what is a cell
fundamental/basic unit of life
all organisms are made of either a single cell/grp of cells
who were the first individuals to observe cells
robert hooke - 1665
described chambers of cork as “cells”
was looking at empty walls, the remains of dead cells
anton van leeuwenhoek - 1673-1700
early light microscopist - improved mag power of microscope lenses
saw “animalcules” in pond water
who is robert hooke
1665 - one of the first to observe cells
chambers of cork - “cells”
empty, dead cell walls
who is anton van leeuwenhoek
1673-1700 - one of the first to observe cells
early light microscopist - improved mag power of microscopes
“animalcules” in pond water
what are 3 kinds of microscopy to view cells
light, electron, fluorescence
what are the 3 tenets to the cell theory
- all living organisms are comped of one (unicellular) or more (multicellular) cells
- each cell is the structural and functional unit of life
- cells can arise only from pre-existing cells
schleiden & schwann - 1, 2
virchow - 3
who made the main contributions to the cell theory
- schleiden (1839) - german botanist
all plant tissues composed of cells; plant embryos arise from single cell - schwann (1839) - german zoologist
same conclusion abt animals; plants & animals similar - virchow (1855) - german zoologist
added the third tenet
what are the 2 classes of cells
prokaryote (before nucleus)
- most abundant organisms on earth
- includes bacteria and archaea
eukaryote (true nucleus)
- includes eukarya
what are basic properties of cells?
- all enclosed by physical barrier (cell membrane)
- cytoplasm: all contents found in cell membrane
- cytosol: jelly-like internal fluid environ of a cell (cytoplasm less organelles), contains h2o, dissolved ions, molecules - genetic program: DNA and central dogma
- can produce more of themselves: duplicate genetic material before division
- acquire and utilize energy (bioenergetics)
- ex. light energy -> chem energy in plants - carry out a variety of chem reactions
- ex. metabolic pathways (cellular metabolism) such as glycolysis and citric acid cycle - engage in numerous mechanical activities
- ex. material transported in/out of/thru cell - can respond to stimuli (receptors)
- capable of self-regulation
- inability: uncontrolled growth
what are exceptions to the cell theory
- viruses
- small amnts of nucleic acids w/ protein coat
- outside of living cell -> inert
- host cell is needed for viral reproduction - viroids
- small circular rna lacking protein coat
- need host machinery to replicate - prions
- proteinaceous infectious particles
- no nucleic acids
how do nucleic acids store and transfer info
cells contain a stable blueprint of info in a molecular form as deoxyribonucleic acid (DNA)
molecular structure and base pairing of dna double helix ensures fidelity during replication - make more copies of dna
what are prokaryotes
single cell organisms that don;’t have nucleus/membrane bound organelles
simple organization
how does information flow from dna to rna to protein?
the central dogma is the theory that info flows from dna to rna to protein
a gene is th edna code for the info necessary to produce a functional product (product is usually protein)
dna is initially transcribed into rna message, then changed into a similar language of nucleic acids
rna message -> translated into protein, change from nucleic acids to amino acids
what are the 2 prokaryotic domains
both have single circular chromosome
- bacteria - many have plasmids, cell wall surrounding cell membrane
- archaea - isoprenoid cell membrane, often inhabit extreme environments
what are features of prokaryotes
rely primarily on cell wall and internal rigid protein framework for support
what are fungi
have cell walls with chitin - modified polysaccharide
includes yeasts, rusts, smuts, mildews, molds and mushrooms
heterotrophs - dependent on preformed organic molecules for carbon and energy, absorb directly from environment
what are eukaryotes
cells have a membrane bound nucleus
includes: protists, fungi, plants, animals
what are protists
diverse grp - mostly single cells but some form colonies
includes: algae, water molds, slime molds, protozoa
what are plants
multicellular and have cell walls made of polysacch
have large water filled vacuoles - contributes to turgor pressure
have intercellular connections - plasmodesmata
are autotrophs - make their own food, chloroplasts convert sun’s energy to chem energy
brief overview of eukaryote features
membrane bound nucleus (stores chromosomes)
organized by:
- internal protein scaffolding known as cytoskeleton (can be remodelled quickly)
- dynamic membranes (endomembrane sys)
what are animals
multicellular, don’t have cell walls
heterotrophs - gain energy/carbon thru preformed org molecules
distinct mode of early development
what is the cytoskeleton and what is its role
provides internal support for cells
all eukaryotes have 2 cytoskeletal elements (microfilaments and microtubules)
animals have a third cytoskeletal element (intermediate filaments)
what is an intermediate filament
strong fiber composed of intermediate filament protein subunits
what is a microfilament
double helix of actin monomers
