1.2 Cell Structure and Function

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Questions and Answers

Which of the following best describes the primary role of structural proteins within a cell?

To catalyze biochemical reactions as enzymes.

To form the cytoskeleton and maintain cell shape and structure. (correct)

To provide the cell with energy through ATP production.

To transport molecules across the cell membrane.

What is the key characteristic of lipids that allows them to group together and be distinct from other substances in the cell?

Their ability to dissolve in organic solutions. (correct)

Their high water solubility.

Their structural role in the cell membrane.

Their role as primary energy sources.

How do integral proteins in the cell membrane facilitate the movement of specific substances?

By creating a fluid layer for substances to move through.

By providing specific pathways through the membrane. (correct)

By creating a non-selective barrier.

By actively transporting water-soluble substances.

What is the primary function of phospholipids in cellular structures?

To form structural components of the membrane that separates cellular compartments. (C) Signup and view all the answers

Which characteristic of the cell membrane allows it to impede the penetration of water-soluble substances?

Its composition of proteins and lipids, with hydrophobic lipid regions. (D) Signup and view all the answers

What is a characteristic of functional proteins in the cell?

They are primarily enzymes that play a mobile catalytic role. (C) Signup and view all the answers

The cell membrane's thickness is approximately:

7.5 to 10 nanometers (B) Signup and view all the answers

Which of these is NOT a major intracellular ion?

Sodium (C) Signup and view all the answers

Which cellular component is primarily responsible for providing structural support and determining cell shape?

Cytoskeleton (D) Signup and view all the answers

What is the main function of the nuclear pores found in the nuclear envelope?

To allow molecules to pass easily in and out of the nucleus (C) Signup and view all the answers

Which process describes the ingestion of large particles into a cell, such as bacteria?

Phagocytosis (D) Signup and view all the answers

What is the primary role of lysosomes in cellular function?

Digesting cellular waste and damaged cell parts (B) Signup and view all the answers

Which type of endoplasmic reticulum is primarily involved in synthesizing lipids like phospholipids and cholesterol?

Smooth ER (B) Signup and view all the answers

What is the function of the Golgi apparatus in the cell?

Processes and packages substances formed in the ER (B) Signup and view all the answers

In cell membrane transport, what is the driving force behind the process of diffusion?

Concentration gradients and entropy (C) Signup and view all the answers

What is the process where a cell degrades and recycles its own components, like old organelles?

Autophagy (C) Signup and view all the answers

How do proteins synthesized in the rough ER reach the Golgi apparatus?

They are transported via transport vesicles (B) Signup and view all the answers

What is the term for the process where lysosomes release their digestive enzymes, leading to the breakdown of cellular tissue?

Lysis (B) Signup and view all the answers

Which of the following substances can diffuse directly through the cell membrane?

Lipid-soluble substances (B) Signup and view all the answers

Which type of filaments within the cytoskeleton provide strong, rope-like support and are found in all cells, although their structure varies?

Intermediate filaments (C) Signup and view all the answers

What is the purpose of the nuclear lamina within the nucleus?

To provide structural support to the nuclear envelope and its shape (B) Signup and view all the answers

What is a key characteristic of active transport across the cell membrane?

Requirement of protein carriers and energy expenditure (A) Signup and view all the answers

What is the primary function of the lipid bilayer's hydrophobic core in the plasma membrane?

To prevent the passage of most water-soluble molecules. (D) Signup and view all the answers

Which type of protein spans the entire cell membrane?

Integral proteins (D) Signup and view all the answers

What happens to the residual bodies after digestion inside of a cell?

They are excreted from the cell by exocytosis (C) Signup and view all the answers

What is the primary role of the glycocalyx on the cell's outer surface?

To give the cell surface an overall negative charge and aid in cell-to-cell attachment. (C) Signup and view all the answers

Which organelle is responsible for synthesizing new protein molecules in the cell?

Rough endoplasmic reticulum (C) Signup and view all the answers

What is the role of the Golgi apparatus in cellular function?

Processing and packaging molecules for transport. (A) Signup and view all the answers

What is the main function of lysosomes within a cell?

To break down damaged cellular structures and waste. (D) Signup and view all the answers

What is the primary function of the Golgi apparatus in the context of protein secretion?

To sort, modify, and package proteins into secretory vesicles. (A) Signup and view all the answers

How do peroxisomes differ from lysosomes in cellular function?

Peroxisomes are self-replicating and lysosomes are formed from the Golgi apparatus. (D) Signup and view all the answers

Approximately how long does it take for newly formed proteins to be secreted from a cell after initial amino acid uptake?

1 to 2 hours (A) Signup and view all the answers

What is the main function of the cristae within the mitochondria?

To provide a large surface area for oxidative phosphorylation. (C) Signup and view all the answers

What is the main role of mitochondria in cellular metabolism?

To produce ATP through oxidative reactions. (B) Signup and view all the answers

Which molecules is primarily responsible for giving the cell membrane its selective permeability?

Lipids (C) Signup and view all the answers

If a substance is being transported across the cell membrane against its electrochemical gradient, what type of transport is most likely involved?

Active transport (D) Signup and view all the answers

What type of energy storage does ATP primarily utilize?

High-energy phosphate bonds. (A) Signup and view all the answers

Besides the mitochondria, where does a small portion of ATP formation occur within a cell?

In the cell cytoplasm through glycolysis. (D) Signup and view all the answers

What type of molecules mostly make up the cell's glycocalyx?

Carbohydrates (D) Signup and view all the answers

How are most substances that are formed within the cell released to the outside, according to this text?

