B 1 - The Cell Flashcards
Describe the four tenets of Cell Theory
1 - All livings things are composed of cells
2 - the cell is the basic functional unit of life
3 - cells arise only from preexisting cells
4 - cells carry genetic info in the form of DNA. This genetic material is passed on from parent to daughter cell.
Are viruses considered living organisms?
No, because they are acellular, cant reproduce without assistance of a host cell, and may use RNA as their genetic material
Describe what makes eukaryotes unique from prokaryotes
Eukaryotes have membrane-bound organelles, a nucleus, and may form multi-cellular organisms
Describe the makeup of cell membrane and membranes of organelles
Contain phospholipids, which organize to form hydrophilic interior and exterior surfaces with a hydrophobic core
Define the cytosol
Cytosol suspends the organelles and allows diffusion of molecules through-out the cell
Describe the NUCLEUS
Nucleus contains DNA organized into chromosomes.
It is surrounded by the nuclear membrane/envelope, a double membrane that contains nuclear pores for two-way exchange of materials between the nucleus and cytosol.
DNA is organized into coding regions called genes.
Define the NUCLEOLUS
Nucleolus is a subsection of the nucleus in which ribosomal RNA (rRNA) is synthesized
Define the MITOCHONDRIA
Mitochondria contain an outer and inner membrane. The outer membrane forms a barrier with the cytosol; the inner membrane is folded into cristae and contains enzymes for the electronic transport chain.
Between the membranes is the intermembrane space; inside the inner mitochondrial membrane is the mitochondrial matrix.
Mitochondria can divide independently of the nucleus via binary fission and can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm.
Define the LYSOSOME
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.
Define the ENDOPLASMIC RETICULUM (ER)
The endoplasmic reticulum is a series of interconnected membranes and is continuous with the nuclear envelope.
The rough ER (RER) is studded with ribosomes, which permit translation of proteins destined for secretion.
The smooth ER (SER) is used for lipid synthesis and detoxification.
Define the GOLGI APPARATUS
Golgi apparatus consists of stacked membrane-bound sacs in which cellular products can be modified, packages, and directed to specific cellular locations.
Define the PEROXISOME
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.
Define the CYTOSKELETON
Cytoskeleton provides stability and rigidity to the overall structure of the cell, while also providing transport pathways for molecules within the cell.
Define MICROFILAMENTS
Microfilaments are composed of actin. They provide structural protection for the cell and can cause muscle contraction through interactions with myosin. They also help form the cleavage furrow during cytokinesis in mitosis.
Define MICROTUBULES
Microtubules are composed of tubulin. They create pathways for motor proteins like kinesin and dynein to carry vesicles.
They also contribute to the structure of cilia and flagella, where they are organized into nine pairs of microtubules in a ring with two microtubules at the center (9+2 structure).
Centrioles are found in centrosomes and are involved in microtubule organization in the mitotic spindle.
Define INTERMEDIATE FILAMENTS
Intermediate filaments are involved in cell-cell adhesion and maintenance of the integrity of the cytoskeleton; they help anchor organelles. Common examples include keratin and desmin.
Define EPITHELIAL TISSUES
Epithelial tissues cover the body and line its cavities, protecting against pathogen invasion and desiccation.
Some epithelial cells absorb or secrete substances or participate in sensation.
Define PARENCHYMA
In most organs, epithelial cells form the parenchyma, or the functional parts of the organ.
How are epithelial cells oriented?
Epithelial cells may be polarized, with one side facing a lumen or the outside world, and the other side facing blood vessels and structural cells.
What are the LAYERS of Epithelial Cells?
Simple epithelia have one layer
Stratified epithelia have many layers
Psuedostratified epithelia appear to be multi-layered due to differences in cell heights, but actually have only one layer
What are the SHAPES of Epithelial Cells?
Cuboidal Cells are cube-shaped
Columnar Cells are long and narrow
Squamous Cells are flat and scalelike
Define CONNECTIVE TISSUES
Connective tissues support the body and provide a framework for epithelial cells
Define STROMA of connective tissues and what it creates
In most organs, connective tissues form the stroma or support structure by secreting materials to form an extracellular matrix
Give examples of CONNECTIVE TISSUES
Bone, cartilage, tendons, ligaments, adipose tissues and blood
Define PROKARYOTE
Prokaryotes do not contain membrane-bound organells; they contain their genetic material in a single circular molecule of DNA located in the NUCLEOID REGION
What are the 3 overarching domains of life?
Prokaryotes (Archaea and Bacteria)
Eukaryotes
Define ARCHAEA
Archaea are often extremophiles, living in harsh environments (high temp, salinity, no light) and often use chemical sources of energy (chemosynthesis) rather than light (photosynthesis).
They have similarities to both eukaryotes (start translation with methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding)
Define BACTERIA
Bacteria have many similar structures to eukaryotes, and have complex relationshisp with humans, including MUTUALISTIC SYMBIOSIS and PATHOGENESIS
Define EUKARYA
Eukarya are the only non-prokaryotic domain
What are the classifications of BACTERIA by shape?
Cocci - spherical bacteria
Bacilli - rod-shaped bacteria
Spirilli - Spiral-shaped bacteria
What are the classifications of BACTERIA by metabolic process?
