Cell Membrane and Transport Mechanisms Quiz

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Questions and Answers

Which of the following molecules requires a carrier protein to cross the cell membrane?

Urea

Oxygen (O2)

Glucose (correct)

Carbon Dioxide (CO2)

What primarily drives the movement of oxygen (O2) into cells?

A higher concentration of O2 outside the cell (correct)

The cell's energy consumption

Active transport mechanisms

Lower concentration of O2 outside the cell

Which of the following correctly describes the movement of carbon dioxide (CO2) across the cell membrane?

It moves passively into the cell.

It moves out of the cell via active transport.

It diffuses out of the cell due to higher intracellular concentration. (correct)

It requires carrier proteins for facilitated diffusion into the cell.

What is a key characteristic of lipid-soluble substances in relation to diffusion across the cell membrane?

Their rate of diffusion is directly proportional to their lipid solubility. (C) Signup and view all the answers

Which of the following is a key characteristic of protein channels on the cell membrane?

They are often selectively permeable to certain substances. (A) Signup and view all the answers

What does 'voltage gating' in the context of cell membrane protein channels refer to?

The molecular conformation of the gate responding to the electrical potential. (A) Signup and view all the answers

A cell at rest has a strong negative charge inside the membrane. How does this affect the sodium (Na) gates in the cell membrane?

The Na gates remain tightly closed. (A) Signup and view all the answers

Which type of transport mechanism does not require energy from the cell?

Both facilitated and simple diffusion. (A) Signup and view all the answers

What is primarily responsible for the depolarization phase of an action potential?

The opening of sodium channels. (C) Signup and view all the answers

What best describes the state of the cell membrane interior immediately after an action potential is initiated?

It becomes positively charged. (C) Signup and view all the answers

Which of the following is responsible for the repolarization phase of an action potential?

The opening of voltage-gated potassium channels. (D) Signup and view all the answers

How do chemically gated channels function?

They open in response to specific chemical molecules. (B) Signup and view all the answers

What is the effect of acetylcholine binding to its channel?

It opens a channel, allowing uncharged molecules and positive ions to pass. (A) Signup and view all the answers

What is facilitated diffusion primarily used for?

The movement of charged or large polar molecules across the membrane. (C) Signup and view all the answers

Which of the following is an example of facilitated diffusion described in the text?

The movement of glucose into a cell. (D) Signup and view all the answers

Which of the following best describes voltage-gated potassium channels?

They open when the inside of the cell membrane becomes positively charged. (C) Signup and view all the answers

Which type of transport uses the energy stored in an ion concentration gradient to move another molecule against its own concentration gradient?

Secondary active transport (B) Signup and view all the answers

Which cellular process involves the secretion of hormones and neurotransmitters from the cell?

Exocytosis (C) Signup and view all the answers

What is the primary function of a phagosome?

To engulf large, solid material into the cell (D) Signup and view all the answers

Which type of endocytosis is considered non-selective and involves the intake of extracellular fluid?

Pinocytosis (D) Signup and view all the answers

A cell engulfs a clump of bacteria using pseudopods. What is this process called?

Phagocytosis (B) Signup and view all the answers

In secondary active transport, what is the role of ATP?

It is used to form a concentration gradient of ions (B) Signup and view all the answers

What is the main difference between pinocytosis and phagocytosis?

Pinocytosis involves uptake of fluid, while phagocytosis involves uptake of large particles (C) Signup and view all the answers

Which process is the reverse of exocytosis?

Endocytosis (C) Signup and view all the answers

What is the main purpose of the sodium-potassium pump in nerve cells?

To maintain an electrical gradient across the cell membrane (C) Signup and view all the answers

How many sodium ions does the Na+/K+ pump move out of the cell for each ATP molecule used?

3 (A) Signup and view all the answers

Which other primary active transport mechanism is mentioned, apart from the sodium-potassium pump?

Calcium pump (D) Signup and view all the answers

What characteristic of the intracellular concentration of calcium ions is emphasized?

It is significantly lower than that in extracellular fluid. (A) Signup and view all the answers

Where in the body is the active transport of hydrogen ions particularly important?

In the gastric glands and kidneys (D) Signup and view all the answers

What is the function of the SERCA pumps mentioned?

To maintain calcium concentration by storing it (D) Signup and view all the answers

In nerve cells, the inside of the cell has what sort of electrical charge relative to the outside?

Negative charge (D) Signup and view all the answers

What drives the secondary active transport process when a molecule moves down its concentration gradient?

The release of energy associated with the molecule's movement (B) Signup and view all the answers

What is the primary reason glucose cannot cross the lipid bilayer via simple diffusion?

Glucose is a polar molecule and the lipid bilayer is nonpolar. (B) Signup and view all the answers

What is the function of glucose transporters (GLUTs) in facilitated diffusion?

To bind to glucose and transport it across the membrane. (B) Signup and view all the answers

What is the role of insulin in glucose transport in skeletal muscle, heart, and adipose tissue?

Insulin moves GLUT4 from the cytoplasm to the membrane, increasing glucose uptake. (B) Signup and view all the answers

Which of the following is NOT a characteristic of osmosis?

Osmosis requires a carrier protein to facilitate the movement of water. (D) Signup and view all the answers

What is the term used to describe two solutions with the same concentration of solutes?

Isotonic (D) Signup and view all the answers

What would happen to a red blood cell placed in a solution with a higher concentration of solutes than the cell's cytoplasm?

The red blood cell would shrink and become crenated. (B) Signup and view all the answers

Which of these is NOT a characteristic of facilitated diffusion?

