Cell Structure and Function Quiz

Cell Structure

Basic Unit of Life: Cells are the fundamental units of structure and function in all living organisms.
Cell Types:
- Prokaryotic Cells: Lack a nucleus, smaller, simpler (e.g., bacteria).
- Eukaryotic Cells: Have a nucleus and organelles, larger and more complex (e.g., plant and animal cells).
Common Components:
- Cell Membrane: Semi-permeable barrier that controls movement of substances in and out.
- Cytoplasm: Gel-like fluid where cellular processes occur; contains organelles.
- Nucleus: Contains DNA, controls cell activities and reproduction.
- Mitochondria: Powerhouse of the cell, site of ATP production (energy).
- Ribosomes: Sites of protein synthesis, can be free-floating or attached to the endoplasmic reticulum.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes, synthesizes proteins.
  - Smooth ER: No ribosomes, synthesizes lipids and detoxifies.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
- Lysosomes: Contains digestive enzymes to break down waste materials and cellular debris.
- Cytoskeleton: Network of fibers providing structural support, shape, and facilitating movement.

Enzyme Function

Definition: Enzymes are biological catalysts that speed up chemical reactions without being consumed.
Characteristics:
- Specificity: Each enzyme works on a specific substrate or group of substrates.
- Active Site: Region on the enzyme where substrate binds, resulting in a reaction.
Mechanism:
- Enzyme-Substrate Complex: Formed when substrate binds to the active site; lowers activation energy required for the reaction.
- Induced Fit Model: Enzyme changes shape slightly to better fit the substrate upon binding.
Factors Affecting Enzyme Activity:
- Temperature: Each enzyme has an optimal temperature; extreme heat can denature enzymes.
- pH: Each enzyme has an optimal pH; deviations can reduce activity or denature the enzyme.
- Concentration: Higher substrate concentrations can increase reaction rates until saturation is reached.
Cofactors and Coenzymes: Non-protein molecules that assist in enzyme function; cofactors are typically metal ions, while coenzymes are organic molecules (e.g., vitamins).
Inhibition:
- Competitive Inhibition: Inhibitor competes with substrate for active site.
- Non-competitive Inhibition: Inhibitor binds elsewhere on the enzyme, altering its function.
Applications: Enzymes are used in various industries (e.g., biotechnology, food processing, pharmaceuticals) and in metabolic pathways within organisms.

Cell Structure

Cells serve as the basic unit of life, essential for structure and function across all living organisms.
Prokaryotic cells are smaller and simpler, lacking a nucleus (e.g., bacteria), while eukaryotic cells are larger, more complex, and contain a nucleus and organelles (e.g., plant and animal cells).
Common components include:
- Cell Membrane: A semi-permeable barrier that regulates substance movement in and out of the cell.
- Cytoplasm: A gel-like fluid that houses organelles and facilitates cellular processes.
- Nucleus: Contains DNA; plays a crucial role in controlling cell activities and reproduction.
- Mitochondria: Known as the powerhouse of the cell, where ATP, the energy currency, is produced.
- Ribosomes: Sites for protein synthesis, existing as free-floating or bound to the endoplasmic reticulum.
The Endoplasmic Reticulum (ER) consists of:
- Rough ER: Studded with ribosomes; primarily involved in protein synthesis.
- Smooth ER: Lacks ribosomes; functions in lipid synthesis and detoxification.
Golgi Apparatus: Responsible for modifying, sorting, and packaging proteins and lipids, either for secretion or internal use.
Lysosomes: Contain digestive enzymes that break down waste materials and cellular debris.
Cytoskeleton: A network of fibers providing structural support, maintaining cell shape, and facilitating movement.

Enzyme Function

Enzymes are biological catalysts that accelerate chemical reactions without being consumed in the process.
Key characteristics include:
- Specificity: Each enzyme acts on a specific substrate or group of substrates.
- Active Site: The specific region on an enzyme where the substrate binds, triggering a reaction.
The reaction mechanism involves the formation of an Enzyme-Substrate Complex, which lowers the activation energy needed for the reaction.
The Induced Fit Model suggests that an enzyme slightly alters its shape to better accommodate the substrate when they bind together.
Factors influencing enzyme activity include:
- Temperature: Each enzyme has an optimal temperature; excessive heat can denature enzymes.
- pH: Each enzyme has a preferred pH level; variations can diminish activity or lead to denaturation.
- Concentration: Increasing substrate concentration generally enhances reaction rates until saturation occurs.
Cofactors and Coenzymes: Non-protein molecules that support enzyme function; cofactors are typically metal ions, and coenzymes are organic molecules (e.g., vitamins).
Inhibition can occur through:
- Competitive Inhibition: Inhibitors compete with the substrate for the active site.
- Non-competitive Inhibition: Inhibitors bind to a different site on the enzyme, altering its function.
Enzymes have various applications across sectors, including biotechnology, food processing, pharmaceuticals, and play vital roles in metabolic pathways in organisms.