Biology Chapter 2.1: Cell Structure and Function
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Questions and Answers

What is the primary effect of solute concentration on water potential?

  • It decreases water potential. (correct)
  • It has no effect on water potential.
  • It causes water potential to fluctuate.
  • It increases water potential.

What does the variable 'i' represent in the formula for solute potential?

  • Temperature constant
  • Molar concentration of solute
  • Pressure potential
  • Ionization constant (correct)

Which statement best describes pressure potential (𝚿P) in plant cells?

  • It can be negative if the cell loses water.
  • It is often positive due to turgor pressure. (correct)
  • It has no significant impact on water potential.
  • It is always negative due to atmospheric pressure.

According to the formula for water potential, what happens to water potential as solute potential increases?

<p>Water potential decreases. (C)</p> Signup and view all the answers

What must be included in the calculation of solute potential according to the formula 𝚿s = -iCRT?

<p>Molar concentration along with ionization constant. (D)</p> Signup and view all the answers

What is the primary function of mitochondria in the cell?

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

Which structure within chloroplasts is responsible for light-dependent reactions?

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

What is the main role of lysosomes in a cell?

<p>Breaking down waste materials (C)</p> Signup and view all the answers

How do peroxisomes contribute to cellular function?

<p>Detoxifying harmful substances (B)</p> Signup and view all the answers

What structure in plant cells maintains turgor pressure?

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

Which components belong to the endomembrane system?

<p>Rough ER and plasma membrane (B)</p> Signup and view all the answers

Which type of filament is responsible for supporting cell shape and enabling movement?

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

What is the primary distinction between energy organelles and the endomembrane system?

<p>Energy organelles are involved in energy conversion. (B)</p> Signup and view all the answers

What is primarily affected by the size of a cell in terms of metabolism?

<p>Efficiency of metabolic processes (A)</p> Signup and view all the answers

Why do smaller cells have a metabolic advantage over larger cells?

<p>They have a higher surface area relative to their volume (D)</p> Signup and view all the answers

What happens to a cell when it grows too large?

<p>The surface area to volume ratio decreases. (C)</p> Signup and view all the answers

What consequence does a high surface area to volume ratio (SA:V) have for cells?

<p>Faster diffusion of substances (B)</p> Signup and view all the answers

Which structure helps to increase a cell's surface area without significantly increasing its volume?

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

What happens to the surface area to volume ratio as a cell increases in size?

<p>It decreases (C)</p> Signup and view all the answers

In terms of temperature regulation, why is a high SA:V ratio advantageous for cells?

<p>It allows for rapid loss of heat (C)</p> Signup and view all the answers

What is a primary function of the plasma membrane?

<p>To control the entry and exit of substances. (A)</p> Signup and view all the answers

The phospholipid bilayer is characterized by which property?

<p>Hydrophobic heads facing outward, tails inward. (B)</p> Signup and view all the answers

Which of the following is NOT a consequence of a high surface area to volume ratio?

<p>Slower cellular respiration (D)</p> Signup and view all the answers

What does it mean for the plasma membrane to be selectively permeable?

<p>It selectively allows some substances to pass while blocking others. (C)</p> Signup and view all the answers

What is the main reason larger cells face challenges in material exchange?

<p>Decreased surface area to volume ratio (A)</p> Signup and view all the answers

Which formula would be used to calculate the volume of a cuboidal cell?

<p>s^3 (D)</p> Signup and view all the answers

How do eukaryotic cells increase their internal surface area?

<p>Through compartmentalization and organelles. (D)</p> Signup and view all the answers

What impact does a reduced surface area to volume ratio have on metabolic activity?

<p>Hinders the ability to support high metabolic activity. (C)</p> Signup and view all the answers

What characteristic of phospholipids allows them to form a bilayer within the plasma membrane?

<p>Amphipathic nature. (D)</p> Signup and view all the answers

What is the primary function of the cell wall?

<p>Providing structural support and maintaining cell shape (B)</p> Signup and view all the answers

Which type of substance can diffuse easily across the plasma membrane?

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

What characterizes passive transport?

