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Ion Transport in Cell Membrane: Glands, Proteins, and Channels, Exams of Biology

University of WestminsterBiology

An in-depth exploration of cell membranes, focusing on the functions of exocrine and endocrine glands, membrane proteins, and ion channels. Topics covered include the structure and functions of exocrine and endocrine glands, the composition and roles of membrane proteins, and the mechanisms of passive and active ion transport. Students will gain valuable insights into the intricacies of cellular communication and the role of membranes in maintaining the internal environment.

Typology: Exams

2023/2024

Available from 03/26/2024

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1Biology 251 Exam 1 WSU solution (15p)
updated 2024
What are the four levels of organization in the body? - ANS>> Cells, Tissues, Organs,
Organ Systems
What are the three major functions of cells? Cells independently carry out all life
processes. - ANS>> - Perform chemical reactions that use oxygen and nutrients to
produce energy
- Produce CO2, wastes
- Synthesize Complex Molecules
What are the four common characteristics of cells? - ANS>> - Sensitive to internal
environment
- Communicate with other cells
- Cell growth
- Cell division; most cells
What is differentiation? - ANS>> The process by which cells become specialized to
perform specific functions, resulted from altered gene expression in response to locally
produced molecules
What is an undifferentiated cell? - ANS>> A Stem Cell--not assigned a specific job yet
What are two main categories of undifferentiated cells? - ANS>> 1) Embryonic stem
cells-pluripotent (can become any type of future fetus) **Totipotent cell (=zygote, first
few divisions)--can become any cell including placenta
2) Tissue-specific stem cells-partially specialized, found in many adult tissues
What are the four types of tissues in the body? - ANS>> 1) Epithelial
2) Muscle
3) Nerve
4) Connective
What is the function of Epithelial tissue? - ANS>> