1. Intro to cells Flashcards
The cell definition
a self-contained membrane-bound unit which carries out the functions of life; organized, autonomous, and internally regulated
reductionist
- takes one theory to be reduced to another theory
* thinking about life in reduced terms
Cell Biology is reductionist in nature
- Knowledge of the parts may explain the whole
- some may view cell as a machine, but many of the components are still unknown (very complex)
- understanding the workings of cells can reveal much about the nature of life
7 facts on cells
- reproduce themselves
- acquire and use energy
- perform chemical reactions (metabolism)
- reproduce themselves (meiosis and mitosis)
- are dynamic (capable of movement)
- respond to stimuli (have to be responsive (chemicals most of the time))
- self-regulate (grow? die? divide? change metabolic rate?)
In humans, over _____ different types of cells, yet all arose from ________ cell. There are _____ of subcell types within the ______ cell types.
200, single, hundreds, 200
what’s interesting about cells? (7)
- their complexity
- inter-relations of cells
- intra-relations of cells
- how cells respond to their environment
- their ability to live and reproduce
- their ability to grow and change
- they are what makes up you and the food you eat
The study of cells started with the development of __________
microscopes
Robert Hooke (1665)
- described cells in cork (empty, dead cells)
- he looked dat the cross section of cork
- he was looking at dried up, dead cells
- came up with the term cells
Anton Van Leeuwenhoek (1665-1675)
- first to describe living cells
- used a handheld microscope
- studied on animalcules (microscopic animals)-vorticella (sedentary, single celled aquatic animals with a contractile stalk and a bell-shaped body bearing ring of cilia)
- father of microbiology
how many tenets of cell theory are there?
three
which people are involved wit the tenets of cell theory?
Theodor schwann (1839) Rudolf Virchow (1855)
Theodor Schwann (1839)
- first two tenets of cell theory
- started realized common properties
1. all organisms composed of one or more cells
2. cells are the structural unit of life
Rudolf Virchow (1855)
- third tenet
3. cells can arise only by division from pre-existing cells
volvox
a simple multicellular organism
green single-celled aquatic organism which forms minute free-swimming spherical colonies
Common plan of all cells (4)
- all enclosed by a physical barrier (cell membrane-> can have complexity outside of membrane (Cell wall))
- All have a blueprint - DNA
- blueprint directs the construction of machinery to get energy from environment
- use energy to duplicate blueprint and machinery
two classes of cells:
prokaryotes and eukaryotes
Prokaryotes
-before nucleus
*single celled organisms
*1-10 um (recently, rare exceptions have been found to be larger)
*loosely packed DNA lies free in the cytoplasm
*DNA is not associated with DNA-condensing proteins
*include bacteria and archaea (extremophiles)
*binary fission is division process
*smaller than eukaryotes
*no membrane bound organelles
(bacterial flagellum, ribosomes, DNA of nucleoid, plasma membrane, cell wall, capsule)
Eukaryotes
- true nucleus
- protists, fungi, plants, animals
- membrane-bound nucleus; more DNA than prokaryotes
- typically 10-100um in diameter
- cells have organelles (mitochondria, endoplasmic reticulum, Golgi apparatus, etc..)
- divide by mitosis/meiosis
- cells have more complex cytoskeletons and motility machinery than prokaryotes
- big in comparison to prokaryotes
Viruses
- crossroads between living and non-living matter
- reproduce only in cells
- inert (lacking the ability or strength to move AKA not chemically reactive) out side of cells
- viruses are bits of nucleic acids that have a protein coat
- once attached onto the cell surface the virus exposes nucleic acid
* tricks cell into making more viruses (cell does the replicating) - organic, biomolecules
- highjack/infect other cells
Are viruses alive?
they are not alive because they lack the ability to reproduce without the aid of a host cell and don’t use typical cell division to replicate
Viroids
- circular RNA without protein coat
- nucleic acid only
- effect plants (plants make more viroids)
Prions
- proteinaceous infectious particles (infectious proteins)
- no nucleic acid
- can self replicate
- finds other similar proteins and stick to them
how are prokaryotes and eukaryotes related? (6)
- similar plasma membranes
- same genetic code
- similar mechanisms for “decoding” genetic cod
- many of the same metabolic pathways
- similar use of ATP for energy
- similar mechanisms of photosynthesis (cyanobacteria and plants)
how many species have been used more extensively in cell biology research than any other species?
six
- e.coli
- saccharomyces cerevisiae
- arabidopsis thaliana
- caenorhabditis elegans
- drosophila melanogaster
- mus musculus
E. coli
our first understanding of DNA replication, transcription, and translation
- small
- lots of tools to work with
- started molecular bio
- found in poop feces
Saccharomyces cerevisiae
simplest eukaryote many mutants yeast quick to reproduce small, can have lots
arabidopsis thaliana
fast growing plant small genome (genome-organisms complete wet of DNA, including all of its genes. each genome contains all the info needed to build and maintain the organism)
Caenorhabditis elegans
~ 1000 cells
- short life cycle
- free living
- transparent nematode
- live in temperate soil environments
Drosophila melanogaster
- 1000s of mutants
- best characterized genome
- transflies
mus musculus
- 1000s of mutants
- rats
- easiest mammal for genetics studies
- hairless
- small
why are cells small?
- if surface area drops, difficult to take up nutrients and rid wastes
- cells depend on diffusion to move substances -large cells unable to diffuse quickly
to maintain a proper surface area/volume ratio
-as cell size increases, surface area/volume decreases
-if surface area drops, difficult to take up nutrients and rid wastes (large cells unable to diffuse quickly. Need to be able to move cells out quickly)
A=4(pi)r^2
V=4/3(pi)r^3
Large celled exceptions
- absorptive epithelium-microvilli for absorption
- eggs-small amount of protoplasm on big yolk
- nerve cells-long length, narrow width
Chemical composition of a cell:
Elements
- 59% H
- 24% O
- 11% C
- 4% N
- 2% Others, P, S, etc..
Note: Carbon based but not the most common
Chemical composition of a cell:
Molecules
- 70% water (by weight)
- 15% protien
- 5% nucleic acid
- 5% carbohydrates
- 3% lipids
- 2% other
Cells are the _________ unit of _______.
smallest, life
