Cell Structure and Function

Cell Biology

Cell Structure

• Cell membrane (plasma membrane): Semi-permeable membrane separating the cell from its environment
  • Composed of phospholipid bilayer with embedded proteins
  • Regulates the movement of molecules in and out of the cell
• Cytoplasm: Jelly-like substance inside the cell membrane
  • Contains water, salts, sugars, and various organelles
  • Site of many metabolic processes
• Nucleus: Control center of the cell
  • Contains most of the cell's genetic material (DNA)
  • Surrounded by a double membrane called the nuclear envelope
• Mitochondria: Organelles responsible for generating energy (ATP) through cellular respiration
  • Have their own DNA and ribosomes
  • Found in the cytoplasm
• Endoplasmic reticulum (ER): Network of membranous tubules and cisternae
  • Involved in protein synthesis, transport, and modification
  • Rough ER has ribosomes attached, while smooth ER does not
• Ribosomes: Small organelles found throughout the cytoplasm
  • Site of protein synthesis
  • Composed of RNA and proteins

Cell Functions

• Metabolism: Chemical reactions that occur within the cell to maintain life
  • Includes anabolic (building) and catabolic (breakdown) reactions
• Cell signaling: Communication between cells through signaling molecules (e.g., hormones, neurotransmitters)
  • Allows cells to respond to changes in their environment
• Cell division: Process by which a cell divides into two daughter cells
  • Includes mitosis (nuclear division) and cytokinesis (cytoplasmic division)
• Cell transport: Movement of molecules across the cell membrane
  • Passive transport (diffusion, osmosis) and active transport (requiring energy)

Cell Cycle

• Interphase: Longest stage of the cell cycle
  • Consists of G1 (growth and preparation), S (DNA replication), and G2 (preparation for cell division)
• Mitosis: Nuclear division resulting in two identical daughter cells
  • Consists of prophase, metaphase, anaphase, telophase, and cytokinesis
• Checkpoint: Regulatory mechanisms that ensure the cell cycle progresses correctly
  • Monitors for DNA damage, proper chromosome alignment, and other cellular processes

Cellular Processes

• Photosynthesis: Process by which cells convert light energy into chemical energy
  • Occurs in chloroplasts of plant cells and some algae
• Cellular respiration: Process by which cells generate energy from glucose
  • Includes glycolysis, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation
• Protein synthesis: Process by which cells create proteins from amino acids
  • Involves transcription (mRNA synthesis) and translation (protein assembly)

Cell Structure

• Cell membrane is semi-permeable, separating cell from environment, and regulates molecule movement in and out of cell
• Cell membrane is composed of phospholipid bilayer with embedded proteins
• Cytoplasm is jelly-like substance inside cell membrane, containing water, salts, sugars, and organelles, and site of many metabolic processes
• Nucleus is control center of cell, containing most of cell's genetic material (DNA), and surrounded by nuclear envelope
• Mitochondria are organelles responsible for generating energy (ATP) through cellular respiration, have their own DNA and ribosomes, and are found in cytoplasm
• Endoplasmic reticulum (ER) is network of membranous tubules and cisternae, involved in protein synthesis, transport, and modification, with rough ER having ribosomes attached and smooth ER not
• Ribosomes are small organelles found throughout cytoplasm, site of protein synthesis, and composed of RNA and proteins

Cell Functions

• Metabolism includes anabolic (building) and catabolic (breakdown) reactions, maintaining life
• Cell signaling is communication between cells through signaling molecules (e.g., hormones, neurotransmitters), allowing cells to respond to changes in environment
• Cell division is process by which cell divides into two daughter cells, including mitosis (nuclear division) and cytokinesis (cytoplasmic division)
• Cell transport is movement of molecules across cell membrane, including passive transport (diffusion, osmosis) and active transport (requiring energy)

Cell Cycle

• Interphase is longest stage of cell cycle, consisting of G1 (growth and preparation), S (DNA replication), and G2 (preparation for cell division)
• Mitosis is nuclear division resulting in two identical daughter cells, consisting of prophase, metaphase, anaphase, telophase, and cytokinesis
• Checkpoint is regulatory mechanism that ensures cell cycle progresses correctly, monitoring for DNA damage, proper chromosome alignment, and other cellular processes

Cellular Processes

• Photosynthesis is process by which cells convert light energy into chemical energy, occurring in chloroplasts of plant cells and some algae
• Cellular respiration is process by which cells generate energy from glucose, including glycolysis, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation
• Protein synthesis is process by which cells create proteins from amino acids, involving transcription (mRNA synthesis) and translation (protein assembly)

Cell Biology

Cell Structure

• Cell membrane is semi-permeable, separating the cell from its environment while allowing certain substances to pass through
• Cytoplasm is the jelly-like substance inside the cell membrane where metabolic processes, like cellular respiration, occur
• Nucleus is the control center of the cell where DNA is stored, regulating cell growth, division, and function
• Mitochondria generate energy for the cell through cellular respiration, converting glucose into ATP
• Endoplasmic reticulum (ER) is a network of membranous tubules and cisternae involved in protein synthesis and transport
• Ribosomes are the site of protein synthesis, translating mRNA into amino acid chains
• Lysosomes contain digestive enzymes, breaking down and recycling cellular waste and foreign substances
• Golgi apparatus is a complex of flattened sacs involved in protein modification, sorting, and transport

Cellular Organelles

• Chloroplasts are organelles found in plant cells responsible for photosynthesis, converting light energy into chemical energy
• Cilia are hair-like structures involved in movement, sensing, and communication in eukaryotic cells
• Flagella are whip-like structures involved in movement, helping cells swim and navigate
• Centrioles are involved in the formation of cilia and flagella, playing a crucial role in cell division and movement
• Peroxisomes are organelles involved in the breakdown of fatty acids and amino acids, regulating cellular metabolism
• Vacuoles are membrane-bound sacs involved in storage, digestion, and waste management in eukaryotic cells

Cellular Processes

• Cell division is the process by which a cell divides into two daughter cells, involving mitosis or meiosis
• Mitosis results in two identical daughter cells, while meiosis results in four non-identical daughter cells
• Cellular respiration is the process by which cells generate energy from glucose, involving aerobic or anaerobic respiration
• Photosynthesis is the process by which plants and some other organisms convert light energy into chemical energy
• Protein synthesis is the process by which cells create proteins from amino acids, involving transcription and translation
• Cell signaling is the process by which cells communicate with each other, regulating cell function and behavior

Cell Transport

• Passive transport involves the movement of molecules from an area of high concentration to an area of low concentration, without energy input
• Diffusion is the random movement of molecules from high to low concentration, while osmosis is the movement of water molecules through a selectively permeable membrane
• Active transport involves the movement of molecules from an area of low concentration to an area of high concentration, requiring energy input
• Carrier proteins help transport molecules across the cell membrane, while pumping involves the use of energy to transport molecules against their concentration gradient