section 4 Flashcards
(72 cards)
The light microscope originally
around since the early 1600’s. Robert hooke used it to first find the description of a cell
Antoni Van Leeuwenhoek
the father of biology– was a fabric merchant who saw Robert Hooke’s work and was inspired to make his own light microscope which magnified up to 200-250x
what kinds of structures did Leeuwenhoek funk
sperm muscle cells red blood cells capillaries protists bacteria
visual angle
an angle subtended at the eye by an object
how microscopes generally work
increase the size of an image on the retina. THIS IMAGE SIZE IS GOVERNED BY VISUAL ANGLE. the size of an image is directly proportional to the visual angle
step by step how micrsoscopes work
light from larger object close to the eye hits the eye at a large visual angle producing a large image on the retina
objects a long way away or small objects make a tiny visual angle with he eye and the lense focuses a tiny image on the retina
microscopes bend light to increase the visual angle and give more info to the retina
3 main points in microscopy
- magnification: ratio of image size to real size
- resolution: min distance by which two points can be separated and still seen as two points
- contrast: diff between light and dark areas in an image. can be done wit staining or labelling certain structures within a cell
what limits light microscope
the wavelength of light. objects smaller than half the wavelength of light used to illuminate the specimens effectively hide within the wavelength and cant be resolved
cell fractination
biologists help couple structure with function- homogenize
repeated centrifugations at increasing speeds
cell components can be separated starting with largest structures which can be identified using a light microscope
differences between prokaryotes and eukaryotes
- size: E are generally 10x bigger
- arrangement of DNA: E have proper membrane bound nucelus containing DNA. P have a nuceloid region
- internal compartments: E have membrane bound organleeld and P do not
common traits of Prokaryotes and Eukaryotes
- plasma membrane
- cytosol/ cytoplasm
- chromosomes (DNA)
- ribosomes
smallest prokaryote cells
mycoplasmas
prokaryotes general info
they have a lower size limit set by requirements for DNA , cellular machinery, etc. to run essentials of life
upper size limit for eukaryotes
there is no very big unicellular organisms because of SA/V ratio
importance of SA/V ratio
cells aqquire nutrient molecules and remove waste by moving them across the cell membrane and all parts of a cell must be in molecular communication with the membrane meaning that surface area must be big enough for efficient exchange of molecules and volume must be small enough for the same reason
the natural limit of max size of a cell
the idea SA/V ratio that allows efficient molecular transfer throughout the cell. Big organisism solve this SA/V ratio bu being made of lots of tiny cells each having its own membrane and surrounded by extracellular fluid
jobs of integral/ peripherla proteins
- transportaion of hydrophillic molecules
- enzyme activity: preform metabolic processes at the edge of the cell both inside and outside
- signal transduction: signalling molecules, cause a cascade of activities to happen inside the cell like dorbells
- cell-cell recognition: recognizing other cells by binding to carb ID tags attached to membrane proteins
- intercellular joining: cells join together to make tissues. long lasting binding of cells, tight and gap juctions
- attachments to cyto and exoskeleton: give stronger framework.
glycoproteins
carbohydrate ID tags attatched to membrane protiens. This is important in blood types, immune system recognition of foreign bodies, and embryology (sorting of cells)
temeprature buffer
cholestrol. keeps particles from closely packing in cold temperatures and stabilizes them in warmer temperatures so they don’t become too leaky.
memrane proteins
integra (transmembrane) and peripheral proteins
what affects membrane fluidity
temperature and nature of hydrocarbon tails (striaght of bendy chains)
2 ways of getting through the membrane
- direct
2. through the membrane
what type of molecuels can directly dissolve through the membrane
small, hydrophobic, non polar molecuels such as o2, co2, and somewhat water even tough it is charged because it is small
what molecules have to go through the membrane
polar, charged, hydrophillic molecules have to go through TARGET SPECIFIC channel and carrier proteins