Cell transport

• What is the characteristic of the plasma membrane?

  It is partially permeable.
• What does the plasma membrane separate?

  It separates the cell's contents from the external environment.
• What conditions does the plasma membrane allow?

  It allows different conditions to be established inside the cell.
• Which substances can membranes be permeable to?

  Water, carbon dioxide, and oxygen.
• What type of membranes do the nucleus, chloroplast, and mitochondria have?

  They have double membranes.
• What are the types of membrane proteins and their functions?

  • Ion channels: Allow specific ions to pass through.
  • Transport proteins: Transport specific molecules.
  • Glycoproteins: Involved in cell recognition.
  • Receptors: Binding sites for hormones.
• What is a glycoprotein?

  It is a protein with a polysaccharide chain extending outwards.
• What do glycoproteins facilitate?

  They are involved in cell recognition.
• What do membrane proteins allow to pass through?

  They allow water-soluble molecules and ions through.
• What is the fluid mosaic model?

  It describes the structure of the plasma membrane as a mosaic of various proteins floating in or on the fluid lipid bilayer.
• What is the structure of the phospholipid bilayer?

  It consists of a polar head and a non-polar tail.
• What is the function of a protein channel in the membrane?

  It allows water-filled pores for molecules to pass through.
• What is the role of cholesterol in the plasma membrane?

  It controls membrane fluidity and allows for flexibility.
• What are extrinsic proteins?

  They are proteins located on the inner or outer surface of the membrane.
• What is the function of intrinsic proteins?

  They span the whole width of the membrane.
• What do intrinsic proteins allow to diffuse across the membrane?

  They allow water-soluble ions to diffuse across the membrane.
• What is diffusion?

  Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
• Why do particles move randomly during diffusion?

  Particles have kinetic energy, which causes them to move randomly.
• What types of molecules can pass through the cell membrane by simple diffusion?

  Small, non-polar molecules such as oxygen and carbon dioxide can pass through.
• What are the inputs of a cell?

  • Oxygen
  • Enzymes
  • Hormones
  • Glucose
  • Amino acids
  • Nutrients
• What are the outputs of a cell?

  • Carbon dioxide
  • Hormones
  • Enzymes
  • Urea
• Where do all exchanges occur in a cell?

  All exchanges occur across the plasma membrane.
• What are the passive processes involved in cellular transport?

  • Simple diffusion
  • Facilitated diffusion (co-transport)
  • Osmosis
• What is simple diffusion?

  Simple diffusion is the movement of small non-polar molecules down a concentration gradient until evenly distributed.
• Give an example of simple diffusion in the human body.

  Oxygen moves from alveoli to blood.
• What adaptations facilitate diffusion across cell membranes?

  Adaptations include a partially permeable membrane, large surface area, one cell thick structure, and good blood supply.
• How does temperature affect the rate of diffusion?

  Higher temperatures increase the kinetic energy of particles, leading to a greater rate of diffusion.
• What is Fick's law of diffusion?

  Fick's law states that the rate of diffusion is proportional to the surface area, the difference in concentration, and inversely proportional to the thickness of the exchange surface.
• What is facilitated diffusion?

  Facilitated diffusion is the movement of charged ions and polar molecules across the membrane using a channel protein down a concentration gradient.
• What role do carrier proteins play in facilitated diffusion?

  Carrier proteins bind specific molecules and change shape to transport them across the membrane.
• What is active transport?

  Active transport is the movement of molecules against a concentration gradient using ATP and carrier proteins.
• How does active transport differ from diffusion?

  Active transport requires metabolic energy in the form of ATP and moves substances against the concentration gradient.
• What happens to ATP during active transport?

  ATP splits into ADP and inorganic phosphate, releasing energy for the transport process.
• Describe the process of active transport.

  1. Molecule binds to specific receptor sites on the carrier protein.
  2. ATP binds to the carrier protein.
  3. ATP splits into ADP + Pi, causing the protein to change shape.
  4. The molecule is released on the opposite side of the membrane.
  5. Inorganic phosphate detaches, reverting the protein to its original shape.
• What is co-transport?

  Co-transport is the process where sodium ions move into the cell, bringing glucose with them against its concentration gradient.
• Why is there a higher concentration of glucose in the ileum than in the blood?

  Glucose is continuously removed by cells for use in respiration, creating a concentration gradient.
• How does glucose move from the ileum into the blood?

  Glucose moves from the ileum into the blood via facilitated diffusion after being co-transported with sodium ions.
• What is endocytosis?

  The process of capturing a substance from outside the cell by engulfing it with the cell membrane
• How does the cell membrane behave during endocytosis?

  The membrane folds over the substance and encloses it
• Describe the process of sodium-potassium pump in active transport.

  1. Sodium ions (Na⁺) are actively transported into the blood.
  2. Potassium ions (K⁺) are also pumped in.
  3. This creates a lower concentration of sodium ions in the cell.
  4. Sodium ions move into the cell by co-transport, bringing glucose with them.