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


  • 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


  • Catalysts that speed up reactions
  • Activity can be affected by environment (temperature, pH, chemicals)


  • Nonprotein enzyme helpers
  • Organic and inorganic (e.g., metal ions)
  • Include vitamins (e.g., vitamin C)


  • 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)


  • Made of RNA and protein
  • Carry out protein synthesis


  • Cellular respiration occurs
  • Smooth outer membrane, inner membrane folded into cristae
  • Contain DNA

Endosymbiont Theory

  • Explains the origins of mitochondria


  • 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


  • Sacs of hydrolytic enzymes
  • Digest macromolecules
  • Work best in acidic environments


  • Food vacuoles formed by phagocytosis
  • Contractile vacuoles pump excess water out of cells
  • Central vacuoles found in plants, hold organic compounds


  • 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


  • Spontaneous movement of molecules from high concentration to low concentration

Passive Transport

  • Movement of molecules through membranes without energy input


  • Separation of solutes


: 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).