Title [ Q1W8 ] GenBio Q1 Reviewer.pdf ✅

GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 8: CELLULAR TRANSPORT – PPT & lecture-based – 1.0 TRANSPORT MECHANISMS PASSIVE TRANSPORT ACTIVE TRANSPORT NO requirement of ATP/energy Requirement of ATP/energy High to low concentration gradient Low to high concentration gradient (against) Types/Examples for each transport mechanism: ● Passive Transport a) Diffusion b) Osmosis c) Facilitated Diffusion ● Active Transport a) Sodium-Potassium Pump b) Vesicular/Bulk Transport 2.0 PASSIVE TRANSPORT 2.1 DIFFUSION ● Moves from high to low concentration gradient ● Tendency for molecules to spread out evenly to achieve equilibrium. ● Diffusion occurs during gas exchange for humans (lung cells): GAS EXCHANGE Alveoli Tiny air sacs; site of gas exchange Red Blood Cells (RBCs) Transport oxygen from the lungs to the various tissues of the body; carry carbon dioxide (waste product of cellular respiration) back to the lungs for exhalation ● During inhalation, the alveoli contains high oxygen concentration. ● RBCs pass close to these air sacs, and diffusion occurs; - The oxygen in alveoli (high concentration of O2) is being transported to RBCs (low concentration of O2) - The carbon dioxide from RBCs (high concentration of CO2) is being transported to alveoli (low concentration of CO2) for exhalation. 2.2 OSMOSIS ● Water molecules move from high to low concentration gradient ● Diffusion of water across a selectively permeable membrane ● Water movement depends on solute concentration: - Water diffuses from low to high solute concentration. ● Osmosis is connected with tonicity. ● Tonicity: ability of a solution to cause a cell to gain or lose water. a) Hypertonic WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 1
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 8: CELLULAR TRANSPORT b) Isotonic c) Hypotonic (further explanation of tonicity in 2.2.1.) 2.2.1 TONICITY ● Effect of solution on the osmotic water movement across the cell membrane. ● Ability of a solution to cause a cell to gain or lose water. ● Three main categories of tonicity: a) Hypertonic b) Isotonic c) Hypotonic Tonicity Animal Cell Plant Cell Hypertonic Shriveled Plasmolyzed Isotonic Normal Flaccid Hypotonic Lysed Normal (turgid) ● Hypertonic ➔ Solute concentration: Outside > Inside ➔ Animal cell: Shrink/Shrivel ➔ Plant cell: Plasmolyze (cell will shrink, but will maintain its rectangular shape due to the presence of cell wall). ● Isotonic ➔ Solute concentration: Outside = Inside ➔ Animal cell: Normal ➔ Plant cell: Flaccid (soft/limp; between turgid and plasmolyzed states). ● Hypotonic ➔ Solute concentration: Outside < Inside ➔ Animal cell: Lysed/Burst ➔ Plant cell: Normal/Turgid (promotes turgor pressure; essential for supporting the plant’s structure and maintaining rigidity) 2.3 FACILITATED DIFFUSION Q: What’s the difference between simple and facilitated diffusion? In simple diffusion, molecules pass through the phospholipid bilayer. Certain molecules that could not pass through the bilayer utilize facilitated diffusion instead, wherein the molecules move through transport proteins. WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 2
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 8: CELLULAR TRANSPORT ● Moves from high to low concentration gradient ● Transport proteins speed the passive movement of molecules across the plasma membrane. ● Transport proteins can either be: a) Channel proteins b) Carrier proteins ● Channel proteins: form hydrophilic pores to provide permanent open pathways that enable the passage of molecules/ions across the membrane, provided they are a compatible fit. - e.g. Aquaporins: Facilitate the passage of water molecules ONLY; abundant in the excretory/urinary system for reabsorption of water. ● Carrier proteins: bind to specific molecules or ions and change their form to transport these molecules across the membrane. - Can facilitate transport of molecules against their concentration gradient (active transport). 3.0 ACTIVE TRANSPORT 3.1 SODIUM-POTASSIUM PUMP WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 3
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 8: CELLULAR TRANSPORT ● Moves from low to high concentration gradient (against). ● Involves two positively charged ions: sodium (Na+) and potassium (K+). ● The pump contains binding sites that fit three Na+ molecules, and two K+ molecules. ● Six steps: 1) The pump starts with three sodium ions (Na+) binding to it from the inside of the cell. 2) A phosphate group from ATP attaches to the pump, providing the energy needed for the pump to function. 3) The energy causes the pump to change its shape, expelling the three sodium ions to the outside of the cell. 4) Simultaneously, two potassium ions (K+) from the outside bind to the pump. 5) The binding of the potassium ions triggers the release of the phosphate group. 6) The pump returns to its original shape, releasing the two potassium ions into the cell and preparing to start the process again. Q: In step 2, how did the phosphate break down from ATP? It involves a process known as hydrolysis. Within ATP, there exists an adenosine molecule attached to three phosphates, each linked by energized bonds. Consequently, these bonds are broken using water, leading to the release of energy. One phosphate group is released, converting ATP to ADP along with a single phosphate molecule that will be used for phosphorylation (addition of a phosphate group to a molecule). ● Abundant in the nervous system. ● Importance: To create/maintain an electrochemical gradient essential for nerve cell signaling and the proper functioning of the nervous system. 3.2 VESICULAR/BULK TRANSPORT ● Moves from low to high concentration gradient (against). ● Essential for transportation of substances that are too large to be transported through the lipid bilayer or transport proteins. ● Types of vesicular/bulk transport: 1) Endocytosis (3.2.1.) a) Phagocytosis b) Pinocytosis c) Receptor-mediated endocytosis 2) Exocytosis (3.2.2.) 3.2.1 ENDOCYTOSIS ● “Endo” : inside WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 4