Membranes

• What is osmosis?

  Diffusion of water across a membrane
• What does osmosis occur across?

  A partially permeable membrane
• What is the direction of water movement in osmosis?

  Down a water potential gradient
• What is water potential represented by?

  Psi (ψ)
• What does a more negative water potential indicate?

  A higher concentration of solutes
• What is the room temperature mentioned in the study material?

  25 °C
• What happens to water movement when cells have a lower water potential than pure water?

  Water moves into the cells
• In which condition is the rate of water movement fastest?

  In a solution with 2000 water potential
• Why is the rate of movement slowest in 1200 water potential?

  The water potential gradient is least steep
• What is cytolysis?

  Cell bursting due to excess water
• What does turgid mean in plant cells?

  Cells are swollen with water
• What happens to cells in a hypotonic solution?

  They become turgid but do not burst
• What is the role of the cell wall in plant cells?

  Provides structure and prevents bursting
• What does isotonic mean for cells?

  Cells are in equilibrium with their environment
• What is flaccid in terms of plant cells?

  Cells are limp due to water loss
• What is plasmolysis?

  When cytoplasm pulls away from the cell wall
• What is the process of DNA replication called?

  Semiconservative replication
• What happens to DNA strands during replication?

  DNA strands unwind
• What lines up along both strands during DNA replication?

  Nucleotides
• What type of pairing occurs between DNA bases?

  Complementary base pairing
• What type of bonds are formed between DNA bases?

  Hydrogen bonds
• What type of bonds form between adjacent mononucleotides?

  Phosphodiester bonds
• What type of reaction forms phosphodiester bonds?

  Condensation reaction
• What enzyme is responsible for unwinding DNA?

  DNA helicase
• What is active transport?

  Molecules move against a concentration gradient
• In which direction do molecules move during active transport?

  Lower to higher concentration
• What is required for active transport?

  Energy from respiration
• What molecule provides energy for active transport?

  ATP
• What type of cells have many mitochondria for active transport?

  Cells involved in active transport
• How selective is active transport?

  Very selective process
• What type of proteins perform active transport?

  Specific carrier proteins
• How does facilitated diffusion differ from active transport?

  Facilitated diffusion does not use ATP
• What type of proteins are involved in facilitated diffusion?

  Channel or carrier proteins
• What is the direction of movement in facilitated diffusion?

  Down a concentration gradient
• What is the direction of movement in active transport?

  Against a concentration gradient
• What happens when a molecule binds to a carrier protein?

  It causes a change in shape
• What happens to ATP during active transport?

  It splits into ADP and phosphate
• What is bulk transport used for?

  Transporting large molecules
• What are the two types of bulk transport?

  • Endocytosis: transport into cells
  • Exocytosis: transport outside cells
• What is phagocytosis?

  Transport of solids into cells