Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Molecular
Unit 3 Exam
| Term | Definition |
|---|---|
| What are the functions of cell membranes? | Act as selective barriers, controlling what enters and exits the cell. |
| What are the vital functions of cell membranes? | channels and transporters, flexibility, signaling, separation, and organization. |
| Transport (cell membrane) | channels and transporters for molecule movement. |
| Flexibility(cell membrane) | allows cell growth, shape change, and movement. |
| Signaling (cell membrane) | receptor proteins detect environmental signals. |
| Separation (cell membrane) | isolates internal and external aqueous environments. |
| Organization (cell membrane) | forms a 2D layer for component movement. |
| plasma membrane | Separates the cell from the outside environment, maintaining unique composition |
| Eukaryotic cells | Have internal membranes that form organelle compartments. |
| What are the components of cell membranes? | Main structure is lipid bilayer. The main molecular components are Lipids (phospholipids, cholesterol, glycolipids), Proteins (perform functions; ~50% of mass in animal membranes), and Carbohydrates (attached to lipids/proteins) |
| What are the different components of a phospholipid? hydrophilic head and a hydrophobic tail | Phosphatidylcholine, a common phospholipid, has five parts |
| What makes them able to form membranes? | amphipathic nature. allows the lipids to self-assemble into bilayers. |
| Amphipathic | Possessing both hydrophilic and hydrophobic parts; both water-loving and water-fearing parts. |
| Hydrophilic | molecules attract water, dissolves in water; forms Hydrogen-bonds or electrostatic interactions. |
| Hydrophobic | molecules repel water |
| What makes membranes fluid? | crucial. The lipid bilayer is a flexible 2D fluid, and membrane lipids move around within the bilayer. |
| How can they be more or less fluid? | temperature and the type of hydrocarbon tails present, specifically their length and number of double bonds. Bacteria and yeast adjust the length and saturation of their tails to adapt to varying temperatures. |
| What do Shorter chains in membrane fluid do | increase fluidity b/c less van der Waals attractions. |
| What do Unsaturated tails in membrane fluid do | (those with double bonds) increase fluidity by preventing tight packing. |
| What does Cholesterol do in membrane fluid? | modulates the fluidity of animal membranes filling the space between neighboring phospholipids. |
| What happens to membranes in the ER? | Membrane assembly. Phospholipids made by enzymes on the cytosolic side → scramblase evens phospholipid distribution. |
| What does scramblase do? | Scramblase |
| What happens to membranes in the Golgi? | Establishes membrane asymmetry. |
| What does flippase do? | uses ATP hydrolysis to move specific phospholipids from one side to the other |
| Why are membranes asymmetric? | phospholipids and glycolipids are distributed unevenly(plasma membrane) which gives membranes distinct properties(inside and outside). Orientation is maintained during vesicle transport via vesicle budding and fusing. |
| What are the functions of membrane proteins? | Act as channels, transporters, receptors — specialized for each cell type |
| How can proteins be associated with the lipid bilayer? | A polypeptide chain can cross the lipid bilayer as an alpha-helix, a beta-barrel ( beta-sheets rolled into cylinders) |
| Why do polypeptide chains fold into alpha helices and beta sheets? | The backbone of a polypeptide chain polar → form internal H-bonds (α-helix/β-sheet) in hydrophobic environment. |
| How do amino acids contribute to protein folding? | hydrophobic side chains |
| How does folding help membrane proteins cross the lipid bilayer? | Internal bonding protects the hydrophilic backbone to safely cross the hydrophobic core of the lipid bilayer.of the bilayer. |
| How can we study proteins away from the lipid bilayer? | Detergents are used to disrupt the hydrophobic associations of the lipid bilayer. Detergents are small, Amphipathic with one hydrophobic tail. Used to purify proteins and reconstitute them in vesicles. |
| SDS (Sodium dodecyl sulfate) | is a strong ionic detergent with a charged hydrophilic end |
| Triton X-100 | is a nonionic detergent with a polar hydrophilic end. Triton X-100 is often the best choice for studying a membrane protein away from its typical cellular environment. |
