Lecture 2 Flashcards

Question

What is diffusion?

Answer 1

Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached. These particles move from an area of high concentration to an area of low concentration. expample is spraying perfume and the perfume moves to an area where there was no perfume. It has moved from where it was concentrated to where it’s not concentrated so high to low

Answer 2

- All these physiological processes occur by diffusion Gaseous exchange(oxygen and carbon dioxide are lipid soluble) -Absorption of digested nutrients -Propagation of nerve impulses -Movement of hormones and other metabolites towards their target organ.

Answer 3

Molecular: Lipid solubility(more lipid soluble molecules diffuse into the cell quickly) Molecular size and weight(smaller molecular weights and size diffuse more quickly) Temperature(Higher temperatures accelerate diffusion rates because molecules move more rapidly) Membrane related: Surface area(A larger surface area enhances the rate of diffusion by allowing more molecules to pass through the membrane simultaneously) Concentration gradient(A concentration gradient refers to the difference in solute concentration across a membrane. - **Impact on Diffusion:** The steeper the concentration gradient (i.e., the greater the difference in concentration between two sides of the membrane), the faster the rate of diffusion.) Electrical gradient ( the electrical gradient refers to the difference in electrical charge (voltage) across a biological membrane that influences the movement of ions:The electrical gradient complements the concentration gradient in influencing ion movement. The electrochemical gradient takes into account both the concentration gradient and the electrical gradient of ions across the membrane. - **Direction of Movement:** Ions will move across the membrane in a manner that tends to equalize both their concentration and electrical potentials between the two sides of the membrane - Positively charged ions (cations) move towards areas of lower positive charge (more negative inside the cell), while negatively charged ions (anions) move towards areas of higher positive charge (more positive inside the cell

Answer 4

Facilitated diffusion requires the help of carrier and channel proteins These particles move from an area of high concentration to an area of low concentration. Facilitated diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped”. Proteins in the cell membrane form channels for large molecules to pass through. Facilitated diffusion requires the help of carrier and channel proteins These particles move from an area of high concentration to an area of low concentration. Proteins that form channels (pores) are called protein channels

Answer 5

1. **Carrier Proteins in Diffusion:** - **Mechanism:** Carrier proteins facilitate facilitated diffusion, a type of passive transport where molecules move down their concentration gradient (from high to low concentration). - **Process:** - A molecule or ion binds to the specific binding site on the carrier protein located on one side of the membrane. - The carrier protein undergoes a conformational change, transferring the bound molecule or ion across the membrane to the other side. - The molecule or ion is released from the carrier protein, which returns to its original conformation, ready to transport another molecule. - **Examples:** Glucose transporters (e.g., GLUT proteins) and amino acid transporters utilize carrier proteins to facilitate their movement across cell membranes. 2. **Channel Proteins in Diffusion:** - **Mechanism:** Channel proteins facilitate passive diffusion by forming aqueous pores or channels through the membrane. - **Process:** - Channel proteins are selective based on size, charge, or other chemical properties, allowing specific ions or molecules to pass through. - Substances move through the channel down their electrochemical gradient, without requiring energy input (passive transport). - The rate of diffusion through channel proteins is typically faster compared to carrier proteins, as it depends on the size of the channel and the concentration gradient of the substance. - **Examples:** Ion channels such as sodium channels, potassium channels, and chloride channels are examples of channel proteins that allow ions to diffuse across cell membranes. **Comparison:** - **Specificity:** Carrier proteins exhibit specificity for their substrate molecules or ions, binding and transporting them across the membrane. Channel proteins are selective based on size and charge, allowing only certain substances to pass through. - **Mechanism:** Carrier proteins undergo conformational changes to transport substances, while channel proteins provide a direct pathway (channel) for passive diffusion. - **Rate of Diffusion:** Channel proteins generally facilitate faster diffusion rates compared to carrier proteins, as they provide a continuous pathway for molecules or ions to move across the membrane. In summary, both carrier proteins and channel proteins facilitate the movement of molecules and ions across membranes through diffusion. Carrier proteins are involved in facilitated diffusion by binding to specific molecules and undergoing conformational changes, while channel proteins form pores that allow substances to passively diffuse across the membrane based on their electrochemical gradient. **Carrier Proteins:** - **Function:** Transport specific molecules (such as glucose, amino acids, and ions) across cell membranes. - **Mechanism:** Bind to their substrate, undergo conformational changes, and facilitate transport across the membrane. - **Examples:** GLUT (glucose transporter proteins) proteins (for glucose), amino acid transporters, and ion transporters like the sodium-potassium pump. **Channel Proteins:** - **Function:** Form pores or channels in membranes for ions or water to pass through. - **Mechanism:** Provide a pathway for passive diffusion based on size, charge, and selectivity. - **Examples:** Ion channels (e.g., sodium and potassium channels) and aquaporins (for water transport).

