The Cell Flashcards
The four basic tenets of cell theory
- All living things are composed of ells
- The cell is the basic functional unit of life
- Cells arise only from pre-exsisting cells
- Cells carry genetic information in the form of DNA; this genetic material is passed on from parent to daughter cell
Are viruses considered living things? Why or why not?
They are not considered living things because they are acellular, cannot reproduce without the assistance of a host cell, and may contain RNA as their genetic material
Eukaryotes
They have membrane-bound organelles, a nucleus, and may form multicellular organisms
Cell membrane & membranes of organelles
They contain phospholipids, which organize to form hydrophilic interior and exterior surfaces with a hydrophobic core
Cytosol
Suspends the organelles and allows diffusion of molecules throughout the cell
Nucleus
Contains DNA organized into chromosomes
Nuclear membrane/envelope
A double membrane that surrounds the nucleus and contains nuclear pores
Nuclear pores
Facilitate two-way exchange of materials between the nucleus and cytosol
Genes
DNA is organized into these coding regions
Nucleolus
A subsection of the nucleus in which rRNA is synthesized
Mitochondria
Contain an outer and inner membrane; can divide independently of the nucleus via binary fission; they can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm
Outer membrane of the mitochondria
Forms a barrier with the cytosol
Inner membrane of the mitochondria
Folded into cristae and contains enzymes for the ETC
Intermembrane space
Space between the outer and inner membranes of the mitochondria
Mitochondrial matrix
Space inside the inner mitochondrial membrane
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 occur
Endoplasmic reticulum (ER)
A series of interconnected membranes and is continuous with the nuclear envelope
Rough ER (RER)
Studded with ribosomes, which permit translation of proteins destined for secretion
Smooth ER (SER)
Used for lipid synthesis and detoxification
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
Provides stability and rigidity to the overall structure of the cell, while also providing transport pathways for molecules within the cell
Microfilaments
Composed of actin; they provide structural protection from the cell and can cause muscle contraction through interactions with myosin; they also help form the cleavage furrow during cytokinesis in mitosis
Microtubules
Composed of tubulin; they create pathways for motor proteins like chines and dyne to cary vesicles; they also contribute to the structure of cilia and flagella
9 + 2 structure
In eukaryotes, cilia and flagella are organized into nine pairs of microtubules in a ring with two microtubules at the center
Centrioles
Found in centrosomes and are involved in microtubule organization in the mitotic spindle
Intermediate filaments
Involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; they help anchor organelles
Epithelial tissues
Cover the body and line its cavities, protecting against pathogen invasion and desiccation; some absorb or secrete substances, or participate in sensation
Parenchyma
In most organs, epithelial cells form this, which are the functional parts of the organ
Polarization of epithelial cells
They may have one side facing a lumen or the outside world, and the other side facing blood vessels and structural cells
Types of epithelia (3) Simple epithelia
Simple (have one layer)
Stratified (have many layers)
Pseudostratified (appear to have multiple layers because of differences in cell heights, but actually only have one layer)
Eukaryote shape classifications (3)
Cuboidal cells (cube-shaped) Columnar cells (long and narrow) Squamous cells (flat and scale-like)
Connective tissues
Support the body and provide a framework for epithelial cells
Stroma
In most organs, connective tissues form this, or support structure by secreting materials to form an extracellular matrix
Connective tissues (6)
Bone Cartilage Tendons Ligaments Adipose tissue Blood
Prokaryotes
Do not contain membrane-bound organelles; they organize their genetic material in a single circular molecule of DNA concentrated in the nuclei region
Archaea
Often extremophiles, living in harsh environments (high temperature, high salinity, no light) and often using alternate sources of energy, like chemosynthesis
Similarities of archaea to eukaryotes (3)
- Start translation with methionine
- Similar RNA polymerases
- Histones
Similarities of archaea to bacteria (2)
- Single circular chromosome
2. Divide by binary fission or budding
Bacteria
Have many similar structures to eukaryotes, and have complex relationships with humans, including symbiosis and pathogenesis
Eukarya
The only non-prokaryotic domain
Bacteria shape classifications (3)
Cocci (spherical bacteria)
Bacilli (rod-shaped bacteria)
Spirilli (spiral-shaped bacteria)
Obligate aerobes
Bacteria that require oxygen for metabolism
Obligate anaerobes
Bacteria that cannot survive in oxygen-containing environments and can only carry out anaerobic metabolism
Facultative anaerobes
Bacteria that can survive in environments with or without oxygen and will toggle metabolic processes based on the environment
Aerotolerant anaerobes
Bacteria that cannot use oxygen for metabolism, but can survive in an oxygen-containing environment
What is the bacterial envelope formed from and what do they control?
