Biology Chapter 5: Cell Signaling and Diffusion
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Questions and Answers

What role does the G protein play in the signaling process described?

  • It binds to adenylate cyclase. (correct)
  • It activates cytoplasmic enzymes directly.
  • It converts ATP to cAMP.
  • It amplifies the metabolic effects in the cell.

What is the result of adenylate cyclase activity?

  • Inactivation of kinases.
  • Synthesis of guanosine triphosphate (GTP).
  • Conversion of ATP to cyclic AMP (cAMP). (correct)
  • Direct activation of cytoplasmic enzymes.

What is the primary function of cAMP in the signaling pathway?

  • To inhibit enzyme activity.
  • To synthesize GTP.
  • To directly bind to receptors.
  • To activate kinases. (correct)

Which statement best describes the consequence of activating kinases in the cell?

<p>They can activate some enzymes while deactivating others. (A)</p> Signup and view all the answers

What happens to ATP in the signaling pathway when adenylate cyclase is activated?

<p>It is converted to cyclic AMP (cAMP). (B)</p> Signup and view all the answers

What defines simple diffusion?

<p>Net movement from high concentration to low concentration (D)</p> Signup and view all the answers

Which factor does NOT affect the rate of diffusion through a membrane?

<p>Color of the substance (B)</p> Signup and view all the answers

In osmosis, water moves from an area of ___ concentration to an area of ___ concentration.

<p>Higher; lower (D)</p> Signup and view all the answers

What role do solute particles play in the process of osmosis?

<p>They draw water from the other side of a membrane (C)</p> Signup and view all the answers

Which of the following statements about diffusion is true?

<p>Diffusion continues until equilibrium is reached (B)</p> Signup and view all the answers

What energy source does a primary active transport carrier protein use?

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

How many sodium ions are expelled from the cell per cycle of the sodium-potassium pump?

<p>3 (C)</p> Signup and view all the answers

What effect does the sodium-potassium pump have on K+ and Na+ concentrations within the cell?

<p>Higher K+ and lower Na+ (D)</p> Signup and view all the answers

What is one of the main functions of the sodium-potassium pump?

<p>Maintaining a negatively charged resting membrane potential (D)</p> Signup and view all the answers

Which transporter relies on the sodium-potassium pump for its operation?

<p>Sodium-glucose transporter (SGLT) (A)</p> Signup and view all the answers

What type of transport is characterized by the movement of solutes through a carrier without direct use of ATP?

<p>Secondary active transport (B)</p> Signup and view all the answers

What does the sodium-glucose transporter (SGLT) primarily transport into the cell?

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

How much of the daily calories are utilized for the activity of the sodium-potassium pump?

<p>50% (C)</p> Signup and view all the answers

Which of the following cell shapes is characterized as being thin and flat?

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

What is the main conclusion of Louis Pasteur's work regarding cell theory?

<p>Cells arise only from other cells. (D)</p> Signup and view all the answers

Which type of cell is most likely to be described as round to oval?

<p>Spheroid to ovoid (D)</p> Signup and view all the answers

In the study of cytology, who is credited with coining the term 'cellulae'?

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

What is the typical size range for most cells mentioned?

<p>10-15 μm (A)</p> Signup and view all the answers

Which cell shape is characterized as thread-like?

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

What is the role of aquaporins in osmosis?

<p>They enhance the diffusion of water across membranes. (B)</p> Signup and view all the answers

Which of the following groups of cells is NOT part of the cell theory's principles?

<p>Cells contain properties that differ from those of biological molecules. (A)</p> Signup and view all the answers

Which type of cell has an irregularly angular shape with multiple sides?

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

What happens to a cell in a hypotonic solution?

<p>The cell absorbs water and swells. (C)</p> Signup and view all the answers

How does the osmolarity of 1 M NaCl compare to that of 1 M glucose?

<p>1 M NaCl has a higher osmolarity. (B)</p> Signup and view all the answers

What is the defining structure for contractile vacuoles in Paramecium?

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

What is osmotic pressure?

<p>The pressure needed to stop water diffusion. (B)</p> Signup and view all the answers

Which cell type is typically taller than it is wide?

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

What is indicated by a hypertonic solution concerning cell behavior?

<p>Cells will lose water and crenate. (A)</p> Signup and view all the answers

What characterizes an isotonic solution?

<p>Equal concentration of nonpermeating solutes as the cell cytoplasm. (A)</p> Signup and view all the answers

What is the primary factor that determines tonicity?

<p>The concentration of nonpermeating solutes. (C)</p> Signup and view all the answers

What process is reverse osmosis used for?

<p>Purifying water by applying mechanical pressure. (C)</p> Signup and view all the answers

What type of vesicular transport involves the engulfing of large particles by a cell?

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

What is the function of the rough endoplasmic reticulum?

<p>Produces phospholipids and proteins (A)</p> Signup and view all the answers

Which of the following organelles is responsible for intracellular digestion?

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

What is the main purpose of receptor-mediated endocytosis?

<p>Taking in specific molecules that bind to receptors (A)</p> Signup and view all the answers

What are the primary components of the cytoskeleton?

<p>Microtubules, microfilaments, and intermediate fibers (B)</p> Signup and view all the answers

Which organelle is known as the 'powerhouse of the cell'?

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

What do peroxisomes primarily utilize molecular oxygen for?

<p>Oxidizing organic molecules (D)</p> Signup and view all the answers

What role do motor proteins dynein and kinesin serve in exocytosis?

<p>Transporting vesicles to the plasma membrane (B)</p> Signup and view all the answers

Which structure forms the basis of the cytosolic network for the organization of cell contents?

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

Which of the following best describes transcytosis?

<p>Movement of materials into and out of the same cell (D)</p> Signup and view all the answers

What is autophagy?

<p>Digesting the cell's surplus organelles (D)</p> Signup and view all the answers

Which vesicular transport mechanism requires specific binding to receptors?

<p>Receptor-mediated endocytosis (B)</p> Signup and view all the answers

What do lysosomes primarily contain to aid in digestion?

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

Flashcards

Cell Theory

A fundamental theory in biology stating that all living organisms are composed of cells, cells are the basic functional unit of life, and new cells arise from pre-existing cells.

Cell Size

Most cells are microscopic, ranging from 10-15 micrometers in diameter, with a large surface area to volume ratio.

Cell Shape

Cells have diverse shapes depending on their function. Some examples include squamous (flat), cuboidal (cube-shaped), columnar (tall and narrow), and stellate (star-shaped).

Squamous Cells

These cells are thin and flat, like scales, and are found in the epidermis of the skin and lining of the oral cavity.

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Cuboidal Cells

These cells are cube-shaped and are found in structures like kidney tubules and thyroid follicles.

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Columnar Cells

These cells are taller than they are wide and are found in the lining of the digestive tract and trachea.

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Polygonal Cells

These cells have irregular, angular shapes with multiple sides and are found in the liver.

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Stellate Cells

These cells have a star-like shape and are found in the brain and spinal cord, forming the nervous system.

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Spheroid Cells

These cells are round or oval and are found in blood cells like neutrophils and lymphocytes.

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Spontaneous Generation

The outdated theory that living organisms can arise from nonliving matter, refuted by Louis Pasteur.

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What are G proteins?

G proteins are small, signaling proteins that transmit signals from receptors on the cell surface to target proteins inside the cell. They act as molecular switches, cycling between an active state bound to GTP and an inactive state bound to GDP.

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What is Adenylate cyclase?

Adenylate cyclase is an enzyme that converts ATP (adenosine triphosphate) into cAMP (cyclic adenosine monophosphate). It is activated by a G protein.

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What is cAMP?

cAMP is a secondary messenger that mediates the effects of many hormones and neurotransmitters. It is produced by adenylate cyclase and acts as a signal that activates various cellular processes.

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What are Kinases?

Kinases are enzymes that transfer a phosphate group from ATP to other molecules (proteins), a process known as phosphorylation. This can activate or deactivate the target molecule, allowing for precise control of cellular activity.

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How does a G protein activate adenylate cyclase?

When a G protein binds to adenylate cyclase, it activates the enzyme to start the conversion of ATP into cAMP. This is an important step in signal transduction pathways.

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Simple Diffusion

The movement of particles from a region of high concentration to a region of low concentration due to random molecular motion.

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Concentration Gradient

The difference in concentration of a substance between two areas.

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Factors Affecting Diffusion Rate

Temperature, molecular weight, steepness of concentration gradient, membrane surface area, and membrane permeability all influence how fast diffusion occurs.

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Osmosis

The net movement of water through a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

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Solute's Role in Osmosis

Solutes that cannot cross the membrane draw water from the area with a higher water concentration.

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Aquaporins

Channel proteins in cell membranes that facilitate the passage of water molecules, enhancing the rate of osmosis.

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Osmotic Pressure

The hydrostatic pressure required to stop the flow of water across a selectively permeable membrane due to osmosis.

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Reverse Osmosis

The process of applying mechanical pressure to overcome osmotic pressure, forcing water to move against its concentration gradient.

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Osmolarity

The total concentration of dissolved particles in a solution, expressed as osmoles per liter of solution.

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Tonicity

The ability of a solution (bath) to affect the volume and pressure of a cell by influencing water movement.

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Hypotonic Solution

A solution that has a lower concentration of nonpermeating solutes than the intracellular fluid (ICF), causing cells to absorb water and swell.

