cell structure + division

• distinct nucleus with a nuclear envelope -DNA is associate with proteins called histones -there are no plasmids and DNA is linear -membrane bound organelles such as mitochondria are present -chloroplasts present in plants and algae -ribosomes are larger (80s) • when present, cell wall is made mostly of cellulose, or chitin in fungi -no capsule

-no true nucleus, only an area where DNA is found -DNA is not associated with proteins -some DNA may be in the form of circular strands called plasmids -no membrane bound organelles -no chloroplasts, only bacterial chlorophyll associated with the cell-surface membrane in some bacteria -ribosomes are smaller (70s) -cell wall made of murein (peptidoglycan) -may have an outer mucilaginous layer called a capsule (slime capsule)

description: the membrane found on the surface of animal cells and just inside the cell wall of other cells. its mainly made of lipids and proteins function: regulates the movement of substances into and out of the cell. it alos has receptor molecules on it which allow it to respond chemicals like hormones

description: a large organelle surrounded by a nuclear envelope (double membrane) which contains many pores. the nucleus contains chromosomes which are made from protein bound DNA and one or more structures called a nucleolus function: the nucleus controls the cells activities by controlling the transcription of DNA. DNA contains instructions to make proteins. the pores allow substances e.g RNA to move between the nucleus and cytoplasm. the nucleolus makes ribosomes

description: oval shaped with a double membrane- the inner one is folded to form structures called cristae. the inside is the matrix which contains enzymes involved in respiration function: the site of aerobic respiration, where ATP is produced. theyre found in large numbers in cells that are very active and require a lot of energy

chloroplasts are a small, flattened structure found in plant and algal cells. its surrounded by a membrane and also has membranes inside called thylakoid membranes. these membranes are stacked up in some parts of the chloroplast to form grana. grana are linked together by lamellae- think, flat pieces of thylakoid membrane function: the site where photosynthesis takes place. some parts of photosynthesis happen in the grana and other parts happen in the stroma- a thick fluid found in chloroplasts

description: a group of fluid filled, membrane bound flattened sacs. vesicles are often seen at the edges of the sacs function: it processes and packages new lipids and proteins. it also makes lysosomes

description: a small fluid filled sac in the cytoplasm, surrounded by a membrane. they’re produced by the golgi apparatus function: stores lipids and proteins made by the golgi apparatus and transports them out of the cell via the cell surface membrane

description: a round organelle surrounded by a membrane, with no clear internal structure function: contains hydrolytic enzymes. these are kept separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell

description: a very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. it is made up of proteins and RNA. it is NOT surrounded by a membrane function: site where proteins are made

description: a system of membranes enclosing a fluid filled space. the surface is covered with ribosomes function: folds and processes proteins that have been made at the ribosomes

description: a system of membranes enclosing a fluid filled space- similar to RER but with no ribosomes function: synthesises and processes lipids

description: a rigid structure that surrounds cells in plants, algae and fungi. in plants and algae it is mainly made out of the carbohydrate cellulose, in fungi it it made of chitin function: supports cells and prevents them from changing shape

description: a membrane bound organelle found in the cytoplasm of plant cells. it contains cell sap- a weak solution of sugar and salts. the surrounding membrane is called the tonoplast function: helps to maintain pressure inside the cell and keeps the cell rigid. this stps plants from wilting. vacuoles are also involved in the isolation of unwanted chemicals inside the cell

1) in multicellular eukaryotic organisms, specialised cells re grouped together to form tissues 2) a tissue is a group of cells working together to perform a particular function e.g epithilial tissues or xylem 3) different tissues work together to form organs. e.g epithilial tissues, muscular tissue and glandular tissues form the stomach 4) different organs make up an organ system e.g the stomach, small/ large intestines and the liver make up the digestive system

cell fractionation is a process where cells are broken up and the different organelles they contain are separated out based on their size/ mass using gravity cell fractionation is a three step process: 1) homogenisation 2) filtration 3) centrifugation

the solution is cold to reduce enzyme activity which may break down organelles the solution is isotonic (same water potential as the original tissue) to prevent organelles from lysing/ shrinking due to osmotic gain/loss the solution is buffered to maintain a constant pH as any changes to the pH may denature proteins/ enzymes within the cells

• the tissue is homogenised (blended) to break open cell membranes and release any organelles • the homogenate is filtered to remove any large debris as these will be heavy and sink to the bottom of the test tube • the mixture is centrifuged- the faster the spinning speed the greater the force. so at slower speeds, the larger organelles collect at the bottom of the tube forming a pellet and the smaller organelles remain suspended at the top of the tube in a liquid called the supernatant. once the first pellet has formed, the supernatant is poured into a new test tube to be spun at a slightly higher speed to form pellets of the other, smaller organelles. this method is repeated until all of the organelles or the wanted organelles have formed their own pellet

nuclei chloroplasts mitochondria lysosomes endoplasmic reticulum ribosomes

magnification is the degree to which the size of an image is larger than the object itself

resolution is the degree to which it is possible to distinguish between two objects that are very close together. the higher the resolution, the greater detail you can see

light microscopes use a beam of light to form larger, more detailed images they have a resolving power of 0.2um

light microscopes have a low wavelength they can magnify up to 1500x

light microscopes produce 2D coloured images as as a stain is needed to view the cell components. smaller organelles such as ribosomes cannot be seen