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What is the primary function of biological membranes?

  • Act as barriers that define the cell's internal environment (correct)
  • Produce cellular waste products
  • Facilitate energy production in cells
  • Serve as a site for protein synthesis

Which of the following statements about phospholipids is true?

  • They are entirely hydrophobic.
  • They are only found in prokaryotic cells.
  • They contain both fatty acid tails and hydrophilic heads. (correct)
  • They have identical structures that vary only in fatty acid chain length.

What role do proteins embedded in the membrane primarily serve?

  • To compose the majority of membrane structure
  • To create energy through ATP synthesis
  • To function solely as enzymes for chemical reactions
  • To stabilize the membrane's structure and facilitate molecular attachment (correct)

What characterizes the selective permeability of cellular membranes?

<p>They permit selective import and export of specific molecules. (A)</p> Signup and view all the answers

In what way do lipids contribute to biological membranes?

<p>They form the hydrophobic component necessary for membrane integrity. (A)</p> Signup and view all the answers

What is the significance of the fatty acid tail in phospholipids?

<p>It contributes to the fluidity of the membrane bilayer. (A)</p> Signup and view all the answers

What type of transport requires energy in biological membranes?

<p>Active transport (A)</p> Signup and view all the answers

How do carbohydrates, such as glycans, contribute to membrane function?

<p>They are involved in cell recognition and signaling. (A)</p> Signup and view all the answers

What is the main role of pancreatic acinar cells in the digestive system?

<p>They secrete pancreatic digestive enzymes into the GI tract. (B)</p> Signup and view all the answers

What mechanism allows for the direct passage of ions and small molecules between two cells?

<p>Gap junctions (A)</p> Signup and view all the answers

Which type of extracellular signaling involves a cell releasing a signaling molecule that only affects itself?

<p>Autocrine (B)</p> Signup and view all the answers

What is the correct sequence of processes involved in cell signaling?

<p>Reception, Transduction, Response (D)</p> Signup and view all the answers

Which class of signaling molecules primarily uses intracellular receptors for signal transduction?

<p>Lipophilic molecules (A)</p> Signup and view all the answers

Which type of signaling would likely have a slower effect on target cells but act over a longer distance?

<p>Endocrine signaling (B)</p> Signup and view all the answers

What is primarily responsible for the rapid onset of effects in modified responses?

<p>Class of the signaling molecule (C)</p> Signup and view all the answers

Which mechanism is primarily associated with local diffusion of chemical messengers?

<p>Paracrine signaling (D)</p> Signup and view all the answers

Which factor causes an increase in the diffusion coefficient D according to the stokes-Einstein equation?

<p>Increase in temperature (A)</p> Signup and view all the answers

What effect does increasing the viscosity of the diffusion medium have on the rate of diffusion?

<p>It decreases the rate of diffusion (D)</p> Signup and view all the answers

According to Fick's First Law, what happens to the rate of diffusion (J) if the area (A) across which diffusion is occurring increases?

<p>J increases (B)</p> Signup and view all the answers

Which condition is NOT a consideration when diffusing across lipid membrane barriers?

<p>pH of solution (C)</p> Signup and view all the answers

Which of the following correctly describes osmosis?

<p>The diffusion of water down its concentration gradient. (D)</p> Signup and view all the answers

What is the result when osmotic pressure and hydrostatic pressure are at equilibrium?

<p>Water movement ceases. (C)</p> Signup and view all the answers

Which of the following has a direct impact on the rate of net diffusion across the plasma membrane?

<p>Concentration of solute (B)</p> Signup and view all the answers

What does a larger molecular weight imply about the rate of net diffusion (Q)?

<p>Q decreases (B)</p> Signup and view all the answers

What is the primary function of ligand-gated ion channels?

<p>Changing membrane potential in milliseconds (C)</p> Signup and view all the answers

Which of the following is NOT a class of downstream effects mentioned?

<p>Hormonal regulation (A)</p> Signup and view all the answers

What type of receptor is involved in gene transcription and takes hours to exhibit cellular effects?

<p>Nuclear receptors (A)</p> Signup and view all the answers

Which receptor type directly phosphorylates tyrosine amino acids upon ligand binding?

<p>Enzyme-linked receptors (D)</p> Signup and view all the answers

How does a Ca2+ conducting channel primarily affect a cell?

<p>By acting as a second messenger (C)</p> Signup and view all the answers

Which protein is likely affected by enzyme-linked receptors like insulin receptors?

<p>Growth factor proteins (D)</p> Signup and view all the answers

What happens to a neuron's likelihood to fire an action potential when Cl- channels are activated?

