Chapter 1: The Cell Flashcards
cell theory
- all living things are composed of cells
- the cell is the basic functional unit of life
- cells only arise from preexisting cells
- cells carry genetic information in the form of deoxyribonucleic acid (DNA). this genetic material is passed on from parent to daughter cell.
membrane
Each cell has one that encloses cytosol.
Most eukaryotic organelles enclosed by membranes.
Eukaryotic membranes have phospholipid bilayer–hydrophobic interior, hydrophilic exterior
phospholipid bilayer
Hydrophilic exterior allows electrostatic interactions inside and outside of cell
Hydrophilic interior allows for selective permeability between interior of cell and environment
cytosol
Allows for diffusion of molecules throughout the cell
nucleus
Most heavily tested organelle on MCAT
Only present in eukaryotes
Surrounded by nuclear membrane/envelope (double membrane)
Contains all of genetic material necessary for replication (DNA), which is organized into chromosomes
Nuclear pores allow for selective two way exchange between cytoplasm and nucleus
nuclear envelope
Double membrane around nucleus
Allows for selective two way exchange between nucleus and cytoplasm via nuclear pores
Creates two distinct environments in the cell (nucleus and cytoplasm)
Allows for compartmentalization of transcription and translation
DNA
Contains coding regions called genes
Wound around organizing proteins called histones
Further wound into linear strands called chromosomes
Location in nucleus allows for compartmentalization of DNA transcription separate from RNA translation
nucleolus
Subsection of nucleus
Where rRNA is synthesized
25% of nucleic volume
mitochondria
Eukaryotic organelle
Powerhouse of the cell
Contains outer and inner membrane
Semi-autonomous (unlike other organelles)
Contain some of own genes and replicate independently of nucleus via binary fission
Thought to have come about when anaerobic prokaryote engulfed aerobic prokaryote
Capable of killing cell by release of enzymes from ETC
outer mitochondrial membrane
Barrier between cytosol and inner environment of mitochondria
inner mitochondrial membrane
Thrown into numerous infoldings (cristae)
Contains molecules and enzymes necessary for electron transport chain
cristae
Folds in inner mitochondrial membrane
Increases surface area available for electron transport chain enzymes
intermembrane space
Space between outer and inner mitochondrial membranes
matrix
Space inside inner mitochondrial membrane
Pumping of protons from matrix to intermembrane space establishes proton-motive force
proton-motive force
Pumping of protons from matrix to intermembrane space establishes proton-motive force
These protons flow through ATP synthase to generate ATP during oxidative phosphorylation
apoptosis
Programmed cell death
Kick started when mitochondria releases enzymes from ETC
Also can happen when lysosome release hydrolytic enzymes
lysosome
Membrane bound organelles that contain hydrolytic enzymes capable of breaking down substances like cellular waste and substances ingested during endocytosis
autolysis
When lysosome releases hydrolytic enzymes to result in apoptosis
Lead to degradation of cellular components
endoplasmic reticulum
Series of interconnected membranes that are contiguous with nuclear envelope
Surround nucleus
Single membrane is folded into multiple invaginations, which creates complex structures with central lumen
Two kinds: rough and smooth
rough ER
Studded with ribosomes
Permit translation of proteins destined for secretion directly in lumen
smooth ER
Lacks ribosomes
Utilized primarily for lipid synthesis and drug/poison detoxification
Transports proteins from rough ER to Golgi apparatus
Golgi apparatus
Consists of stacked membrane bound sacs
Right outside ER
Materials from ER to Golgi are transported in vesicles
Modifies ER products by addition of various groups, like carbohydrates, phosphates, and sulfates
Can add signal sequence to products that direct delivery of product to specific cellular location
Products are then repacked into vesicles and transferred to correct cellular destination
exocytosis
Release of secretory products
After release from Golgi apparatus, secretory storage vesicle merges with cell membrane and contents are released
vesicle
Materials created in RER are transported to Golgi apparatus (via SER) in vesicles
Vesicles also transport materials from Golgi to cellular destination
If product destined for secretion, vesicle will merge with cell membrane for exocytosis release
distribution of organelles
Different cells have different organelle amounts
Cells that require locomotion (i.e. sperm) have high concentration of mitochondria (energy!)
