Biochemistry – Chap. 2 Cell Biology – Chap. 3 Cytology Biochemistry – Chap. 2 Cell Biology – Chap. 3

Cellular Membrane Transport

Learner Outcomes: To describe the characteristics and identify the monomers of lipids, proteins, carbohydrates, and nucleic acids and to define their role in biochemical processes. To analyze and explain the chemical reactions that provide energy for the body. To investigate and describe the integration of the chemical and physical properties that contribute to homeostasis in cells. To compare the structures and functions of organelles within cells of the body. To describe the processes involved in the cell cycle.

Cellular Homeostasis – the plasma membrane Semi-permeable or Selectively permeable 2 methods used in crossing the membrane – active and passive Active transport requires the use of ATP. Which organelle provides this high-powered molecule for the cell? Passive transport uses the principles of diffusion to cross the membrane and does not require the use of ATP.

Diffusion The random movement of molecules from an area of high concentration to an area of low concentration. The characteristics of the cell membrane allow for certain molecules to diffuse across the membrane. What are the characteristics of the cell membrane? What molecules might be able to diffuse through it?

Diffusion Lipid membrane so – lipid-soluable materials. Alcohols Hormones Very small molecules too. Oxygen Carbon dioxide Many elements

Osmosis Diffusion of water across a plasma membrane. There must be a concentration gradient for this to occur until dynamic equilibrium is met. Normally body fluids are isotonic – there is an equal concentration of solutes and solvent on both sides of the membrane. Hypotonic solutions cause cells to swell and go through lysis (burst). Hypertonic solutions cause the cells to shrink and crenate. These changes are a result of osmotic pressure.

Fig. 3.8a

Fig. 3.8b

Fig. 3.8c

Filtration Diffusion aided by blood pressure. Occurs in the kidney’s where blood is filtered of nitrogenous waste. Large substances stay behind the filtration membrane and smaller ones and water pass through.

Facilitated Transport Diffusion, from high to low concentration, using an integral protein carrier (examples: amino acids or glucose). Movement includes attachment to the protein embedded in the membrane.

Active Transport Movement is against the concentration gradient (low to high concentration). Requires a protein carrier and the use of ATP. ATP is used by the carrier to modify the shape of the protein. Example: Sodium-Potassium Pump.

Fig. 3.9

Endocytosis Also called phagocytosis or pinocytosis. Process in which a portion of the plasma membrane invaginates to engulf a substance and then pinches off the membrane to form a vesicle.

Exocytosis A process where a vesicle fuses with the other plasma membrane as secretion of the contents occur.

End of Cell Transport

Fig. 3.10

Fig. 3.11

Fig. 3.12

Fig. 3.14

Fig. 3.15

Protein Synthesis Transcription – synthesis of the mRNA from the DNA in the nucleus. RNA polymerase – enzyme that assists in obtaining the genetic information. mRNA leaves the nucleus through the nuclear pores of the envelope.

Fig. 3.13

Protein Synthesis Translation – occurs in the cytoplasm associated with a ribosome (rRNA). The mRNA, tRNA, and rRNA all come together to bind the amino acids together into the proper proteins as dictated by the DNA.

End of Protein Synthesis