Biology Chapter 7 Flashcards

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Questions and Answers

Which of the following statements about a typical plasma membrane is correct?

The two sides of the plasma membrane have different lipid and protein composition. (correct)

The plasma membrane is entirely composed of carbohydrates.

The two sides of the membrane have the same lipid and protein composition.

All membrane functions are the same on both sides.

Which of the following best describes the structure of a biological membrane?

Two layers of phospholipids with proteins either crossing the layers or on the surface of the layers. (correct)

A single layer of phospholipids.

A rigid protein layer.

A carbohydrate-based membrane.

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

Temperature.

The presence of covalent bonds.

The surface area of the membrane.

The types of transport proteins in the membrane. (correct)

Which of the following is least likely to be important in holding the components of a biological membrane together?

Covalent interactions between the phospholipid and protein components of the membrane. Signup and view all the answers

What makes the structure of the plasma membrane selectively permeable?

The hydrophobic nature of the lipid bilayer. Signup and view all the answers

Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane?

Ions and hydrophilic molecules Signup and view all the answers

What is referred to as selective permeability in a plasma membrane?

The ability to pass some solutes while blocking others. Signup and view all the answers

What will occur to a red blood cell placed in a 3.21% (m/v) NaCl solution?

Crenation Signup and view all the answers

Which factor does not affect membrane permeability?

The polarity of membrane phospholipids. Signup and view all the answers

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar, whereas sugars are polar. Signup and view all the answers

Osmosis is a type of diffusion.

True Signup and view all the answers

What property of dishwashing liquid makes it useful to wash grease from pans?

Amphipathic nature. Signup and view all the answers

Which of the following particles could diffuse easily through a cell membrane?

Oxygen (O2) Signup and view all the answers

The water-soluble portion of a phospholipid is the polar head.

True Signup and view all the answers

If a red blood cell bursts in a salt solution, what is the tonicity of the solution?

Hypotonic. Signup and view all the answers

Which statement about osmosis is correct?

The presence of aquaporins should speed up the process of osmosis. Signup and view all the answers

In facilitated diffusion, what is the role of the transport protein?

Transport proteins provide a hydrophilic route for the solute to cross the membrane. Signup and view all the answers

What cycle does active transport by the sodium-potassium pump follow?

Three Na+ ions bind, are phosphorylated, and three Na+ are released outside. Signup and view all the answers

Which of the following statements correctly describes the driving forces for diffusion of Na+ and K+ ions?

Na+ diffusion is facilitated by the Na+ concentration gradient. Signup and view all the answers

What is the mechanism of glucose uptake in animal cells?

Cotransport with Na+ ions. Signup and view all the answers

What distinguishes facilitated diffusion from simple diffusion?

Membrane proteins help move molecules across the membrane. Signup and view all the answers

Which transporter does not use passive transport?

Sodium-Potassium Pump Signup and view all the answers

Active transport does not require energy.

False Signup and view all the answers

What is the role of transporter proteins in glucose movement across a membrane?

Transporters assist in the movement of glucose from higher to lower concentration. Signup and view all the answers

What is typically true about the net movement of an ion across a membrane by passive diffusion?

Ions tend to move towards regions of unlike charge. Signup and view all the answers

During active transport via the sodium-potassium pump, ATP hydrolysis pumps three sodium ions into the cell.

False Signup and view all the answers

What type of transport is used to move lactose into the cell when its concentration is higher inside?

Active transport. Signup and view all the answers

How can the cell increase phosphate concentration in the cytosol when it is lower outside?

Active transport. Signup and view all the answers

What is the mechanism of glucose movement against a concentration gradient?

Cotransport with Na+ ions. Signup and view all the answers

How do active and passive transport differ?

Active transport requires energy whereas passive does not. Signup and view all the answers

What happens during endocytosis?

Substances are taken into the cell by folding in of the plasma membrane. Signup and view all the answers

Which movement is due to osmosis when a plant cell is placed in concentrated salt water?

Water moves out of the cell. Signup and view all the answers

What affects the rate of osmotic movement of water?

Differences in solute concentrations. Signup and view all the answers

What occurs when solutions reach osmotic equilibrium?

There is no net movement of water across the membrane. Signup and view all the answers

Study Notes

Plasma Membrane Structure and Composition

Plasma membranes have distinct lipid and protein compositions on either side, facilitating different functions for the cytoplasmic and exterior surfaces.
Composed of two layers of phospholipids with proteins embedded or attached to the bilayer, providing structural complexity and functionality.

Membrane Permeability

Membrane permeability for polar solutes depends on the presence of specific transport proteins, as the lipid bilayer is generally impermeable to polar or charged substances.
Small nonpolar molecules, e.g., O2 and CO2, can diffuse directly through the bilayer, while ions and larger polar molecules require transport proteins.
Water molecules can pass through the membrane slowly but efficiently via aquaporins, specialized transport proteins.

Tonicity and Effects on Cells

Crenation occurs when a red blood cell shrinks in a hypertonic solution (e.g., 3.21% NaCl), while hemolysis is the bursting of a cell in a hypotonic solution (e.g., distilled water).
Solutions classified as isotonic to red blood cells (e.g., 0.9% NaCl) maintain cell shape.

Mechanisms of Transport

Simple diffusion is the process by which small, nonpolar molecules pass through the membrane without assistance.
Facilitated diffusion employs transport proteins to help molecules cross, while active transport requires ATP to move substances against their concentration gradient.
The sodium-potassium pump is crucial for maintaining Na+ low within cells and K+ high, pumping three Na+ out for every two K+ in.

Energetics of Transport

Active transport mechanisms use energy (e.g., from ATP hydrolysis) to move substances against their electrochemical gradient, including the cotransport of glucose with sodium ions.
Osmosis, the diffusion of water, can occur even when solutes cannot cross the membrane, with water moving toward higher solute concentration until equilibrium is reached.

Special Transport Mechanisms

Endocytosis and exocytosis involve vesicles that transport substances without them crossing the membrane directly.
Micelles formed by detergents illustrate how amphipathic molecules can encapsulate grease and eliminate it through washing.

Concentration Gradients and Transport

An electrochemical gradient influences ion movement, with Na+ favoring entry and K+ favoring exit, but inhibited by charge differences.
The rate of osmotic movement is affected by temperature, pressure, and the concentration gradient of solutes across a selectively permeable membrane.

Osmotic Equilibrium

At osmotic equilibrium, water molecules remain in dynamic equilibrium, with continuous movement but no net directional flow across the membrane.

Key Transport Proteins

Specific transporters such as GLUT-1 facilitate glucose diffusion, exemplifying facilitated diffusion, while the sodium-potassium pump exemplifies active transport requiring ATP.

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Test your knowledge of the concepts in Chapter 7 of Mastering Biology with these flashcards. Focus on the structure and functions of biological membranes, including the differences in lipid and protein composition. Perfect for reinforcing your understanding of plasma membranes!