typical human body cell
many times smaller than a grain of sand
scientists became aware of cells
whem microscopes were invented in 1600
Robert Hooke
used a crude microscope to observe a thin slice of cork 1665 he saw a lot of little boxes, reminded him of room monks lived in,he called them cells later observe cells in roots of plants
Anton van Leeuwenhock
Dutch scientist used microscope to view water from a pond discovered small living creaturescalled it animalcules or tiny animals, today we know not animals but single-celled organisms
metric system
International System of Measurements abbriviate SI decimal system unites based on powers of 10
light microscopes
use 2 lenses called compound light microscope light bulb in base shines up through specimen mounted on glass slide
objective lens
closest to specimen collects the light travels to ocular lens closest to eye both lenses magnify 40x objective and 10x oculur lens = 400x
most powerful light microscope
magnify 2000x see small as 0.5 um in diameter
how see small objects?
wavelength of the light beam must be shorter than the wavelength of visible light electron beams have a much shorter wavelength than visible light electron microscope more powerful than light microscopes
electron microscopes
magnify 200,000x can be used to study very small structures inside cells or cell surfaces both electron beam and specimen must be placed in vacuum chamber so the electron in beam won't bounce off gas molecules in air not view living cells cause can't surv
transmission electron microscope
a microscope that transmits a beam of electrons through a very thin slice of specimen and that can magnify up to 200,000 times (abbreviation, TEM)
scanning electron microscope
a microscope that produces an enlarged, three-dimensional image of an object by using a beam of electrons rather than light
SEM
SCANNING TUNNELING MICROSCOPE
microscope that measures differences in voltage of electrons leaving the surface of an object and creates a three-dimensional image of the object; can be used to study living organisms
Mattias Schleiden
german botanist says cells make up not only stems and roots but whole plant
theodor schwann
german zoologist says animals have cells
rudolph virchow
1858 german physician says cells come from other cells
cell theory
all living things are made of cells one or more
cells are basic units of structure and function in organisms
all cells arise from existing cells
cell size
small cells fuction more efficiently than large ones. 100 trillion cells in human body ranging from 5 um to 20 um in diameter
what is advantage of having many tiny cells instead of fewer large ones?
all substances that enter or leave a cell must cross the cell's surface. if cell surface area-to-volume ratio is too low substances cant enter and leave the cell in numbers large enough to meet cells needs. small cells can exchange substances more easily
total surface area of cube
side length squared x number sides = units squared
volume of cube
length squared x heigth= units cubed
surface are to volume ration
total surface are 96 = 3
volume 64 2
prokaryote
a single-celled organism that does not have a nucleus or membrane-bound organelles; examples are archaea and bacteria
early prokaryote
lived 3.5 billion years ago 2 billion years proaryote only organisms on earth
actin fibers
a kind of cytoskelton fibers: long, slender microfilaments made of the protein actin determine shape of animal cells
microtubules
are hollow tubes, like plumbing pipes that maintain the shape of the cell and serve as tracks for organelles to move along within the cell RNA molecules are transported alon microtubular rails
intermediate fibers
Moderately thick and mainly anchor organelles and enzymes to certain parts of the cell.
cell membrane
The lipid bilayer that forms the outer boundary of the cell controls what leaves and gets through
mitrochondria
eukaryotic energy warehouse; access energy called ATP by cellular respiration; folds are cristae; has its own DNA
chloroplasts
organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis
central vacuole
a large, fluid-filled organelle that stores not only water but also enzymes, metabolic wastes, and other materials
plant cells have 3 that animals lack
a cell wall,chloroplasts central vacuole
all cells have?
cell membrane, cytoplasm, ribosomes and DNA
PROKARYOTIC CELL
LACK INTERNAL COMPARTMENTS
Lipid bilayer
made of cell membrane made double layer of phospholipid molecules
lysosomes
digest recycle cells used components