Cell Biology Chapter Quiz
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Questions and Answers

Which cell will be filled with molecules faster if the transport rate is the same?

  • Cell A will be faster due to larger volume
  • Cell A will be faster due to larger surface area (correct)
  • Both cells will fill at the same rate regardless of size
  • Cell B will be faster due to larger volume

What two factors affect the efficiency of cell metabolism?

  • Surface area and volume ratio (correct)
  • Transport rate and cell age
  • Cell shape and membrane thickness
  • Nutrient availability and cell age

What structural adaptation allows cells to overcome limitations on size?

  • Folding of the cell membrane (correct)
  • Reduction in cell size
  • Addition of more organelles
  • Increased cell wall thickness

How does compartmentalization benefit eukaryotic cells?

<p>It segregates incompatible processes (D)</p> Signup and view all the answers

Why is maintaining a high surface area to volume ratio crucial for cells?

<p>It enhances nutrient uptake and efficient metabolism (D)</p> Signup and view all the answers

Which statement about transport proteins is correct?

<p>Glucose carrier proteins only transport glucose and not its isomers. (D)</p> Signup and view all the answers

What role do carrier proteins play in facilitated diffusion?

<p>They bind to molecules and change shape to facilitate transport. (A)</p> Signup and view all the answers

How do gated ion channels function?

<p>They open or close in response to specific stimuli. (D)</p> Signup and view all the answers

What happens to potassium ion channels in nerve cells during an electrical stimulus?

<p>They open to facilitate potassium ion transport. (B)</p> Signup and view all the answers

What is the primary factor that determines how easily a substance can pass through the plasma membrane?

<p>Polarity and molecular size of the substance (C)</p> Signup and view all the answers

What defines diffusion in terms of particle movement?

<p>Movement of particles that spreads them evenly into available space (B)</p> Signup and view all the answers

What is the significance of the selective permeability of membranes?

<p>It allows only specific substances to enter or exit the cell. (D)</p> Signup and view all the answers

Which statement best describes a concentration gradient?

<p>The difference in concentration of a substance between two regions (C)</p> Signup and view all the answers

What type of molecules require transport proteins for membrane crossing?

<p>Hydrophilic substances that cannot cross the lipid bilayer alone. (C)</p> Signup and view all the answers

What role does the plasma membrane play in cellular function?

<p>It controls the exchange of materials between the cell and surroundings (C)</p> Signup and view all the answers

What condition is caused by a dysfunctional Cl- channel?

<p>Cystic fibrosis (B)</p> Signup and view all the answers

How do hydrophobic molecules interact with the phospholipid bilayer?

<p>They dissolve in the lipid bilayer and pass through rapidly (D)</p> Signup and view all the answers

What is the primary function of channel proteins?

<p>They create a hydrophilic pathway for specific molecules or ions. (D)</p> Signup and view all the answers

What happens at dynamic equilibrium during diffusion?

<p>Equal numbers of molecules cross the membrane in both directions (B)</p> Signup and view all the answers

Which type of molecules have the most difficulty crossing the plasma membrane due to its hydrophobic interior?

<p>Small hydrophilic (polar) molecules (D)</p> Signup and view all the answers

What occurs to a cell when placed in a hypertonic solution?

<p>The cell shrinks as it loses water (C)</p> Signup and view all the answers

What role do cell-surface proteins play in relation to HIV?

<p>They facilitate the entry of HIV into immune cells. (D)</p> Signup and view all the answers

What is a consequence of lacking the CCR5 co-receptor?

<p>Immunity to HIV infection. (B)</p> Signup and view all the answers

What is the primary function of tight junctions in epithelial tissues?

<p>Preventing leakage of extracellular fluid. (D)</p> Signup and view all the answers

Which structure is responsible for cell-to-cell communication in animal cells?

<p>Gap junctions (D)</p> Signup and view all the answers

What type of junction anchors cells together in strong sheets?

<p>Desmosomes (A)</p> Signup and view all the answers

What is the main function of plasmodesmata in plant cells?

