Cellular and Molecular Biology: Energy, Cells, and Membranes
CH6: Energy
Kinetic, Thermal, Potential, Chemical Energy
- Kinetic: motion
- Thermal: random movement of atoms
- Potential: matter possesses due to location/structure
- Chemical energy: potential energy available for release in chemical reaction
Organisms are Open Systems
- Thermodynamics: study of energy transformations
- 1st law: energy is constant
- 2nd law: every energy transfer increases disorder
Entropy
- Increases from liquid to gas
Spontaneous and Non-Spontaneous Reactions
- Spontaneous: without energy input
- Non-spontaneous: requires energy
Exergonic and Endergonic Reactions
- Exergonic: releases energy
- Endergonic: requires energy
Energy Coupling
- Use of an exergonic process to drive an endergonic one
- Mediated by ATP
Enzymes
- Catalysts that speed up reactions
- Activity can be affected by environment (temperature, pH, chemicals)
Cofactors
- Nonprotein enzyme helpers
- Organic and inorganic (e.g., metal ions)
- Include vitamins (e.g., vitamin C)
Inhibitors
- Bind to enzymes and decrease activity
- Competitive: bind to active site, competing with substrate
- Noncompetitive: bind to another part of the enzyme, reducing active site effectiveness
CH4: Basic Features of Cells
All Cells Have:
- Chromosomes (DNA)
- Nucleoid (prokaryotes) or nucleus (eukaryotes)
- Plasma membrane
- Cytoplasm or cytosol
- Ribosomes (make proteins)
Prokaryotic Cells
- Non-membrane-bound organelles
- Archaea and bacteria
Eukaryotic Cells
- Membrane-bound nucleus
- Cytoskeleton
- Centrioles (animal cells only)
- Chloroplasts (plant cells only)
Chromosomes and Nuclear Envelope
- Chromosomes are chromatin
- Nuclear envelope encloses the nucleus and separates it from the cytoplasm
- Double membrane with two phospholipids
Nuclear Lamina
- Maintains nucleus shape
- Cytoskeleton protein (intermediate filaments)
Ribosomes
- Made of RNA and protein
- Carry out protein synthesis
Mitochondria
- Cellular respiration occurs
- Smooth outer membrane, inner membrane folded into cristae
- Contain DNA
Endosymbiont Theory
- Explains the origins of mitochondria
Chloroplasts
- Photosynthesis occurs
- Own DNA and two membranes
- Thylakoids: stacks of granum, thylakoid space inside each stack
- Stroma: fluid around granum
Endoplasmic Reticulum (ER)
- Rough ER: synthesizes proteins to be secreted, sent to lysosomes or plasma membrane proteins, distributes vesicles
- Smooth ER: synthesizes lipids, metabolizes carbohydrates, detoxifies drugs, stores calcium ions
Golgi Apparatus
- Consists of sacs called cisternae and golgi bodies
- Modifies proteins from ER and ships proteins to their destination
Lysosomes
- Sacs of hydrolytic enzymes
- Digest macromolecules
- Work best in acidic environments
Vacuoles
- Food vacuoles formed by phagocytosis
- Contractile vacuoles pump excess water out of cells
- Central vacuoles found in plants, hold organic compounds
Cytoskeleton
- Microtubules (thickest): maintain cell shape, motility (animal cells only)
- Microfilaments (thinnest): muscle contraction, cytoplasmic streaming, motility and division
- Intermediate filaments: cell shape, anchorage of nucleus
Flagella and Cilia
- Flagella: beating back and forth
- Cilia: power stroke, recovery stroke
- 9 doublets, 2 singlets
- Motor proteins (dynein proteins) with the help of ATP
Microfilaments and Extracellular Matrix
- Microfilaments in the cortex, under plasma membrane (pseudopods, cleavage furrow)
- Extracellular matrix: networks of proteins and carbohydrates
- Animal cells lack cell wall but are covered by an elaborate extracellular matrix
- Made of glycoproteins, collagen, proteoglycans (part sugar protein)
- Connect to fibronectin, which connects to the anchor called integrin (trans-membrane protein)
- Connect to the microfilaments
CH.5: Membranes
Cholesterol and Membrane Fluidity
- Cholesterol has different effects on membrane fluidity at different temperatures
- Acts as a fluidity buffer
Functions of Membrane Proteins
- Transporter
- Enzyme
- Cell surface receptor
- Cell surface identity marker
- Cell to cell adhesion
- Attachment to cytoskeleton
Polar Molecules and Membrane Permeability
- Polar molecules cannot cross membranes easily
Channel Proteins
- Provide corridors for molecules to cross
- Have a hydrophilic channel that certain molecules/ions can use as a tunnel
Carrier Proteins
- Bind to molecules and change shape to shuttle them across the membrane
Diffusion
- Spontaneous movement of molecules from high concentration to low concentration
Passive Transport
- Movement of molecules through membranes without energy input
Dialysis
- Separation of solutes
Osmosis
: the diffusion of water across a selectively permeable membrane. Water diffuses across a membrane from the lower solute concentration to higher concentration. *Isotonic: where blood cells are at its normality, no water movement across plasma membrane. *Hypertonic: high salt envio. blood cells crenate or become shrivelled, cell loses water. *Hypotonic: pure water, blood cells become lysed and explode, cell gains water. WORKS BEST FOR PLANTS BC OF CELL WALL. *Osmoregulation: the control of solute concentrations and water balance. Paramecium is hypertonic and has a contractile vacuole that acts as pump. *Facilitated Diffusion: transports proteins speed the passive movement of molecules across the plasma membrane, Only for polar molecules. Passive. Down its concentration gradient, requires no energy. *Membrane Potential: voltage difference across a membrane, you get it by differences in the distribution of + and – ions across a membrane. *Cotransport: occurs when active transport of solute drives transport of other solutes. *Bulk transport: requires energy. *Exocytosis: export their products, transports vesicles migrate to membrane. *Endocytosis: reversal of exocytosis (Phagocytosis: cellular eating) (Pinocytosis: cellular drinking).