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Hypertonic Solution

A solution that has a higher concentration of nonpermeating solutes than the intracellular fluid (ICF), causing cells to lose water and shrink.

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Primary Active Transport

A type of membrane transport where a carrier protein moves a solute against its concentration gradient using ATP as an energy source.

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Sodium-Potassium Pump

An example of primary active transport where a carrier protein moves three sodium ions out of the cell and two potassium ions into the cell, using ATP as energy.

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Sodium-Potassium Pump Functions

Maintains a steep sodium concentration gradient for secondary active transport, regulates cell volume, maintains membrane potential, and generates heat.

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Secondary Active Transport

A type of membrane transport where a carrier protein uses the energy stored in a concentration gradient to move a solute against its concentration gradient.

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Sodium-Glucose Transporter (SGLT)

An example of secondary active transport where a carrier protein moves glucose into the cell along with sodium, which is moving down its concentration gradient.

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SGLT Function in Kidney Cells

Prevents loss of glucose to urine by reabsorbing glucose from the filtrate.

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Uniport

A type of carrier protein that transports a single type of molecule.

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Antiport

A type of carrier protein that simultaneously transports two different molecules in opposite directions.

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What is vesicular transport?

A process of transporting large particles, fluid droplets, or numerous molecules across the cell membrane using membrane-bound sacs called vesicles.

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What is endocytosis?

A type of vesicular transport that brings material into the cell.

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What is phagocytosis?

A type of endocytosis where the cell engulfs large particles, like bacteria or debris.

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What is pinocytosis?

A type of endocytosis where the cell takes in small droplets of extracellular fluid.

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What is receptor-mediated endocytosis?

A highly specific type of endocytosis where particles bind to receptors on the cell membrane before being brought inside.

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What is exocytosis?

A type of vesicular transport that releases material from the cell.

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What is the cytoskeleton?

A network of protein filaments and cylinders that provides structural support, organizes cell contents, and helps move materials within the cell.

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What are the components of the cytoskeleton?

The cytoskeleton is made up of microfilaments, intermediate filaments, and microtubules.

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What are microfilaments?

Thin, protein filaments made of actin that help form the cell's shape and movement.

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What are intermediate filaments?

Thick, protein filaments made of keratin that provide structural support and resist stress.

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What are microtubules?

Thick, hollow tubes made of tubulin that maintain cell shape, transport organelles, and form cilia and flagella.

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What are organelles?

Specialized structures inside a cell that perform specific functions.

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What is the nucleus?

The largest organelle, containing the cell's genetic material (DNA) and controlling cellular activities.

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What is the endoplasmic reticulum (ER)?

A network of interconnected membranes that synthesize proteins and lipids.

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What are ribosomes?

Small particles that manufacture proteins by translating genetic code from mRNA.

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Study Notes

Cell Structure and Function

  • Cells are the fundamental units of life.
  • Cells exhibit biochemical similarities across species.
  • Cells function as structural and functional units in organisms.

Cell Shapes and Sizes

  • There are approximately 200 different cell types in the human body.
  • Cell shapes vary depending on their locations and function.
  • Cells have a range of sizes; most cells have a diameter of 10-15 micrometers (µm).
  • Cell size is limited by the ratio of volume to surface area. An increase in volume increases more than surface area.

Cell Theory

  • Organisms are composed of cells.
  • Cells originate only from preexisting cells.
  • Cells exhibit similar compositions and metabolic processes.
  • Cell structure and functions are due to the activities of cells.

Microscopes

  • Development of light microscopy allowed for identification of organelles within cells.
  • Transmission electron microscopes (TEM) and scanning electron microscopes (SEM) improved resolution and revealed details about internal structures and surface features.

The Plasma Membrane

  • The plasma membrane defines the boundaries of the cell.
  • It's a selectively permeable barrier.
  • Plasma membranes have intracellular and extracellular faces.
  • The plasma membrane regulates the passage of material into and out of the cell.
  • Made up of a bilipid layer.
  • Contains proteins and cholesterol.

Membrane Lipids

  • Most of the membrane molecules are lipids.
  • Phospholipids make up 75% of the membrane lipids.
  • Phospholipids have hydrophilic heads that face the outside and hydrophobic tails that face the inside of the membrane.
  • Cholesterol molecules are interspersed throughout the phospholipid bilayer, increasing the membrane's solidity.
  • Glycolipids are carbohydrate chains attached to phospholipids.

Membrane Proteins

  • Membrane proteins make up 50% of the membrane by weight.
  • Integral proteins penetrate the membrane completely passing through the membrane.
  • Peripheral proteins do not penetrate the membrane.
  • Integral proteins have hydrophilic regions facing the fluid inside and outside the cell, and hydrophobic regions passing through the lipid layer.
  • Proteins play various roles, including transport, recognition, communication, and binding.

