What are the four tenets of cell theory?
1) All living things are composed of cells
2) The cell is the basic functional unit of life
3) Cells arise
... [Show More] only from preexisting cells
4) Cells carry genetic info as DNA and DNA is heritable
What is the nucleus of a cell composed of?
The nucleus contains DNA organized into chromosomes and is surrounded by a double membrane nuclear envelope that contains nuclear pores for a two-way exchange of materials. Additionally, a subsection of the nucleus is called the nucleolus and is where rRNA is synthesized
What is the structure of a mitochondrion?
The mitochondrion has a double membrane. The outer membrane forms a barrier with the cytosol while the inner membrane is folded into cristae that contain enzymes for electron transport. The membranes are separated by an intermembrane space where there is a high concentration of protons. Mitochondria also contain their own DNA and divide independently
What is the structure of the ER?
The ER is an interconnected series of membranes continuous with the nuclear envelope. The rough ER has ribosomes to translate secreted proteins. The smooth ER is used for lipid synthesis and detox.
What is the structure of the Golgi apparatus?
The Golgi consists of stacked sacs that modify cellular products to direct to specific locations
What are perioxisomes?
Organelles that contain H2O2 and break down long chain fatty acids via beta-oxidation.
What is the structure of the cytoskeleton?
1) Microfilaments composed of actin that provide structure, cause muscle contraction with myosin, and form a cleavage furrow during cytokinesis
2) Microtubules composed of tubulin that create pathways for motor proteins (kinesin and dynein0 and contribute to the structure of flagella and cilia with a 9+2 structure
3) Centrioles are found in centrosomes and involve microtubule organization in the mitotic spindle
4) Intermediate filaments that do cell-cell adhesion and maintain integrity of cell and anchor organelles (subtypes are keratin and desmin)
Which cells line body cavities and organs?
Epithelial cells, which form parenchyma around organs. they are usually polarized and can be classified into simple, stratified, and pseudostratified (one layer of varying cell height). Epithelial cells can be cuboidal, columnar, or squamous (flat)
What are the different shapes of bacteria?
1) Cocci (spherical)
2) Bacilli (rod shape)
3) Spirilli (spiral)
How are bacteria categorized by metabolic processes?
1) Obligate aerobes (need oxygen)
2) Obligate anaerobes (cannot survive in oxygen-containing environments)
3) Facultative anaerobes (can toggle between anaerobic and aerobic)
4) Aerotolerant anaerobes (cannot use oxygen but can tolerate its presence)
What is the structure of gram-negative bacteria?
1) Thin cell wall composed of peptidoglycan
2) Outer membrane composed of phospholipids and lipopolysaccharides
What is the structure of gram-positive bacteria?
1) Thick cell wall composed of peptidoglycan and lipoteichoic acid
How do you tell the difference between gram-positive and gram-negative bacteria?
Gram staining -- use a crystal violet stain and then counterstain with safranin
- Gram-positive turn purple while gram-negative turn pink-red
What is chemotaxis?
Movement of an organism in response to a chemical stimulus, such as the flagellar activation of a bacteria toward food or away from immune cells
How is electron transport in prokaryotes different from eukaryotes?
In eukaryotes, electron transport is done on the inner mitochondrial membrane. In prokaryotes, electron transport is done on the cell membrane
Compare prokaryotic ribosomes to eukaryotic
Prokaryotic ribosomes are smaller (30S and 50S) than eukaryotic ribosomes (40S and 60S)
What is binary fission?
The method of prokaryotic reproduction, in which a chromosome replicates while a cell grows in size. Then, the cell wall grows inward along the midline of the cell and divides into two identical daughter cells
What are plasmids?
Plasmids are small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like virulence factors or antibiotic resistance and can be passed between bacteria
What are episomes?
Plasmids that can integrate into the host genome
What are the methods of bacterial genetic recombination?
1) Transformation - genetic material is taken up by the cell and incorporated into the bacterial genome
2) Conjugation - genetic material is transferred across bacteria through a conjugation bridge. A plasmid can be transferred from F+ to F- cells or part of a genome can be transferred from an Hfr cell to a recipient
3) Transduction - transfer of genetic material from one bacterium to another via a bacteriophage vector
4) Transposon - genetic elements that can insert into or remove themselves from the genome
What are the stages of bacterial growth?
1) Lag - adapt to new conditions
2) Exponential (log) phase - growth increases exponentially
3) Stationary phase - resources are reduced and growth levels off
4) Death - resources are depleted
What are the components of a virus?
1) Genetic material
2) Protein coat (capsid)
3) Lipid-containing envelope (sometimes)
How do bacteriophages target bacteria?
Bacteriophages inject genetic material into the bacterium through a tail sheath by attaching itself via tail fibers
Compare positive sense from negative sense viruses.
Both are ssRNA viruses but positive sense can be translated directly by the host cell while negative sense must first synthesize a complementary strand via RNA replicase
What are retroviruses?
ssRNA viruses that form a complementary DNA strand through reverse transcriptase that can be integrated into the host genome
Compare the lytic vs lysogenic cycle.
During the lytic cycle, a bacteriophage will produce more virions until the cell lyses, and bacteria are termed virulent. In the lysogenic cycle, the virus integrates into the host genome and can reproduce with the cell
What are prions?
Infectious proteins that trigger misfolding of other proteins. This is done by converting an alpha-helical structure to a beta pleated sheet that promotes aggregation
What are viroids?
Plant pathogens that are small circles of complementary RNA. They can turn off genes that are critical for cell function [Show Less]