USMDO Medical Biology Practice Flashcards

A comprehensive set of 500 practice flashcards covering medical biology, genetics, human physiology, and disease pathologies based on lecture transcript notes.

Macromolecules

Large biological molecules including carbohydrates, lipids, proteins, and nucleic acids that are essential for life.

Polymers

Long chains of repeating subunits that make up most macromolecules.

Carbohydrates

Macromolecules that serve as energy sources and structural materials.

Lipids

Group including fats, oils, and phospholipids which are important for energy storage and membrane structure.

Proteins

Molecules that perform diverse functions such as catalysis, transport, and structural support.

Nucleic Acids

Biological molecules responsible for storing and transmitting genetic information.

Nucleus

The control center of the cell that holds DNA and directs cellular activities.

Nucleolus

A dense structure inside the nucleus responsible for producing ribosomes.

Mitochondria

The 'powerhouse' of the cell that converts nutrients into ATP through cellular respiration.

Rough Endoplasmic Reticulum (RER)

A membrane network dotted with ribosomes involved in making and transporting proteins.

Smooth Endoplasmic Reticulum (SER)

A membrane network lacking ribosomes that synthesizes lipids and helps detoxify chemicals.

Centrosomes

Organelles that help organize microtubules and regulate cell division.

Lysosomes

The cell's waste disposal system containing digestive enzymes to break down old parts and foreign invaders.

Ribosomes

Tiny structures where proteins are assembled.

Golgi Complex

The packaging and distribution center that sorts proteins and lipids before sending them to final destinations.

Cell Membrane

The outer barrier that controls what enters and exits the cell.

Nuclear Envelope

A double-layered membrane that surrounds and protects the nucleus.

Cytoskeleton

A network of fibers and tubules giving the cell its shape and aiding in movement.

Glycoprotein

A composite of a carbohydrate chain and a protein found on the cell membrane.

Glycolipid

A composite of a carbohydrate chain and a membrane lipid.

Hydrophilic phosphate head

The 'water loving' portion of a phospholipid.

Hydrophobic lipid tails

The 'water hating' portion of a phospholipid.

Peripheral protein

A protein located on the surface of the cell membrane.

Integral protein

A protein embedded within the membrane; can be channel or transmembrane proteins.

Cholesterol (membranes)

A lipid component that helps the cell membrane remain flexible.

Fluid Mosaic Model

The structural model describing the arrangement and movement of molecules that make up a cell membrane.

Enzymes

Proteins or catalytic RNAs that increase the rate of reactions by lowering activation energy.

Ribozyme

A catalytic RNA that functions as an enzyme.

Activation Energy

The energy barrier that enzymes lower to catalyze metabolic pathways.

Rate of reaction ($k$)

A measure of how fast a reactant is used up or a product is produced.

Paracrine Signaling

Local signaling targeting cells close to the releasing cell via diffusion through extracellular fluid.

Synaptic signaling

An example of paracrine signaling occurring between nerve cells.

Endocrine Signaling

Long-distance signaling where hormones are released into the bloodstream to reach far-away organs.

Autocrine Signaling

A type of signaling where a cell sends a signal to its own receptors.

Juxtacrine Signaling

Communication through direct physical touch between cells.

Gap junctions

Tiny water-filled channels in animal cells used to share small signaling molecules during direct contact.

Plasmodesmata

Water-filled channels in plant cells used for direct communication.

Mitosis

The process of cell division resulting in two genetically identical daughter cells.

Prophase

The first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and the spindle forms.

Prometaphase

Stage where the nuclear envelope fully disassembles and microtubules attach to kinetochores.

Metaphase

Stage of mitosis where chromosomes line up along the center of the cell at the metaphase plate.

Anaphase

Stage of mitosis where sister chromatids are pulled apart toward opposite poles.

Telophase

The final stage of mitosis where chromosomes decondense and new nuclear envelopes form.

Cytokinesis

The physical division of the cytoplasm separating the parent cell into two daughter cells.

Meiosis I

The first round of meiosis characterized by homologous chromosomes pairing and trading pieces.

Prophase I

The stage of meiosis where chromosomes pair up and trade pieces (crossing over).

Telophase I

Stage where the cell divides into two cells with half the normal chromosomes.

Meiosis II

The second round of meiosis resulting in four unique cells with half the original chromosome count.

Law of Dominance

Principle stating one allele may mask another in physical appearance.

Law of Segregation

Principle stating the two paired alleles for a trait separate randomly during gamete formation.

Law of Independent Assortment

Principle that alleles for different traits are sorted and passed on independently of one another.

Autosomes

Chromosome pairs 1 through 22 in humans.

Sex Chromosomes

The 23rd pair of chromosomes, typically XX or XY.

B-DNA

The standard right-handed helix structure of DNA found in vivo.

A-DNA

A DNA helix form occurring under dehydrated laboratory conditions.

Z-DNA

A transient, left-handed helix appearing in segments with alternating purines and pyrimidines during transcription.

Major Groove

The wider groove of DNA that serves as the primary binding site for regulatory proteins like transcription factors.

Mitochondrial DNA (mtDNA)

Circular DNA that lacks histones, encodes 37 genes, and is inherited strictly via maternal lineage.

Helicase

Enzyme that unwinds the double helix at the replication fork by breaking hydrogen bonds using ATP.

Topoisomerases

Enzymes that relieve torsional strain (positive supercoiling) created ahead of the replication fork.

Type II Topoisomerase

Enzyme (like DNA Gyrase) that cleaves both strands of DNA and requires ATP to relieve strain.

DNA Polymerase

Enzymes that synthesize new DNA only in the $5' \rightarrow 3'$ direction requiring a free 3'-OH group.

Primase

Enzyme that synthesizes an RNA primer to provide the 3'-OH group needed for DNA synthesis.

3' to 5' exonuclease activity

Proofreading mechanism embedded in DNA polymerases to excise mismatched bases.

Nucleotide Excision Repair (NER)

Pathway that removes bulky, helix-distorting lesions like UV-induced pyrimidine dimers.

Xeroderma Pigmentosum

Clinical disease caused by defective NER, characterized by extreme UV sensitivity and skin cancers.

Mismatch Repair (MMR)

Pathway that corrects mispaired bases and short indels that escaped proofreading.

Lynch Syndrome

Clinical condition also known as HNPCC caused by defective MutS/MutL homologues (MSH2, MLH1).

Base Excision Repair (BER)

Pathway fixing non-bulky alterations such as the spontaneous deamination of cytosine to uracil.

DNA Glycosylase

Enzyme in Base Excision Repair that creates an AP site by removing a single base.

Homologous Recombination (HR)

Error-free repair of double-strand DNA breaks using a sister chromatid as a template.

Fanconi Anemia

A clinical disease associated with defects in Homologous Recombination (HR).

Non-Homologous End Joining (NHEJ)

Fast but error-prone pathway rejoining broken double-strand ends without a template.

Ataxia-Telangiectasia

Clinical disease associated with defective Non-Homologous End Joining (NHEJ).

DNA Methylation

The addition of methyl groups to cytosine within CpG islands to silence gene expression.

Histone Acetylation

Modification where HATs add acetyl groups to lysine, converting heterochromatin to euchromatin.

Competitive Inhibitors

Inhibitors that bind to the active site, increasing $K_m$ while leaving $V_{max}$ unchanged.

Noncompetitive Inhibitors

Inhibitors that bind allosterically, lowering $V_{max}$ while leaving $K_m$ unchanged.

DNA Polymerase III

The primary elongation enzyme used in prokaryotic (E. coli) replication.

DNA Polymerase I

Prokaryotic enzyme that removes RNA primers using $5' \rightarrow 3'$ exonuclease activity.

Telomerase

Eukaryotic enzyme required to finish lagging strand ends of linear DNA.

Ciprofloxacin

Fluoroquinolone antibiotic that inhibits Bacterial Topoisomerase II (DNA Gyrase).

Zidovudine (AZT)

Antiviral drug (NRTI) that terminates HIV replication due to the lack of a 3'-OH group.

Transcription

Process where RNA Polymerase adds matching RNA bases to DNA to form an mRNA strand.

Translation

Process where tRNA carries amino acids to the ribosome to build proteins based on mRNA codons.

Codon

A triplet of mRNA bases read during translation.

AUG

The universal start codon, corresponding to methionine.

Enhancers

DNA regions that transcription factors bind to in order to increase transcription.

Operons

Functional units in prokaryotes that regulate gene expression (e.g., the Lac operon).

Introns

Portions of mRNA transcript that are removed before final protein synthesis.

Exons

The portions of mRNA that remain after splicing and are used for protein coding.

Capsid

The protein coat protecting the genetic information of a virus.

Enveloped virus

A virus with a lipid bilayer stolen from host membranes; sensitive to alcohol.

Parvovirus B19

An exception among DNA viruses because it is single-stranded DNA ($ssDNA$).

Poxviruses

Exception among DNA viruses that are $dsDNA$ but replicate entirely in the cytoplasm.

Positive-sense RNA (+ssRNA)

Viral RNA that acts directly as mRNA for immediate translation.

Negative-sense RNA (-ssRNA)

Viral RNA that must be converted to positive sense by RNA-dependent RNA polymerase before translation.

Retroviruses

Viruses like HIV that use reverse transcriptase to convert RNA into DNA to integrate into the host genome.

Peptidoglycan

Polymer of alternating NAG and NAM linked by $\beta$-1,4-glycosidic bonds in bacterial cell walls.

Gram-Positive Bacteria

Bacteria with a thick peptidoglycan layer containing teichoic acids; stains purple.