Receptor Protein Function

  • Receptors bind specific chemical messengers.
  • Enzymes catalyze chemical reactions.
  • Channels allow specific substances through the lipid bilayer.
  • Cell identity markers distinguish cells from foreign cells.
  • Cell adhesion molecules enable cells to bind to one another.

Peripheral Proteins

  • Peripheral proteins are bound to one face of the membrane.
  • Receptors bind chemical signals
  • Second messenger systems communicate within the cell
  • Enzymes catalyze reactions of substance digestion and messenger production
  • Channel proteins allow substances to pass through
  • Some are always open.
  • Ligand-gated and voltage-gated channels respond to specific signals.
  • Mechanically-gated channels respond to physical stresses.

Transport

  • Carriers:bind solute and transfer across membrane
  • Uniport:carries one type of solute
  • Symport:carries two or more solutes in the same direction
  • Antiport:carries two or more solutes in opposite directions

Secondary Active Transport

  • Carrier moves solute through membrane indirectly using energy of sodium gradient

Vesicular Transport

  • Transport of large particles, molecules, and fluid into the cell (endocytosis) and out of the cell (exocytosis).
  • Endocytosis: Phagocytosis, Pinocytosis, Receptor-mediated Endocytosis.
  • Exocytosis: Replacement of plasma membrane.

Cytoskeleton

  • Cytoskeleton provides internal framework for cell shape and movement.
  • It is composed of microfilaments, intermediate fibers, and microtubules.
  • Microfilaments: made of actin.
  • Intermediate filaments: give cells their shape.
  • Microtubules: made of tubulin.

Organelles

  • Organelles are the internal structures within a cell performing functions.
  • Membranous organelles contain membranes, such as the nucleus.
  • Nonmembranous organelles do not contain membranes, such a ribosomes.

Nucleus

  • Nucleus: largest organelle- contains DNA (genetic information).
  • Nuclear envelope: double membrane that separates the nucleus from the cytoplasm. Nuclear envelope has nuclear pores to regulate molecular traffic.
  • Nucleolus: site of rRNA synthesis and ribosome assembly.
  • Chromatin: is composed of DNA and protein.

Endoplasmic Reticulum

  • Endoplasmic reticulum is a system of channels (cisternae).
  • Rough ER: covered with ribosomes and involved in protein synthesis.
  • Smooth ER: lacks ribosomes and involved in lipid synthesis and processing of substances including alcohol and drugs.

Ribosomes

  • Ribosomes are small granules of protein and RNA.
  • Ribosomes are sites of protein synthesis.
  • Ribosomes can be found in free cytosol or bound to rough ER.

Golgi Complex

  • Modifies, sorts, and packages proteins and lipids produced in the ER.
  • Transports proteins to other organelles or to the plasma membrane for secretion.
  • Golgi vesicles are small sacs formed off the Golgi complex.

Lysosomes

  • Lysosomes are a package of enzymes bound by a membrane.
  • They perform intracellular digestion of materials.

Peroxisomes

  • Peroxisomes resemble lysosomes but have different enzymes.
  • They use molecular oxygen to oxidize organic molecules into water and oxygen.

Proteosomes

  • Proteosomes dispose of surplus proteins.
  • They contain proteins that break down proteins into shorter peptides and amino acids.

Mitochondria

  • Mitochondria are double-membraned organelles.
  • They generate energy (ATP) through cellular respiration.

Centrioles

  • Centrioles are short cylindrical assemblies of microtubules arranged in nine groups of three microtubules each (9x3).
  • Centrioles form basal bodies of cilia and flagella.
  • Centrioles play a role in cell division.

Inclusions

  • Inclusions are stored cellular products.
  • Inclusions can include materials like glycogen, pigments, fat droplets, foreign substances like viruses, or even bacteria.
  • Inclusions are not essential for cell survival

Cilia

  • Hair-like projections that move substances across the cell surface in one direction.
  • Cilia are involved in various cellular activities such as movement, sensory perception, and fluid transport.
  • The structure of cilia is a 9 + 2 arrangement containing microtubules and dynein arms.

Flagella

  • A tail-like structure that moves the cell.
  • The structure of flagella is identical to cilia and uses similar mechanisms for movement.
  • Flagella are found on sperm cells, enabling them to propel themselves.

Pseudopods

  • Continuously changing extensions of the cell that change in shape and size
  • Useful for cellular locomotion and capturing foreign particles.

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Description

Test your knowledge on the mechanisms of cell signaling and diffusion processes with this quiz. Explore key concepts such as the role of G proteins, adenylate cyclase activity, and the definition of osmosis. Assess your understanding of how substances move across membranes and the impact of solute concentration.

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