Chapter 1: Cellular Biology

Question 1

Pathophysiology

Answer 1

The study of physiological changes in the body that result from a disease and includes elements of both pathology

Question 2

Prokaryotes

Answer 2

• Has no distinct nucleus
• Lacks histones and organelles
• The genetic information is contained in a single circular chromosome
• Includes blue-green algae, bacteria, and rickettsiae

Question 3

Eukaryotes

Answer 3

• Has a well defined nucleus
• Has a complex cellular organization
• Has membrane bound organelles
• The genetic information is contained in several or many chromosomes
• Includes higher animals, plants, fungi, protozoa, and most algae

Question 4

Differences in biochemical activity

Answer 4

• Protein Synthesis
• Transport across outer cell membrane
• Enzyme content

Question 5

Cellular Functions

Answer 5

• Specialized through differentiation or maturation so they may perform one kind of function
• Includes; movement, conductivity, metabolic absorption, secretion, excretion, respiration, reproduction, and communication

Question 6

Question: Which cellular function occurs in all cell types?

Answer 6

Metabolic absorption
- This is because all cells can take in and use nutrients and other substances.

Question 7

Eukaryotic Cell

Answer 7

• Consists of plasma membrane, cytoplasm, and intracellular organelles

Question 8

Nucleus

Answer 8

• Largest membrane-bound organelle
• Found usually in the cell’s center
• The chief functions of the nucleus are cell division and control of genetic information

Question 9

Cytoplasm, or the cytoplasmic matrix

Answer 9

• An aqueous solution (cytosol) that fills the space between the nucleus and the plasma membrane.
• It represents about half of the volume of the cell.
• Function: Cytoplasmic organelles.

Question 10

The organelles

Answer 10

• Suspended in the cytoplasm and are enclosed
  in biologic membranes.

Question 11

Ribosomes

Answer 11

• Eukaryotic organelle
• RNA-protein complexes that provide sites for cellular protein synthesis.
• Synthesized in the nucleolus.

Question 12

Endoplasmic reticulum

Answer 12

• Eukaryotic organelle
• A network of tubular channels (cisternae) that extend throughout the outer nuclear membrane.
  -It specializes in the synthesis, folding, and transport of protein and lipid components of most of the organelles, as well as in sensing cellular stress.

Question 13

Golgi complex

Answer 13

• Eukaryotic organelle
• A network of smooth membranes and vesicles located near the nucleus.
• Responsible for processing and packaging proteins into secretory vesicles that break away from the Golgi complex and migrate to a variety of intracellular and extracellular destinations, including the plasma membrane
• Cytoskeleton

Question 14

Lysosomes

Answer 14

• Eukaryotic organelle
• Saclike structures
• Contains digestive enzymes
• Cellular injury leads to a release of the lysosomal
  enzymes, causing cellular self-digestion
• They also serve as signaling hubs in a network for cellular adaptation

Question 15

Peroxisomes

Answer 15

• Eukaryotic organelle
• Appear similar to lysosomes but contain several enzymes that either produce or use hydrogen peroxide and their reactions detoxify waste products and make them harmless.

Question 16

Mitochondria

Answer 16

• Eukaryotic organelle
• Contain the metabolic machinery necessary for cellular energy metabolism
• The enzymes of the respiratory chain
  (electron-transport chain), found in the inner membrane of the mitochondria, generate most of the cell’s ATP
• Has role in; osmotic regulation, pH control, calcium homeostasis, and cell signaling

Question 17

Cytoskeleton

Answer 17

• Eukaryotic organelle
• It is the “bone and muscle” of the cell
• The internal skeleton is composed of a network of protein filaments, including microtubules and actin filaments (microfilaments)
• They also form cell extensions (microvilli, cilia, flagella)

Question 18

Question: The function of cellular energy metabolism and generation of most of the cell’s adenosine triphosphate (ATP) occurs in the?

Answer 18

Mitochondria

Question 19

Plasma membrane

Answer 19

• Encloses the cell and, by controlling the movement of substances across it
• Exerts a powerful influence on metabolic pathways
• Other functions include;
• Cell-to-cell recognition
• Cellular mobility
• Maintenance of cellular shape.

