MCAT Biology Chapter 1

Cell theory

All living things are made of cells

Cell is basic fucntional unit of life

Cells arise from pre-existing cells

Cells cary and pass down genetic info through DNA

Viruses are considered ___ because ___

Non-living; cannot reproduce on their own, so they violate the 3rd and 4th tenets

Prokaryotic organisms

Single celled

No nucleus

Organelles

Float in cytosol

Membrane bound, in eukaryotes

Nucleus

Contains genetic material

Surronded by membrane/envelope with nuclear pores to exchange material w/ cytosol

Seperates DNA transcription from RNA translation

Eukaryotic DNA

Linear, wound around histones, forms chromosomes

Nucleolus

Where ribosomal RNA is synthesized

Mitochondria contains

Outer membrane, inter-membrane space, inner membrane, matrix

Cristae

Folds of inner membrane, make more surface area for ETC

Inter-membrane space and matrix exchange

Protons through ATP synthase to produce ATP through oxidative phosphorylation

Mitochondria semi-autonimity

Self-replicates through binary fission

Cytoplasmic/Extranuclear inheritance

Genetic material transmission w/o nucleus

Mitochondria kills the cell by

Releasing enzymes from ETC, starting apoptosis

Lysosomes

Membrane bound, contains hydrolytic enzymes to break down waste

Works with endosomes

Endosomes

Controls transport, packaging, and sorting of material to and from cell membrane

Can send material to Golgi, cell membrane, lysosome

Lysosome can kill cell by

Autolysis, releasing its enzymes

Endoplasmic Reticulum

Folded membrane extending from nucleus

Rough endoplasmic reticulum

Has ribosomes for protein translation

Smooth endoplasmic reticulum

No ribosomes, used for lipid synthesis, detox, and transporting proteins from RER to Golgi

Golgi Apparatus

Stacked membrane bound sacs

Recevies material from ER, modifies it with carbohydrates, phosphate, sulfur, signal sequences for delivery

Repackages and secretes material in vesicles

Peroxisomes

Contain hydrogen peroxide, and enzymes involved in PPP

Perform beta oxidation

Synthesizes phospholipids

Cytoskeleton

Contains microtubules, microfilaments, intermediate filaments

Gives cell structure, shape, and way of transport

Organelle distribution in cells

Varies based on cell function

Microfilaments

Made of actin, resists compression, fracture to protect the cell

Forms cleavage furrow in mitosis, seperates daughter cells

Microtubules

Made of tubulin proteins, provides pathways for motor proteins kinesin and dyesin to carry vesicles

Make up cilia, flagella, centrioles

Cilia and flagella

Transport material on cell surface, moves cell

In eukaryotes, ring of 9 microtubules with 2 inside

Centrioles

Release kinetochores (microtubes) to seperate chromatids in mitosis

In centrosomes

Intermediate filaments

Involved in cell-cell adhesion, mantaining cytoskeleton, anchoring organelles

Rigid, withstands tension

Keratin, demin, vimentin, lamin

Tissue types

Epithelial, nervous, connective, muscle

Epithelial tissue

Skin, lines body cavities

Protects from pathogens

Involved in absorption, secretion, sensation

Form basement, membrane, parenchyma

Basement membrane

Layer of connected epithelial cells attached to connective tissue layer

Parenchyma

Functional part of organ

Simple epithelia

One layer of cells

Stratefied epithelia

Multiple layers of cells

Pseudostratefied epithelia

One layer of cells with different heights

Cuboidal cells are ___ shaped

Columnar cells are ___ shaped

Squamous cells are ___ shaped

Cube; long and thin; flat

Connective tissue

Gives framework for epithelial cells

Makes stroma, support structure

Produce and secrete collagen and elastin for ECM

Light microscopy

Visible light and lenses to magnify specimen 200 nm or larger

Confocal microscopy

Uses pinhole to block out light and focus on the specimen, with computer modeling, immunohistochemistry

Scanning vs. transmission electron microscopy

Topographical map of specimen vs. can visualize subcellular structures

Prokaryotes

No membrane bound organelles

One circular DNA molecule coiled around histone-like protein in nucleoid region

Domains of life

Archaea, bacteria, eukarya

Archaea

Single celled, visually like bacteria metabolically like eukaryotes

Can use alternative sources of energy

Extremophiles

Resistant to antibiotics

Thought to share origin with eukaryotes

Bacteria contain

Cell membrane, cytoplasm, flagella or fimbraiae (cilia)

Antibiotics target

Ribosomes, bacterial flagella

Bacteria - mutualistic symbiotes

Human and bacteria benefit, like producing vitamin K, biotin

Bacteria - pathogens/parasites

Cause disease, can be intra or extracellular

Cocci

Spherical bacteria

Bacilli

Rod-shaped bacteria

Spirilli

Spiral-shaped bacteria

Obligate aerobes

Require oxygen for metabolism

Obligate anaerobes

Cannot survive in an environment with oxygen due to the production of free radicals triggering apoptosis