<p>It does not require energy for movement (B)</p> Signup and view all the answers

What is the defining feature of osmosis?

<p>Passive transport of water across a semipermeable membrane (A)</p> Signup and view all the answers

How do channel proteins function in facilitated diffusion?

<p>They form pores to allow specific molecules to pass through (C)</p> Signup and view all the answers

What is the role of the Sodium-Potassium Pump?

<p>To maintain resting membrane potential by exchanging ions (D)</p> Signup and view all the answers

Which of the following correctly describes facilitated diffusion?

<p>It helps larger or polar molecules cross the membrane (B)</p> Signup and view all the answers

In what situation is active transport necessary?

<p>When moving substances from lower to higher concentration (C)</p> Signup and view all the answers

What is the primary role of the plasma membrane in a cell?

<p>To regulate selective permeability (C)</p> Signup and view all the answers

Which of the following correctly describes the fluid mosaic model?

<p>A flexible mosaic of various proteins within a lipid bilayer (A)</p> Signup and view all the answers

How does temperature affect membrane fluidity?

<p>Higher temperatures increase fluidity (D)</p> Signup and view all the answers

What effect do unsaturated fatty acids have on membrane fluidity?

<p>They increase fluidity because of kinks in their tails (B)</p> Signup and view all the answers

What is the role of cholesterol in membrane fluidity?

<p>It stabilizes membranes at high temperatures and increases fluidity at low temperatures (B)</p> Signup and view all the answers

What distinguishes integral proteins from peripheral proteins?

<p>Integral proteins penetrate the lipid bilayer; peripheral are on the surface (D)</p> Signup and view all the answers

What role do carbohydrates play when attached to proteins or lipids in the plasma membrane?

<p>They assist in cell recognition and communication (B)</p> Signup and view all the answers

What is a key function of the plant cell wall?

<p>It prevents excessive water uptake and maintains cell shape. (C)</p> Signup and view all the answers

Flashcards

Mitochondria function

Mitochondria are the powerhouses of cells, generating ATP (energy) through cellular respiration.

Mitochondria structure

Mitochondria have a double membrane; the inner membrane is highly folded (cristae) to increase surface area for ATP production.

Chloroplast function

Chloroplasts are sites of photosynthesis, converting light energy into chemical energy (glucose).

Lysosomes function

Lysosomes contain digestive enzymes to break down cellular waste, debris, and old cell parts.

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Peroxisomes function

Peroxisomes detoxify harmful substances and break down fatty acids, producing hydrogen peroxide.

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Vacuoles

Storage organelles. They maintain turgor pressure in plant cells and store substances in animal cells.

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Cytoskeleton function

The cytoskeleton provides structural support, aids cell division, and enables movement (e.g., microfilaments, microtubules, intermediate filaments).

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Endomembrane System function

Processes and transports proteins and lipids including: nuclear envelope, rough & smooth ER, Golgi, lysosomes, vesicles and plasma membrane

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Cell Metabolism

The chemical reactions occurring within a cell to maintain life, including breaking down nutrients, synthesizing proteins, and removing waste.

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Surface Area to Volume Ratio (SA:V)

A measurement comparing a cell's surface area to its volume. Higher SA:V means more surface area relative to volume.

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Why is a high SA:V ratio beneficial?

It allows for faster and more efficient exchange of materials (like oxygen, nutrients, and waste) between the cell and its environment.

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SA:V and Exchange of Materials

Cells rely on diffusion to exchange materials. A higher SA:V ratio ensures faster diffusion of substances.

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SA:V and Metabolic Efficiency

Smaller cells with high SA:V can distribute nutrients and remove waste more efficiently, allowing for faster metabolism.

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SA:V and Temperature Regulation

Cells with high SA:V can lose heat faster, helping maintain an optimal temperature for enzyme activity.

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SA:V and Cell Size

As cell size increases, volume grows faster than surface area, leading to a decrease in SA:V ratio. This makes material exchange and metabolism more difficult.

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Why are larger cells challenged?

Larger cells have a lower SA:V ratio, making it harder to exchange materials and maintain efficient metabolism.