<p>Decreases due to hyperpolarization (B)</p> Signup and view all the answers

What is the time frame for transcriptional changes in response to receptor activation?

<p>Hours (D)</p> Signup and view all the answers

What type of bond is formed between the ammonium group and the acid group in proteins?

<p>Ionic bond (C)</p> Signup and view all the answers

Which functional group undergoes oxidation to form disulphide bonds in proteins?

<p>-SH groups (B)</p> Signup and view all the answers

Which of the following describes the structure of fibrous proteins?

<p>Trimer of alpha helical polypeptide chains (D)</p> Signup and view all the answers

What is the main function of haemoglobin in the body?

<p>Carries oxygen (B)</p> Signup and view all the answers

What is meant by activation energy in chemical reactions?

<p>The minimum energy required to initiate a reaction (A)</p> Signup and view all the answers

What is the primary role of enzymes in metabolic pathways?

<p>To lower the activation energy for reactions (B)</p> Signup and view all the answers

What is the significance of maintaining a human body temperature of 37 degrees?

<p>To ensure enzymes function optimally (B)</p> Signup and view all the answers

Which technique is used to determine the three-dimensional structure of proteins?

<p>X-ray Crystallography (D)</p> Signup and view all the answers

What is the primary function of the enzyme fumarase in the citric acid cycle (CAC)?

<p>To add H2O to fumarate forming malate (D)</p> Signup and view all the answers

Which product is generated from one cycle of the citric acid cycle per Acetyl CoA input?

<p>3 NADH, 1 FADH2, and 1 GTP (C)</p> Signup and view all the answers

What is the fate of NADH and FADH2 produced in the citric acid cycle?

<p>They move to the electron transport chain to generate ATP (B)</p> Signup and view all the answers

What is the role of oxidative phosphorylation in ATP production?

<p>It couples oxidation of carbon fuels to ATP synthesis (B)</p> Signup and view all the answers

How many ATP does each NADH and FADH2 generate during oxidative phosphorylation?

<p>2.5 ATP from each NADH and 1.5 ATP from each FADH2 (C)</p> Signup and view all the answers

What occurs during the electron transport chain (ETC)?

<p>Electrons flow through protein complexes, pumping protons across the membrane (D)</p> Signup and view all the answers

What is the significance of creating a proton gradient in oxidative phosphorylation?

<p>It creates electrical potential for ATP synthesis (A)</p> Signup and view all the answers

Which of the following statements about ATP requirements is accurate?

<p>The body reserves are insufficient for daily ATP needs (D)</p> Signup and view all the answers

Flashcards

Biological Membrane Function

Biological membranes are selectively permeable barriers and gatekeepers that regulate transport of molecules in and out of cells and organelles, and facilitate signal transmission and energy transfer.

Membrane Structure

Membranes are made of a phospholipid bilayer with embedded proteins and other lipids, and carbohydrates on the outer surface.

Phospholipid Structure

Phospholipids have a hydrophilic (water-loving) head and hydrophobic (water-fearing) tail.

Selective Permeability

Membranes allow some molecules to pass through while blocking others.

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Membrane Proteins

Membrane proteins facilitate transport, signaling, and support the membrane's structure.

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Lipid Bilayer

Two layers of lipids forming the fundamental structure of biological membranes.

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Cytoplasmic Face

The inner side of membrane facing the inside of a cell.

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Exoplasmic Face

The outer side of membrane facing the outside environment or the inside of an organelle.

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Diffusion factors

Factors that influence how quickly molecules move from one place to another through diffusion.

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Diffusion Coefficient (D)

A measurement of how fast molecules diffuse. Higher D means faster diffusion.

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Fick's First Law

Describes how fast substances move across a barrier, such as a membrane.

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Membrane permeability (P)

How easily molecules pass through a membrane. A higher P means easier movement.

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Osmosis

The diffusion of water across a membrane, from a higher to a lower water concentration.

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Cell volume regulation

Maintaining a constant cell size; balancing water and pressure inside the cell.

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Simple vs complex molecule gradients

Both play essential roles in biology, like gas exchange and hormone effects.

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Diffusion across lipid bi-layer

Hydrophobic molecules pass easily, while hydrophilic or charged ones need help like channels or pores.

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Citric Acid Cycle (CAC)

A series of enzymatic reactions that oxidize acetyl-CoA, generating electron carriers (NADH and FADH2), and producing ATP. It's a central metabolic pathway that links carbohydrate, fat, and protein metabolism.

