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?

Water potential decreases. Signup and view all the answers

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

Molar concentration along with ionization constant. Signup and view all the answers

What is the primary function of mitochondria in the cell?

Cellular respiration Signup and view all the answers

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

Thylakoids Signup and view all the answers

What is the main role of lysosomes in a cell?

Breaking down waste materials Signup and view all the answers

How do peroxisomes contribute to cellular function?

Detoxifying harmful substances Signup and view all the answers

What structure in plant cells maintains turgor pressure?

Central vacuole Signup and view all the answers

Which components belong to the endomembrane system?

Rough ER and plasma membrane Signup and view all the answers

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

Microfilaments Signup and view all the answers

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

Energy organelles are involved in energy conversion. Signup and view all the answers

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

Efficiency of metabolic processes Signup and view all the answers

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

They have a higher surface area relative to their volume Signup and view all the answers

What happens to a cell when it grows too large?

The surface area to volume ratio decreases. Signup and view all the answers

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

Faster diffusion of substances Signup and view all the answers

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

Microvilli Signup and view all the answers

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

It decreases Signup and view all the answers

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

It allows for rapid loss of heat Signup and view all the answers

What is a primary function of the plasma membrane?

To control the entry and exit of substances. Signup and view all the answers

The phospholipid bilayer is characterized by which property?

Hydrophobic heads facing outward, tails inward. Signup and view all the answers

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

Slower cellular respiration Signup and view all the answers

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

It selectively allows some substances to pass while blocking others. Signup and view all the answers

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

Decreased surface area to volume ratio Signup and view all the answers

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

s^3 Signup and view all the answers

How do eukaryotic cells increase their internal surface area?

Through compartmentalization and organelles. Signup and view all the answers

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

Hinders the ability to support high metabolic activity. Signup and view all the answers

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

Amphipathic nature. Signup and view all the answers

What is the primary function of the cell wall?

Providing structural support and maintaining cell shape Signup and view all the answers

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

Small nonpolar molecules Signup and view all the answers

What characterizes passive transport?

It does not require energy for movement Signup and view all the answers

What is the defining feature of osmosis?

Passive transport of water across a semipermeable membrane Signup and view all the answers

How do channel proteins function in facilitated diffusion?

They form pores to allow specific molecules to pass through Signup and view all the answers

What is the role of the Sodium-Potassium Pump?

To maintain resting membrane potential by exchanging ions Signup and view all the answers

Which of the following correctly describes facilitated diffusion?

It helps larger or polar molecules cross the membrane Signup and view all the answers

In what situation is active transport necessary?

When moving substances from lower to higher concentration Signup and view all the answers

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

To regulate selective permeability Signup and view all the answers

Which of the following correctly describes the fluid mosaic model?

A flexible mosaic of various proteins within a lipid bilayer Signup and view all the answers

How does temperature affect membrane fluidity?

Higher temperatures increase fluidity Signup and view all the answers

What effect do unsaturated fatty acids have on membrane fluidity?

They increase fluidity because of kinks in their tails Signup and view all the answers

What is the role of cholesterol in membrane fluidity?

It stabilizes membranes at high temperatures and increases fluidity at low temperatures Signup and view all the answers

What distinguishes integral proteins from peripheral proteins?

Integral proteins penetrate the lipid bilayer; peripheral are on the surface Signup and view all the answers

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

They assist in cell recognition and communication Signup and view all the answers

What is a key function of the plant cell wall?

It prevents excessive water uptake and maintains cell shape. Signup and view all the answers

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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Description

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.