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SA:V Ratio

The surface area to volume ratio of a cell. A higher SA:V ratio means more surface area relative to volume, which is essential for efficient nutrient uptake and waste removal.

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Why is a high SA:V ratio important?

A high SA:V ratio allows for efficient diffusion of nutrients and waste products across the cell membrane. It also supports high metabolic activity, ensuring cell function and survival.

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What happens when a cell gets too big?

As a cell grows larger, its SA:V ratio decreases, meaning there's less surface area available for exchange relative to the volume. This slows down diffusion and hinders metabolic processes.

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Microvilli

Tiny finger-like projections on the surface of cells that increase surface area without significantly increasing volume. This helps improve nutrient absorption and waste removal.

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Flattened Shapes

Some cells adopt flattened shapes (like red blood cells) to maximize surface area relative to volume. This helps them efficiently exchange gases and nutrients.

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Compartmentalization

Eukaryotic cells have internal membranes and organelles that divide the cell into compartments, increasing the internal surface area for metabolic activities.

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Plasma Membrane

The outer boundary of a cell that controls what enters and exits, maintaining a stable internal environment. It's composed of a phospholipid bilayer, proteins, and carbohydrates.

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Phospholipid Bilayer

The foundation of the plasma membrane, composed of two layers of phospholipid molecules. Each phospholipid has a hydrophilic head and hydrophobic tails, forming a barrier to water.

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Selective Permeability

The ability of a cell membrane to allow certain substances to pass through while blocking others, maintaining the cell's internal environment for survival and function.

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Fluid Mosaic Model

Describes the plasma membrane as a flexible, fluid structure where proteins move freely within a lipid bilayer, like a mosaic.

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What increases membrane fluidity?

Unsaturated fatty acids in the membrane, due to kinks in their tails. Also, cholesterol at low temperatures prevents tight packing of phospholipids.

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What decreases membrane fluidity?

Saturated fatty acids in the membrane, due to their straight tails, and cholesterol at high temperatures, which stabilizes the membrane.

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Integral Proteins

Proteins that penetrate the hydrophobic core of the lipid bilayer, acting as channels or transporters for molecules.

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Peripheral Proteins

Proteins attached to the exterior or interior surfaces of the membrane, often involved in signaling or maintaining the cell's shape.

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Membrane Carbohydrates

Sugars attached to proteins (glycoproteins) or lipids (glycolipids) on the outer side of the membrane, crucial for cell recognition and communication.

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Plant Cell Wall

A rigid, supportive structure outside the plasma membrane of plant cells, primarily composed of cellulose, that maintains shape and prevents excessive water uptake.

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Passive Transport

Movement of substances across the membrane without using energy. It's like going downhill, no effort needed!

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Simple Diffusion

Molecules move from a high concentration area to a low concentration area until evenly spread out. Imagine a smelly perfume spreading in a room.

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Osmosis

Diffusion of water across a semipermeable membrane, moving from an area with less solute (more water) to more solute (less water).

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Facilitated Diffusion

Uses proteins to help larger or polar molecules cross the membrane. Imagine a special helper bringing groceries into your house.

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Active Transport

Requires energy (ATP) to move substances against their concentration gradient, from low to high concentration. Like pushing a boulder uphill!

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Sodium-Potassium Pump

A pump that moves 3 sodium ions out of the cell and 2 potassium ions in, using one ATP molecule per cycle.

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What is the function of the cell wall?

The cell wall provides structural support, maintains cell shape, and prevents bursting in hypotonic environments by providing a counter-pressure.

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Water Potential (𝚿)

The overall tendency of water to move from one area to another, influenced by pressure and solute concentration.

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Solute Potential (𝚿s)

The effect of solute concentration on water potential. More solutes mean lower water potential, as water is drawn in.

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Pressure Potential (𝚿P)

The pressure exerted on or by a cell, often positive due to turgor pressure from the cell wall.

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What does a negative solute potential mean?

A negative solute potential means the solution has a higher concentration of solutes compared to pure water, making it more likely for water to move into the solution.

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How does solute potential affect water movement?

Solute potential influences the direction of water movement. Water moves from areas of higher water potential (lower solute concentration) to areas of lower water potential (higher solute concentration).

