MCAT Biology Section 1: Cells

MCAT - Biology Section 1. Cells 1.1. Cell Theory All organisms are made out of cells Cells are the basic functional unit of life Cells come from pre-existing cells Cells carry genetic info (DNA) 1.2. Eukaryotic Cells Nucleus ○ Double-layered envelope containing DNA ○ Nucleolus synthesizes rRNA Mitoc...

MCAT - Biology Section 1. Cells 1.1. Cell Theory All organisms are made out of cells Cells are the basic functional unit of life Cells come from pre-existing cells Cells carry genetic info (DNA) 1.2. Eukaryotic Cells Nucleus ○ Double-layered envelope containing DNA ○ Nucleolus synthesizes rRNA Mitochondria ○ Outer membrane, intermembrane space, inner membrane, matrix ○ Proton-motive force: H+ pumped from matrix to intermembrane space ○ Apoptosis via release of cytochrome C from ETC Lysosomes ○ Autolysis via release of hydrolytic enzymes from cells Endoplasmic reticulum ○ Rough ER Studded ribosomes and translates secreted proteins ○ Smooth ER Lipid synthesis, detoxification, protein transport Golgi apparatus ○ Modify materials from ER Peroxisomes ○ H2O2 production to break down VLCFA ○ Assists in phospholipid synthesis and pentose phosphate pathway Cytoskeleton ○ Microfilaments (actin rods) Protection, muscle contraction (w/ myosin), cleavage furrow ○ Microtubules (tubulin tubes) Motor protein pathway (kinesis and dynein) and centrioles Cilia (cell surface movement) and flagella (overall cell movement) 9+2 structure found only in eukaryotes ○ Intermediate filaments (keratin, desmin, vimentin, lamins) Cell-cell adhesion, maintain cytoskeleton, cell rigidity, anchor organelles Types of tissues ○ Epithelial Lines body/cavities and forms parenchyma Squamous, cuboidal, columnar Simple, pseudostratified, stratified ○ Connective Supports body and forms framework for epithelia, forms stroma Secretes collagen/elastin to form ECM ○ Cardiac (more info in Cardiovascular System) ○ Nervous (more info in Nervous System) 1.3. Prokaryotic Cells Bacteria ○ Structure (cocci → spheres, bacilli → rods, spirilla → spiral) Single circular chromosome in nucleoid Envelope (cell wall and plasma membrane) Gram staining Flagella (filament, hook, basal body → chemotaxis) ○ O2 requirement Obligate aerobes (no oxygen → death) Facultative anaerobes (switch between O2 or no O2) Microaerophiles (tolerates only low amounts of oxygen) Aerotolerant anaerobes (can tolerate oxygen) Obligate anaerobes (oxygen → death) ○ Recombination Transformation (acquired from environment) Conjugation (transferred between bacteria) Transduction (acquired by viruses) ○ Growth stages Lag phase Log phase Stationary phase Death phase Archaea (compared to bacteria) ○ Similarities Singular circular chromosome, similar structure (no LPS/PDG), binary fission ○ Differences Start translation w/ methionine, histones, and similar RNA pol to eukaryotes 1.4. Viruses Virions (nucleocapsid) ○ DNA viruses (DNA genome, nucleus, host machinery) dsDNA (identical to host DNA) Host replication and transcription ssDNA Host replication and transcription ○ RNA viruses (RNA genome, cytoplasm, own machinery) dsRNA (occurs in eukaryotes if targeted) Replication w/ RdRp inside capsid, no transcription ssRNA(+) Replication w/ RdRp, no transcription ssRNA(–) RdRp performs replication and transcription ○ Retroviruses (two copies of ssRNA, has reverse transcriptase → cDNA from RNA) ○ Life cycle (bacteriophages only) Lytic (virulent, virus replicates fast and lyses host cell) Lysogenic (temperate, virus integrated into host genome) Viroids (small circular ssRNA w/ no capsid, affects plants except for Hep. D in humans) Prions (misfolded proteins, α helices to β-pleated sheets → solubility ↓, degradation ↓)