Ch. 1: The Cell Flashcards
Cell Theory
- All living things are composed of cells
- The cell is the basic functional unit of life
- Cells arise only from preexisting cells
- Cells carry genetic info in the form of DNA– it is passed from parent to daughter cell
Eukaryotes
membrane bound organelles, nucleus and can form multicellular organisms
Cell Membrane and Membranes of Organelles
contain phospholipids which organize to form hydrophilic interior and exterior surfaces w a hydrophobic core
Cytosol
Suspends organelles and allows diffusion of molecules throughout the cell
Nucleus
Contains linear DNA wound around organizing proteins called histones then is wound/organized into linear strands called chromosomes
- In nucleus allows for compartmentalization of DNA transcription separate from RNA translation
Nuclear Membrane/Envelope
Double membrane w nuclear pores for two-way exchange of materials between the nucleus and cytosol; maintains a nuclear environment separate and distinct from cytoplasm
Nuclear Pores
In the nuclear membrane, allow selective two-way exchange of material between the cytoplasm and the nucleus
Genes
Arrangement of DNA, coding regions
Nucleolus
Subsection of the nucleus where ribosomal (rRNA) is synthesized, can be identified as a darker spot in the nucleus, takes up 25% of nucleus volume
Mitochondria
Contain an outer and inner membrane
-Outer membrane: forms barrier w cytosol
- Inner membrane: folded into cristae, contains enzymes for the electron transport chain
-Intermembrane space: between the membranes
-Matrix: inside the inner mitochondrial membrane
Can divide independently from nucleus via binary fission (paradigmatic example of cytoplasmic or extranuclear inheritance,
cytoplasmic or extranuclear inheritance
The transmission of genetic material independent of the nucleus
Mitochondria triggering apoptosis
can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm (Bax Bcl thing)
- Kidney senses when oxygen is low
- Kidney releases EpO which leads to production of RBCs
- EpO releases Bcl which inhibits Bax
- Bax: forms the pore in mitochondria that releases cytochrome C
which activate caspases (ETC enzymes) which lead to apoptosis
Lysosomes
Contain hydrolytic enzymes that can break down substances ingested by endocytosis and cellular waste products. When these enzymes are released, autolysis of the cell can occur
Endosomes
Transport, package, and sort cell material travelling to and from the membrane: capable of transporting material to the trans-golgi, to the cell membrane, or to the lysosomal pathway for degradation
Endoplasmic Reticulum
Series of interconnected membranes and is continuous w nuclear envelope. Double membrane of ER is folded into numerous invaginations, creating complex structures w a central lumen
- Rough ER: studded w ribosomes which permit translation of proteins destined for secretion (endomembrane sys)
- Smooth ER: used for lipid synthesis and detoxification
Endomembrane System
Endomembrane System: starts at the ER which releases vesicles that go to golgi, where vesicle is sent to its proper place like lysosomes, plasma membrane, blood etc
- Targeting signal: ~20 amino acids long @ start of polypeptide (N terminal), Used to get protein into SRP to go to the ER, binds to receptor which lets it into lumen of ER
- Signal Recognition Protein (SRP), binds to targeting signal, pauses translation, Binds to surface of ER
- When the ribosome/mRNA/targeting protein/SRP complex binds to the surface of ER: SRP comes off, translation continues, polypeptide snakes into lumen of ER via a pore, A polysaccharide is covalently attached to polypeptide coming in (it’s a glycoprotein), Polypeptide starts folding up– HSP90 chaperone there that is helping w/ folding inside, An enzyme chops off targeting signal, Golgi modifies polysaccharide and sends out vesicle w protein to lysosome, cell membrane or back to ER based on a secondary signal on protein
Golgi Apparatus
Consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations
Peroxisomes
Contain hydrogen peroxide and can break down very long chain fatty acids via beta oxidation. They also participate in phospholipid synthesis and the pentose phosphate pathway.