Facultative anaerobes

Can switch between aerobic and anaerobic metabolism

Aerotolerant anaerobes

Cannot use oxygen, but can tolerate its presence

Envelope

Cell wall and membrane

Bacterial cell wall can be ____ or ____

Gram-positive; gram-negative

Gram-positive bacteria

Has thick peptidoglycan layer, made of AA + sugar for protection against host’s immune system

Lipoteichoic acid also present

Gram-negative bacteria

Less peptidoglycan, seperated from cell membrane by periplasmic space

Outer membrane with lipopolysaccharides, triggeres more of an immune response than lipoteichoic acid

Chemotaxis

Cell’s ability to move away or towards chemical stimuli

Bacterial flagella made of

Filament made of flagellin

Basal body anchors flagellum to cytopasmic membrane, acts as motor

Hook connects filament and basal body, allowing filament to spin when basal body rotates

Plasmids

External source of DNA , not necessary for survival, can do genetic recombination

May contain antiobiotic resitance, virulence factors to increase pathogenecity

Episomes

Plasmids capapble of inegrating into genome of bacteria

Prokaryotes differences from eukaryotes

No mitochondira, so ETC is in cell membrane

Simple cytoskeleton

Smaller ribosome

Binary fission

Asexual reproduction in prokaryotes, faster than mitosis

Circular crhomosome attaches to cell wall, replicates as cell grows

Cell wall and membrane invaginate, produces two identical daughter cells

Genetic recombination processes

Transformation, conjugation, transduction

Transformation

Host genome integrates foreign genetic material, which can be from gram negative bacteria

Host has to be in competence

Transformation efficiency

# of colony forming units divided by mass of DNA added to the cells

Conjugation

Bacterial sexual reproduction, through donor male transferring genetic material through sex pili forming a conjugation bridge

Bacteria needs sex factor plasmids, like fertility factors in E. Coli

Hfr

High frequency of recombination, cells that have undergone conjugation

Transduction

Needs a vector, a bacteriophage carrying genes from one bacterium to another

Virus can incorporate part of host genetic info when it tries to infect it, and if it infects another bacterium, it can insert the other bacteria’s genes

Transposons

Genetic elements that can insert and remove themselves into a genome, prokaryotic and eukaryotic

Bacteria growth stages

Lag, exponential/log, stationary, death

Lag phase

Bacteria adapt to conditions

Exponential/log phase

Bacteria divides rapidly

Stationary phase

Bacterial division slows as resources lessen

Death phase

Resources run out, can no longer support bacteria

Viruses contain

Capsid, genetic material, and sometimes an envelope of lipids

No organlle, nucleus

Capsid

Protein coat, may have an envelope

Enveloped viruses

Sensitive to heat, detergent, dessicants

Fuse with host’s plasma membrane to insert

Virions are produced by ___

Viruses using host cell to replicate, since its an obligate intra-cellular parasite

Bacteriophage

Virus that infects bacteria thoruhg injection

Has tail sheath, tail fibers

Tail sheath ___, tail fibers ____

Injects genetic info; recognize and connect to right host cell

Single-stranded viral RNA can be ___ or ___

Positive sense; negative sense

Positive sense RNA

Can be directly translated by host ribosomes

Negative sense RNA

Acts as template for complementary strand, which is then used for protein synthesis

Needs RNA replicase to make virions

Retroviruses

Enveloped, single-strand RNA viruses

Carries reverse transcriptase to make DNA that is integrated by host

Viruses can only infect cells with ___

Certain receptors

Viruses can infect via

Fusion, endocytosis, insertion

Viral life cycle

Infection, translation, progeny assembly

Viruses induce translation by

Translocation of genetic material

DNA/retro viruses enter the nucleus to be transcribed

RNA viruses are translated in cytoplasm

Viral progeny is released through

Induced apoptosis/lysis, kills the cell and stops further virion production

Extrusion, occurs in productive cycle, fuses with membrane to leave, keeps cell alive

Lytic cycle

Virulent bacteriophages maximizes host’s cell virion production then lysis

Lysogenic cycle

Bacteriophage integrates into host genome as provirus/prophage, replicates via bacteria reproducing

Lysogenic cycle may ___ to lytic cycle

Revert

Prions

Infectious proteins, triggers misfolding of alpha helices to beta sheets, reducing solubility, makes it resitant to degradation

Viroids

Infect plants, small pathogens with short ciruclar single-stranded RNA that bind to RNA to silence genes

Prevents protein synthesis, disrupts metabolism, and causes structural damage