Answer 6

Carrier proteins Active transport processes primarily involve carrier proteins that use the energy derived from ATP hydrolysis to move molecules or ions against their concentration gradients across biological membranes Active transport primarily utilizes carrier proteins that are specifically designed to transport molecules or ions against their concentration gradients using energy from ATP hydrolysis. These carrier proteins include: 1. **Sodium-Potassium Pump (Na+/K+ ATPase):** - **Function:** Actively transports three sodium ions (Na+) out of the cell and two potassium ions (K+) into the cell per ATP hydrolyzed. - **Role:** Maintains cell volume, establishes an electrochemical gradient, and supports nerve signal transmission. - **Location:** Found in the plasma membranes of most animal cells. 2. **Calcium Pump (Ca2+ ATPase):** - **Function:** Actively transports calcium ions (Ca2+) out of the cytoplasm across cell membranes against their concentration gradient. - **Role:** Regulates calcium levels in cells, which is crucial for muscle contraction, signal transduction, and enzyme regulation. - **Location:** Found in the plasma membranes and membranes of organelles like the sarcoplasmic reticulum in muscle cells. 3. **Proton Pump (H+ ATPase):** - **Function:** Actively transports protons (H+) across membranes, creating a proton gradient. - **Role:** Involved in pH regulation, generating electrochemical gradients, and supporting nutrient uptake. - **Location:** Found in the plasma membranes of various cells, as well as in intracellular organelles like lysosomes and plant vacuoles. 4. **ABC Transporters (ATP-Binding Cassette Transporters):** - **Function:** Actively transport a wide range of substrates, including ions, sugars, lipids, and drugs, across membranes. - **Mechanism:** ATP hydrolysis provides energy for conformational changes that facilitate substrate transport. - **Role:** Involved in drug resistance, nutrient uptake, and removal of toxic substances. - **Location:** Found in various cellular membranes, including the plasma membrane and intracellular organelles. ABC transporters have a characteristic structure with two nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). The ATP binding and hydrolysis in the NBDs provide the energy needed for the transport process. • Examples: Notable examples include the multidrug resistance proteins (MDRs) that can pump out drugs from cells, contributing to drug resistance.