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CAC Input

The CAC starts with acetyl-CoA, a 2-carbon molecule derived from the breakdown of carbohydrates, fats, and proteins.

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CAC Output

The CAC produces 2 molecules of CO2, 3 NADH, 1 FADH2, and 1 ATP (or GTP) per acetyl-CoA.

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Role of NADH and FADH2

NADH and FADH2 are electron carriers produced in the CAC. They transfer electrons to the electron transport chain (ETC) to generate ATP.

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Electron Transport Chain (ETC)

A series of protein complexes embedded in the mitochondrial membrane that use the energy from electrons transferred by NADH and FADH2 to pump protons across the membrane, generating a proton gradient.

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Oxidative Phosphorylation

The process of ATP synthesis powered by the electron transport chain. It uses the proton gradient created by ETC to drive ATP production.

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ATP Production from NADH & FADH2

Each NADH molecule generates 2.5 ATP molecules, while each FADH2 molecule generates 1.5 ATP molecules.

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Regulated Exocytosis

A process where cells release specific substances outside the cell in response to signals. The release is controlled and occurs in bursts.

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ATP Recycling

Our bodies recycle ATP constantly because our daily ATP needs far exceed our reserves. ADP is converted back to ATP 300 times per day per molecule.

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Pancreatic Acinar Cells

Specialized cells in the pancreas that produce and release digestive enzymes into the small intestine.

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VIP and Secretin

Hormones that stimulate the release of pancreatic enzymes by increasing cAMP levels in acinar cells.

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GRP and Ach

Neurotransmitters that trigger the release of pancreatic enzymes by increasing calcium levels in acinar cells.

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Gap Junctions

Direct channels between neighboring cells that allow the passage of ions and small molecules.

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Cell-Surface Markers

Specific molecules on the cell surface that enable cells to recognize and interact with each other.

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Extracellular Chemical Messengers

Molecules released by cells to communicate with other cells, acting locally or at a distance.

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Signal Transduction Pathway

A series of molecular events initiated by a signal that ultimately leads to a cellular response.

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Ionic Interactions in Proteins

Attractive forces between oppositely charged amino acid side chains, like a positive ammonium group and a negative acid group, contribute to protein structure.

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Disulfide Bridge

A strong covalent bond formed between two cysteine amino acids in a protein, holding different protein chains or loops within a single chain together.

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Collagen: Fibrous Protein

Collagen is a fibrous protein made of three alpha-helical polypeptide chains twisted together, forming a rigid structure resistant to stretching. It's found in connective tissues like skin, bones, tendons, and ligaments.

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Hemoglobin: Globular Protein

Hemoglobin is a globular protein composed of four polypeptide chains, primarily alpha-helical, forming a round shape. It binds and transports oxygen throughout the body.

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Quaternary Structure

The overall three-dimensional arrangement of multiple polypeptide subunits (chains) in a protein. It can be fibrous, like collagen, or globular, like hemoglobin.

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X-ray Crystallography

A technique used to determine the three-dimensional structure of a protein by analyzing how X-rays diffract when they pass through a crystal of the protein.

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Metabolism Defined

The sum of all chemical reactions happening in cells, driven by enzymes. It's a complex network of reactions involving the breaking and forming of chemical bonds.

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Metabolic Pathways

A series of connected chemical reactions, each catalyzed by a specific enzyme, starting with a specific molecule and producing a desired product.

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Signal Transduction: Why is it Important?

Signal transduction is the process by which cells receive and respond to external signals, allowing them to adapt to changes in their environment and maintain normal function.

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Types of Signal Transduction

There are four main types: 1. Direct contact, 2. Paracrine, 3. Endocrine and 4. Synaptic.

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What are Receptor Proteins?

Receptor proteins are specialized molecules on the cell surface or inside the cell that bind to specific signaling molecules.

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What are Downstream Effects?

Downstream effects are the changes that occur inside a cell as a result of a signal being received and processed. These changes include altered gene expression, protein synthesis, and cellular activity.

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Ligand-Gated Ion Channels

These channels open or close in response to the binding of a specific signaling molecule, allowing ions to flow across the cell membrane, changing the membrane potential.

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G-Protein Coupled Receptors (GPCRs)

These receptors activate a signaling pathway involving G proteins, which can lead to changes in cellular activity, such as the release of calcium or the activation of enzymes.

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Kinase-Linked Receptors

These receptors activate enzymes called kinases, which add phosphate groups to proteins, leading to a change in their activity.

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Nuclear Receptors

These receptors located inside the nucleus bind to signaling molecules that can pass through the cell membrane, leading to changes in gene expression.

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