Cytoskeleton (not under organelles):
Provides stability and rigidity to the overall structure of the cell while also providing transport pathways for molecules within the cell:
Microfilaments
part of cytoskeleton: Composed of actin, provide structural protection for the cell and can cause muscle contraction through interactions with myosin, also help form the cleavage furrow during cytokinesis in mitosis
Microtubules
Composed of tubulin (non covalently bonded), create pathways for motor proteins like kinesin and dynein to carry vesicles, contribute to cilia and flagella structures where they are organized into 9 pairs of microtubules in a ring w 2 microtubules at the center (9+2 structure)
- Centrioles: found in centrosomes and are involved in microtubule organization and the mitotic spindle
Cilia vs Flagella
Both made of microtubules , cilia move materials along, flagella moves cell itself
Intermediate filaments
Involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; help anchor organelles, common examples include keratin and desmin
Epithelial Tissues
Cover the body and line its cavities, protecting against pathogen invasion and desiccation. Tightly joined to each other and and to an underlying layer of connective tissue known as the basement membrane. Some epithelial cells absorb or secrete substances, or participate in sensation:
Parenchyma
Functional parts of the organ, formed of epithelial cells
Epithelial cells
often polarized: one side facing a lumen or outside world and the other side facing blood vessels and structural cells
Epithelia classification by layers
Simple epithelia: one layer
Stratified epithelia: many layers
Pseudostratified epithelia: appear to have multiple layers bc of differences in cell heights, but actually have only one layer
Epithelia classification by shapes of cells
Cuboidal cells: cube shaped
Columnar cells: long and narrow
Squamous cells: flat and scalelike
Connective Tissues (not part of epithelia):
Support the body and provide a framework for epithelial cells: bone, cartilage, tendons, ligaments, adipose tissue, blood
Stroma
Support structure, formed of connective tissues that secrete materials to form an extracellular matrix
Prokaryotes
Do not contain membrane-bound organelles; organize their genetic material in a single circular molecule of DNA concentrated in the nucleoid region
3 overarching domains of life
- Archaea: often extremophiles, live in harsh environments (high temp, high salinity, no light), often use alternative sources of energy like chemosynthesis, similarities to both eukaryotes (start translation w methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding)
- Bacteria: many similar structures to eukaryotes, and have complex relationships w humans including mutualistic symbiosis and pathogenesis
- Eukarya: only non-prokaryotic domain
Bacteria relationship to humans
Mutualistic symbiotes: both humans and bacteria benefit vs Pathogens or parasites
Bacteria classification by shape
- Cocci: spherical
- Bacilli: rod shaped
- Spirilli: spiral shaped
Bacteria classification by metabolic processes
- Obligate aerobes: require oxygen for metabolism
- Obligate anaerobes: cannot survive in oxygen-containing environments and can only carry out anaerobic metabolism
- Facultative anaerobes: can survive in environments with or without oxygen and will toggle metabolic processes based on the environment
- Aerotolerant anaerobes: cannot use oxygen for metabolism, but can survive in an oxygen containing environment
Envelope
Formed by cell wall and cell membrane of bacteria, together control the movement of solutes into and out of the cell
Bacteria classification by Gram staining
Color their cell walls turn during Gram staining w crystal violet stain followed by a counterstain w safranin.
- Gram positive: turn purple, thick cell wall composed of peptidoglycan (polymeric substance made from amino acids and sugars) and lipoteichoic acid (may activate human immune sys)
- Gram negative bacteria: pink-red, thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides
Bacterial movement:
Bacteria may have 1, 2 or many flagella that generate propulsion to move the bacterium toward food or away from immune cells. Bacterial flagella contain a filament composed of flagellin, a basal body that anchors and rotates the flagellum and a hook that connects the two
Chemotaxis
moving in response to chemical stimuli
Motion by flagella
Composed of a filament, a basal body, and a hook:
- filament: hollow helical structure composed of flagellin
- basal body: complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum
- hook: connects the filament and basal body so that as the basal body rotates, it exerts torque on the filament, which can spin and propel the bacterium forward
Prokaryotes carry out the electron transport chain using
The cell membrane
Prokaryotic ribosomes are ______ than eukaryotic ribosomes
Smaller than (30S and 50S vs 40S and 60S)
Binary fission
Method by which prokaryotes multiply, circular chromosome attaches to cell wall and replicates while cell grows in size until cell wall begins to grow inward along the midline of the cell and divides it into two identical daughter cells. Proceeds rapidly, fewer steps than mitosis
Plasmids
In addition to single circular chromosome in prokaryotes, extrachromosomal material can be carried in plasmids, may contain antibiotic resistance genes or virulence factors
Episomes
Plasmids that can integrate into the genome
Bacterial genetic recombination:
Increases bacterial diversity: transformation, conjugation, transduction, transposons
Transformation
Acquisition of genetic material from the environment, which can be integrated into the bacterial genome
Conjugation
Transfer of genetic material from one bacterium (+) to another (-) across a conjugation bridge made from appendages called sex pili found on the donor male (+): a plasmid can be transferred from F^+ cell to F^- cells or a portion of the genome can be transferred from an Hfr cell to a recipient.
