Cell Biology: Organelles and Functions

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Questions and Answers

What characteristic of fat-soluble drugs facilitates their movement into cells?

They have a high charge.

They are polar molecules.

They require a transport mechanism.

They can easily pass through the lipid layer. (correct)

What type of molecules pass through the plasma membrane most easily by simple diffusion?

Ions

Polar substances

Non-polar gases (correct)

Large proteins

Which type of cell does HIV primarily target?

Muscle cells

T-helper cells (correct)

Epithelial cells

Liver cells

What mechanism allows viruses like HIV to enter host cells?

Mimicry of glycoproteins Signup and view all the answers

Why do small ions struggle to pass through the plasma membrane despite their size?

Their charge prevents easy movement across the lipid core. Signup and view all the answers

Why is producing an effective vaccine against HIV very challenging?

HIV rapidly evolves through mutation. Signup and view all the answers

Which statement best describes the process of diffusion?

It is a passive movement of substances down their concentration gradient. Signup and view all the answers

What is necessary for polar substances to transport across the plasma membrane?

They need assistance from specific transport proteins. Signup and view all the answers

Which cells are most specifically affected by the hepatitis virus?

Liver cells Signup and view all the answers

What effect does a greater concentration gradient have on the rate of diffusion?

It accelerates the rate of diffusion. Signup and view all the answers

What role do antibodies play in the immune response to viruses?

They recognize and destroy the virus. Signup and view all the answers

How does the concept of tonicity relate to passive transport?

It describes the concentration of solute in a solution. Signup and view all the answers

What type of molecules typically require special transport mechanisms for crossing the plasma membrane?

Small ions and large polar molecules Signup and view all the answers

What is the primary function of the plasma membrane regarding substance transport?

To selectively allow substances while protecting the cell Signup and view all the answers

In which scenario does diffusion create a potential energy dissipation?

When substances move from high to low concentration. Signup and view all the answers

What is the primary consequence of mutations in viral surface markers?

Decreased effectiveness of antibodies. Signup and view all the answers

What effect does an increase in solvent density have on the rate of diffusion?

It decreases the rate of diffusion. Signup and view all the answers

Which factor does NOT influence the rate of diffusion?

Color of the solution Signup and view all the answers

How do temperature changes impact the movement of molecules during diffusion?

Higher temperatures increase molecular energy and movement. Signup and view all the answers

What role do transport proteins play in facilitated diffusion?

They form channels or carriers to assist material passage across the membrane. Signup and view all the answers

What defines osmosis compared to general diffusion?

Osmosis only refers to the movement of water molecules. Signup and view all the answers

What type of molecules typically require facilitated transport across the plasma membrane?

Large polar substances Signup and view all the answers

Which concentration gradient direction does facilitated diffusion move substances?

From high to low concentration Signup and view all the answers

What happens to the rate of diffusion as the distribution of material approaches equilibrium?

The rate of diffusion decreases. Signup and view all the answers

What is the primary function of receptors on the plasma membrane?

They bind with specific substances to transmit messages into the cell. Signup and view all the answers

What aspect of the plasma membrane does the fluid mosaic model emphasize?

The dynamic and flexible nature of the membrane structure. Signup and view all the answers

What is the primary role of tissue factor when it binds to another factor in the extracellular matrix?

To cause platelet adhesion and vessel constriction Signup and view all the answers

How do pathogens like viruses utilize the specificity of surface receptors?

They mimic specific substances to gain entry into the cell. Signup and view all the answers

What type of junction is characterized by a watertight seal between adjacent animal cells?

Tight junction Signup and view all the answers

What role do the plasma membrane markers play during early development?

They enable cells to recognize one another. Signup and view all the answers

What is suggested by the term 'fluid' in the fluid mosaic model?

Lipids and proteins can move laterally within the membrane. Signup and view all the answers

Which of the following best describes the function of gap junctions in animal cells?

To connect cytoplasm of adjacent cells for communication Signup and view all the answers

Which intercellular junction helps maintain the structural integrity of tissues that experience stretching?

Desmosome Signup and view all the answers

What are metabolic pathways associated with surface receptors primarily responsible for?