The cell wall and cell membrane; together, they control the movement of solutes into and out of the cell
Gram-positive bacteria
Turn purple from Gram staining with a crystal violet stain
Have a thick cell wall composed of peptidoglycan and lipoteichoic acid
Gram-negative bacteria
Turn pink-red from Gram counterstaining with safranin
Hav a thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides
Chemotaxis
Moving in response to chemical stimuli
Bacterial flagella composition
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 ETC?
Using the cell membrane
How do prokaryotic ribosomes differ from eukaryotic ribosomes?
They are smaller (30S and 50S, rather than 40S and 60S)
Binary fission
Prokaryotes multiply this way, in which the chromosome replicates while the cell grows in size, until the cell wall begins to grown inward along the midline of the cell and divides it into two identical daughter cells
Plasmids
Can carry extrachromosal material; may contain antibiotic resistance genes or virulence factors
Episomes
Plasmids that can integrate into the genome
What process increases bacterial diversity?
Bacterial genetic recombination
Bacterial transformation
The acquisition of genetic material from the environment, which can be integrated into the bacterial genome
Bacterial conjugation
The transfer of genetic material from one bacterial to another across a conjugation bridge
How can a plasmid or portion of the genome in bacteria be transferred?
A plasmid can be transferred from F+ cells to F- cells
A portion of the genome can be transferred from an Hfr cell to a recipient
Bacterial transduction
The 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 the genome
Bacterial growth pattern
Lag phase > log phase > stationary phase > death phase
Lag phase
The bacteria adapt to new local conditions during this time
Exponential (log) phase
Growth increases exponentially during this time
Stationary phase
As resources are reduced, growth levels off during this time
Death phase
As resources become insufficient, bacteria undergo this phase
What does a virus contain?
Genetic material, a protein coat (capsid), and sometimes a lipid-containing envelope
What is meant by viruses being obligate intracellular parasites?
They cannot survive and replicate outside of a host cell
Virions
Individual virus particles
Bacteriophages
Viruses that target bacteria
What does a bacteriophage contain?
It contains a tail sheath and tail fibers
Tail sheath
Injects the genetic material into a bacterium
Tail fibers
Allow the bacteriophage to attach to the host cell
What are viral genomes made of?
DNA or RNA that may be single- or double-stranded
Single-stranded RNA virus characteristics
May be positive sense or negative sense
Positive sense ssRNA
Can be translated by the host cell
Negative sense ssRNA
A complementary strand must be synthesized using RNA replicase, which can then be translated
Retroviruses
Contain an ssRNA genome, to which a complementary DNA strand is made using reverse transcriptase; the DNA can then integrated into the genome
How do viruses infect cells?
By attaching to specific receptors, and then (1) either fusing with the plasma membrane, being brought in by endocytosis, or (2) injecting their genome into the cell
How do viruses reproduce?
By replicating and translating genetic material using the host cell’s ribosomes, tRNA, amino acids, and enzymes
How are viral progeny released?
Through cell death, lysis, or extrusion
Lytic cycle (bacteriophages)
The bacteriophage produces massive numbers of new visions until the cell lyses; bacteria in this phase are termed virulent
Lysogenic cycle (bacteriophages)
The virus integrated into the host genome as a pro-virus or prophage, which can then reproduce along with the cell; the provirus then leaves the genome in response to a stimulus at some later time and enters the lytic cycle
Prions
Infectious proteins that trigger misfiling of other protein, usually converting an alpha-helical structure to a beta-pleated sheet; this decreases the solubility and degradability of the misfiled protein
Viroids
Plan 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
