Chapter 4 - general features of the cell Flashcards
which monomers of macromolecules were produces prior to the existence of cells?
nucleotides and amino acids
four overlapping stages @ origin of life
- nucleotide and amino acids produces prior to the existence of cells
- nucleotides and amino acids polymerized into DNA, RNA, and proteins
- likely formed on clay surfaces (not aqueous solution) - aggregate of prebiotic molecules became enclosed in membranes
- Polymers enclosed in membranes acquired cellular properties
which macromolecule were the first of protobionts (non-living organic molecules in a membrane)
RNA
Advantages of a DNA, RNA, and protein world
- evolution of DNA relieves RNA of informational role and allowed RNA to perform other functions
- DNA less likely to undergo mutations
- Protein have a greater catalytic potential and efficiency (better for metabolic functions)
- proteins also useful for structure and transport
cell theory
- all living organisms are composed of one or more cells
- cells are the smallest units of life
- new cells come only from pre-exiting cell by cells division
3 visual adjustments in microscopy
- resolution
- the ability to observe two adjacent objects as distinct from one another - contrast
- how different structures look from one another
- can be enhanced by special dyes (most cells are transparent, many dyes have an affinity to the nucleus) - magnification
- ratio between the size of an image produced by a microscope and its actual size
two kinds of microscopes
- light microscope
- 0.2 micrometer resolution (200nm)
- election microscope
- 2nm resolution (100x better than light)
two methods of fluorescent microscopy
- standard - used to specifically label a particular type of protein or organelle
- confocal - computer takes image in slices so its less blurry
two types of electron microscopes
- Transmission electron microscopy (TEM)
- bean of electrons transmitted through sample
- thin slices stained with heavy metals
- some electrons are scattered while others pass through to form an image - scanning electron microscopy (SEM)
- sample coated with heavy metal and beam scans surface to make 3D image
prokaryotes
- simple cell structure with DNA but no nucleus (nucleoid)
- aren’t very complicated but can still be interesting (extremophiles)
- 1-10 micrometers in diameter
- about 10x smaller than eukaryotes
eukaryotes
- DNA enclosed within membrane-bound nucleus (double membrane)
- internal membranes form organelles
how polar vs non polar molecules get through the membrane
- polar molecules use transmembrane proteins
- non polar molecules can diffuse through the membrane
two types of prokaryotes
- bacteria
- very abundant in the environment and our body
- vast majority is not harmful to humans but some can cause disease - archaea
- less common
- often found in extreme environments
parts of bacterial cell
inside plasma membrane
- cytoplasm
- nucleoid region
- ribosomes
outside plasma membrane
- cell wall
- glycocalyx
- pili and flagella
cytoplasm
all substance between the plasma membrane and the nucleus
cytosol
fluid part of the cytoplasm
nucleoid region
part of prokaryotic cells where DNA congregates
ribosomes
site of protein synthesis
cell wall
provides support to plant cells
glycocalyx
- gel-like material that is sticky and allows cells to adhere to surfaces to live on
- helps protect the cell, especially from pathogens
cell appendages
- pilli (attachment)
- flagella (movement)
characteristics of eukaryotic cells
- DNA housed inside membrane-bound nucleus
- organelles
- variety in shape, size, and function
- compartmentalization - allows for more specialization
oganelles
membrane-bounds compartments found in eukaryotic cells that have a unique structure and function
how does cell morphology vary?
- eukaryotic cells have lots of variation and shape
- even cells with the same genome can have different morphologies
- ex: brain cells are designed so they can have lots of contact with other cells
what do plant cells have that animal cells don’t?
- Central Vacuole - provides storage for waste and regulation of cell volume (prevents lysing)
- cell wall - provides support to the cell
- chloroplast - makes sugar that the cell breaks down for energy
Centrosome
site where microtubules grow and centrioles are found
nuclear pore
passage way for molecules into and out of the nucleus