Question 20

PM: The basic structure of plasma membrane

Answer 20

• Is the lipid bilayer, which is studded with various proteins

Question 21

PM: Composition of lipid bilayer

Answer 21

• Solid-gel phase
• Fluid-liquid crystalline phase
• Liquid-ordered phase

Question 22

PM: Lipid bilayer

Answer 22

• Determines the structure of the membrane
• Each lipid molecule is polar, or amphipathic
• The head is hydrophilic (“water loving”) and the tail is hydrophobic (“water hating”)
  -The membrane is organized in two layers, with the tails inward and the heads outward.
• This provides a barrier to the diffusion of
  hydrophilic substances, while allowing lipid-soluble molecules to diffuse through readily.
• O2 and CO2 diffusion
• Molecular glue

Question 23

PM: Proteins

Answer 23

• Performs most of the plasma membrane tasks
• Functions
• Receptors
• Transport channels/carriers
• Enzymes
• Surface markers
• Cell adhesion molecules (CAMs)
• Catalysts
• Proteins determine the functions of the membrane.
• Proteins perform most of the plasma membrane’s tasks.
• Proteins act as recognition and binding units for substances moving in and out of the cell, pores and transport channels, enzymes that drive pumps or maintain ion concentrations, cell surface markers, cell adhesion molecules, and catalysts of chemical reactions. - Proteins form cellular receptors that recognize and bind with smaller molecules called ligands.

Question 24

PM: Membrane Proteins

Answer 24

• Membrane proteins can extend across the bilayer, be in the bilayer but primarily on one side or the other, or can exist outside of the bilayer.
• Membrane proteins, like other proteins, are synthesized by the ribosome and then translocate, called trafficking, to different locations in the cell.
• Trafficking places unique demands on membrane proteins for folding, translocation, and stability.
• Mis-folded proteins are emerging as an important cause of disease.

Question 25

Proteostasis (protein regulation)

Answer 25

• Proteostasis is the state of cell balance of the processes of protein synthesis, folding, and dehydration (protein homeostasis).
• The proteostasis network is composed of;
• Ribosomes (makers)
• Chaperones (helpers)
• Protein breakdown or proteolytic systems.
• Malfunction of these systems is associated with human disease.
• Proteolytic systems
• Lysosomes
• Ubiquitin-proteasome system (UPS)

Question 26

Carbohydrates

Answer 26

• The carbohydrates on the outside of the plasma membrane form a coating (glycocalyx) that protects the cell from mechanical damage and creates a slimy surface that assists in mobility.
• Carbohydrates also function in cell-cell recognition and adhesion.
  Function Summary
• Protection
• Lubrication
• Recognition
  *Adhesion

Question 27

Cellular Receptors

Answer 27

• Ligands
• Bind with cellular receptors to activate or inhibit the receptor’s associated signaling or biochemical pathway
• Plasma membrane receptors
• Determine response to binding

Question 28

1. Cell-to-Cell Adhesions

Answer 28

• Cell-to-cell adhesions are formed on plasma membranes, thereby allowing the formation of tissues and organs.
• Cells are held together by three different means:
  (1) The extracellular membrane
  (2) Cell adhesion molecules in the cell’s plasma membrane
  (3) Specialized cell junctions

Question 29

2. Cell-to-Cell Adhesions

Answer 29

The extracellular matrix (ECM)
- is secreted by cells and is a meshwork of fibrous proteins in a gel-like substance.
- It provides a pathway for diffusion of nutrients, wastes, and other water-soluble substances.
- The ECM includes three groups of macromolecules:
(1) Fibrous structural proteins (collagen and elastin)
(2) Adhesive glycoproteins,
(3) Proteoglycans and hyaluronic acid.
- The matrix helps regulate cell growth, movement, and differentiation.

Question 30

3. Cell-to-Cell Adhesions

Answer 30

Basement membrane
- is a specialized type of ECM that is very thin, tough, and flexible.
- It lies under the epithelium of many organs and
is also called the basal lamina
-Sheet of matrix: thin, tough, flexible
- Located:
* Beneath epithelial cells
* Between two cell sheets
* Around individual muscle, fat, Schwann cells

Question 31

4. Cell-to-Cell Adhesions

Answer 31

Cell junctions
- Are the contacts between neighboring cells.
- They can hold cells together with a tight seal, provide strong mechanical attachments, provide a chemical communication, and maintain polarity of cells.
- Cell junctions can be classified as symmetric and
asymmetric.
- Symmetric junctions include
* Tight junctions
* Belt desmosome and desmosomes
* Gap junctions.
- Asymmetric junction is the
* Hemidesmosome.
- Gating
* Enables uninjured cells to protect themselves from injured neighbors

Question 32

Cellular Communication

Answer 32

• Cells communicate in three main ways:
• they form protein channels (gap junctions)
• they display receptors that affect intracellular
  processes or other cells in direct physical contact
• they use receptor proteins inside the target cell.
• Primary modes of intercellular signaling include *contact-dependent
  *paracrine, hormonal
  *neurohormonal
  *neurotransmitter.

