,bacteria all of cell takes colour.
Iodine solution-stainning living plant cells~very dark blue starch grains.
Acidified phloroglucinol-staining lignin~bright red.
Acetic orcein-stainning nuclei and chromosomes~red.
Eosin-stainning cytoplasum and some organelles~pink.
Light green-stainning plant cell walls~green.

Electron microscope-no colours

Allows great resolution as it uses electron beams rather than light these are smaller so fit through smaller gaps so you can distinguish 2 items appart even if they look like 1 on a light microscope.

400x better resolution than a light microscope, you can distinguish items only 0.5um apart.

Up to 300 000 magnification.

There are 2 types: Transmission Electron Microscope(2D, thin specimens, stained with heavy metals as this makes the ions positive so the electrons are avsorbed and dont pass through); Scanning Electron Microscope(3D, bounces electron beams of the objective surface.

Magnification

magnification=size of image/real size of object

Light microscope

Poor resolution-waves cant pass through.

Magnification-1400xmagnification is the most possible.

You can magnify higher but theres no point as the resolution wont increase so it will be blurry.

Electron microscope

Big.

Expensive.

No colour, any colour seen is a false colour which is added after the image has been captured.

Nucleus

-Almost all cells have nucleus, exceptions are red blood cells(mamels)and phloem sieve tubes in plants.

-Largest organelle in cell normally.

-The nucleus is surrounded by two membranes these are called the nuclear envelope, there are small gaps all over these gaps these are called nuclear pores.

-This contains DNA in chromosomes, normally these aren't visible but chromatin is, this is the tangle of chromosmes strings.

 Endoplasmic reticulum

-Ribosomes=RER, No ribosomes=SER

-RER~normally attached to nucleur envelope, the membrances enclose areas theses are called cisternae, most protein synthesis takes place in the ribosomes attached to them and this comes together as the cisternae is where these proteins are stored.

-SER~different in different cells, examples-in the ovaries the SER is the site of steroid hormone production or in liver cells its the place where toxins are broken down and made harmless.

Golgi apparatus

-They are not stable, they are constantley changing

-At one side tiny membrane bound vesicles move towards the golgi apparatus, when they reach the golgi apparatus they fuse together making a new layer of stack(from , on the opposite side they breack off forming new vesciles which move away from the golgi apparatus.

-The golgi apparateus packages and processes the proteins added from the ER to make them into the required product. The vesicles which leave the other side can contain the new proteins to transfer them to outside the cell. This transfer is called endocytosis.

-The production of and release of useful substances is called secretion.

-Lysosomes are vesicles which stay within the cell for example digestive enzymes.

Lysosomes

-these are tiny bags of digestive enzymes.

-They are surrounded by a single membrane.

-They are about 5um diameter.

-The main purpose is to fuse with other vesicles which contain stuff which needs to be digested.

-They also help destroy worn out cells/unwanted organelles.

Chloroplasts

-Found in some plant cells but no animal cells

-Photosynthesis occurs here.

-Contained in a doubble membrane(envelope) which sepperates the reactions in the chloroplasts and in the rest of the cell.

-Within the chloroplasts there are sacks of membrane which are called grana. rana contain chloropyll, which is where the  light dependant photosythesis occurs. Light captured-> used to split water to give hydrogen ions-> make ATP and NADP->reduced and used to make carbs(using CO2). Stacks of grana are called thylakoids.

-Light independant reations take place in the stroma which is what fills the rest of the chloroplast.

-Chloroplasts often contain starch grains, starch is a carb used as an energy store in plants.

Mitochondria

-Found in plant and animal cells

-Like chloroplast it's surrounded by a doubble mambrane(envelope)

-This is where aerobic respiration occurs, ATP is made here from glucose and oxygen, each cell has to make its own ATP so some cells require more than others for example muscle cells need more.

-Mitochondria membrane is folded inside to form cristae.

-ATP here is made in a similar way to the membranes on the inside of chloroplasts.

-The matrix is the background of mitochondria, this is where the part of the aerobic respiration called the Krebs cycle occurs.

Vacuole

-Membrane bound organelle, it contains liquid

-Cell sap is contained in the vacuole of a mature plant cell.

-Cell sap contains lots of stuff which the cell needs: sugars, pigments and enzymes

-The membrane which surrounds the vacuole is called tonoplast.

Plasma membrane

-Made of lipid and protein molecules

-It conrols what enters and leaves a cell

-All cells have one of these known as cell surface membrane

Centrioles

-These are only found in animal cells, they organise microtubles->made of tubulin

-In cell division microtubules make the spindle for cell division, they move the chromosomes around in the cell, and pull them to opposite parts(microtubles are in plant cells but not organised by cetrioles)

Cillia and Flangella

-Long thin extensions from the cell(tails), they allow movement, they are found in some animal cells and occasionally in plant cells.

-Cillia~short, many of them                                     Flangella~long, only one or two

-Both are arranged in a 9+2 arrangment. 2 in the middle and a ring of 9 around the outside.

-The microtubules sliding over each other allows movement, cilliated cells all move in harmony, they can move fluid over the surface of a cell.

Cytoskeleton

-All plant and animal cells have  network of microfilaents, which act as a skeleton giving the cell structure and shape. Along with the microtubules they make up the cytoskeleton.

-As well as providing the cell with mechanical strength it also allows organelles to move within the cell as it gives it tracks which the microtubules can pull the organeeles along. They can also aid the movement of the whole cell.

Cell walls

-Plant cells all have cell walls, these are made of cellulose~the cellulose is arranged in a criss cross function which makes them very strong. They are held together by a matrix which contains pectin.

-The matrix gives it lots of strength, e.g the cell can fill with water but the cell wall will hold firm to prevent the cell from bursting.

-The middle lamella also contains pectin, these cement one cell to another.

Prokaryotic

-'before nucleus' single celled organisums,with no nucleus

-In a prokaryotic cell the DNA is free in the cytoplasm, the DNA is also in a circular formation, it is also always attached to the plasma membrane.

-They lack complex membrane bound organelles for example:mitochondria, chloroplasts and ER. However they do contain ribosomes but they are much smaller and free in the cytoplasm.

-Prokaryotic cells have a cell wall which is made of fibres of peptidoglycan, it also stops the cell from bursting if it expands.

Prokaryotic->Eukaryotic

No nucleus or envelope or nucleolus-> usually present with envelope with a nucleolus

No mitochondria-> Usually present

No chloroplasts-> some plant cells

No ER-> always present

20nm ribosomes-> 30nm in diameter

No cytoskeleton-> always there, made of microfilaments and microtubules

Circular DNA no histones->several long strands, with histones(protein molecules assosiated with DNA in chromosomes)

Always have a cell wall made of peptidoglycan-> cellulose in some plant cell walls

Flagella sometimes present(not like eukaryoic cells)-> cillia and flagella somtimes present.