Biology A2.2

Mitochondria

Site of ATP (energy molecule) production by aerobic respiration

Have their own dna

Smooth outer membrane with folds in the inner membrane, called crisrae (to increase surface area)

Double membrane and has their own ribosomes

Ultra structure of Cells

• Main idea: Eukaryotes have much more complex cell structure than prokaryotes

• Prokaryote-> no nucleus (pro, without, karyote, nucleus)

• Eukaryote-> has nucleus (eu, true, karyote, "")

electron microscope vs light microscope

• Light microscopes can only use wavelengths of visible light

• Electrons have very short wavelength, so electron microscopes have higher resolution

• Light microscopes show the structure, electron microscopes the ultrastructure

• Ultra structures is the structure of a specimen of at least .1nm in their smallest dimension

• Electron microscopes can see viruses(0.1µm), but light microscopes cant

Chloroplast

PLANT ONLY

Many but not all plant cells have them

Double membrane surrounds chloroplast

Inside are stacks of thylakoids (each thylakoid is a disc made of flattened membrane

Shape changes but usually ovoid

Site of photosynthesis and where glucose is produced

Starch grains many be present if photosynthesis is happening quickly

Centrioles

Consists of two groups of nine triple microtubules

Are mainly in animal cells

Help control cell division during mitosis

Microtubules

Small cylindrical fibres

Have many functions i.e. part of flagella and part of cell division

Cilia

ANIMALS ONLY (but with some rare plant cells)

thin, short projections from cell surface

contain microtubules

used to move cell or fluids next to cell

Flagellum (flagella)

ANIMAL ONLY (with a few plant cell exceptions)

Thin projection usually single from the cell surface

Contains micotubes

Motile-> used for movement/ motility (note: don't use mobile)

Usually pretty visible

Lined with mitochondria to give it energy

Lysosomes

Usually spherical w/ single membrane

formed from Golgi vesicles

contain digestive enzymes, which are used to breakdown ingested food in vesicles and unwanted/damaged organelles in cell

high concentration of enzymes, so stains dark

Usually not found in plant cells

Vacuoles

Single membrane with fluid inside

In plant cells large and permanent, makes up majority of cell

In animal cells smaller and temporary and used for many reasons (like absorbing food and digesting it)

Vesicles

Single membrane with fluid inside

Very small

Transports materials inside of cell

Internal packages that cell uses to move things around

Seen as small hollow circles

Free ribosomes

80S (about 20nm diameter) larger than prokaryotic ribosomes

No membrane

Only produce proteins for within the cell, doesn't go outside of the cell

Appear as dark spots in cytoplasm

Golgi apparatus

Modifies proteins before they exit the cell, which are then packaged into vesicles for transportation

Also made of flattened membranes sacs called cisternae like rER

Different to rER in that they:

• no attached ribosomes

• often close to the plasma membrane

• the cisternae are shorter and more curved

Nucleus

Usually spherical w/ a double membrane

Has pores in membrane

Contains genetic information in chromosomes (dna and other histone proteins)

Uncoiled chromosomes called chromatin, are concentrated at edge of nucleus (stain dark)

mRNA leaves nucleus though pores (dna too large)

Rough endoplasmic reticulum

Semi-penetrable membrane controlling what goes in and out of the cell

Made of flattened membrane sacs, called cisternae

Usually near nucleus

Have 80S ribosomes

RER makes/synthesises proteins are transported by vesicles to Golgi apparatus for editing, then are put outside of the cell

Prokaryotes vs Eukaryotes

• Prokaryotes are smaller because they came first in evolution

• Eukaryotes have membrane bound organelles, while prokaryotes don't

E coli

A common type of bacteria, which is found in the human body which both helps and can hinder the body. Model organism

Prokaryotic division

Binary fission is much simpler than mitosis

Reproduce asexually, DNA is replicated, makes 2 DNA loops that attach to membrane

Membrane gets linger and pinches off (cytokinesis) separates, forming 2 separate daughter cells

Compartmentalized cell structure Advantages

Occurs in eukaryote cells

Efficacy of metabolism

Enzymes and substrates can be localised/concentrated

o Localised conditions

pH and other factors can be kept at optimal level

o Toxic/damaging substances can be isolated

o Numbers and locations of organelles can be changed

Cell wall

Extracellular component, not organelle, secreted by all plant cells and some fungi + protists

Mainly made of cellulose which is

• Permeable - things can move in and out of cell

• Strong - gives support+ prevents it from bursting under pressure

• Hard to digest - resistant to being broken down, lasts long time w/o replacement

Plasma membrane

controls passage of materials in and out of the cell

Mitochondria electron micrograph

Chloroplast electron micrograph

Golgi apparatus electron micrograph

Endoplasmic Reticulum electron micrograph

nucleus electron micrograph

circle on the right