Question 33

Signal transduction

Answer 33

• Signal transduction involves signals or instructions from extracellular chemical messengers that are conveyed to the cell’s interior for execution.
• If deprived of appropriate signals, cells undergo a form
  of cell suicide known as programmed cell death or apoptosis.
• Binding of the extracellular signaling messenger (first messenger) to the membrane receptors causes
• the opening or closing of channels that regulate ion movement
• the transfer of the signal to an intracellular messenger (second messenger) that triggers a cascade of events in the cell.

Question 34

Cellular Metabolism

Answer 34

• The chemical tasks of maintaining essential cellular functions are referred to as cellular metabolism.
• Anabolism is the energy-using process of metabolism
• Catabolism is the energy-releasing process.
• Adenosine triphosphate (ATP) functions as an energy-transferring molecule.
• It is fuel for cell survival.
• Energy is stored by molecules of carbohydrate, lipid, and protein, which, when catabolized, transfers
  energy to ATP.
• The phases of catabolism are;
• Digestion
  ~ Extracellular breakdown of proteins, fats, polysaccharides to subunits
• Glycolysis
  ~ Intracellular breakdown of subunits to pyruvate, then to acetyl CoA
  ~ Limited ATP produced
• Oxidation
• Citric acid cycle
  ~ Also called Krebs cycle or the tricarboxylic acid cycle (TCA)
  ~ Much ATP produced via oxidative phosphorylation if oxygen present
  ~ Waste products excreted

Question 35

Oxidative phosphorylation

Answer 35

• Oxidative phosphorylation occurs in the mitochondria
• It is the mechanism by which the energy produced from carbohydrates, fats, and proteins is transferred to ATP.
• Involves the removal of electrons from various intermediates via a coenzyme such as nicotinamide adenine dinucleotide (NAD) to transfer electrons
• Anaerobic glycolysis: if oxygen not available, CHO (glucose) is converted to pyruvic acid (pyruvate) in cytoplasm with production of two ATP molecules, which is insufficient for energy needs; pyruvate then converted to lactic acid
• Process reverses when oxygen becomes available and lactic acid is converted back to either pyruvic acid or glucose, which moves into the mitochondria and enters the citric acid cycle

Question 36

Membrane Transport (1 of 5)

Answer 36

Cellular intake and output

• Cells continually take in nutrients, fluids, and chemical messengers from the extracellular environment and expel metabolites, or the products of metabolism, and end products of lysosomal digestion
• The two main classes of membrane transport proteins are transporters and channels.

Question 37

Membrane Transport (2 of 5)

Answer 37

Passive Transport

• Molecules move easily from a region of high concentration to a region of low concentration.
• Does not require the expenditure of energy; rather, it is driven by physical effects.
• Passive transport mechanisms include
  diffusion, hydrostatic pressure/filtration, and osmosis.
• Water and small, electrically uncharged molecules move through pores in the plasma membrane’s lipid bilayer via passive transport.

Active Transport

• Flows “uphill”
• Requires expenditure of metabolic energy by the
  cell by means of ATP
• Larger molecules and molecular complexes
  are moved into the cell by active transport.
  *The active transport of Na+ and K+ is found in virtually all cells.
• Around 60-70% of ATP synthesized by cells is used to maintain the transport of Na+ and K+
• Pumps, endocytosis, and exocytosis
• The largest molecules (macromolecules) and fluids are transported by membrane-bound vesicles through the processes of endocytosis (ingestion) and exocytosis (expulsion).
• Endocytosis, or vesicle formation, is when the substance to be transported is engulfed by a segment of the plasma membrane, forming a vesicle that moves into the cell.
• Pinocytosis is a type of endocytosis in which fluids and solute molecules are ingested through formation of small vesicles.
• Phagocytosis is a type of endocytosis in which large particles, such as bacteria, are ingested through
  formation of large vesicles, called vacuoles.