OBLIGATE AEROBES - require oxygen for metabolism
OBLIGATE ANAEROBES - cant 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 between metabolic processes based on the environment
AEROTOLERANT ANAEROBES - cannot use oxygen for metabolism, but can survive in an oxygen-containing environment
Define the cell’s ENVELOPE
The ENVELOPE is made up of the cell wall and cell membrane of bacteria. Together, control movement of solutes into and out of the cell
Describe GRAM STAINING process and results based on bacterial cell walls
Bacteria can be classified by the color their cell walls turn during Gram Staining with a crystal violet stain, followed by a counterstain with safranin.
Gram-Positive bacteria turn purple
Gram-Negative bacteria turn pink-red
Describe the chemical structure of the cell wall of a GRAM-POSITIVE BACTERIA
Gram-positive bacteria have a thick cell wall composed of peptidoglycan and lipoteichoic acid
Describe the chemical structure of the cell wall of a GRAM-NEGATIVE BACTERIA
Gram-negative bacteria have a thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides
Describe motility for bacteria
Bacteria may have one, two or many flagella that generate propulsion to move the bacterium toward food or away from immune cells.
Moving in response to chemical stimuli is called CHEMOTAXIS
Bacterial flagella contain a filament composed of flagellin, a basal body that anchors and rotates the flagellum, and a hook that connects the two
How do prokaryotes carry out the Electron Transport Chain?
Prokaryotes use the CELL MEMBRANE to carry out ETC
How are ribosome sizes different between pro- and eu- karyotes?
Prokaryotic ribosomes are smaller than eukaryotic ribosomes
Pro- 30S & 50S
Eu- 40S and 60S
Define BINARY FISSION
Prokaryotes multiply thru BINARY FISSION, in which the chromosome replicates while the cell grows in size, until the cell wall begins to grow inward along the midline of the cell and divides into two identical daughter cells
Define PLASMIDS
Plasmids are extrachromosomal material , which may contain antibiotic resistance genes (VIRULENCE FACTORS).
Plasmids are contained potentially within prokaryotes, along with their singular/circular chromosome
Define EPISOMES
Episomes are plasmids that can integrate into the genome
What are the 4 types of BACTERIAL GENETIC RECOMBINATION?
Transformation
Conjugation
Transduction
Transposons
Define TRANSFORMATION
Transformation occurs when genetic material from the surroundings is taken up by a cell, which can incorporate this material into its genome
Define CONJUGATION
Conjugation is the transfer of genetic material from one bacterium to another across a CONJUGATION BRIDGE
e. g. a PLASMID can be transferred from F+ cells to F- cells
e. g. a portion of the genome can be transferred from an Hfr cell to a recipient
Define TRANSDUCTION
Transduction is the transfer of genetic material from one bacterium to another via a bacteriophage vector
Define TRANSPOSONS
Transposons are genetic elements that can insert into or remove themselves from the genome
Define BACTERIAL GROWTH pattern
1 - LAG PHASE - bacteria adapt to new local conditions
2 - EXPONENTIAL (LOG) PHASE - growth then increases exponentially
3 - STATIONARY PHASE - as resources are reduced, growth levels off
4 - DEATH PHASE - as resources are depleted, bacteria die
What are the components of a VIRUS?
Viruses contain genetic material, a protein coat (called a CAPSID), and sometimes a lipid-containing envelope
Define OBLIGATE INTRACELLULAR PARASITE
Viruses are obligate intracellular parasites, meaning they cannot survive and replicate outside of a host cell
Define VIRION
An individual virus particle
Describe a BACTERIOPHAGE
Bacteriophages are viruses that target bacteria
In addition to other structures, they contain a TAIL SHEATH and TAIL FIBERS
Tail Sheath - Injects the genetic material into a bacterium
Tail Fiber - allows the bacteriophage to attach to the host cell
How are VIRAL GENOMES composed?
They can exist in many different forms: DNA or RNA, single- or double- stranded
Define POSITIVE SENSE Viruses
Positive Sense viruses are SINGLE-STRANDED RNA viruses that can be TRANSLATED by the host cell
Define NEGATIVE SENSE Viruses
Negative Sense viruses are SINGLE-STRANDED RNA viruses, but require a complementary strand to be synthesized by RNA replicase enzyme before translation
Define RETRO Viruses
Retroviruses contain a single-stranded RNA genome, from which a complementary DNA strand is made using REVERSE TRANSCRIPTASE enzyme
The DNA strand can then be integrated into the genome
How do viruses infect/integrate into host cells?
Viruses infect cells by attaching to specific receptors, and can then enter the cell by fusing with the plasma membrane, being brought in by endocytosis, or injecting their genome into the cell
How do viruses reproduce?
Viruses reproduce by replicating and translating genetic material using the host cell’s ribosomes, tRNA, amino acids, and enzymes
How are viral progency released into host to infect other cells?
Viral progeny are released through cell death, lysis or extrusion
What are the 2 life cycles possible for bacteriophages?
Lytic Cycle
Lysogenic Cycle
Define LYTIC CYCLE
Bacteriophage produces massive numbers of new virions until the cell lyses. Bacteria in the lytic phase are termed VIRULENT
Define LYSOGENIC CYCLE
Virus integrates into the host genome as a pro-virus or pro-phage, which can then reproduce along with the cell
The provirus can remain in the genome indefinitely, or may leave the genome in response to a stimulus and enter the lytic cycle
Define PRIONS
Prions are infectious proteins that trigger misfolding ofo other proteins, usually converting alpha-helical structure to a beta-pleated sheet
This decreases the solubility of the protein and increases its resistance to degradation
Define VIROIDS
Viroids are plant pathogens that are small circules of complementary RNA that can turn off genes, resulting in metabolic and structural changes and, potentially, cell death
