2. The Cell Flashcards
what are the 3 rules of cell theory
- all organisms are made of 1 or more cells
- cells are basic units of organization in all organisms
- A cell can only arise from division of previously existing cell
why are cells small
small cell is advantageous in terms of surface area to volume ratio
smaller flatter cell with large surface area to volume ratio is more efficient in diffusion and removal of wastes
what happens to the cell in terms of volume and surface area as it gets larger
volume increases at faster rate than surface area (lower surface area to volume ratio)
what does light microscopes operate on
visible light
what is the function of the first and second lens in a light microscope
first lens focuses image onto second lens
image is magnified and is focused on back of eye
what are compound microscopes
microscopes that magnify using multiple lenses
at what measurements can light microscopes resolve
structures that are at least 200nm apart
what does an electron microscope operate on
electrons
how much more resolving power do electron microscopes have compared to light microscopes
1000x more
how do transmission e- microscopes work
e- transmit through the material
at what measurements can transmission e- microscopes resolve
resolves images 0.2mm apart
how do scanning e- microscopes work
beams e- onto surface of specimen
e- reflect back from surface and other e- from specimen are released from bombardment
e- amplified and transmitted to screen
produces 3D image
what are the 4 major features that all cells have in common
nucleoid/nucleus
cytoplasm
ribosomes
plasma membrane
what is the purpose of the nucleoid/nucleus
contains DNA
where is DNA found in prokaryotes
in centre of cell in nucleoid
where is DNA found in eukaryotes
DNA found in nucleus
what surrounds the nucleus in eukaryotes
double membrane called nuclear envelope
what is the cytoplasm
semi fluid matrix filling the cells interior
what does the cytoplasm contain
all of amino acids, proteins and sugars essential to the cell
what role does the ribosome play
protein synthesis
what is the plasma membrane
phospholipid bilayer with proteins embedded
what does the plasma membrane do
encloses the cell and separates the internal components of cell from environment
what are the 2 types of proteins in plasma membrane
transport and receptor
what is the purpose of transport proteins
help ions/molecules move across plasma membranes
what is the purpose of receptor proteins
bring about changes in the cell when receptors come into contact with molecules (eg hormones)
what are the 3 outside layers of a prokaryote cell from outside to inside
cell wall
plasma membrane
cytoplasm
are DNA and cellular constituents membrane bound in prokaryotes
no they have access to entire interior of cell
what are the 2 domains of prokaryotes
bacteria and archaea
what does the bacterial cell wall consist of
peptidoglycan
what does the cell wall do for bacteria - 3 things
maintain shape of cell
protect cell
prevent excessive loss/uptake of water
what can bacteria have that surrounds the cell wall
protective capsule
what does the cell wall of archae consist of
pseudopeptidoglycan
what do flagella allow
movement