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Study Notes

LT2.1 Cell Structure and Function

  • Cells are the fundamental units of all living organisms
  • Cells arise from pre-existing cells
  • All living organisms are composed of one or more cells
  • The cell is the basic unit of life

Types of Cells

  • Prokaryotic cells: Simpler, smaller, found in bacteria and archaea
    • Lack a nucleus
    • Lack membrane-bound organelles
    • DNA in a nucleoid region
    • May have cell walls, plasma membranes, ribosomes, flagella, or pili
  • Eukaryotic cells: More complex, larger, found in plants, animals, fungi, and protists
    • Have a true nucleus enclosed by a nuclear membrane
    • Have various membrane-bound organelles
    • Exhibit compartmentalization for specialized functions and efficiency

Key Organelles

  • Nucleus: Control center, houses DNA, regulates growth, metabolism, and reproduction

  • Ribosomes: Protein synthesis sites; can be free-floating or attached to rough ER

  • Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis and modification

    • Rough ER: Studded with ribosomes
    • Smooth ER: Lacks ribosomes

  • Golgi apparatus: Modifies, sorts, and packages proteins and lipids for transport

  • Mitochondria: "Powerhouses" of the cell, generate ATP through cellular respiration

  • Chloroplasts: Sites of photosynthesis, convert light energy into chemical energy (in plant cells)

  • Lysosomes: Contain digestive enzymes, break down waste materials and cellular debris

  • Peroxisomes: Contain enzymes that detoxify harmful substances and break down fatty acids

  • Vacuoles: Storage organelles, especially large central vacuole in plant cells maintaining turgor pressure

  • Cytoskeleton: Provides structural support and facilitates cell movement

  • Microfilaments, microtubules, and intermediate filaments

LT2.2 Cell Size

  • Cells must be small to function efficiently. The size impacts metabolism, SA:V ratio, and overall efficiency
  • Slower diffusion rates Larger cells struggle to obtain nutrients and oxygen or remove waste quickly
  • Metabolic Inefficiencies: Reduced SA:V can hinder high metabolic activity and affect growth & reproduction
  • Strategies to increase SA:V ratio: Microvilli, flattened shapes, and compartmentalization

LT2.3 Cell Membrane

  • The plasma membrane (cell membrane) is a vital structure surrounding the cell

    • Provides protection and support
    • Controls what enters and leaves the cell
    • Maintains homeostasis

  • Phospholipid bilayer forms the base of the membrane:

    • Hydrophilic (water-loving) heads face outward
    • Hydrophobic (water-fearing) tails face inward

  • Selective Permeability Allows some substances to pass through

  • Fluid Mosaic Model: Lipids and proteins are able to move within the membrane

    • Fluidity affects membrane function

  • Factors affecting fluidity: Temperature, fatty acid composition, and cholesterol

LT2.4 Cell Transport

  • Passive transport: Movement of substances across the membrane without energy
    • Simple diffusion: Molecules move from high to low concentration
    • Osmosis: Water moves from low to high solute concentration
    • Facilitated diffusion: Uses proteins to help larger molecules or ions cross the membrane
      • Channel proteins or carrier proteins
  • Active transport: Movement of substances against their concentration gradient requiring energy.
    • Pumps: Move ions across the membrane (sodium-potassium pump, proton pumps)

LT2.5 Tonicity and Osmoregulation

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

    • Isotonic: Solute concentration is equal inside and outside the cell
    • Hypotonic: Solute concentration outside is lower than inside the cell. Water enters cell causing swelling/bursting
    • Hypertonic: Solute concentration outside is higher than inside the cell. Water leaves cell causing shrinking/crenation

  • Importance to plant and animal cells.

  • Water potential (Ψ) The measure of potential energy in water predicts direction of water movement.

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U2 Reading Guide PDF - Cell Structure and Function

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Explore the fundamental concepts of cell structure and function in this quiz. Learn about prokaryotic and eukaryotic cells, their unique characteristics, and the key organelles that play crucial roles in cellular processes. Test your knowledge on the basic unit of life and the role of cells in living organisms.

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