Question 38

Membrane Transport (3 of 5)

Answer 38

Mediated transport

• Moves solute particles singly or two at a time
• Symport: two molecules moved simultaneously in one direction
• Antiport: two molecules moved simultaneously in opposite directions
• Uniport: single molecule moved in one direction

Question 39

Membrane Transport (4 of 5)

Answer 39

A diagram of a membrane transport

Question 40

Membrane Transport (5 of 5)

Answer 40

Electrolytes

• Two types of solutes exist in body fluids: electrolytes and non-electrolytes.
• Electrolytes are electrically charged and dissociate into constituent ions when placed in solution.
• Non-electrolytes do not dissociate when placed in solution.

*Account for ~95% of solutes in body fluids

*Electrically charged
~Cations
~Anions

*Measured in milliequivalents per liter (mEq/L) or milligrams per deciliter (mg/dl)
~Milliequivalent indicates the chemical-combining activity of an ion, which depends on the electrical charge, or valence (number of plus or minus signs)
~ Monovalent—one charge (+)
~ Divalent—2 charges (++)

Question 41

Passive Transport (1 of 3)

Answer 41

Diffusion

• Movement of solutes from area of greater concentration to area of lesser concentration
• Rate of diffusion influenced by difference of electrical potential across the membrane
  ~Also influenced by size of molecules and lipid solubility

Filtration

*Movement of water and solutes through a membrane because of greater force on one side than on the other
~ Hydrostatic pressure
~ Blood pressure

Question 42

Passive Transport (2 of 3)

Answer 42

Osmosis

*Movement of water down a concentration gradient
~Membrane must be more permeable to water than solutes
~Concentration of solutes on one side greater than the other

*Controls the distribution of water between body compartments
*Osmotic pressure
*Related to hydrostatic pressure and solute concentration
*Oncotic pressure or colloid osmotic pressure
*Tonicity

• Osmosis is the movement of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration. - The amount of hydrostatic pressure
  required to oppose the osmotic movement of water is called the osmotic pressure of solution.
• The overall osmotic effect of colloids,
  such as plasma proteins, is called the oncotic pressure or colloid osmotic pressure.

Question 43

Passive Transport (3 of 3)

Answer 43

Osmolality
*Measures the number of milliosmoles per kilogram (mOsm/kg) of water
*Concentration of molecules per weight of water

Osmolarity
*Measures the number of milliosmoles per liter of solution
*Concentration of molecules per volume of solution

Question 44

Cellular Reproduction: The Cell Cycle

Answer 44

• Mitosis vs. cytokinesis

1. Cellular reproduction in body tissues involves mitosis (nuclear division) and cytokinesis (cytoplasmic division).
2. Only mature cells are capable of division. Maturation occurs during a stage of cellular life called interphase (growth phase).
3. The cell cycle is the reproductive process that begins after interphase in all tissues with cellular turnover. There are four phases of the cell
   cycle:
   ~ G1 phase (G = gap) - the period between the M phase and the start of DNA synthesis
   ~ S phase (S = synthesis) - during which DNA synthesis takes place in the cell nucleus
   ~ G2 phase - the period between the completion of DNA synthesis and the next phase in which RNA and protein synthesis occurs
   ~ M phase (M = mitosis)- which involves both nuclear and cytoplasmic division.
4. The M phase (mitosis) involves four stages:
   *prophase
   *metaphase,
   *anaphase
   * telophase.
5. Cellular division and growth are regulated by intracellular programs and several extracellular signal molecules. Mitogens induces or simulates mitosis. Growth factors stimulate an increase in cell mass
   or cell growth. Survival factors inhibit the programmed cell death called apoptosis.

Question 45

Question: Active mediated transport involves

Answer 45

Expenditure of metabolic energy

• Active mediated transport involves life, biologic activity, and the cell’s expenditure of metabolic energy. Active transport expends energy.
• Passive mediated transport moves solute molecules without expending metabolic energy. Passive mediated transport movement is driven by osmosis, hydrostatic pressure, or diffusion.
• Osmosis moves water down a concentration gradient. Active transport moves molecules against or up the concentration gradient.
• Filtration is the movement of water and solutes through a membrane because of a greater pushing pressure on one side of the molecule than on the other side.