| What is the cell cortex? | Network of filaments under the membrane that supports and shapes the plasma membrane |
| What forms the cortex in red blood cells? | Spectrin forms a lattice linked to transmembrane proteins. Defects → anemia. |
| How can mobility of membrane proteins be restricted? | being tethered to the cortex. being tethered to extracellular matrix molecules or blocked by diffusion barriers. |
| What is on the surface of cells that helps protect them and give cell recognition? | carbohydrates; form a sugar coating called the glycocalyx outside the membrane. |
| glycocalyx | functions to protect the cell surface, helps with motility, and aids in cell recognition and adhesion. |
| How do rolling leukocytes work? | Leukocytes (specifically neutrophils) rely on cell-surface carbohydrate recognition to move to infection sites |
| Lectin | on the blood vessel wall; recognize the carbohydrates on the neutrophils, allowing the neutrophils to slow down, leave the bloodstream, and travel to infected tissue. |
| What is FRAP? | Fluorescence Recovery After Photobleaching measures lateral diffusion of membrane proteins |
| What is SPT? | Single-particle tracking. SPT is often employed because tracking individual molecules is impossible using FRAP. |
| How does SPT work? | tagging protein molecules with antibody-coated gold nanoparticles that can then be tracked using video microscopy. This technique reveals that membrane proteins can exhibit a variety of movement patterns. |
| What properties allow molecules to travel across membranes at different rates? | Pure lipid bilayers block most water-soluble molecules except CO₂, O₂, and H₂O. Small, hydrophobic molecules diffuse fastest. Most needed solutes are polar and need transport proteins to cross. |
| What is a channel? | - transmembrane protein that forms a pore in the membrane. - ion-selective and gated, based on size and electric charge, letting specific ions diffuse rapidly (millions per second) down their electrochemical gradient when open—no shape change needed. |
| What is a transporter? | A transporter is a membrane transport protein that transfers molecules or ions that fit into specific binding sites on the protein. It binds a solute, changes shape, and moves it across the membrane. Transporters can perform passive or active transport. |
| What is the concentration of Na+, K+, and Ca2+ inside the cell compared to outside of the cell? | Na+ is pumped out of the cell by the Na+ - K+ pump while K+is pumped into the cell. Ca+ is kept at a low concentration in the cytosol via ATP-driven Ca2+ pumps in the plasma membrane and ER. |
| Passive transport | Spontaneous solute movement down its gradient via a transport protein; no energy needed. |
| Active transport | Moves solute against its gradient; requires energy input. |
| How do concentration gradient and membrane potential influence the movement of ions across membranes? | Ions move according to their electrochemical gradient which is concentration gradient + membrane potential. |
| Membrane potential | voltage across the membrane from charge imbalance in plasma membrane. At rest, the inside is negative, pulling positive ions in and pushing negative ions out. Uncharged molecules flow only from high → low concentration. |
| How does water move across membranes? | Water is small and uncharged, so it diffuses slowly, or faster through aquaporins channels. Moves by osmosis — from low solute to high solute concentration. |
| Aquaporins | facilitate the transport of water across cell membranes. |
| Osmosis | - from low solute to high solute concentration. - Swelling can occur if cell's total solute concentration passes external concentration. |
| How do cells cope with osmotic swelling? | Protozoans use contractile vacuoles to expel water Animal use transmembrane pumps to remove solutes that draw in water. Plants use cell walls to create turgor(osmotic) pressure (prevents wilting). |
| How does the Na+, K+ pump work? | ATP-driven pump using ~30% of cell ATP (crucial in animals) .Uses ATP hydrolysis to pump Na⁺ out and K⁺ in in a repeating 10 ms cycle. |
| How does the Ca2+ pump work? | ATP-driven pump in plasma membrane and ER keeps cytosolic Ca²⁺ low. Similar to Na⁺ pump but only moves Ca²⁺, no second ion or binding needed. |