Cells involved in secretion (pancreatic/endocrine tissue) have high concentration of RER and Golgi apparatus
Transport cells (RBC’s) have no organelles at all
peroxisomes
Contain hydrogen peroxide
Allow for breakdown of very long fatty acid chains via beta-oxidation
Synthesis of phospholipids
Contain some pentose phosphate pathway enzymes
cytoskeleton
Maintain structure/shape of cell
Transport of materials around cell
Components: microfilaments, microtubules, and intermediate filaments
microfilaments
Made of rods of actin
Actin filaments organized into bundles & networks–resistant to breakage and compression
Cell protection
Filaments can also use ATP to generate force for movement by interacting with myosin (muscle contraction)
Play role in cytokinesis–division of materials between daughter cells
Pinch off connection between daughter cells
microtubules
Hollow polymers of tubulin
Primary pathways for vesicle carrying via motor proteins (kinesin and dynein)
Make up cilia and flagella
cilia
Projections from cell primarily involved in material movement along surface of cell
Mucus movement in respiratory tract
Composed of microtubules
eukaryotic flagella
Involved in movement of cell itself
Composed of microtubules made of tubilin
9+2 arrangement
9+2 structure
Cilia and flagella microtubule arrangement
9 pairs of microtubules in outer ring
2 microtubules at center
Only seen in eukaryotic cells of motility
centrioles
Found in centrosome
9 microtubules with hollow center
Organize mitotic spindle during mitosis when migrate to opposite poles of dividing cells
Attach to chromosomes via kinetochores and exert pulling apart force on sister chromatids
Intermediate filaments
Diverse group of filamentous proteins (keratin and desmin) Cell-to-cell adhesion Maintenance of cytoskeleton integrity Make cell more rigid Anchor organelles like nucleus
epithelial tissue
Cover body and line cavities
Protection against pathogen invasion and desiccation
Absorption, secretion, sensation
Cells tightly joined together and to underlying basement membrane
Polarized: one side interacts with lumen/outside world, the other side interacts with blood vessels and structural cells
parenchyma
Functional part of an organ
Nephrons in kidney, hepatocytes in liver, acid producing cells in stomach
Consists of epithelial cells
Stroma is support structure (thanks to connective tissue)
simple epithelia
One layer of cells
stratified epithelia
Multiple layers of cells
psuedostratified epithelia
Appear to have multiple layers, really only has one
connective tissue
Supports body and provides framework for epithelial cells to carry out functions
Main contributors of stroma (support structure) when epithelial cells contribute to parenchyma of organ
Bone, cartilage, tendons, ligaments, adipose tissue, blood
Most cells produce and secrete materials like collagen and elastin to form extracellular matrix
prokaryotes
Simplest of all organisms
No membrane bound organelles
Single circular molecule of DNA concentrated in nucleoid region
DNA not coiled around histones
No membrane bound organelles, but may have plasmids
30S and 50S ribosomes
nucleoid region
Where circular DNA molecule in prokaryotes is concentrated
This DNA not carried around histones
May have plasmids
archaea
Single celled organisms that are visually similar to bacteria
Contain genes and metabolic pathways that are more similar to eukaryotes (start translation w/ methionine, contain similar RNA polymerases, associate DNA with histones)
Extremophiles
Resistant to many antibiotics
Divide by binary fission or budding
bacteria
All contain cell membrane and cytoplasm
Some have flagella and fimbriae (analogous to cilia)
Outnumber human cells in the body 10:1
Do not form multicellular organisms, so responsible for protecting self from environment
mutualistic symbiotes
Bacteria in the gut produce vitamin K (clotting) and biotin
Some bacteria prevent overgrowth of other bacteria
Babies are not colonized with bacteria yet, so given a vitamin K shot at birth to aid in clotting
obligate aerobes
Require oxygen for metabolism
anaerobes
Use fermentation or other metabolism that does not require oxygen
obligate anaerobes
Cannot survive in oxygen containing environment
facultative anaerobes
