Cell Membrane Structure and Function Quiz

Questions and Answers

What is the primary function of carrier proteins in passive transport?

To selectively allow water to pass through the membrane.

To form vesicles for bulk transport of substances into the cell.

To facilitate the movement of specific molecules across a membrane through conformational changes. (correct)

To use energy for transporting molecules against their concentration gradient.

In osmosis, the movement of water is primarily determined by what factor?

The presence of active transport mechanisms.

The temperature of the solution.

The size of the water molecules in the solution.

The relative concentration of solute on either side of the membrane. (correct)

What characterizes active transport compared to passive transport?

It occurs without energy expenditure irrespective of the electrochemical gradient.

It requires energy to move molecules against their electrochemical gradient. (correct)

It exclusively transports large molecules through vesicles.

It is limited to the passive movement of ions through ion channels.

Which component is NOT involved in exocytosis?

Carrier protein. Signup and view all the answers

Endocytosis can encompass various forms. Which of the following describes phagocytosis?

Engulfs large particulate matter external to the cell. Signup and view all the answers

What is the role of the Na+-K+ pump in cellular transport?

Maintains the electrochemical gradient by transporting Na+ out and K+ into the cell. Signup and view all the answers

What distinguishes receptor-mediated endocytosis from other forms of endocytosis?

It requires specific binding of substances to plasma receptors before uptake. Signup and view all the answers

Which of the following describes the process of pinocytosis?

The uptake of extracellular fluid and small solutes. Signup and view all the answers

Which of the following is NOT a structural component of the cytoplasm?

Plasma membrane. Signup and view all the answers

How do mitochondria proliferate within eukaryotic cells?

By fission of preexisting mitochondria. Signup and view all the answers

Which structure of the Golgi complex faces the endoplasmic reticulum?

Cis face. Signup and view all the answers

What main function is associated with lysosomes?

Degrade material using acid hydrolases. Signup and view all the answers

What is the primary theory regarding the origin of mitochondria?

They evolved from prokaryotic cells through endosymbiosis. Signup and view all the answers

Which component of the Golgi apparatus sorts proteins for their final destinations?

Trans Golgi network (TGN). Signup and view all the answers

What special proteins do lysosomes possess for their function?

Acid hydrolases. Signup and view all the answers

What is the structural characteristic of cisternae in the Golgi complex?

Disk-shaped and slightly curved. Signup and view all the answers

Which of the following best describes the lifespan of mitochondria?

Typically have a lifespan of about 10 days. Signup and view all the answers

Which type of cell component would you find in the Golgi complex?

Cisternae. Signup and view all the answers

Which physiological process most directly involves phosphorylation of ADP to ATP?

Oxidative processes in mitochondria. Signup and view all the answers

What is the primary role of ATP-powered proton pumps in lysosomes?

To maintain an acidic pH Signup and view all the answers

Which type of lysosome is produced by the fusion of a phagocytic vacuole with a late endosome?

Phagolysosome Signup and view all the answers

What do residual bodies in lysosomes contain?

Undegraded material Signup and view all the answers

Peroxisomes are identified in cells by a reaction for which enzyme?

Catalase Signup and view all the answers

Which of the following is NOT a characteristic of peroxisomes?

They contain a nucleoid Signup and view all the answers

What type of lysosomes are formed when cell components to be destroyed are enveloped by membranes from the RER?

Autophagolysosomes Signup and view all the answers

Which of the following substances do peroxisomes NOT detoxify?

Urate Signup and view all the answers

What forms when an early endosome containing endocytic vesicles fuses with a late endosome?

Multivesicular body Signup and view all the answers

What is a function of peroxisomes related to long-chain fatty acids?

They oxidize long-chain fatty acids Signup and view all the answers

What are autophagic vacuoles formed from?

Smooth areas of membranes from RER Signup and view all the answers

What is the primary role of the centrosome within the cell?

Microtubule organization and spindle formation Signup and view all the answers

Which structures are contained within the pericentriolar cloud of the centrosome?

Gamma tubulin ring complexes Signup and view all the answers

What are microtubules primarily composed of?

Alpha and beta tubulin dimers Signup and view all the answers

Which of the following correctly describes the diameter of microtubules?

25 nm Signup and view all the answers

Which proteins are associated with microtubules to facilitate movement within the cell?

Kinesin and cytoplasmic dynein Signup and view all the answers

What is not a function of the cytoskeleton?

Cellular respiration Signup and view all the answers

What is the primary function of integral proteins within the plasma membrane?

They function as membrane receptors and transport proteins. Signup and view all the answers

What characteristic of the glyocalyx is true regarding its composition?

It includes polar oligosaccharide side chains linked to proteins and lipids. Signup and view all the answers

Which type of membrane protein is known to be associated with the cytoskeleton?

Peripheral proteins Signup and view all the answers

Which statement best describes passive transport?

It involves the movement of molecules without the use of energy down their concentration gradient. Signup and view all the answers

Facilitated diffusion is characterized by which of the following?