Answer 7

Active transport refers to the movement of molecules or ions across a cell membrane against their concentration gradient, requiring energy usually derived from ATP hydrolysis. There are several types of active transport mechanisms: 1. **Primary Active Transport:** - **Mechanism:** In primary active transport, energy from ATP hydrolysis directly powers the movement of molecules or ions against their concentration gradient. - **Example:** The sodium-potassium pump (Na+/K+ ATPase) actively transports sodium ions (Na+) (3sodium molecules) out of the cell and potassium ions (K+) (2 molecules of potassium) into the cell, maintaining ion gradients crucial for cellular functions. 2. **Secondary Active Transport:** - **Mechanism:** Secondary active transport utilizes the energy stored in an electrochemical gradient (usually of ions like sodium or hydrogen ions) to drive the transport of other molecules or ions against their concentration gradient. When something moves **against** a concentration gradient, it is moving **up the gradient**. This means it is moving from an area of lower concentration to an area of higher concentration, which typically requires energy input, such as ATP. In contrast, moving **down the gradient** would mean moving from an area of higher concentration to an area of lower concentration, which generally does not require energy and occurs via passive transport. - **Types:** - **Symport (Cotransport):** Transport of two different molecules or ions in the same direction across the membrane. One molecule moves down its concentration gradient, providing the energy to transport another molecule against its gradient. Example: SGLT (Sodium-Glucose Transporters or Symporter). This is behind ORS drink concept - **Antiport (Countertransport):** Transport of two different molecules or ions in opposite directions across the membrane. Example: Sodium-calcium exchanger (NCX), which exchanges sodium ions for calcium ions or sodium hydrogen antiporter which is usually found in the kidneys and is used to regulate acid base in blood. It does this by reabsorbing sodium and pushing out hydrogen from the blood and this regulates the body’s acidity Here are clinically relevant examples of antiport and symport transporters: **Antiport Examples:** 1. **Sodium-Calcium Exchanger (NCX):** This exchanger is crucial in cardiac muscle cells, where it helps regulate intracellular calcium levels, which is important for proper heart function. 2. **Chloride-Bicarbonate Exchanger (AE1):** Found in red blood cells and involved in maintaining acid-base balance by exchanging chloride ions and bicarbonate ions. 3. Sodium-Hydrogen Exchanger (NHE): Exchanges one sodium ion (Na+) inward for one hydrogen ion (H+) outward. **Symport Examples:** 1. **Sodium-Glucose Co-Transporter (SGLT):** Found in the kidneys and intestines, this transporter is significant for glucose reabsorption. Inhibitors of SGLT2 (a subtype) are used to treat diabetes by promoting glucose excretion in urine. 2. **Sodium-Iodide Symporter (NIS):** Essential for thyroid function, it helps transport iodide into thyroid cells for the synthesis of thyroid hormones. Dysfunction can lead to thyroid disorders. 3. **Sodium-Amino Acid Co-Transporters:** These transporters are crucial for the absorption of amino acids from the gut, which is essential for nutrition and overall health.

Answer 8

Sarcoplasmic reticulum

Answer 9

Sodium potassium ATpase The terms E1 and E2 refer to specific conformations or states of an ion pump, such as the sodium-potassium pump (Na+/K+ ATPase), during its function in active transport: 1. **E1 Conformation:** - **Definition:** The E1 conformation of the pump is characterized by its binding sites facing the intracellular side of the membrane.(intracellular because at this stage, it is not picking sodium from the inside) - **Function:** In this state, the pump has a high affinity for sodium ions (Na+), binding three Na+ ions from the cytoplasm. - **Energy Consumption:** ATP hydrolysis occurs at this stage to provide energy for the subsequent conformational change. 2. **E2 Conformation:** - **Definition:** The E2 conformation occurs after ATP is hydrolyzed, causing a conformational change in the pump. - **Function:** In the E2 state, the pump undergoes a change in its structure, causing the binding sites to face the extracellular side of the membrane.( Extracellular because at this conformation is where sodium is pumped out of the cell and potassium is pumped in) - **Ion Release:** This change leads to the release of sodium ions (Na+) to the outside of the cell. - **Ion Binding:** Simultaneously, the E2 state allows for the binding of two potassium ions (K+) from the of them Palest? Jahren

Answer 10

Integral proteins- embedded in the lipid bilayer Transmembrane proteins- span membrane and function as ion channels, carrier molecules, enzymes, receptors. We have single and multiple trans membrane proteins. Peripheral proteins- loosely bound to other proteins and phospholipids usually on the cytosolic side.they function mainly as part of the cytoskeleton Where do these proteins fall? Adhesion proteins using glycocalyx or something Transport proteins - they’re gates Receptor proteins- insulin binding to a receptor to make the cell know that it must synthesize sugar channels to push glucose into the cell Recognition protein Types of gates; Gates: molécule binding before door opens. It’s called a ligand. Ligand gated channel Electrical current or signal is action potential is what will come and make the gates open. It’s a voltage. So the channels are called voltage gated channel Mechanically gates channels Note: Carrier proteins can pick things from the surface and change conformation to send to the other side of the cell while channels just open for the molecule to pass through it to come out at the other side. Membrane proteins channels which have surface proteins that also have enzymatic action. The channels are lock and key so if the ion aren’t the right keys for the protein channels, the door won’t open.

