Biology Chapter 5: Membrane Transport

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Questions and Answers

What is a primary function of channel proteins in the membrane?

They form hydrophilic channels for substance passage. (correct)

They catalyze metabolic reactions.

They transmit signals to the interior of the cell.

They help cells attach to the cytoskeleton.

Which type of protein is primarily involved in cell-cell recognition?

Carrier proteins involved in active transport.

Integral proteins that form tight junctions.

Peripheral proteins that induce shape changes.

Glycoproteins serving as identification tags. (correct)

What role do membrane carbohydrates play in cellular function?

They stabilize the structure of integral proteins.

They contribute to unique cell surface identity for recognition. (correct)

They form channels for ion transport.

They catalyze reactions within the membrane.

How do carrier proteins transport substances across the membrane?

By changing shape to shuttle substances. Signup and view all the answers

What is the function of glycoproteins in the membrane?

To serve as recognition signals between cells. Signup and view all the answers

Which function is NOT performed by integral proteins?

Loosely binding to the membrane surface. Signup and view all the answers

What is a characteristic of peripheral proteins in membranes?

They are loosely bound to the membrane surface. Signup and view all the answers

What is the main role of membrane proteins in enzymatic activity?

To expose active sites to adjacent substrates. Signup and view all the answers

What is the primary function of the Link Reaction in cellular respiration?

Convert pyruvate into acetyl-CoA Signup and view all the answers

How many molecules of CO₂ are produced per pyruvate during pyruvate oxidation?

1 CO₂ Signup and view all the answers

Which molecule is formed from the combination of acetyl-CoA and oxaloacetate in the citric acid cycle?

Citrate Signup and view all the answers

What is the end product of the electron transport chain?

Water Signup and view all the answers

What type of reaction primarily occurs during oxidative phosphorylation?

Redox reactions Signup and view all the answers

What is produced alongside ATP during one turn of the citric acid cycle?

3 NADH and 1 FADH₂ Signup and view all the answers

What is the role of the H⁺ ions in chemiosmosis?

They create a proton gradient to drive ATP production. Signup and view all the answers

How many ATP are generated from one molecule of glucose after two turns of the citric acid cycle?

2 ATP Signup and view all the answers

What type of molecules can easily pass through the lipid bilayer of a membrane?

Hydrophobic molecules Signup and view all the answers

Which function do channel proteins serve in a membrane?

To form hydrophilic tunnels for specific molecules. Signup and view all the answers

How do passive transport processes, like diffusion, occur?

Without energy, down a concentration gradient Signup and view all the answers

What is the primary role of aquaporins in cell membranes?

To facilitate the passage of water molecules Signup and view all the answers

What defines a concentration gradient in the context of passive transport?

The difference in concentration between two regions Signup and view all the answers

What occurs during osmosis?

Water moves from low solute to high solute concentration Signup and view all the answers

Why are carrier proteins important in cell membranes?

They transport specific molecules across the membrane. Signup and view all the answers

What distinguishes active transport from passive transport?

Active transport requires energy to move substances. Signup and view all the answers

What is the primary role of enzymes in chemical reactions?

To weaken chemical bonds and reduce activation energy Signup and view all the answers

Which model describes the precise fit between an enzyme and its substrate?

Lock-and-Key Model Signup and view all the answers

What happens to enzymes at high temperatures?

They get denatured, losing shape and function Signup and view all the answers

What defines a competitive inhibitor?

It binds to the active site, blocking substrate access Signup and view all the answers

What is the optimal pH range for the enzyme amylase?

6.7-7.0 Signup and view all the answers

Which factor is least likely to affect enzyme activity directly?

Color of the enzyme Signup and view all the answers

What type of non-protein molecules are coenzymes typically composed of?

Organic molecules like vitamins Signup and view all the answers

What is a shared characteristic of both competitive and non-competitive inhibitors?

They both decrease enzyme activity Signup and view all the answers

What effect does a hypotonic solution have on plant cells?

Causes cells to swell and increase turgor pressure. Signup and view all the answers

Which process describes the movement of substances against their concentration gradient?

Active transport Signup and view all the answers

What happens to plant cells in a hypertonic solution?