Energy production, synthesis of substances, and waste disposal. Signup and view all the answers

According to the fluid mosaic model, what contributes to the integrity of the plasma membrane?

The ability of components to flow while maintaining the membrane's structure. Signup and view all the answers

What is the primary function of plasmodesmata in plant cells?

To allow for the transport of nutrients and signaling molecules Signup and view all the answers

What distinguishes tight junctions from other types of intercellular junctions?

They form seals to prevent leaks between cells. Signup and view all the answers

Which of the following best describes the components of the plasma membrane as outlined in the fluid mosaic model?

They represent a diverse mix of proteins, lipids, carbohydrates, and cholesterol. Signup and view all the answers

In which type of tissue are tight junctions most commonly found?

Epithelial tissue Signup and view all the answers

Which cell junction is found in both plant and animal cells allowing for communication and transport?

Gap junction Signup and view all the answers

What defines the movement of water during osmosis?

Water moves from high to low concentration of free water molecules. Signup and view all the answers

What happens when a cell is placed in a hypotonic solution?

The cell gains water and may swell. Signup and view all the answers

During osmosis, which component can freely diffuse through a semipermeable membrane?

Water molecules. Signup and view all the answers

Osmolarity is defined as which of the following?

The total amount of solutes dissolved in a specific amount of solution. Signup and view all the answers

Which statement correctly describes the principle of diffusion?

Molecules will spread evenly in a medium if they can. Signup and view all the answers

Which term relates the osmolarity of a cell to that of the extracellular fluid?

Tonicity. Signup and view all the answers

What occurs when the concentration gradient of water in a system goes to zero?

Water diffusion stops. Signup and view all the answers

When considering the movement of water, what is the primary driver?

Concentration of solute. Signup and view all the answers

Study Notes

Peroxisomes

Small, round organelles enclosed by single membranes
Carry out oxidation reactions, breaking down fatty acids and amino acids
Detoxify poisons, such as alcohol
Hydrogen peroxide, a byproduct, is safely broken down by peroxisomal enzymes into water and oxygen

Animal Cells vs. Plant Cells

Animal cells have centrioles, centrosomes, and lysosomes; plant cells do not
Plant cells have cell walls, chloroplasts, plasmodesmata, plastids, and a large central vacuole; animal cells do not

Cell Wall

Rigid covering that protects the cell
Provides structural support and gives shape to the cell
Fungal and protist cells also have cell walls
Major organic molecule in plant cell walls is cellulose, a polysaccharide made of glucose

Chloroplasts

Contain DNA and ribosomes, similar to mitochondria
Function in photosynthesis, using carbon dioxide, water, and light energy to produce glucose and oxygen
Outer and inner membranes, with thylakoids (stacked sacs) inside the inner membrane
Fluid-filled space surrounding the grana (stacks of thylakoids) called stroma

Endosymbiosis

Strong evidence suggests mitochondria and chloroplasts originated as separate organisms
Host cells and bacteria formed a mutually beneficial endosymbiotic relationship
Ingested bacteria evolved into mitochondria (aerobic) and chloroplasts (photosynthetic)
Mitochondria and chloroplasts have their own DNA and ribosomes, just as bacteria do

Central Vacuole

Large, central vacuole occupies most of the plant cell
Regulates water concentration and turgor pressure
Stores proteins
Discourages consumption by insects and animals by having a bitter taste

Extracellular Matrix of Animal Cells

Animal cells release glycoproteins and collagen into the extracellular space forming the extracellular matrix
Holds cells together and allows for cellular communication

Intercellular Junctions

Plasmodesmata: Plant cells have junctions called plasmodesmata, channels between cell walls allowing for communication and nutrient transport
Animal cells: Tight junctions, desmosomes, and gap junctions connect animal cells
- Tight junctions create a watertight seal
- Desmosomes act like spot welds
- Gap junctions are channels for communication

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Description

Test your knowledge on cell biology with this quiz focusing on organelles such as peroxisomes, chloroplasts, and the differences between animal and plant cells. Discover the roles these structures play in cellular function and metabolism. Perfect for biology students!