Can use oxygen for aerobic metabolism if present or can switch to anaerobic metabolism if no oxygen
aerotolerant anaerobes
Unable to use oxygen but not harmed by it
envelope
Cell wall + cell membrane in prokaryotes
cell wall
In prokaryotes, forms outer barrier of cell
Provides structure and controls movement of solutes into and out of bacterium
Allows for maintenance of concentration gradient relative to environment
Two types of cell walls: (dependent on Gram staining process)
a) gram positive
b) gram negative
gram positive bacteria
Absorbs crystal violet stain Appears deep purple Consist of thick layer of peptidoglycan Provides protection from host organisms immune system Also contains lipoteichoic acid No outer membrane
peptidoglycan
Polymetric substance made from amino acids and sugars
Present in gram+ bacteria, and gram- (but in small amounts)
Penicillin targets the enzyme that catalyzes the cross-linking of peptidoglycan–if a gram+ cell can’t cross-link cell wall, it’s no longer an effective barrier
lipoteichoic acid
Present in gram+ bacteria
Function unknown, but human immune system may be activated by exposure to this chemical
gram negative bacteria
Do not absorb crystal violet stain
Absorb safranin counterstain, and appear pink-red
Thin layer of peptidoglycan
Contain lipopolysaccharides and phospholipids
chemotaxis
Ability of a cell to detect chemical stimuli and move towards or away from them
bacterial flagella
Made of flagellin
Composed of hook, filament, and basal body
filament
Part of flagella
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, rotating at rates of up to 300 hz
hook
Connects filament and basal body so that, as basal body rotates, it exerts torque on the filament, which can thereby spin and exert the bacterium forward
plasmids
Small circular structures on which DNA acquired from external sources may be carried
This DNA is not vital to survival of bacterium, but may carry advantage (like antibiotic resistance)
May contain virulence factors, which increase how pathogenic it is
binary fission
Simple form of asexual reproduction seen in prokaryotes
Circular chromosome attaches to cell wall and replicates while cell continues to grow
Plasma membrane pinches towards midline to produce two identical daughter cells
Proceeds more rapidly than mitosis, because requires fewer events
virulence factors
Traits that increase how pathogenic a bacterium is, like toxin production, projections that allow it to attach to cells, or evasion of immune system
Carried in plasmids
episomes
Subset of plasmids
Capable of integrating into genome of bacterium
Help recombination and thus evolution of bacterial species over time
transformation
Form of recombination process
Results from integration of foreign genetic material into host genome
Often from lysed bacteria that spill genetic contents into vicinity of bacteria capable of bacterium capable of transformation
Most gram- rods
conjugation
Form of recombination process
Bacterial form of mating
Two cells form conjugation bridge that allows for the transfer of genetic material
Transfer is unidirectional (from donor male (+) to recipient female (-))
Bridge is made from appendages called sex pili found on donor male
Rapid acquisition of antibiotic of antibiotic resistance or virulence factors throughout a colony
F factor example:
Bacteria that possess F factor are called F+ cells; without are F-
F+ replicates F factor during conjugation and donates to F-
F- is now F+
sex factor
Certain plasmids that are necessary for the formation of sex pili which creates the conjugation bridge
Relevant to conjugation
Best studied sex factor is the F (fertility) factor in E. coli
F (fertility) factor
Best studied sex factor (in E. coli)
Type of plasmid
Bacteria that possess it are called F+ cells; without are F-
F+ replicates F factor during conjugation and donates to F-
F- is now F+
transduction
Type of recombination process
Only recombination process that requires a vector–a virus that carries genetic material from one bacterium to another
Viruses can accidentally trap segment of host DNA during assembly inside host during reproduction, and when bacteriophage infects another bacterium, it can release this trapped DNA into new host cell.