They undergo plasmolysis, causing the membrane to pull away from the wall. Signup and view all the answers

How do channel proteins function in facilitated diffusion?

They change shape to transport molecules across the membrane. Signup and view all the answers

What defines an isotonic solution for plant cells?

Equal concentrations of solutes inside and outside the cell. Signup and view all the answers

Which type of transport specifically engulfs large particles into a vacuole?

Phagocytosis Signup and view all the answers

What is the primary function of the sodium-potassium pump?

To maintain sodium and potassium concentration differences essential for cell functions. Signup and view all the answers

What are the waste products released during cellular respiration?

H₂O and CO₂ Signup and view all the answers

What is the general equation for aerobic cellular respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (36-38 ATP) Signup and view all the answers

Which of the following statements is true regarding anaerobic respiration?

It includes processes like fermentation. Signup and view all the answers

What role does oxygen play in cellular respiration?

It is necessary for aerobic respiration and ATP production. Signup and view all the answers

What is the net yield of ATP at the end of glycolysis?

2 ATP produced with a net yield of 2 ATP. Signup and view all the answers

Which stage of cellular respiration occurs in the cytoplasm?

Glycolysis. Signup and view all the answers

What happens to the electrons during the energy payoff phase of glycolysis?

They are transferred to NAD⁺, forming NADH. Signup and view all the answers

What is the primary function of ATP in cellular processes?

It powers various cellular processes such as muscle contraction. Signup and view all the answers

Why is it necessary to breathe in relation to cellular respiration?

It supplies oxygen for aerobic respiration and removes carbon dioxide. Signup and view all the answers

Study Notes

Chapter 5: Membrane transport and cell signaling

Plasma membrane: A boundary separating the living cell from its external environment. It exhibits selective permeability, allowing some substances to cross more easily than others.
Selective permeability: Crucial for maintaining cellular homeostasis. Small nonpolar molecules cross more easily than large polar molecules or ions.
Plasma membrane function: Controls material exchange, which is essential for cellular homeostasis.

Concept 5.1: Cellular Membranes Are Fluid Mosaics of Lipids and Proteins

Phospholipid Structure and Membrane Composition

Phospholipids: The most abundant lipids in membranes.
Amphipathic properties: Phospholipids have both hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails.
- Hydrophilic head: Composed of a phosphate group, facing the aqueous external and internal environments.
- Hydrophobic tail: Composed of fatty acids, facing inward and shielded from water.
Phospholipid bilayer: Forms a stable barrier between aqueous regions, like the cytoplasm and extracellular fluid.

Membrane Proteins

Amphipathic: Most membrane proteins are amphipathic, with hydrophilic portions exposed to water and hydrophobic regions interacting with the lipid core.
Fluid mosaic model: Membranes are fluid structures with embedded or attached proteins in a phospholipid bilayer.
Lateral movement: Proteins and lipids can move laterally within the membrane layer.
Specialized regions/rafts: Some proteins and lipids associate in specific regions or rafts, creating specialized functional patches.

Fluidity of Membranes

Lateral movement: Lipids and proteins move rapidly (lipids) to more slowly (proteins). Some proteins are anchored in place by cytoskeletal attachments.
Temperature effects: Temperature affects membrane fluidity, leading to a solid state at lower temperatures (saturated fatty acid tails pack tightly) and a more fluid state at higher temperatures (unsaturated fatty acid tails create kinks that prevent tight packing)
Cholesterol's role: Cholesterol regulates membrane fluidity; it prevents close packing at low temperatures and restricts movement at high temperatures.

Membrane Proteins and Their Functions

Variety of functions: Membrane proteins perform a variety of functions, including transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix (ECM).
Integral proteins: Span the entire lipid bilayer, often acting as channels or carriers for substances to pass across.
Peripheral proteins: Bound loosely to the surface of the membrane, often attached to integral proteins, cytoskeleton or ECM.

Six major functions of membrane proteins

Transport: Channel and carrier proteins allow certain molecules and ions to pass through.
Enzymatic activity: Membrane-bound enzymes catalyze reactions in the membrane environment.
Signal transduction: Specific signal molecules bind to protein receptors, initiating a signaling pathway within the cell.
Cell-cell recognition: Glycoproteins serve as identification tags.
Intercellular joining: Membrane proteins form connections, such as gap junctions or tight junctions.
Attachment to the cytoskeleton and ECM: Linking the membrane protein to internal support or the extracellular environment.

