2.1.1 cell structure

purpose of the cytoskeleton

- provides mechanical strength to cells

- aids transport within cells

- enables cell movement

prokaryotic cells have no membrane bound organelles so do not contain:

- nucleus

- mitochondria

- chloroplasts

flagella + cilia function

flagella - enables cell movement

cilia - move substances across cell surfaces

structure of flagella + cillia

cylinder containing 11 microtubules (9 in a circle, 2 in the centre)

flagella are longer than cilia

cytoskeleton structure

microfilaments (made of actin) control cell movement and cytokinesis

microtubules (made of tubulin) regulate shape and organelle movements, and form centrioles and spindle fibres

golgi apparatus function

modifying proteins + packing them into vesicles

golgi apparatus structure

stack of flattened sacs (similar to SER)

rough endoplasmic reticulum function

protein synthesis

rough endoplasmic reticulum structure

cisternae bound to ribosomes (made of RNA; can also appear loose in the cytoplasm)

smooth endoplasmic reticulum function

lipid and carbohydrate synthesis

smooth endoplasmic reticulum structure

flattened membrane-bound sacs (cisternae)

lysosomes function

breaks down waste, e.g. old organelles

lysosomes structure

specialised vesicles containing hydrolytic enzymes

mitochondria function

produces ATP through aerobic respiration

mitochondria structure

- double membrane, inner membrane folds to form cristae

- fluid filled, called the matrix

nucleus function

contains genetic information

nucleus structure

- surrounded by a nuclear envelope (containing pores)

- contains chromatin (DNA + histone proteins) which condenses to form chromosomes

- contains a nucleolus (produces rRNA)

cell wall structure in prokaryotic cells

Rigid outer covering made of peptidoglycan

capsule structure in prokaryotic cells?

Protective slimy layer which helps the cell to retain moisture and adhere to surfaces

plasmid

Circular piece of DNA

flagellum function in prokaryotic cells

A tail-like structure which rotates to move the cell

pili in prokaryotic cells

Hair-like structures which attach to other bacterial cells

ribosome function in prokaryotic cells

Site of protein production

magnification equation

size of image/size of real object

magnification

the ratio of an object's image size to its real size

resolution

the extent to which two objects can be distinguished as separate structures

scanning electron microscope

detailed image of the surface of a specimen

transmission electron microscope

detailed image of the organelles inside a specimen

highest resolution

transmission electron microscope

lowest resolution

light microscope

gram positive bacteria

- retains the crystal violet stain

- susceptible to penicillin, inhibits cell wall formation

gram negative bacteria

- thinner cell walls so stain lost easily

- cell walls not susceptible to penicillin

protein transport (part 1)

- proteins are produced on the ribosomes

- proteins which are produced on the surface on RER are folded and processed in the RER

protein transport (part 2)

- the proteins are then transported from the RER to the Golgi apparatus in vesicles

- they are then modified in the Golgi apparatus

protein transport (part 3)

- golgi apparatus packages proteins into vesicles to be transported around the cells to where they're required.

- some of the proteins such as extracellular enzymes leave the cell by exocytosis.

prokaryotic cell organelles

Cell wall -Rigid outer covering made of peptidoglycan

Capsule - Protective slimy layer which helps the cell to retain moisture and adhere to surfaces

Plasmid -Circular piece of DNA

Flagellum- a tail like structure which rotates to move the cell

Pili - Hair-like structures which attach to other bacterial cells

Ribosomes- Site of protein production

double membrane organelles

- nucleus

- mitochondria

- chloroplast