<p>Connecting plant cells for transport of water and small solutes. (A)</p> Signup and view all the answers

Which type of protein is responsible for attaching the cytoskeleton to the extracellular matrix (ECM)?

<p>Integrins (B)</p> Signup and view all the answers

Which component is NOT part of the cytoskeleton structure?

<p>Endoplasmic reticulum (D)</p> Signup and view all the answers

What role does cholesterol play in cell membranes at high temperatures?

<p>Restrains movement of phospholipids (C)</p> Signup and view all the answers

Which type of membrane protein spans the membrane and consists of hydrophobic regions?

<p>Transmembrane proteins (C)</p> Signup and view all the answers

How do fibronectin and other extracellular matrix proteins interact with cellular components?

<p>They bind to integral proteins in the membrane (B)</p> Signup and view all the answers

What is required for the activation of receptor tyrosine kinases (RTK)?

<p>Lateral movement of proteins in the membrane (C)</p> Signup and view all the answers

What is a key characteristic of integral proteins compared to peripheral proteins?

<p>They penetrate the hydrophobic core of the membrane (B)</p> Signup and view all the answers

What initiates dimerization in receptor tyrosine kinases for signaling?

<p>The binding of a signaling molecule (ligand) (A)</p> Signup and view all the answers

What effect does cholesterol have on membrane fluidity at low temperatures?

<p>Prevents tight packing of phospholipids (D)</p> Signup and view all the answers

What function do membrane proteins primarily serve within the cell membrane?

<p>Determine most of the membrane's functions (B)</p> Signup and view all the answers

What is the primary function of glucose transporter 1 (GLUT 1) in red blood cells?

<p>To facilitate glucose diffusion into red blood cells (B)</p> Signup and view all the answers

What type of proteins are involved in active transport processes?

<p>Carrier proteins (A)</p> Signup and view all the answers

Which mechanism requires ATP to move substances against their concentration gradient?

<p>Active transport (B)</p> Signup and view all the answers

What is the result of the sodium-potassium pump's activity in cells?

<p>Higher concentration of K+ inside the cell (B)</p> Signup and view all the answers

What does membrane potential refer to?

<p>The voltage across a membrane due to ion distribution (A)</p> Signup and view all the answers

How does the inside of the cell typically compare to the outside regarding charge?

<p>It is negatively charged relative to the outside. (D)</p> Signup and view all the answers

What ultimately drives the transport of glucose into red blood cells after it is phosphorylated?

<p>The concentration gradient of glucose (B)</p> Signup and view all the answers

What is maintained by the active transport of ions in cells?

<p>Solute concentrations that differ from the environment (D)</p> Signup and view all the answers

Flashcards

Cholesterol's Role in Membrane Fluidity

Cholesterol acts as a fluidity buffer in animal cell membranes, preventing excessive fluidity at high temperatures and excessive rigidity at low temperatures.

Peripheral Membrane Proteins

Peripheral proteins are associated with the surface of the cell membrane, loosely bound to the phospholipid bilayer or other membrane proteins.

Integral Membrane Proteins

Integral proteins penetrate the hydrophobic core of the cell membrane, spanning the entire bilayer.

Transmembrane Proteins

Transmembrane proteins are a type of integral protein that extend completely through the cell membrane, with portions exposed on both sides.

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Extracellular Matrix (ECM)

The ECM is a network of glycoproteins that surrounds animal cells, providing structural support and facilitating cell-cell interactions.

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Integrins

Integrins are receptor proteins in the plasma membrane that bind to ECM proteins like fibronectin, mediating cell adhesion and signaling.

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Receptor Tyrosine Kinases (RTKs)

RTKs are a class of protein receptors involved in cell growth and division, activated by binding to specific signaling molecules (ligands).

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RTK Activation and Deactivation

RTK activation requires dimerization (two polypeptides coming together) upon ligand binding, allowing trans-autophosphorylation and signal transduction. Deactivation involves the reverse process.

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Cell-Surface Proteins and HIV

HIV enters immune cells by binding to cell-surface protein CD4 and a co-receptor CCR5. People lacking CCR5 are resistant to HIV infection.

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What are cell junctions?