The Role of Membrane Carbohydrates in Cell-Cell Recognition

Carbohydrates attached to proteins and lipids: Form glycoproteins and glycolipids, which influence cell recognition and interactions.
Varied characteristics: Carbohydrate structures vary between species, individuals, even cell types, giving unique surfaces.

Concept 5.2: Membrane Structure and Selective Permeability

Selective permeability: Membranes control molecule and ion passage for maintaining proper internal conditions.
Lipid bilayer permeability: Hydrophobic molecules (hydrocarbons, CO2, O2) cross easily, while hydrophilic molecules (ions, polar molecules) cross less readily.
Transport Proteins: Allow hydrophilic substances to cross, including channel and carrier proteins

Transport Proteins

Channel proteins: Form hydrophilic tunnels enabling some molecules and ions to cross.
Aquaporins: Specialized channel proteins facilitating water movement.
Carrier proteins: Change shape to transport molecules across the membrane.

Concept 5.3: Passive Transport/ Concept 5.4: Active transport

Concentration gradient: Difference in concentration between regions.
Passive transport: No energy needed; substances move down their concentration gradient (high to low)
- Diffusion Molecules spread out evenly; move from high to low concentration via random motion.
- Osmosis Water moves from low solute concentration (high water concentration) to high solute concentration (low water concentration).
Active transport: Requires energy (ATP); substances move against their concentration gradient (low to high).
Sodium-Potassium Pump: Example of active transport; maintains concentration differences vital for cell functions (three sodium ions pumped out, two potassium ions pumped in).

Transport of Large Particles

Endocytosis: Engulfs particles from the outside into a vacuole within the cell. Types include phagocytosis, pinocytosis and receptor-mediated endocytosis.
Exocytosis: Vesicles fuse with the plasma membrane to expel contents out of the cell.

Chapter 7: Cellular Respiration & Fermentation

Cellular respiration: A series of metabolic reactions converting biochemical energy from nutrients to ATP, releasing CO2 and H2O.
General Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (36-38 ATP)
Types of Cellular Respiration:
- Aerobic respiration: Requires oxygen; produces 36-38 ATP per glucose molecule.
- Anaerobic respiration (fermentation): Occurs without oxygen; produces 2 ATP per glucose. Examples include alcohol fermentation and lactic acid fermentation.

Stages of Cellular Respiration

Glycolysis: The first step in breaking down glucose into two pyruvate molecules in the cytoplasm.
Pyruvate oxidation: Converts pyruvate to acetyl-CoA in the mitochondrial matrix.
Citric acid cycle (Krebs cycle): Further breaks down acetyl-CoA, generating NADH, FADH2, and ATP in the mitochondrial matrix.
Oxidative phosphorylation (Electron transport chain): Electrons from NADH and FADH2 are passed down an electron transport chain generating ATP and oxygen acts as the final electron acceptor; in the inner mitochondrial membrane.
ATP synthase: Enzyme that synthesizes ATP during oxidative phosphorylation (using a proton gradient).

Why Do You Need to Breathe?

Breathing is required to supply oxygen for aerobic cellular respiration.
Without oxygen, cells must use fermentation, which produces less ATP and can have negative consequences for the body.

Enzymes

Enzymes are proteins that act as biological catalysts, speeding up chemical reactions by lowering the activation energy needed for them to proceed.
Factors Affecting Enzyme Activity include temperature, pH, ionic concentration and presence of cofactors or inhibitors (like competitive or noncompetitive ones)
Enzyme Mechanism Enzyme-substrate interaction, Activation Energy reduction by catalysis, Product formation.
Important Graphs Showing Enzyme-Substrate Interaction, Graphs Showing the effects of temperature and pH on enzyme activity.

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Explore the essential concepts of membrane transport and cell signaling in Chapter 5 of your biology textbook. This quiz covers the plasma membrane's structure and functions, including selective permeability and phospholipid composition. Test your understanding of these critical biological processes.