By secretion through vesicles that pinch off from the Golgi apparatus. (D) Signup and view all the answers

What is the purpose of the Krebs cycle in cellular respiration?

To split acetyl-CoA into hydrogen and carbon dioxide. (A) Signup and view all the answers

Which of these is NOT a primary function of ATP within the cell?

Direct production of pyruvate. (B) Signup and view all the answers

What is the significance of the inner membrane of the mitochondria being folded into cristae?

To increase surface area for ATP production. (A) Signup and view all the answers

How does amoeboid movement of a cell primarily occur?

By the continual formation of new cell membrane at the leading edge and reabsorption at the rear. (C) Signup and view all the answers

How does the structure of the endoplasmic reticulum contribute to its function in cellular process?

Its membrane networks allow for the processing and transport of molecules. (B) Signup and view all the answers

What is the primary function of enzymes found in lysosomes?

To break down cellular waste products. (B) Signup and view all the answers

What are chemotaxis substances responsible for in cellular movement?

They initiate amyloid locomotion of a cell. (C) Signup and view all the answers

How do motile cilia move fluids?

Through rapid, whip-like strokes followed by slow recovery. (D) Signup and view all the answers

In which two primary locations in the human body do motile cilia function in fluid transport?

Respiratory airways and fallopian tubes (B) Signup and view all the answers

How do nonmotile primary cilia function?

As cellular sensory antennas. (B) Signup and view all the answers

What type of movement is characteristic of sperm cells?

Quasi-sinusoidal waves. (C) Signup and view all the answers

Defects in signaling of non-motile cilia might contribute to which disorder?

Polycystic kidney disease. (B) Signup and view all the answers

What is the immediate precursor to ATP?

ADP. (A) Signup and view all the answers

Study Notes

Cell Structure and Function

Cellular Composition: Most cells, excluding fat, are 70-85% water. Important ions include potassium, magnesium, phosphate, sulfate, bicarbonate, plus small amounts of sodium chloride and calcium. Proteins make up 10-20% of the cell, with structural proteins forming the cytoskeleton (e.g., microtubules, cilia, nerve axons). Functional proteins are primarily enzymes, often mobile and globular.
Lipids: Lipids, hydrophobic substances, comprise about 2% of cell mass. Phospholipids are crucial for cell membranes and intracellular barriers. Cholesterol is also significant.
Carbohydrates: Carbohydrates function in nutrition and structure, generally around 1% intracellularly. Glucose is the primary form in extracellular fluids.

Cellular Organelles

Cell Membrane: A thin (7.5-10 nm), pliable, elastic structure composed primarily of proteins and lipids. It impedes the passage of water-soluble substances. Phospholipids form a bilayer with hydrophilic heads facing outward and hydrophobic tails inward. Integral proteins span the membrane, forming channels/pores or acting as carriers for transport (active or passive).
Endoplasmic Reticulum (ER): A network of tubules and flattened sacs in cytoplasm, responsible for processing and transporting molecules (intra/extracellular). Rough ER contains ribosomes, for protein synthesis. Smooth ER synthesizes lipids and controls glycogen breakdown/drug detoxification.
Golgi Apparatus: Closely related to ER, it further processes substances and synthesizes specific carbohydrates. It packages substances into vesicles for secretion (e.g., lysosomes, transport vesicles).
Lysosomes: Organelles containing digestive enzymes (hydrolases) that degrade cellular waste, damaged structures, ingested food, and invading bacteria. They maintain a protective bilayer to prevent self-digestion.
Peroxisomes: Similar to lysosomes but contain oxidizers instead of hydrolases, utilizing hydrogen peroxide. Essential for oxidizing, e.g., long-chain fatty acids, alcohol.
Mitochondria: Double-membraned organelles with inner folds (cristae); crucial for energy production. Oxidative breakdown of nutrients generates ATP (energy currency).

Cytoskeleton

Cytoskeleton: Network of fibrous proteins (actin, intermediate filaments, microtubules) providing internal support, shape, and movement. Microtubules also act as tracks for intracellular transport.

Nucleus

Nucleus: Control center of the cell, containing DNA which determines protein characteristics. A double membrane (nuclear envelope) with pores facilitating molecular exchange.

Substance Movement

Diffusion: Passive movement of substances across the membrane driven by entropy.
Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP). Specific membrane proteins carry substances actively.
Endocytosis: Cell membrane invaginates to take in large molecules (pinocytosis, phagocytosis).
Exocytosis: Substances expelled from the cell.

Cell Turnover and Repair

Autophagy: Self-digestion of dysfunctional organelles/proteins.
Lysosomal Function in Damage Repair: Lysosomes digest damaged structures or cells via lysis.

Energy Production

ATP Formation: ATP is created mostly in mitochondria but also in glycolysis (5%). ATP is essential for various cellular functions. Glycolysis converts glucose to pyruvate (entering the mitochondria), then forming Acetyl CoA, and continuing through the Krebs cycle.

Cell Movement and Signaling

Amoeboid Movement: Cell protrusion followed by pulling of rest of the cell forward. Receptor interactions are critical.
Cilia and Flagella Movement: Cilia function in fluid movement (e.g., airways, fallopian tubes), while primary cilia acts as flow/sensory receptors, e.g., kidney tubules.
Chemotaxis: Chemical signals guide cell movement.

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Explore the fundamental components of cells, including cellular composition, organelles, and the roles of water, lipids, proteins, and carbohydrates. This quiz will test your understanding of how these elements contribute to cell function and structure. Perfect for students studying biology or life sciences.