Cell junctions are specialized structures that connect adjacent cells in tissues, allowing communication and interaction.

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Tight Junctions

Tight junctions seal the space between cells, preventing leakage of extracellular fluid. They are like a zipper holding cells tightly together.

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Desmosomes (Anchoring Junctions)

Desmosomes fasten cells together into strong sheets. They act like rivets holding structures together.

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Gap Junctions (Communicating Junctions)

Gap junctions create channels between adjacent cells, allowing passage of small molecules and communication.

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Plasmodesmata in Plants

Plasmodesmata are channels connecting plant cells, allowing water, solutes, and sometimes even proteins and RNA to pass.

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Integrin Proteins

Integrin proteins link the cytoskeleton (cell's internal framework) to the extracellular matrix (ECM). They act as bridges between the inside and outside of the cell.

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What is the cytoskeleton?

The cytoskeleton is a network of protein fibers that provides structural support, gives shape to the cell, and helps with movement.

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Selective Permeability

The cell membrane allows some substances to pass through more easily than others.

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Hydrophobic Molecules

Nonpolar molecules that easily pass through the cell membrane because they dissolve in the lipid bilayer.

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Hydrophilic Molecules

Polar molecules that have difficulty passing through the cell membrane because they are repelled by the hydrophobic interior.

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Diffusion

The movement of particles from an area of high concentration to an area of low concentration until they are evenly distributed.

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Concentration Gradient

The difference in concentration of a substance between two areas. This difference drives diffusion.

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Dynamic Equilibrium

The state where the movement of particles across a membrane is equal in both directions, resulting in no net change in concentration.

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Tonicity

The ability of a solution to cause a cell to gain or lose water.

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Osmosis

The movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration.

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Surface Area to Volume Ratio

The ratio of a cell's surface area to its volume. A higher ratio indicates a more efficient cell, allowing for faster nutrient uptake and waste removal.

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Cell Size Limits

Cells have a maximum size due to the limitations of diffusion. As cells get larger, the surface area to volume ratio decreases, making it harder for them to transport necessary nutrients and remove waste efficiently.

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Folding of Membranes

Cells increase their surface area through membrane folding, allowing for more efficient nutrient uptake and waste removal. This is common in cells with high metabolic demands.

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Compartmentalization

Eukaryotic cells divide their internal space into compartments called organelles, each with a specific function. This allows for efficient regulation of cellular processes.

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Amoeba's Shape

Amoebas have a flexible shape that allows them to increase their surface area to volume ratio, aiding in efficient nutrient transport and waste removal.

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Transport Proteins

Specialized proteins embedded in cell membranes that allow specific substances to cross the membrane. They act as selective gates or carriers.

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Facilitated Diffusion

A type of passive transport that uses transport proteins to move specific substances across the cell membrane, following the concentration gradient.

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Channel Proteins

Transport proteins that form hydrophilic channels through the membrane, allowing passage of specific molecules or ions.

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Carrier Proteins

Transport proteins that bind to specific molecules and change shape to shuttle them across the membrane.

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Gated Channels

Ion channels that open or close in response to a specific stimulus, such as a chemical or electrical signal.

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Cystic Fibrosis

A genetic disorder caused by a faulty Cl- channel protein, leading to thick mucus buildup in the lungs and other issues.

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Glucose transporter (GLUT 1)

A specific carrier protein that facilitates the movement of glucose across the cell membrane, following the concentration gradient.

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Passive Transport

Movement of molecules across a membrane without requiring energy. The direction of movement is determined by the concentration gradient, going from high to low concentration.

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Active Transport

The movement of molecules across a membrane against their concentration gradient, requiring energy (often ATP).

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Sodium-Potassium Pump

A type of active transport that pumps 3 sodium ions out of the cell and 2 potassium ions into the cell, using ATP. This maintains the membrane potential.

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Membrane Potential

The difference in electrical charge across a cell membrane, created by the uneven distribution of ions.

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Cytosol

The fluid inside the cell that surrounds organelles, where many metabolic reactions occur.

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ATP

Adenosine triphosphate, the primary energy currency of cells, used to power active transport and many other processes.

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