It occurs through ion channels and carrier proteins that exhibit specificity. Signup and view all the answers

What is the thickness of the glyocalyx layer?

50nm Signup and view all the answers

Which of the following correctly describes simple diffusion?

It is limited to the transport of non-polar or small unchanged polar molecules. Signup and view all the answers

What distinguishes ion channel proteins from other types of membrane proteins?

They form a selective aqueous pore for specific ions to pass through. Signup and view all the answers

Which statement correctly describes the role of proteoglycans in the glyocalyx?

They can bind to integral proteins as part of the glyocalyx. Signup and view all the answers

Study Notes

Glycocalyx

Composed of carbohydrate side chains from glycoproteins and glycolipids.
Forms a fuzzy material on the outer surface of cell membranes.
Thickness is approximately 50 nm.
Contains polar oligosaccharide chains covalently linked to proteins and some lipids.

Membrane Proteins

Integral Proteins: Known as transmembrane proteins, they function as membrane receptors and transport proteins.
Peripheral Proteins: Do not penetrate the lipid bilayer; usually found on the cytoplasmic side, involved in cytoskeleton scaffolding or intracellular signaling.

Plasma Membrane Transport Processes

Passive Transport: Does not require energy; substances move from higher to lower concentration.
- Simple Diffusion: Movement of small non-polar (O2, N2) and small polar molecules (H2O, CO2, Glycerol) based on concentration gradient.
- Facilitated Diffusion: Utilizes ion channels and carrier proteins, demonstrating specificity for particular molecules.
  - Ion Channels: Multi-pass transmembrane proteins that form pores for specific ions to passively flow through the membrane.
  - Carrier Proteins: Transmembrane proteins that change shape to facilitate the movement of specific molecules; can function in both passive and active transport.
- Osmosis: The diffusion of water through a selectively permeable membrane, guided by solute concentrations until equilibrium occurs.
Active Transport: Requires energy to move substances against their electrochemical gradient.
- Na+-K+ Pump: Carrier protein (ATPase) facilitating the antiport of sodium and potassium ions.
- Glucose Transport: Symport mechanism for moving glucose across epithelial layers.
Vesicular Transport: Involves vesicle formation to transport materials into and out of cells.
- Exocytosis: Bulk expulsion of substances by fusion of vesicles with the plasma membrane.
- Endocytosis: Bulk intake of substances via vesicle formation at the plasma membrane.
  - Phagocytosis: Engulfing of large particles or cells (“cell eating”).
  - Pinocytosis: Uptake of interstitial fluid and solutes (“cell drinking”).
  - Receptor-mediated Endocytosis: Specific binding of substances followed by vesicle formation for uptake.

Cytoplasm

Comprised of three main structural components:
- Organelles
- Inclusions
- Elementary Particles (e.g., ATP synthase)

Organelles

Mitochondria: May originate from anaerobic eukaryotic cells engulfing aerobic microorganisms, responsible for oxidative energy processes. Proliferate by fission; typical lifespan is about 10 days.
Golgi Complex: Stack of membrane-bound cisternae engaged in modifying, sorting, and packaging proteins.
- Cis Face: Faces the endoplasmic reticulum, also known as the cis Golgi network.
- Medial Compartment: Region between the cis and trans faces.
- Trans Face: Faces vacuoles/secretory granules, contains the trans Golgi network for protein sorting.
Lysosomes: Membrane-bound organelles containing acidic hydrolases for degrading materials.
- Types of Lysosomes:
  - Multivesicular Bodies: Fusion of early endosomes with late endosomes.
  - Phagolysosomes: Fusion of phagocytic vacuoles with lysosomes.
  - Autophagolysosomes: Formed by fusing autophagic vacuoles with lysosomes.
  - Residual Bodies: Contain undegradable material after lysosomal function is exhausted.
Peroxisomes: Membrane-bound organelles rich in enzymes for oxidizing fatty acids and detoxifying substances like ethanol. Contain catalase for breaking down hydrogen peroxide.

Inclusions

Contain various cellular components like:
- Glycogen
- Lipid Droplets
- Lipofuscin
- Centrosomes: Major microtubule organizing centers crucial for cell division.

Cytoskeleton

Serves as a structural framework within the cytosol.
Functions include maintaining cell shape, stabilizing attachment, facilitating transport and motility.
Major Components:
- Microtubules: Hollow structures made of tubulin, involved in maintaining cell shape and transporting materials.
- Microfilaments: Composed of actin, contribute to cellular movement.
- Intermediate Filaments: Provide tensile strength and structural support.

Microtubules

Composed of 25 nm tubulin dimers, with protofilaments that stabilize their structure.
Associated proteins (MAPs) assist in stabilization and binding to organelles, and motor proteins like kinesin or dynein aid in vesicle movement.

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Description

Test your understanding of cell membrane components, including glycoproteins, glycolipids, and types of membrane proteins. This quiz covers essential functions and structures involved in cellular communication and transport. Perfect for students studying cell biology.