Sex factors
To form the pilus bacteria must contain plasmids know as sex factors that contain the necessary genes. Best studied sex factor is the F (fertility factor) in e. Coli bacteria w this plasmid are termed F+ cells without are called F- cells. During conjugation F+ cell replicates its F factor and donates the copy to the recipient converting it to a F+ cell this allows for rapid aquisition of antibiotic resistance or virulence factors throughout a colony
Transduction
Transfer of genetic material from one bacterium to another using a bacteriophage as a vector
Transposons
Genetic elements that can insert into or remove themselves from a genome
Pattern of bacterial growth
- Lag phase: bacteria adapt to new local conditions
- Exponential (log) phase: growth then increases exponentially
- Stationary phase: as resources are reduced, growth levels off
- Death phase: as resources become insufficient, bacteria begin to die
Capsid
Viruses contain genetic material, a protein coat (capsid) and sometimes a lipid containing envelope– viruses without envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time
Presence of a viral envelope
if an envelope is present, it will surround capsid and is composed of phospholipids and virus-specific protein. It is very sensitive to heat, detergents and desiccations so enveloped viruses are easier to kill
Host cell
Viruses are obligate intracellular parasites, meaning that they cannot survive and replicate outside of a host cell as they dont have the “machinery”: ribosomes for protein synthesis
Virions
Individual virus particles, viral progeny
Bacteriophages
Viruses that target bacteria. Contain a tail sheath which injects the genetic material into a bacterium and tail fibers which allow the bacteriophage to attach to the host cell. Remaining structures stay outside of bacterial cell
Viral Genomes
May be made of various nucleic acids. May be composed of DNA or RNA and may be single or double stranded. Circular or linear. Few genes or several hundred
Positive sense virus
Single stranded RNA viruses have RNA which can be translated by the host cell– like mRNA
Negative Sense virus
Single stranded RNA virus which have RNA where a complementary strand must be synthesized using RNA replicase. Complementary strand can be translated. Must carry RNA replicase in the virion
Retroviruses
Contain a single-stranded RNA genome to which a complementary DNA strand is made using reverse transcriptase. The DNA strand can then be integrated into the genome
Ways viruses infect cells
Attach to specific receptors and then either fuse with the plasma membrane, get brought in by endocytosis, or inject their genome into the cell
Virus Reproduction
Replicate and translate genetic material using host cell’s ribosomes, tRNA, amino acids and enzymes
Viral progeny release methods
Cell death: spilling of viral progeny, lysis as a result of filling w progeny (disadvantage bc virus can no longer use cell for reproduction), or extrusion: keeps cell alive to allow for continued use of the host cell by the virus–productive cycle
Life cycles of bacteriophages
- Lytic cycle: bacteriophage produces massive numbers of new virions until the cell lyses. Bacteria in the lytic phase are termed virulent
- Lysogenic cycle: the virus integrates into the host genome as a provirus or a prophage which can then reproduce along with the cell. The provirus then leaves the genome in response to stimulus at some later time and enters the lytic cycle.
Prions
Infectious proteins that trigger misfolding of other proteins usually converting alpha helical structure into beta pleated sheet decreasing the solubility and degradability of the misfolded protein
Viroids
Plant pathogens that are small circles of complementary RNA that can turn off genes, resulting in metabolic and structural derangements of the cell and–potentially–cell death