| How can the movement of solutes be coupled? | Gradient-driven pumps use stored ion energy (like Na⁺ or K⁺ gradients) to move other solutes against their gradient. These pumps are categorized as symports, antiports, or uniports. |
| Symport (solute movement) | both solutes move in the same direction. |
| Antiport(solute movement) | move opposite directions. |
| Uniport(solute movement) | single solute movement. |
| How does the glucose Na+ pump work? | symport, found in animal cells, uses Na⁺’s high outside concentration gradient to drive glucose uptake. This is an example of a gradient-driven pump using one solute’s gradient to power another’s transport. |
| How do ion channels work? | Transmembrane pores allowing specific ions to diffuse down their electrochemical gradients. They are gated, switching between open and closed. |
| How do selectivity filters work? | Filters determine which ions pass, based on size and charge, at the narrowest point of the channel. |
| Why are K+ leak channels important? | They set the resting membrane potential in animal cells. These channels randomly flicker between open and closed states. K⁺ randomly leaks out, balancing charge and stabilizing internal K⁺ levels which establishes equilibrium |
| What stimuli can influence ion channels to open and close? | Voltage gated, mechanically gated, and transmitter gated. Ion channels are gated, meaning a specific stimulus triggers them to switch between open and closed states. |
| Voltage-gated ion channels | respond to changes in membrane potential (when potential exceeds a threshold, electrical forces cause the channel to open), |
| Mechanically-gated ion channel | , which are pulled open by physical forces (like sound vibrations allowing ions to flow into hair cells). |
| Transmitter-gated ion channels | (ligand-gated channel) on the postsynaptic neuron that open upon binding a neurotransmitter. This changes ion flow, turning the chemical signal back into an electrical one. |
| Excitatory receptors (transmitter channels) | open cation (Na⁺) channels → depolarization. |
| Inhibitory receptors(transmitter channels) | open Cl⁻ channels → harder to depolarize. |
| How do neurons transmit signals? | Neurons are electrically excitable cells that integrate and transmit information through the nervous system. They consist of a cell body, dendrites (receiving signals), and an axon (conducting electrical signals away from the body). |
| What is an action potential? | a traveling wave of electrical excitation that extends the length of the neuron, preventing signals from fading over long distances. - triggered when a stimulus depolarizes the membrane to a threshold value. |
| What happens at synapses? | At synapses, electrical signals convert to chemical ones. |
| How does action potential get down the axon and to the next neuron? | - Voltage-gated Na⁺ channels open → Na⁺ enters → depolarization (+40) - Then Na⁺ channels inactivate, K⁺ channels open → K⁺ exits → repolarization. This wave propagates down the axon, carrying the signal forward. |
| How does a signal go from the presynaptic neuron to the postsynaptic neuron? | - Then Action potential opens voltage-gated Ca²⁺ channels in the presynaptic terminal → Ca²⁺ enters → causes synaptic vesicle fusion → neurotransmitters released into cleft → bind to receptors on postsynaptic cell. |
| Why do our cells break down sugar in a stepwise manner? | carriers can actually capture that energy to do work for the cell. |
| What are catabolic pathways? | Catabolism is a set of enzyme-catalyzed reactions by which complex molecules are broken down into simpler ones. The intermediate molecules formed during this breakdown are called catabolites. |
| What are the steps of glycolysis and the enzymes that catalyze those steps? | Glycolysis has 10 enzyme-catalyzed reactions, each forming a new sugar intermediate. It breaks one 6-carbon, sugar, glucose into two pyruvate molecules. |
| What steps of glycolysis consume energy? | Steps 1 and 3 use 2 ATP total — both are irreversible. |
| What steps of glycolysis release energy? | Steps 7 and 10 generate 4 ATP total due to ATP HYDROLYSIS. Energy is released because pyruvate has electrons at a lower energy level than glucose. |
| Where is NADH made in glycolysis? | In Step 6, where oxidation of G3P forms 1,3-bisphosphoglycerate, transferring 2 electrons to make NADH. energy is stored in the electrons of NADH |
| Where does Glycolysis occur? | in the cytosol of most cells. It does not require molecular oxygen. |