This trapped DNA can integrate into genome, giving host additional genes.
transposons
Genetic elements capable of inserting and removing selves from genome.
Observed in prokaryotes and eukaryotes
lag phase
Bacteria adapt to local conditions
exponential/log phase
Bacteria grow exponentially
Resources reduced
stationary phase
Because resources were reduced in exponential phase, growth is slowed
death phase
environment can no longer support amount of bacteria
viruses
Are not living things; acellular
Lack organelles and a nucleus
Have genetic material, protein coat, sometimes an envelope containing lipids, tail sheath, tail fibers
Genetic material may be SS or DS, circular or linear, RNA or DNA
Lack ribosomes to carry out protein synthesis
capsid
virus protein coat
virus envelope
Surrounds capsid
Sensitive to heat, detergents, and desiccation
Easier to kill
Composed of phospholipids and virus-specific proteins
virions
Viral progeny
Released to infect additional cells
bacteriophages
Viruses that target bacteria
Do not enter bacteria, but inject genetic material
tail sheath
Virus “syringe”, that can inject genetic material into bacterium
tail fibers
help bacteriophage recognize and connect to correct host cell
positive sense
Type of ssRNA virus
Implies the genome may be directly translated to functional proteins by the ribosomes by the host cells, just like mRNA
negative sense
Type of ssRNA virus
Requires the synthesis of an RNA strand complementary to the negative sense RNA strand, which can then be used as a template for protein synthesis
Must carry an RNA replicase in the virion to ensure that the complementary strand is synthesized
retroviruses
Enveloped, ssRNA viruses in the family Retroviridae
Virion usually carries 2 identical RNA molecules
Carry reverse transcriptase, which synthesizes DNA from ssRNA
The DNA then integrates into the host cell genome, where t is replicated and transcribed as if it were the host cell’s own DNA.
Only way to cure the infection is to kill the infected cell itself
viral infection
Viruses can only bind to specific set of cells with proper receptors
Enveloped viruses, like HIV, (which enter the cell intact) fuse with plasma membrane of cell, allowing entry of virion into host cell
Bacteriophages only inset genetic material
Host cell may misinterpret binding of virus to membrane as nutrient, etc, and bring virus into cell via endocytosis
DNA virus reproduction
Must go to the nucleus in order to be transcribed to mRNA
mRNA then goes to cytoplasm to be translated to protein
positive sense virus reproduction
Genetic material stays in cytoplasm, where it’s directly translated to protein by host cell ribosomes
negative sense virus reproduction
Requires synthesis of complementary RNA strand via RNA replicase, which can then be translated to form proteins
retrovirus reproduction
Forms DNA through reverse transcription that travels to nucleus, where it can be integrated into host genome
Must transcribe new copies of ssRNA from DNA that entered host genome to reenter viral genome
lytic cycle
Bacteriophage makes maximal use of cells machinery with little regard for survival of host cell
Once host cell is swollen with new virions, cell lyses, and other bacteria can be infected
Bacteria in the lytic phase are termed virulent
virulent
Bacteria in the lytic phase
Swell with new virions and lyse
lysogenic cycle
If virus does not lyse the bacterium, virus will be replicated as bacterium replicates because it is now part of host’s genome
Virus is known as provirus or prophage
May enter lytic cycle via variety of factors
prion
Infectious proteins
Nonliving things
Cause disease by triggering misfolding of other proteins
Usually involves conversion of a protein from alpha-helical structure to beta-pleated sheet
Drastically reduces solubility of protein, as well as ability of cell to degrade misfolded protein
Eventually reduces function of cell
Known to cause mad cow, Creutzfeldt-Jakob, and familial fatal insomnia
viriods
Small plant pathogens
Consists of very short circular ssRNA
Bind to RNA sequences and silence genes in the plant genome
Prevent synthesis of necessary proteins and can subsequently cause metabolic and structural derangement in the plant cell
Often plant pathogens, but some human pathogens, like Hepatitis D
