Microscopy, Cell Structures, and Membrane Transport: Key Concepts for Biology

What is light microscopy?

Light microscopy is a technique that uses visible light and a system of lenses to magnify images of small samples.

What are the parts of a light microscope?

The main parts of a light microscope include the eyepiece, objective lenses, stage, light source, and focusing knobs.

How can contrast be increased in microscopy?

Contrast can be increased using stains, adjusting the light intensity, or using phase contrast techniques.

What is the difference between SEM and TEM?

Scanning Electron Microscopy (SEM) provides 3D images of the surface of a sample, while Transmission Electron Microscopy (TEM) provides 2D images by transmitting electrons through a thin specimen.

What are the major differences between prokaryotic and eukaryotic cells?

Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and organelles.

What are the major functions of the endomembrane system?

The endomembrane system is involved in the synthesis, modification, transport, and degradation of proteins and lipids.

What structures are part of the endomembrane system?

The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and plasma membrane.

What is the function of the smooth and rough ER?

The rough ER is involved in protein synthesis and modification, while the smooth ER is involved in lipid synthesis and detoxification.

What are lysosomes?

Lysosomes are membrane-bound organelles that contain digestive enzymes to break down waste materials and cellular debris.

What are phagocytosis and autophagy?

Phagocytosis is the process by which cells engulf large particles, while autophagy is the process of degrading and recycling cellular components.

What is the structure and function of mitochondria?

Mitochondria have a double membrane structure and are responsible for producing ATP through cellular respiration.

What is the structure and function of chloroplasts?

Chloroplasts have a double membrane and contain chlorophyll; they are responsible for photosynthesis in plant cells.

What are peroxisomes?

Peroxisomes are organelles that contain enzymes for oxidation reactions, including the breakdown of fatty acids and detoxification of hydrogen peroxide.

What are the generalized functions of the cytoskeleton?

The cytoskeleton provides structural support, facilitates cell movement, and aids in intracellular transport.

What are the 3 main types of cytoskeletal elements?

The three main types are microfilaments (actin filaments), intermediate filaments, and microtubules (tubulin).

What are the major extracellular structures and their functions?

Major extracellular structures include the extracellular matrix and cell walls, which provide support and protection to cells.

What are the types of intracellular junctions in plants and animals?

Types of junctions include tight junctions, gap junctions, and desmosomes in animals, and plasmodesmata in plants, facilitating communication and adhesion.

Why is the plasma membrane considered selectively permeable?

The plasma membrane is selectively permeable because it allows certain substances to pass while blocking others, maintaining homeostasis.

What are the major components of the plasma membrane?

The major components include phospholipids, cholesterol, proteins, and carbohydrates.

What is the structure of phospholipids?

Phospholipids consist of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, making them amphipathic.

What does the fluid mosaic model of membrane structure mean?

The fluid mosaic model describes the plasma membrane as a flexible layer of lipids with embedded proteins that move laterally.

How do temperature and hydrocarbon tail type affect membrane fluidity?

Higher temperatures increase fluidity, while the type of hydrocarbon tail (saturated vs. unsaturated) affects how tightly the phospholipids pack together.

What is cholesterol's function in the plasma membrane?

Cholesterol stabilizes the membrane's fluidity, preventing it from becoming too rigid or too fluid.

What is an integral membrane protein?

Integral membrane proteins are embedded in the lipid bilayer and often function as channels or transporters.

What is a peripheral protein?

Peripheral proteins are attached to the exterior or interior surfaces of the membrane and often play roles in signaling or structural support.

What are the major functions of membrane proteins?

Membrane proteins are involved in transport, enzyme activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and ECM.

What role do membrane carbohydrates play?

Membrane carbohydrates are key in cell-cell recognition and communication.

How do polar/charged/hydrophilic substances cross the membrane?

Polar/charged/hydrophilic substances do not cross the membrane effectively due to the hydrophobic lipid bilayer, while hydrophobic substances can pass through rapidly.

How does diffusion work?

Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

What is passive transport?

Passive transport is the movement of substances across a membrane without the use of energy, occurring down their concentration gradient.

What is osmosis?

Osmosis is the diffusion of water across a semipermeable membrane from a hypotonic solution to a hypertonic solution.

What do hypertonic, hypotonic, and isotonic mean?

Hypertonic refers to a solution with a higher solute concentration, hypotonic has a lower solute concentration, and isotonic has equal solute concentrations.

What are turgid, flaccid, and plasmolyzed states?

Turgid is when a plant cell is swollen with water, flaccid is when it is limp, and plasmolyzed is when it has lost water and shrunk.