| What are the products of glycolysis? | From 1 glucose, glycolysis makes 2 pyruvate, 2 ATP (net), and 2 NADH. |
| How are anaerobic respiration and fermentation different than aerobic respiration? | Fermentation breaks down organic molecules without oxygen. It happens after glycolysis in anaerobic organisms, converting pyruvate into excreted products (like in muscle or yeast). |
| Anaerobic respiration (used by bacteria and archaea) | uses non-oxygen molecules as final electron acceptors. Aerobic respiration requires oxygen. |
| How does phosphate bond energy influence hydrolysis of those phosphates? | A phosphate transfer is energetically favorable when the donor molecule’s ΔG° of hydrolysis is more negative than the acceptor’s. Different glycolysis intermediates have different phosphate bond energies. |
| What links glycolysis to the citric acid cycle? | Pyruvate from glycolysis is pumped into the mitochondrial matrix, where the pyruvate dehydrogenase complex converts it to acetyl CoA. Acetyl CoA then enters the citric acid cycle. |
| What are the steps of the citric acid cycle and the enzymes that catalyze those steps? | The citric acid cycle (TCA) oxidizes the carbons in acetyl CoA through a series of reactions. (The sources do not list the specific names of the steps or the enzymes that catalyze them). |
| Where does the citric acid cycle occur in the cell? | It occurs in the mitochondrial matrix of eukaryotic cells. |
| What are the products of the citric acid cycle? | For each acetyl group, it produces 3 NADH, 1 FADH₂, and 1 GTP, while releasing CO₂. Released energy is stored in activated carriers (NADH, FADH₂, GTP). The acetyl CoA carbons are oxidized to CO. |
| What is a kinase? | Adds a phosphate group to a molecule (usually from ATP). → Think: “Kinase Kicks on a phosphate.” |
| Phosphatase? | Removes a phosphate group from a molecule. → Think: “Phosphatase Pulls off a phosphate.” |
| Isomerase? | Rearranges atoms within a molecule to form an isomer (same formula, different structure). → Think: “Isomerase = rearrange.” |
| Mutase? | Moves a functional group (like phosphate) from one position to another within the same molecule. → Think: “Mutase Moves within.” |
| How can food sources other than carbohydrates drive metabolic processes in the cell? | Fatty acids derived from fats are converted to acetyl CoA in the mitochondrial matrix. Some amino acids are also transported to the mitochondrial matrix to be turned into acetyl CoA or another intermediate of the citric acid cycle. |
| Where does the electron transport chain happen? | inner mitochondrial membrane (or the membrane of aerobic bacteria). |
| How do cells regulate metabolism? | by a network of control mechanisms to control competing pathways using the same substrates (like pyruvate). Regulation occurs through phosphorylation or regulatory molecule binding to enzyme |
| What is Feedback regulation in metabolism? | happens when metabolites bind to enzymes to adjust their activity. |
| What is the structure of the mitochondria? | They have an outer membrane (OMM) and an inner membrane (IMM), creating two spaces |
| What are the functions of the mitochondria? | They produce most ATP by oxidative phosphorylation (OXPHOS) in the IMM. They also help regulate apoptosis and make key metabolites for cell survival and growth. |
| What is the citric acid cycle/TCA/Krebs Cycle? | series of reactions that occur in the mitochondrial matrix of eukaryotic cells that oxidize acetyl groups from acetyl CoA. The carbons in acetyl CoA are transferred to other molecules and oxidized indirectly. The released energy makes activated carriers. |
| What are the products of the citric acid/krebs cycle? | The oxidation energy released is used to produce activated carriers |
| What are the complexes of the mitochondria? | There are 3 main respiratory enzyme complexes in the IMM |
| What to they accept electrons from and donate them to? | They accept high energy electrons from NADH and FADH₂ and pass them step-by-step to oxygen (O₂), the final electron acceptor. |
| How does the amount of ATP produced depend upon where electrons enter the ETC? | |
| What are redox reactions? | Each electron transfer in the ETC is an oxidation-reduction reaction, or redox reaction. |
| What does reduced mean? | The molecule receiving an electron is reduced. |
| Oxidizing agent? | The reciever |
| What is the reducing agent? | The donor |