Answer 11

Great observation! Nuclear pores and nuclear receptors are different structures: • Nuclear pores are large protein complexes embedded in the nuclear envelope. • Their main role is to control the movement of molecules (like RNA and proteins) between the nucleus and the cytoplasm. • They do not function as receptors. • Nuclear receptors are proteins (not pores) that bind specific molecules, like steroid hormones, and then regulate gene expression. • They are inside the cell, often in the cytoplasm or nucleus, and they respond to lipid-soluble signals that can cross the cell membrane. So you’re right — nuclear pores are on the surface of the nucleus, but they’re not receptors. Receptors can be found near or in the nucleus, but they serve a different purpose. Would you like a diagram showing the difference between nuclear pores and nuclear receptors?

Answer 12

Functions of cell membrane: Regulates passage of materials in and out of cell Allows cells to receive or transmit signals through receptors that only allow selected chemicals to bind to them Provide binding sites for enzymes to catalyze the reactions Receptors = communication (receive signals and act) • Recognition proteins = identification (help other cells recognize them) unctions of nucleus: contain DNA in the form of chromatin (genetic material). Function in transmission and expression of genetic materials. Genetic information for RNA and protein synthesis is encoded in the DNA. Functions of Cytosol or cytoplasm: Site of chemical reactions and protein synthesis Contains organelles Stores energy in the form of triglycerides(fatty acids) or glycogen(glucose) in structures called inclusions Stores molecule to be secreted in secretory vesicles Function of Rough ER: Bears ribosomes which function as site for protein synthesis. It holds mRNA in place for the synthesis to occur Smooth ER: Site for lipid synthesis and blood detoxification. Stores calcium ions Sarcoplasmic reticulum is the smooth ER name in the muscle. Golgi: Processes molecules synthesized in the ER and prepares them for transport to their final destinations. Packages molecules into vesicles and directs the vesicles to their appropriate location Mitochondria: Produces energy for the cell in the form of ATP WHATEVER YOU BURN, you can get energy from it to drive reactions. Glucose from food is broken down in the presence of oxygen to produce carbon dioxide plus water plus ATP. Lactic acid production causes the body pains. If you don’t go again, the lactate acid will accumulate. If you go again, it’ll burn Lysosomes: contain enzymes that degrade cellular debris for recycling and excretion of waste Enzymes that help degrade endoctrines vesicles to release their content into the cell Peroxisomes; Degrade molecules such as amino acids, fatty acids and foreign substances. Contains catalase which removes free ROS or radicals ROS causes eclampsia and pre eclampsia in women Centrioles: Direct development of mitosis spindle during cell division Cytoskeleton Provides skeletal framework for cell(mechanical support) Here’s a brief comparison of the three cytoskeletal filaments: 1. Microfilaments (Actin Filaments) • Smallest (7 nm) • Made of actin • Functions: • Cell shape and movement • Muscle contraction • Cell division (cytokinesis) 2. Intermediate Filaments • Medium size (~10 nm) • Made of various fibrous proteins (e.g., keratin) • Functions: • Mechanical strength • Structural support • Anchor organelles 3. Microtubules • Largest (25 nm) • Made of tubulin • Functions: • Intracellular transport (with motor proteins) • Cell division (spindle fibers) • Cilia and flagella movement Mnemonic: “MIM” – Microfilaments, Intermediate, Microtubules (from smallest to largest) Would you like a labeled diagram too? Functions: Cell adhesion Attachment to cytoskeleton via anchoring Cell surface receptor Cell surface recognition or cell surface identity marker Selective transport channel Enzyme: In summary, membrane proteins can act as enzymes by catalyzing chemical reactions at the cell membrane. These proteins have an active site where substrates bind, and they speed up reactions without being consumed. For example, enzymes like adenylyl cyclase convert ATP into cAMP, and ATPases help in energy transfer for active transport. The protein is the enzyme that carries out these catalytic functions. Transport • Move substances across the membrane (e.g., channels, carriers). 2. Receptors • Bind signaling molecules (e.g., hormones) and trigger cell responses. 3. Enzymatic activity • Speed up chemical reactions on the membrane surface. 4. Cell recognition • Help the immune system identify self vs. non-self (e.g., glycoproteins). 5. Cell adhesion • Help cells stick to each other or to the extracellular matrix. 6. Structural support • Anchor the cytoskeleton to maintain cell shape.

