Cell Structure and Organelles

Structure and Components

• Plasma membrane: semi-permeable membrane that separates the cell from its environment
• Cytoplasm: jelly-like substance inside the plasma membrane where metabolic processes occur
• Cytosol: liquid component of cytoplasm where many metabolic reactions take place
• Organelles: specialized structures within the cell that perform specific functions
  • Nucleus: contains DNA and is responsible for cell growth and reproduction
  • Mitochondria: generates energy for the cell through cellular respiration
  • Endoplasmic reticulum (ER): involved in protein synthesis and transport
  • Ribosomes: site of protein synthesis
  • Lysosomes: contains digestive enzymes that break down and recycle cellular waste
  • Golgi apparatus: involved in protein modification and transport

Cellular Functions

• Metabolism: process of converting energy and nutrients into cellular components
• Photosynthesis: process by which plants convert light energy into chemical energy
• Cell signaling: process of communication between cells and their environment
• Cell division: process by which cells reproduce themselves
  • Mitosis: process of cell division that results in two daughter cells with same number of chromosomes as parent cell
  • Meiosis: process of cell division that results in four daughter cells with half the number of chromosomes as parent cell

Cell Types

• Prokaryotic cells: lack a true nucleus and are typically small and simple in structure (e.g. bacteria)
• Eukaryotic cells: have a true nucleus and are typically larger and more complex in structure (e.g. plants, animals)
• Stem cells: undifferentiated cells that have the ability to differentiate into specialized cells

Cellular Processes

• Active transport: process by which cells use energy to move molecules against their concentration gradient
• Passive transport: process by which cells move molecules down their concentration gradient
• Cell growth: process by which cells increase in size and number
• Cell death: process by which cells die and are removed from the body (e.g. apoptosis)

Structure and Components

• Plasma membrane acts as a semi-permeable barrier, controlling the entry and exit of substances, and maintaining homeostasis.
• Cytoplasm is a jelly-like medium supporting organelles and facilitating metabolic reactions.
• Cytosol is the liquid portion of cytoplasm where many biochemical processes take place, including enzyme activity and nutrient transport.
• Organelles are specialized cellular structures, each fulfilling distinct roles essential for cell function.
  • Nucleus houses genetic material (DNA) and orchestrates cell growth, division, and reproduction.
  • Mitochondria are the powerhouses of the cell, producing ATP through cellular respiration, critical for energy supply.
  • Endoplasmic reticulum (ER) comes in two forms—rough (with ribosomes) for protein synthesis and smooth (without ribosomes) for lipid synthesis and detoxification.
  • Ribosomes are the cellular machinery for translating mRNA into proteins, vital for all cellular functions.
  • Lysosomes contain hydrolytic enzymes for degrading waste materials and cellular debris, playing a key role in recycling and cellular cleanup.
  • Golgi apparatus modifies, sorts, and packages proteins and lipids for distribution within or outside the cell.

Cellular Functions

• Metabolism encompasses all chemical reactions converting nutrients into energy and building blocks for the cell.
• Photosynthesis converts light energy into glucose in plants, releasing oxygen as a byproduct, essential for life on Earth.
• Cell signaling involves mechanisms through which cells communicate with one another and respond to environmental stimuli, crucial for coordinating functions.
• Cell division is the method by which cells reproduce, ensuring genetic material is passed on to daughter cells.
  • Mitosis produces two genetically identical daughter cells, maintaining chromosome number, essential for growth and repair.
  • Meiosis results in four genetically diverse daughter cells with half the chromosomes, foundational for sexual reproduction and genetic diversity.

Cell Types

• Prokaryotic cells lack a membrane-bound nucleus, are typically unicellular, and include organisms like bacteria; their simplicity allows for rapid reproduction.
• Eukaryotic cells possess a defined nucleus and complex organelles, are generally larger, and comprise multicellular organisms such as plants and animals.
• Stem cells are unique as undifferentiated cells that can develop into various specialized cell types, important for growth, development, and repair.

Cellular Processes

• Active transport requires energy (ATP) to move molecules against their concentration gradient, essential for nutrient uptake and waste removal.
• Passive transport allows molecules to diffuse across membranes without energy expenditure, following concentration gradients, vital for maintaining equilibrium.
• Cell growth involves both an increase in cellular size and replication, supporting organismal development and tissue maintenance.
• Cell death, or apoptosis, is a regulated process that eliminates excess or damaged cells, ensuring tissue health and homeostasis.

This quiz covers the basic structure and components of a cell, including the plasma membrane, cytoplasm, cytosol, and various organelles like the nucleus and mitochondria.