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General Biology: Cell Structure, Membrane Transport, and Enzymes

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Termini in questo insieme (79)

  • Function of the plasma membrane
    Controls what enters and leaves the cell.
  • Difference between cytoplasm and cytosol
    Cytosol is the fluid inside the cell; cytoplasm includes cytosol plus all structures outside the nucleus.
  • Main components of the cell membrane
    Phospholipids, proteins, cholesterol, and carbohydrates.
  • Why is the membrane selectively permeable?
    The hydrophobic inside of the phospholipid bilayer blocks many charged or polar substances.
  • Role of the nucleus
    Stores DNA and helps control cell activities.
  • Function of ribosomes
    Make proteins.
  • Role of rough endoplasmic reticulum (ER)
    Makes and processes proteins for secretion, membranes, or certain organelles.
  • Role of smooth endoplasmic reticulum (ER)
    Makes lipids and helps with detoxification and calcium storage.
  • Function of the Golgi apparatus
    Modifies, sorts, and packages proteins and lipids.
  • Role of mitochondria
    Make most of the cell’s ATP energy.
  • Function of lysosomes
    Break down waste and worn-out cell parts.
  • Role of peroxisomes
    Break down fatty acids and help detoxify harmful substances.
  • Function of the cytoskeleton
    Supports cell shape and helps movement and transport.
  • Purpose of vesicles
    Move or store materials in the cell.
  • Function of vacuoles
    Store materials; the large plant vacuole also helps support the cell.
  • Role of chloroplasts
    Carry out photosynthesis in plant cells.
  • Structures unique to plant cells
    Cell wall, chloroplasts, and a large central vacuole.
  • Components of the endomembrane system
    Nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, and plasma membrane.
  • Types of proteins traveling through the endomembrane system
    Proteins for secretion, membranes, and certain organelles.
  • What are cytosolic proteins?
    Proteins that stay and function in the cytosol.
  • Integral proteins
    Proteins embedded in the membrane; many cross it.
  • Peripheral proteins
    Proteins attached to the membrane surface.
  • Main types of membrane transport
    Passive transport, active transport, and vesicle transport.
  • Definition of diffusion
    Net movement of molecules from high concentration to low concentration.
  • What is a concentration gradient?
    A difference in a substance’s concentration between two areas.
  • Factors affecting diffusion rate
    Concentration gradient, temperature, particle size, and distance or barrier.
  • Simple diffusion
    Movement directly through the membrane from high to low concentration without energy or transport proteins.
  • Examples of molecules using simple diffusion
    Small nonpolar molecules such as oxygen and carbon dioxide.
  • Facilitated diffusion
    Movement from high to low concentration through a transport protein without cellular energy.
  • Examples of facilitated diffusion
    Glucose through carrier proteins and ions through channels.
  • Definition of osmosis
    Diffusion of water across a selectively permeable membrane.
  • Active transport
    Movement against a concentration gradient using energy.
  • Function of the Na+/K+ pump
    Uses ATP to move 3 sodium ions out and 2 potassium ions into the cell.
  • What is coupled transport?
    One substance’s movement helps drive another substance’s movement.
  • Active coupled transport explained
    A substance moving down its gradient drives another substance against its gradient.
  • How does the Na+/glucose cotransporter work?
    Sodium moves into the cell down its gradient and carries glucose in against its gradient.
  • Uniport transport protein
    Moves one type of substance in one direction.
  • Symport transport protein
    Moves two or more substances in the same direction.
  • Antiport transport protein
    Moves substances in opposite directions.
  • Endocytosis
    The cell brings material in by enclosing it in a membrane vesicle.
  • Exocytosis
    A vesicle joins the plasma membrane and releases material outside the cell.
  • How can a virus enter a cell by endocytosis?
    The cell takes the virus inside a membrane-bound vesicle.
  • What is virotherapy?
    Using viruses, often modified ones, to treat disease, such as targeting cancer cells.
  • What type of macromolecule is an enzyme?
    Usually a protein.
  • Definition of a catalyst
    Something that speeds up a reaction without being used up.
  • Are enzymes catalysts?
    Yes, they are biological catalysts.
  • What is a substrate?
    The reactant an enzyme acts on.
  • What are products in enzyme reactions?
    The substances formed by a reaction.
  • Substrate and products in H2O2 → O2 + H2O
    Substrate: H2O2 (hydrogen peroxide). Products: O2 (oxygen) and H2O (water).
  • Does an enzyme bind substrate or product?
    The substrate.
  • What is activation energy?
    Energy needed to start a chemical reaction.
  • How do enzymes affect activation energy?
    They lower it.
  • Can a reaction happen without an enzyme?
    Yes, but it is usually slower because activation energy is higher.
  • What is the active site of an enzyme?
    The region where the substrate binds.
  • What does it mean that enzymes are recyclable?
    They are not used up and can be used again.
  • What is enzyme specificity?
    An enzyme binds only certain substrates that fit its binding site.
  • Lock-and-key model
    The substrate fits the enzyme’s binding site because their shapes match.
  • How does enzyme shape affect function?
    If shape changes, the substrate may not bind and the enzyme may stop working.
  • What are cofactors?
    Helpers such as metal ions or small molecules that help an enzyme work.
  • Do cofactors usually bind enzymes or substrates?
    They generally bind to enzymes.
  • What is an enzyme’s optimal temperature?
    The temperature where its activity is highest.
  • Effect of cold on enzyme activity
    It slows activity.
  • Effect of high temperature on enzymes
    Extreme heat can change shape and reduce or stop activity.
  • What is denaturation?
    A change in protein shape that can cause loss of function.
  • How does pH affect enzymes?
    Each enzyme has a best pH range; changes can lower activity or change shape.
  • What is an inhibitor?
    A substance that reduces or stops enzyme activity.
  • Irreversible inhibitor
    One that causes lasting enzyme inactivation.
  • Reversible inhibitor
    One that temporarily reduces activity and can detach.
  • Two types of reversible inhibitors
    Competitive and noncompetitive.
  • Competitive inhibitor
    Competes with the substrate for the active site.
  • Noncompetitive inhibitor
    Binds away from the active site and reduces enzyme activity.
  • Effect of reversible inhibitor on cyclooxygenase (COX)
    Binds temporarily and reduces activity; aspirin inhibits COX irreversibly.
  • What is allosteric regulation?
    Controlling an enzyme by binding a molecule away from the active site.
  • Allosteric site
    A regulatory binding site away from the active site.
  • Allosteric activator
    A molecule that binds at an allosteric site and increases activity.
  • Allosteric inhibitor
    A molecule that binds at an allosteric site and decreases activity.
  • Functional metabolic pathway
    A series of enzyme-controlled reactions; each step’s product feeds the next step.
  • What is feedback inhibition?
    The final product inhibits an earlier enzyme to slow production.
  • What is feed-forward activation?
    An earlier pathway molecule activates a later enzyme.