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?

They can activate some enzymes while deactivating others. Signup and view all the answers

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

It is converted to cyclic AMP (cAMP). Signup and view all the answers

What defines simple diffusion?

Net movement from high concentration to low concentration Signup and view all the answers

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

Color of the substance Signup and view all the answers

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

Higher; lower Signup and view all the answers

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

They draw water from the other side of a membrane Signup and view all the answers

Which of the following statements about diffusion is true?

Diffusion continues until equilibrium is reached Signup and view all the answers

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

ATP Signup and view all the answers

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

3 Signup and view all the answers

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

Higher K+ and lower Na+ Signup and view all the answers

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

Maintaining a negatively charged resting membrane potential Signup and view all the answers

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

Sodium-glucose transporter (SGLT) 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?

Secondary active transport Signup and view all the answers

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

Glucose Signup and view all the answers

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

50% Signup and view all the answers

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

Squamous Signup and view all the answers

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

Cells arise only from other cells. Signup and view all the answers

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

Spheroid to ovoid Signup and view all the answers

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

Robert Hooke Signup and view all the answers

What is the typical size range for most cells mentioned?

10-15 μm Signup and view all the answers

Which cell shape is characterized as thread-like?

Fibrous Signup and view all the answers

What is the role of aquaporins in osmosis?

They enhance the diffusion of water across membranes. Signup and view all the answers

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

Cells contain properties that differ from those of biological molecules. Signup and view all the answers

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

Polygonal Signup and view all the answers

What happens to a cell in a hypotonic solution?

The cell absorbs water and swells. Signup and view all the answers

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

1 M NaCl has a higher osmolarity. Signup and view all the answers

What is the defining structure for contractile vacuoles in Paramecium?

Cilia Signup and view all the answers

What is osmotic pressure?

The pressure needed to stop water diffusion. Signup and view all the answers

Which cell type is typically taller than it is wide?

Columnar Signup and view all the answers

What is indicated by a hypertonic solution concerning cell behavior?

Cells will lose water and crenate. Signup and view all the answers

What characterizes an isotonic solution?

Equal concentration of nonpermeating solutes as the cell cytoplasm. Signup and view all the answers

What is the primary factor that determines tonicity?

The concentration of nonpermeating solutes. Signup and view all the answers

What process is reverse osmosis used for?

Purifying water by applying mechanical pressure. Signup and view all the answers

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

Phagocytosis Signup and view all the answers

What is the function of the rough endoplasmic reticulum?

Produces phospholipids and proteins Signup and view all the answers

Which of the following organelles is responsible for intracellular digestion?

Lysosomes Signup and view all the answers

What is the main purpose of receptor-mediated endocytosis?

Taking in specific molecules that bind to receptors Signup and view all the answers

What are the primary components of the cytoskeleton?

Microtubules, microfilaments, and intermediate fibers Signup and view all the answers

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

Mitochondria Signup and view all the answers

What do peroxisomes primarily utilize molecular oxygen for?

Oxidizing organic molecules Signup and view all the answers

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

Transporting vesicles to the plasma membrane Signup and view all the answers

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

Cytoskeleton Signup and view all the answers

Which of the following best describes transcytosis?

Movement of materials into and out of the same cell Signup and view all the answers

What is autophagy?

Digesting the cell's surplus organelles Signup and view all the answers

Which vesicular transport mechanism requires specific binding to receptors?

Receptor-mediated endocytosis Signup and view all the answers

What do lysosomes primarily contain to aid in digestion?

Enzymes Signup and view all the answers

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.