Answer 13

Movement of molecules across membrane down an electrochemical gradient and no energy. It uses the advantage of electrochemical gradient. The steeper the slope, the faster the diffusion or movement. Electric gradient: charge and number of charges on the molecules that are diffusion or number of molecules that have the charge. If the charges are the same, there’s no gradient. If it’s higher on one side than the other side, then there’s a gradient. Chemical gradient: concentration. Example is perfumes moving to lower conc from a high conc So electrochemical gradient is focusing on the concentration of molecules and the charge of the molecules plus the number of molecules that have the charge or the number of charges on the molecules

Answer 14

Simple diffusion: Movement of solute molecules deom down their concentration gradient using their own thermal motion. No membrane proteins are involved Example is water(if it can’t move, you’ll need the channel. If the water is going but it’s not enough you’ll need the channels), oxygen, carbon dioxide. Fat soluble substances due to phospholipid bilayer ( fatty acids, vit ADEK, steroid hormones) Factors affecting: Conc gradient: the steeper it is the faster it is Membranes surface area: Membrane permeability : 1. Concentration Gradient • The steeper the gradient, the faster the diffusion. • More difference = more movement from high to low concentration. 2. Membrane Surface Area • Larger surface area = faster diffusion. • More space for molecules to pass through. 3. Membrane Permeability • Higher permeability = faster diffusion. • Depends on lipid solubility, size of molecule, and presence of channels. Perfect! Here’s a brief summary of the factors influencing membrane permeability, organized for clarity: Factors Affecting Membrane Permeability: 1. Lipid Solubility of the Diffusing Substance • More lipid-soluble = higher permeability • Lipid-soluble substances pass through the phospholipid bilayer more easily. 2. Size and Shape of Diffusing Molecules • Smaller and more compact molecules = higher permeability • Large or irregularly shaped molecules struggle to pass through. 3. Temperature • Higher temperature = higher permeability • Increases molecular movement and membrane fluidity. 4. Membrane Thickness • Thicker membrane = lower permeability • Increases the distance substances must travel. Quick summary line: Smaller, lipid-soluble molecules cross faster—especially with heat and thin membranes. Want a mnemonic to remember this?

Answer 15

Facilitated diffusion: mediated by integral membrane proteins 1. Carrier mediated- trans membrane protein that binds molecules from one side of the membrane and transports them to the other side by means of a conformational change or a change in shape. A carrier possess one or more hiding sites that are specific for the molecules it carries. example : glucose being picked up by transport proteins and sent to the other side(the moment it’s added to sodium, it becomes active transport) , amino acids too 2. Diffusion through membrane ion channels- a channel is a transmembrane protein that transports molecules via a passageway or pore that extends from one side of the membrane to the other. Channels are also specific to certain substances Gated or non gated. Ligand gated or voltage gated. Example is Fluoride channel and sodium channel and aquaporins or water channels( synthesized when ADH binds to receptors on the cells to push water somewhere. Example is kidney tubules) , example of substances that go through channels is potassium and sodium and chloride Sure! Here are clear examples of both: Carrier-Mediated Facilitated Diffusion: • Uses carrier proteins that bind to specific molecules and change shape to transport them across the membrane. • Examples: • Glucose transporters (GLUTs) – transport glucose into cells • Amino acid transporters – move amino acids across membranes • Urea transporter (UT) – for passive movement of urea Channel-Mediated Facilitated Diffusion: • Uses channel proteins that form pores for specific ions or water molecules to pass through without binding. • Examples: • Ion channels (Na⁺, K⁺, Ca²⁺) – voltage or ligand-gated • Aquaporins – water channels • Cl⁻ channels – allow chloride ions to diffuse Summary: • Carrier-mediated = binds, changes shape (e.g., glucose) • Channel-mediated = pore-like, no binding (e.g., ions, water) Here are some more common and well-known examples of carrier- and channel-mediated facilitated diffusion that you’re likely to encounter often: Carrier-Mediated Facilitated Diffusion (Very Common Examples): 1. GLUT1, GLUT2, GLUT4 – Glucose transporters in red blood cells, liver, and muscle/adipose tissue 2. SLC transporters – For amino acids, ions, and drugs 3. Urea transporter (UT-A, UT-B) – Kidney handling of urea 4. L-type amino acid transporters (LAT1) – Move large neutral amino acids 5. Monocarboxylate transporters (MCTs) – Transport lactate and pyruvate Channel-Mediated Facilitated Diffusion (Very Common Examples): 1. Sodium channels (Na⁺) – In nerve and muscle cells 2. Potassium channels (K⁺) – Help reset membrane potential 3. Calcium channels (Ca²⁺) – In muscle contraction and neurotransmitter release 4. Chloride channels (Cl⁻) – Important for fluid balance and neurons 5. Aquaporins (especially Aquaporin-1 and Aquaporin-2) – Water channels in kidneys and other tissues Simple tip: • Glucose, amino acids, urea → carrier • Ions, water → channel Would you like a table format or diagram to make it even easier to recall?

