Biology Cell Transport Mechanisms

Questions and Answers

What is the process called when solvent moves through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration?

Filtration

Active transport

Osmosis (correct)

Diffusion

How would a cell behave if placed in a hypertonic solution?

The cell will maintain its shape and function.

The cell will shrivel as water leaves it. (correct)

The cell will swell and possibly burst.

The cell will absorb solutes from the surrounding fluid.

What term describes a solution with the same osmolality as plasma?

Hypertonic

Isotonic (correct)

Concentrated

Hypotonic

Which of the following describes the mechanism of filtration?

Movement driven by hydrostatic pressure from higher pressure to lower pressure. Signup and view all the answers

What is the primary role of the sodium-potassium pump (Na+/K+ ATPase) in active transport?

To transport sodium out of the cell and potassium into the cell. Signup and view all the answers

Which statement accurately describes the outcome for cells in a hypotonic solution?

Cells will swell as they take on excess water. Signup and view all the answers

What is required for active transport to occur?

Cellular energy (ATP) Signup and view all the answers

What characterizes isotonic solutions regarding water molecules inside and outside cells?

The concentration of water molecules is the same inside and outside the cells. Signup and view all the answers

What characterizes passive transport?

It involves the movement from higher to lower concentration. Signup and view all the answers

Which type of transport uses carrier proteins for movement?

Facilitated diffusion Signup and view all the answers

What factor influences passive transport related to the size of molecules?

Molecules must be smaller than 7 A˚. Signup and view all the answers

What is the main distinction between active and passive transport?

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

Which type of molecule is most likely to passively diffuse through the cell membrane?

Fat-soluble materials Signup and view all the answers

Which factor does NOT influence passive transport?

Presence of ATP Signup and view all the answers

What describes the process of osmosis?

Movement of water across a semi-permeable membrane. Signup and view all the answers

Which molecules are likely to experience facilitated diffusion?

Larger polar molecules Signup and view all the answers

Which type of intercellular junction is responsible for allowing the transfer of ions and molecules between cells?

Gap junctions Signup and view all the answers

What is the primary function of the Rough Endoplasmic Reticulum (RER)?

Protein synthesis Signup and view all the answers

How are chromosomes structured within the nucleus?

They are wrapped around histone proteins to form nucleosomes. Signup and view all the answers

What is the main role of the Golgi apparatus in a cell?

Glycosylation of proteins Signup and view all the answers

In which type of cells would you expect to find a large amount of Smooth Endoplasmic Reticulum (SER)?

Steroid hormone-secreting endocrine cells Signup and view all the answers

What typically occurs to the DNA molecule when it is wrapped around histone proteins?

It is compacted to fit within the nucleus. Signup and view all the answers

What role do oxidases play in the cell?

They detoxify harmful substances by producing hydrogen peroxide. Signup and view all the answers

What is the primary function of cholesterol within the cell membrane?

To give fluidity to the membrane Signup and view all the answers

What is the primary component of the cytoskeleton?

Microtubules Signup and view all the answers

How are cell adhesion molecules (CAMs) important in tissues?

They contribute to intercellular connections and tissue integrity. Signup and view all the answers

Which of the following best describes the structure of phospholipids in the cell membrane?

They are arranged in a double layer with hydrophilic heads towards the extracellular fluid. Signup and view all the answers

What characterizes integral membrane proteins?

They can extend across the entire membrane. Signup and view all the answers

Which of the following is NOT a type of cell adhesion molecule (CAM)?

Keratin Signup and view all the answers

In the context of the cell membrane, what does the term 'amphipathic' refer to?

Molecules that have both hydrophilic and hydrophobic properties. Signup and view all the answers

Which function is associated with peroxisomes in liver cells?

Detoxification of alcohol Signup and view all the answers

What are microtubules primarily responsible for in cells?

Facilitating movement and maintaining cell shape Signup and view all the answers

How does the protein content of the cell membrane vary?

