A2.2 Cell Structure

Formula of magnification

M = I/A

limitations of light microscopes (2)

magnification and resolution

limitations of electron microscopes (2)

black and white and killing the cells

fluorescent stains

absorb and then re-emit light at a different wavelength

immunofluorescence

uses antibodies to bind to different structures, different fluorescent stains bind to different antibodies, creating different coloured images

freeze-fracture electron microscopy (4)

1) quick-freezing

2) fracturing

3) etching

4) replica formation

cryogenic electron microscopy (3)

1) freeze a layer of protein

2) electron microscope

3) computer looks for patterns

plasma membrane

semi-permeable phospholipid bilayer on the outside of cells

cytoplasm

water based suspension/solution where metabolic reaction occur

DNA

genetic material that includes genes that code for proteins

prokaryote cell structure (5)

• lack a nucleus

• have a cell wall

• non-compartmentalised

• 70s ribosome

• naked DNA (no histones)

eukaryotic cell structure (5) (lacking in prokaryotic)

• compartmentalised

• some have cell walls

• nucleus

• 80s ribosome

• mitochondria

nucleus

double membrane with pores that surrounds linear chromosomes that are associated with histone proteins

mitochondria

site of aerobic respiration

processes of life in unicellular organisms

M: metabolism - all of the enzyme-catalysed reactions

R: reproduction - production of offspring

S: sensitivity - react to stimuli in the environment with various responses

H: homeostasis - maintaining a stable internal environment

E: excretion - removal of waste products

N: nutrition - getting the nutrients required for growth/maintenance

G: growth - increase in size or number of cells

functions of life of paramecium (5)

• contractile vacuole

• food vacuole

• cilia

• cytoplasm

• nucleus

functions of life of chlamydomonas (5)

• flagella

• chloroplast

• contractile vacuole

• eye spot

• nucleus

which eukaryotic cells have chloroplasts

plants

which eukaryotic cells have cell walls

plants, fungi

which eukaryotic cells have vacuoles

plants, fungi… animal cells may but are really small

which eukaryotic cells have centrioles

animals

which eukaryotic cells have undulpodia (cilia, flagella)

animals

Atypical cell structure of red blood cells

no nucleus

Atypical cell structure of phloem sieve tube elements

nucleus and organelles break down and these cells connect with companion cells that help them carry out most functions

Atypical cell structure of skeletal muscles

many nuclei in each cell resulting from the fusion of many cells

Atypical cell structure of aseptate fungal hyphae

walls that separate each cell are absent

rough endoplasmic reticulum

flat sacs with ribosomes attached, where protein that will be excreted from the cell are synthesised with vescicles

smooth endoplasmic reticulum

branched membranes which synthesise lipids

golgi apparutus

flat, curved sacs which process proteins from the rough ER and packages them into vesicles for export

lysosome

spheres containing enzymes which can either break down ingested food or destroy cell parts

free ribosome

synthesise protein for use within the cell

chloroplast

site of photosynthesis which has stacks of thylakoid discs

vacuoles and vesicles (small vacuoles)

single membrane filled with fluid

microtubule

small cylindrical fibers that move chromosomes during cell division

centrioles

form an anchor point for the microtubules

cilia and flagella

• made of microtubules

• used for movement or to create a current

origin of eukaryotic cells by endosymbiosis

formation of compartmentalised eukaryotic cells resulting from the engulfing of prokaryotic cells

evidence for the endosymbiotic cell theory (5)

mitochondria and chloroplasts have:

• their own, circular DNA

• 70s ribosome

• synthesise their own proteins

• reproduce independently by binary fission

• double membrane (due to the engulfing process)

how do cells specialise during embryonic development with identical genes?

some genes are expressed and some are not

how does multicellularity happen for animals, plants, fungi, algae?

• all animals

• all plants

• some fungi

• some algae

advantages of multicellularity (3)

• longer lifespans

• larger, so they can fill different roles in ecosystem

• complex and efficient, can differentiate into different cell types