Answer 16

Here’s a concise breakdown of the types of ion channel receptors in the body, with examples: 1. Ligand-Gated Ion Channels (Chemically Gated) • Open when a chemical (ligand) binds to the receptor. • Examples: • Nicotinic acetylcholine receptor – at neuromuscular junction • GABA-A receptor – allows Cl⁻ into neurons • Glutamate receptors – like AMPA or NMDA channels 2. Voltage-Gated Ion Channels • Open/close in response to changes in membrane potential. • Examples: • Voltage-gated Na⁺ channels – initiate action potentials • Voltage-gated K⁺ channels – repolarize membranes • Voltage-gated Ca²⁺ channels – trigger neurotransmitter release 3. Mechanically (or Stress) Gated Channels • Open in response to mechanical stimuli (pressure, stretch). • Examples: • Baroreceptor channels – in blood vessels sensing pressure • Touch and stretch receptors – in skin and muscle • Hair cells in the ear – respond to sound vibrations 4. Always Open (Leak Channels) • Always allow passive ion movement; help maintain resting potential. • Examples: • K⁺ leak channels – maintain negative resting membrane potential • Na⁺ leak channels – minor but contribute to resting potential • Cl⁻ leak channels – help stabilize membrane voltage in some cells Would you like a mnemonic or flashcard version for quick study? Yes, you’re right! In the context of neurotransmission, the main types of ion channels involved are: 1. Ligand-Gated Channels • Activated by neurotransmitters binding to them. • Fast synaptic transmission. • Examples: • Nicotinic ACh receptor • GABA-A receptor • Glutamate receptors (AMPA, NMDA) 2. Voltage-Gated Channels • Activated by changes in membrane potential. • Key for action potential generation and propagation. • Examples: • Voltage-gated Na⁺ channels (for depolarization) • Voltage-gated K⁺ channels (for repolarization) • Voltage-gated Ca²⁺ channels (for neurotransmitter release at synapse) So yes, ligand-gated and voltage-gated channels are the two main types involved in neurotransmission. Need a quick diagram or summary flow of how neurotransmission uses both?