It can significantly change based on the cell’s function. Signup and view all the answers

Which CAM type is dependent on calcium ions for cell-to-cell adhesion?

Cadherins Signup and view all the answers

What is the main role of peripheral proteins in the cell membrane?

They are associated only with the inner or outer surfaces of the membrane. Signup and view all the answers

Which of the following lipids is typically NOT a major component of the cell membrane?

Triglycerides Signup and view all the answers

What is the significance of the fiber system in the cytoskeleton?

It facilitates the movement of proteins and organelles. Signup and view all the answers

What is the impact of membrane proteins on cell function?

They can act as channels, receptors, and enzymes, influencing cell behavior. Signup and view all the answers

Study Notes

Cell Membrane

The cell membrane (plasma membrane) is a semi-permeable barrier, 7.5 to 10 nanometers thick.
Composed of proteins and lipids, following the mosaic model with a variable lipid-to-protein ratio depending on cell function.
Nerve cells have high lipid content; red blood cells have a higher protein content.
Major lipids present include cholesterol (provides fluidity) and phospholipids (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine).
Phospholipids form a bilayer with hydrophilic heads oriented toward water and hydrophobic tails facing inward.
Membrane proteins are classified as integral (intrinsic, embedded) or peripheral (extrinsic, associated with membrane surface).
Proteins constitute about 50% of the membrane mass, with approximately one protein for every 50 phospholipid molecules.
Water-soluble substances like glucose require assistance to cross the membrane due to hydrophobic interactions of phospholipid tails.

Transport Mechanisms

Passive Transport: Movement across the membrane without energy expenditure. Includes:
- Diffusion: Molecule movement from higher to lower concentration (simple and facilitated diffusion).
  - Simple diffusion involves small molecules (e.g., Na, K, H2O, Ca) passing through pores.
  - Facilitated diffusion involves carrier proteins for larger molecules.
  - Influenced by solubility, size, charge, concentration gradient, and surface area.
- Osmosis: Movement of water through a semipermeable membrane based on solute concentration.
  - Tonicity classifications: isotonic (equal concentration to plasma), hypertonic (higher concentration, leads to cell shrinkage), hypotonic (lower concentration, may cause cell bursting).
- Filtration: Uses hydrostatic pressure to push fluid and solutes from high to low pressure areas, crucial in the circulatory and renal systems.
Active Transport: Movement against the concentration gradient requiring energy (ATP).
- Characterized by carrier proteins, e.g., the sodium-potassium pump (Na+/K+ ATPase) transports sodium out and potassium into the cell.

Cytoskeleton

Composed of microtubules, intermediate filaments, and microfilaments, providing structure and enabling cell movement.
Molecular motors transport organelles along the cytoskeletal fibers.
Cell Adhesion Molecules (CAMs) allow cells to attach to each other and the basal lamina, crucial for tissue integrity and functions in development and healing.

Intercellular Connections

Intercellular junctions include:
- Tight Junctions: Bind cells to provide tissue strength and stability.
- Gap Junctions: Create cytoplasmic tunnels for molecular diffusion between neighboring cells.

The nucleus contains chromosomes, composed of DNA, representing the genetic blueprint for species' hereditary characteristics.
Chromosomes exist in pairs (except germ cells), with each consisting of long DNA strands wrapped around histone proteins forming nucleosomes.

Endoplasmic Reticulum (ER)

Rough ER (RER): Associated with protein synthesis and abundant in protein-secreting cells (e.g., endocrine glands).
Smooth ER (SRE): Involved in steroid hormone synthesis and detoxification.
Sarcoplasmic Reticulum (SR): Regulates muscle contraction and relaxation.

Additional Structures

Ribosomes: Bound to RER for protein synthesis.
Golgi Apparatus: Responsible for protein glycosylation.

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Description

Test your understanding of key concepts in cell transport mechanisms, including osmosis, hypertonic solutions, and active transport. This quiz covers essential definitions and the functioning of the sodium-potassium pump. Perfect for biology students looking to reinforce their knowledge on cell membrane dynamics.