It requires energy expenditure by the cell. (C) Signup and view all the answers

What is the primary function of the heart in the context of filtration?

It exerts pressure on blood vessels to facilitate filtration. (D) Signup and view all the answers

Which of the following is a key difference between passive and active transport?

Active transport requires energy while passive transport does not. (B) Signup and view all the answers

What is the normal NaCl concentration inside a human red blood cell?

0.9% (D) Signup and view all the answers

What is an example of active transport listed in the content?

Na+/K+ pump (A) Signup and view all the answers

Which transport method involves the direct hydrolysis of ATP?

Primary active transport (B) Signup and view all the answers

What is the role of ATP in active transport?

It provides energy for movement of substances against their gradient. (A) Signup and view all the answers

What type of transport utilizes protein carriers to assist movement across membranes?

Both A and B (A) Signup and view all the answers

In secondary active transport, how is the energy generated?

By coupling the movement of one molecule down its gradient with another up its gradient. (B) Signup and view all the answers

What characterizes the antiport mechanism in active transport?

It pumps one or more solutes in opposite directions. (C) Signup and view all the answers

Study Notes

Cell Membrane Transport

The cell membrane regulates material entry and exit, crucial for maintaining homeostasis.
The cell membrane's ability to regulate the concentration of substances inside the cell is a vital function.
The membrane is selectively permeable, allowing some substances to cross but not others.

Membrane Permeability to Ions

Cell membranes are impermeable to negatively charged large molecules (e.g., proteins, phosphate groups of ATP) at rest.
Permeability to K+ ions is significantly higher (25-75 times) than Na+ ions.
Permeability to Cl- ions is greater than both Na+ and K+ ions.
Ion channel quantities influence ion permeability across the membrane.
Membranes have more K+ leakage channels and fewer Na+ leakage channels.

Intracellular and Extracellular Distributions of Ions

Extracellular fluids predominantly contain sodium and chloride ions.
Intracellular fluids mainly contain potassium ions and proteins with negatively charged side chains.

Factors Affecting Rate of Diffusion

Fick's laws describe diffusion.
The rate of diffusion is proportional to the concentration gradient, the diffusion pathway length, and the available surface area.

Diffusion Across the Cell Membrane

Simple diffusion: Molecules move directly across the membrane without carrier proteins.
- Hydrophobic molecules (e.g., O2, CO2) and small uncharged polar molecules (e.g., urea) use this method.
Facilitated diffusion: Larger uncharged polar molecules (e.g., glucose), and charged molecules (ions) require carrier proteins.

Diffusion of Lipid-Soluble Substances

Lipid solubility significantly impacts how readily a substance diffuses through the lipid bilayer.
Substances with high lipid solubility (e.g., oxygen, nitrogen, carbon dioxide, alcohols) readily dissolve in the lipid bilayer and diffuse through the membrane.
Diffusion rate is directly proportional to lipid solubility.

Diffusion Through Protein Channels

Protein channels in the cell membrane are often selectively permeable to specific substances.
Many channels can be opened or closed by gates.

Gating of Channels

Voltage gating: Gate conformation changes in response to electrical potential across the membrane.
- Strong negative charge inside the cell (resting state) keeps Na+ gates closed.
- Inside loses negative charge, Na+ gates open.
Chemical (ligand) gating: The binding of a chemical substance (ligand) with a protein causes a conformational change opening or closing the gate.
- Acetylcholine binding is an example impacting sodium channels

Facilitated Diffusion

Large polar or ionic molecules are typically hydrophilic.
They cannot readily cross the phospholipid bilayer.
Facilitated diffusion uses membrane proteins to transport large polar/ionic molecules across.
Glucose is a prime example of facilitated diffusion—using a specific glucose transporter.

Osmosis

Osmosis: Water moves across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.
The goal is to equalize solute concentrations across the membrane.

Tonicity

Isotonic: Solute concentration is equal inside and outside the cell; water movement is balanced.
Hypertonic: Solute concentration is higher outside the cell; water moves out, causing cell shrinkage (crenation).
Hypotonic: Solute concentration is lower outside the cell; water moves in, causing cell swelling (potentially lysis).

Filtration

Filtration: Materials are forced through a membrane by hydrostatic pressure.
This process is important in the body for fluid movement through capillary walls and in the kidneys for glomerular filtration.

Active Transport

Active transport requires energy (ATP) to move substances against their concentration gradient.
Uniport: Pumps one molecule across the membrane.
Symport: Pumps two molecules in the same direction.
Antiport: Pumps two molecules in opposite directions

Vesicular Transport

Includes endocytosis (bringing substances into the cell) and exocytosis (releasing substances from the cell).
- Endocytosis: Includes Phagocytosis (cell eating), Pinocytosis (cell drinking), receptor-mediated endocytosis.
- Exocytosis: Used for secretion and waste removal.

Specific Active Transport Mechanisms

Sodium-Potassium Pump (Na+/K+ ATPase): Maintains ion concentration gradients crucial for nerve and muscle function.
Calcium Pump (SERCA): Keeps intracellular calcium low by pumping Ca2+ ions against their concentration gradient into the endoplasmic reticulum or other storage sacs.
Hydrogen Pump (Gastric H+ ATPase): Involved in stomach acid production and regulation.

Secondary Active Transport

This process relies on an existing electrochemical concentration gradient of one substance to drive the transport of another substance against its own concentration gradient.

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Description

Test your knowledge on the fundamental concepts of cell membranes and transport mechanisms with this quiz. Questions cover topics such as carrier proteins, diffusion characteristics, and action potentials. Perfect for students studying cell biology or related fields.