Answer 17

Primary active: proteins invovled as both transport proteins and enzymes. As enzymes they catalyze ATP hydrolysis to produce energy hence they are also called Atpases. Example is sodium potassium pump( for action potential generation) , hydrogen potassium pump(proton pump and is in the stomach) , calcium pump or calcium Atpase Secondary: transport proteins use the energy generated by the passive flow of one substance to drive the active flow of another substance Example is Sodium glucose co transport Great summary! Based on that, here are a few MCQs on active transport with immediate answers and explanations: 1. Which of the following best describes active transport? A. Movement of molecules along the concentration gradient B. Passive movement using channel proteins C. Movement of molecules against the electrochemical gradient using energy D. Diffusion through the lipid bilayer Answer: C Explanation: Active transport uses energy (usually ATP) to move substances against their gradient, unlike passive processes. 2. What is the main reason ATP is required in active transport? A. To increase membrane surface area B. To maintain membrane fluidity C. To move substances against their electrochemical gradient D. To allow molecules to bind to receptors Answer: C Explanation: Moving substances against the gradient (from low to high concentration) is energy-demanding and requires ATP. 3. Which of the following is a feature of pumps used in active transport? A. They transport molecules randomly B. They do not bind to specific molecules C. They have fixed binding sites and use energy D. They only transport water molecules Answer: C Explanation: Pumps are specific, have fixed binding sites, and use energy (ATP) to move molecules. 4. The sodium-potassium pump moves how many sodium and potassium ions per cycle? A. 2 Na⁺ out, 3 K⁺ in B. 3 Na⁺ out, 2 K⁺ in C. 3 Na⁺ in, 2 K⁺ out D. 2 Na⁺ in, 3 K⁺ out Answer: B Explanation: The Na⁺/K⁺ pump moves 3 Na⁺ out and 2 K⁺ in, using 1 ATP, maintaining ionic gradients in cells. Active transport: ATP is used here. It goes against the electrochemical gradient that’s why it needs energy. Pumps are carriers involved in active ta sport and have the ability to harness energy to drive transport. Pumps are also specific and have a fixed number of binding sites So active transport uses carrier proteins too but with ATp

Answer 18

Primary active: proteins invovled as both transport proteins and enzymes. As enzymes they catalyze ATP hydrolysis to produce energy hence they are also called Atpases. Example is sodium potassium pump( for action potential generation) , hydrogen potassium pump(proton pump and is in the stomach) , calcium pump or calcium Atpase Secondary: transport proteins use the energy generated by the passive flow of one substance to drive the active flow of another substance Uniport- goes in one direction (either it’s going out and another is pushing it in or Vice versa). If you get a uniport going in the left direction, it’ll never go in the right direction too. And Vice versa Antiport- two different substances coming but they go in opposite directions. Counter transport or anti port example is sodium hydrogen exchanger in the renal system. Co transport(symport) - two different substances being carried and they go in the same direction but in terms of electrochemical gradient, they’re moving in opposite directions. Example is sodium linked glucose transport in the GIT In sodium glucose : Which provides the energy for which to go down. The one being pushed is the uphill one and the one going down easily the downhill one. Sodium pushes the glucose. Why??? Confirm the answer The answer is in the 202 cards that include action potential or so Importance of sodium potassium pump is to restore membrane potential back to rest after an action potential. Action potential is stimulation of a nerve to produce a desired effect Certainly! Here are the examples: Antiport: • Sodium-potassium pump (Na⁺/K⁺ ATPase) • Sodium-calcium exchanger (NCX) • Chloride-bicarbonate exchanger (AE1) Symport: • Sodium-glucose symporter (SGLT) • Sodium-amino acid symporter • Proton-sucrose symporter Uniport: • Glucose transporter (GLUT1, GLUT4) • Calcium pump (PMCA) • Chloride channel (CFTR) Let me know if you’d like further details!

Answer 19

Answer is the one with medium chain fatty acids. The answer is secondary active transport. Glucose absorption into enterocytes (intestinal cells): It happens in two steps: 1. Apical (lumen-facing) membrane: • Glucose enters via the SGLT-1 transporter. • This is a secondary active transport mechanism — it uses the Na⁺ gradient created by the Na⁺/K⁺ ATPase pump. • ATP is not used directly here. 2. Basolateral (blood-facing) membrane: • Glucose exits the cell into the blood via GLUT2, by facilitated diffusion. So what’s the correct classification for glucose transport into enterocytes? Answer: Secondary active transport Because: • The Na⁺/K⁺ pump (a primary active transport mechanism) maintains a low intracellular Na⁺ concentration. • The SGLT-1 then uses that Na⁺ gradient to pull glucose in against its concentration gradient. So if the question is asking how glucose gets into the cell from the lumen, the answer is: C. Secondary active transport (Not primary — because ATP is used indirectly) Summary: • Na⁺/K⁺ ATPase = Primary active transport • SGLT-1 glucose uptake = Secondary active transport • GLUT2 glucose exit = Facilitated diffusion

Lecture 2 Flashcards

(44 cards)