| Oxidized? | The molecule donating the electron becomes oxidized. |
| How do metals influence electron carriers? | All 3 respiratory complexes contain tightly bounded metal ions. Electrons bounce between these metal centers. Different metals have different redox potentials, which determine their position in the chain. |
| What happens to redox potential as you go along the ETC? | Redox potentials increase along the ETC. Cytochrome c oxidase is the final electron carrier and has the highest redox potential. Redox potential (ΔE°) shows how strongly a molecule wants to gain electrons. |
| Where does photosynthesis take place? | driven by the eukaryotic organelle called the chloroplast. The main site is the leaf Chloroplasts found mainly in the cells of the mesophyll (the interior leaf tissue). The process involves thylakoids inside the chloroplast, which hold chlorophyll. |
| What are the two stages of photosynthesis? | the light reactions (photo) and the Calvin cycle (synthesis). |
| How does the electromagnetic spectrum influence photosynthesis? | The electromagnetic spectrum is the range of possible frequencies of radiation |
| What are the pigments found in chloroplast? | Chlorophyll a, Chlorophyll b, and Cartenoids |
| Chlorophyll a | main light-capturing pigment in all light reactions |
| Chlorophyll b | accessory pigment. |
| Carotenoids | absorb violet/blue-green light, reflect yellow/orange, and protect by absorbing excess energy (photoprotection) |
| What is a photosystem? | A photosystem is a complex of chlorophyll, proteins, and other molecules. It has a reaction-center complex surrounded by light-harvesting complexes. |
| light-harvesting complex | consists of various pigment molecules bound to proteins. Light-harvesting complexes absorb light and transfer energy to special chlorophyll a molecules in the reaction center |
| reaction-center complex | is an organized association of proteins holding specific chlorophyll a molecules that undergo oxidation upon excitation. |
| How do electrons flow in the light reactions? | electrons are provided by chlorophyll which captures energy from sunlight. |
| What is the Calvin cycle? | The Calvin cycle is the synthesis stage of photosynthesis. The second stage of photosynthesis. It fixes CO₂ into sugar and regenerates RuBP. |
| What are the steps of the Calvin Cycle? | Carbon fixation, reduction, regeneration of RuBP |
| Phase 1 of Calcin Cycle | Carbon Fixation- CO₂ combines with RuBP (5-carbon sugar) via rubisco, forming a 6-carbon intermediate that splits into 2 molecules of 3-phosphoglycerate. |
| Phase 2 of Calvin Cycle | Reduction- Each 3-phosphoglycerate gains a phosphate from ATP, becoming 1,3-bisphosphoglycerate. NADPH reduces it to glyceraldehyde-3-phosphate (G3P). For each CO₂, 2 G3P are made. |
| Phase 3 of Calcin Cycle | Regeneration of RuBP |
| What are alternative methods of carbon fixation plants can do? | C₄ Pathway and CAM Pathway |
| Compare and contrast oxidative phosphorylation and photosynthesis | Both processes use a membrane-based mechanism, utilize ETC that drives protons across a membrane to generate a proton gradient. Both use this proton gradient to drive the synthesis of ATP via ATP synthase. |
| oxidative phosphorylation OXPHOS (mitochondria) | uses electrons from food oxidation, needs oxygen, makes ATP. |
| Photosynthesis (chloroplasts) | uses sunlight from chlorophyll to power electrons, makes sugars from CO₂ and H₂O. |
| CAM Pathway (Crassulacean Acid Metabolism) | CAM plants also conserve water but separate the calvin cycles by time, not space AT NIGHT |
| C4 Pathway | adapts its carbon fixation method for arid weather to conserve water but physically separates the light and Calvin cycles of photosynthesis. This reduces photorespiration |
| C₃ Pathway (Calvin Cycle): | The most common pathway. Efficient in cool, moist climates, but in hot, dry weather, rubisco can bind O₂ instead of CO₂, causing photorespiration, which wastes energy and carbon. They don’t separate the light reactions |
| Whats Plastoquinone ? | In photosynthesis, plastoquinone (PQ) is the electron carrier that transfers electrons from Photosystem II (PSII) to the cytochrome b₆-f complex. |
| Coenzyme Q (Ubiquinone) | carries electrons from Complex I and Complex II to Complex III. |
| Cytochrome c | Cytochrome c then transfers electrons from Complex III to Complex IV, after Coenzyme Q |
Created by:
jordinii