Question 46

Active Transport

Answer 46

• Transport system for Na+ and K+
  -Uses direct energy of ATP
  *ATPase
  *Process leads to electrical potential
• Transport of macromolecules

*Endocytosis
~Vesicle formed and moves into cell
~Pinocytosis—ingestion of fluids
~Phagocytosis—ingestion of large particles

*Exocytosis
~Replaces plasma membrane removed by endocytosis
~Releases synthesized molecules into extracellular matrix

Question 47

Electrical Impulses

Answer 47

• Resting membrane potential
• Action potential
• Depolarization
• Threshold potential
  ~Hyperpolarized vs. hypopolarized
  *Repolarization
  *Refractory period
  ~Absolute and relative

Question 48

Control of Cell Division and Growth

Answer 48

• Organ and body size depend on:
• Cell growth
• Cell division
• Cell survival
• Regulated by extracellular signal molecules
• Mitogens
• Growth factors
• Survival factors

Question 49

Tissues

Answer 49

1. Cells of one or more types are organized into tissues, and different types of tissues compose organs. Organs are organized to function as tracts or systems.
2. Three key factors that maintain the cellular organization of tissues are (1) recognition and cell communication, (2) selective cell-to-cell adhesion, and (3) memory.
3. Fully specialized or terminally differentiated cells that are lost are generated from proliferating precursor cells and they, in turn, have been derived from a smaller number of stem cells. Stem cells are cells with the potential to develop into many different cell types
   during early development and growth. In many tissues, stem cells serve as an internal repair and maintenance system dividing indefinitely. These cells can maintain themselves over very long periods of time, called self-renewal, and can generate all the differentiated
   cell types of the tissue or multipotency.
4. The four basic types of tissues are epithelial, muscle, nerve, and connective tissues.
5. Neural tissue is composed of highly specialized cells called neurons
   that receive and transmit electrical impulses rapidly across junctions called synapses.
6. Epithelial tissue covers most internal and external surfaces of the body. The functions of epithelial tissue include protection, absorption, secretion, and excretion.
7. Connective tissue binds various tissues and organs together, supporting them in their locations and serving as storage sites for excess nutrients.
8. Muscle tissue is composed of long, thin, highly contractile cells or fibers. Muscle tissue that is attached to bones enables voluntary movement. Muscle tissue in internal organs enables involuntary movement, such as the heartbeat.

Question 50

Case Study

Answer 50

An 8-month-old infant is transported into the emergency department via ambulance. The child is currently unresponsive, and medical personnel report that the child has suffered an apparent seizure at home. As a nurse attaches the child to a cardiac monitor (that monitors heart rate, respiratory rate, and blood pressure) and a pulse oximeter (that measures oxygen concentration levels within the bloodstream), another staff member collects numerous tubes of blood for testing. In addition to a complete blood count (that measures the amount of certain types of cells, such as red and white blood cells, in the blood), a complete metabolic panel (that measures electrolytes and the function of the kidneys and liver) is completed. A blood glucose level of 28 mg/dl is noted (normal range is 45 to 150 mg/dl).

Staff members administer an immediate bolus dose of dextrose in an attempt to normalize the infant’s glucose level and prepare a continuous intravenous infusion of saline and glucose. While staff members work with the patient, the mother arrives in the emergency department and informs them the child had a seizure at home and an additional seizure when emergency medical service (EMS) arrived. She reports that the child has a history of mitochondrial disorder and has had seizures in the past, but changes in anti-seizure medications had stopped them for the last month. (The effects of mitochondrial disease are quite varied because the distribution of defective mitochondrial deoxyribonucleic acid [DNA] may vary from organ to organ in the body.)

Mitochondria within the cells are responsible for:

A. Cellular respiration and energy production via metabolism of carbohydrates, lipids, and amino acids
B. Detoxifying waste in the cells or foreign components that may enter the cell
C. Storing carbohydrates and fats and metabolism via enzymatic biochemical reactions
D. Synthesizing steroidal hormones and removing toxic substances from the cell

Correct Answer: A
As the work on the infant continues, further results are returned from the laboratory, and the mother continues to clarify her baby’s disease. She is primarily affected via her muscles, brain, and nerves. These areas typically use more energy than other parts of the body.
For cells to function, they must be able to extract and use the chemical energy contained within the structure of organic molecules. Chemical energy is created through metabolism. Catabolism is a metabolic pathway that breaks molecules down and releases energy.
Mitochondria produce energy from carbohydrates, lipids, and proteins and transfer that energy via a transport molecule such as ATP.

The process of catabolism involves three phases in which order?

A. Digestion, glycolysis, and Krebs cycle
B. Krebs cycle, osmosis, and mediated transport
C. Oxidative phosphorylation, transfer reaction, and citric acid cycle
D. Citric acid cycle, passive transport, and diffusion

Correct Answer: A