How do animal and plant cells control water balance?

Animal cells control water balance through osmoregulation, while plant cells use turgor pressure to maintain their structure.

What is facilitated diffusion?

Facilitated diffusion is the process of transporting substances across a membrane via channel or carrier proteins without using energy.

What are examples of channel proteins?

Examples of channel proteins include aquaporins (water channels) and ion channels (for ions like sodium and potassium).

How do carrier proteins work?

Carrier proteins bind to specific molecules and undergo a conformational change to transport them across the membrane.

What is active transport?

Active transport is the movement of substances against their concentration gradient, requiring energy and carrier proteins.

What are differences between facilitated diffusion and active transport?

Facilitated diffusion does not require energy and moves substances down their concentration gradient, while active transport requires energy and moves substances against their gradient.

What are ion pumps?

Ion pumps are membrane proteins that transport ions across the membrane, often against their concentration gradient.

How does the sodium/potassium pump work?

The sodium/potassium pump transports sodium ions out of the cell and potassium ions into the cell, using ATP for active transport.

What is membrane potential?

Membrane potential is the voltage difference across a cell's plasma membrane, created by the distribution of ions.

What is coupled transport?

Coupled transport is a mechanism where the transport of one substance is linked to the transport of another substance.

What is secondary active transport?

Secondary active transport uses the energy from the electrochemical gradient created by primary active transport to move other substances.

What are endocytosis and exocytosis?

Endocytosis is the process of taking substances into the cell, while exocytosis is the process of expelling substances from the cell.

What are the types of endocytosis?

Types of endocytosis include phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis (specific uptake).

What is the first law of thermodynamics?

The first law of thermodynamics states that energy can be transferred and transformed, but it cannot be created or destroyed.

What is metabolism?

Metabolism is the sum total of all chemical reactions in an organism, including catabolic (breaking down) and anabolic (building) reactions.

What are metabolic reactions composed of?

Metabolic reactions are composed of multiple steps, each catalyzed by a specific enzyme.

What are the different forms of energy?

The different forms of energy include kinetic energy, potential energy, thermal energy, and chemical energy.

How can different forms of energy be interconverted?

Different forms of energy can be converted from one type to another, such as potential energy being converted to kinetic energy.

What is the second law of thermodynamics?

The second law of thermodynamics states that in any energy transfer, the total entropy of a closed system will increase over time.

How do living systems increase the entropy of the universe?

Living systems increase the entropy of the universe by transforming energy and matter, leading to heat loss and disorder.

How do living systems use energy?

Living systems use energy to maintain order and perform work, counteracting the natural tendency toward disorder.

What is free energy (G)?

Free energy (G) is the energy available to do work in a system at constant temperature and pressure.

What is the formula for free energy?

The formula for free energy is ∆G = Gproducts - Greactants.

What does a negative ∆G indicate?

A negative ∆G indicates that a reaction is spontaneous and releases energy, classifying it as exergonic.

What does a positive ∆G indicate?

A positive ∆G indicates that a reaction is not spontaneous and requires energy, classifying it as endergonic.

What are enzymes?

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy (EA) required.

What is an activation barrier?

An activation barrier is the energy threshold that must be overcome for a reaction to occur.

How do enzymes lower the activation energy?

Enzymes lower the activation energy by stabilizing the transition state and providing an alternative reaction pathway.

What is an active site?

An active site is a specific region on an enzyme where substrates bind and undergo a chemical reaction.

What are the basic steps of enzyme catalysis?

The basic steps include substrate binding, transition state formation, product release, and enzyme regeneration.

What factors affect enzyme activity?

Factors affecting enzyme activity include temperature, pH, and the presence of cofactors and coenzymes.

What is competitive inhibition?

Competitive inhibition occurs when a molecule similar to the substrate competes for binding at the active site of the enzyme.

What is noncompetitive inhibition?

Noncompetitive inhibition occurs when an inhibitor binds to an enzyme at a site other than the active site, reducing its activity regardless of substrate concentration.

How are enzymes regulated?

Enzymes are regulated through mechanisms such as allosteric regulation, covalent modification, and feedback inhibition.

What is allosteric regulation?

Allosteric regulation involves the binding of an effector molecule to a site other than the active site, altering enzyme activity.

Where are enzymes localized?

Enzymes have specific localizations depending on their function, such as in mitochondria, membranes, or the cytoplasm.

What is ATP?

Adenosine triphosphate (ATP) is the primary energy carrier in cells, and its hydrolysis is coupled to endergonic reactions.