2 - CELL

• What percentage of a cell's composition is water?

  70-85%
• What is the percentage range of proteins in a cell?

  10-20%
• What percentage of a cell's composition is carbohydrates?

  1-6%
• What are the two main types of proteins in cells and their functions?

  • Structural: Forms microtubules for cytoskeleton
  • Functional: Enzymes in tubular globular form
• What role do carbohydrates play in cells?

  They have little structural function and aid nutrition
• What are the two types of lipids mentioned in cell composition?

  • Phospholipids and cholesterol (2% of cell mass)
  • Neutral fats (triacylglycerides, 95% of cell mass)
• What is the primary function of neutral fats in cells?

  They serve as the main energy storehouse
• What are the membranous structures of the cells?

  • Cell membrane
  • Nuclear membrane
  • Membrane of the endoplasmic reticulum
  • Membrane of mitochondria, lysosomes, and Golgi apparatus
• What is the thickness of the cell membrane?

  7.5-10 nanometers thick
• What is the main composition of the cell membrane?

  55% proteins and 25% phospholipids
• What is the role of lipids in the cell membrane?

  • Barrier to water and water-soluble substances
  • Organized in a bilayer of phospholipid molecules
• What are lipid rafts and their function?

  They regulate signal transduction and protein trafficking
• What are the two types of membrane proteins and their functions?

  • Integral: Channels, pores, carriers, enzymes, receptors
  • Peripheral: Enzymes, intracellular signal mediators, transport controllers
• What percentage of carbohydrates are glycolipids in the cell membrane?

  10%
• What is the function of the glycocalyx?

  It repels negative charges and aids cell interactions
• What are the functions of carbohydrates in the cell membrane?

  • Cell-cell attachments/interactions
  • Role in immune reactions
  • Act as receptors for hormones like insulin
• What is the role of ribosomes in the cytoplasm?

  They synthesize proteins
• What are the functions of the endoplasmic reticulum?

  • RER: Protein synthesis and processing
  • SER: Lipid synthesis and transport vesicle formation
• What is the primary function of the Golgi apparatus?

  Processing and packaging substances for secretion
• What do lysosomes contain and their function?

  They contain hydrolytic enzymes for digestion
• What are the functions of peroxisomes?

  1. Hydrogen peroxide metabolism
  2. Fatty acid oxidation
  3. Lipid biosynthesis
  4. Germination of seeds
  5. Photorespiration
  6. Degradation of purines
  7. Bioluminescence
• What is the primary function of secretory vesicles?

  Store and release proteins synthesized in the RER
• What is the primary function of mitochondria?

  Extraction of energy from nutrients
• What is the role of the cytoskeleton?

  • Provides rigid physical structure
  • Composed of fibrillar proteins
• What is the diameter of nuclear pores?

  100 nm
• What is the function of nuclear pores?

  Allow transport of nutrients and waste
• What are the steps of signal transduction?

  1. Reception
  2. Transduction
  3. Induction/response
• What occurs during the reception step of signal transduction?

  Perception of the environment by receptor molecules
• What happens during the transduction step of signal transduction?

  Converts receptor change to a cellular response
• What can be a response in signal transduction?

  Activation of specific genes or cytoskeleton rearrangement
• What are the factors affecting simple diffusion?

  1. Concentration gradient
  2. Mass/size of molecules
  3. Temperature
  4. Solubility
  5. Solvent density
  6. Surface area and thickness of membrane
• What is facilitated diffusion?

  Carrier-mediated transport of solutes down concentration gradient
• What is the primary difference between primary and secondary active transport?

  Primary uses ATP directly; secondary uses it indirectly
• What are the types of endocytosis?

  • Receptor-mediated endocytosis
  • Pinocytosis
  • Phagocytosis
• What are the potential responses in signal transduction?

  • Change in gene expression
  • Alteration of metabolic enzyme activity
  • Reconfiguration of the cytoskeleton
  • Change in ion permeability
  • Activation of DNA synthesis
  • Cell death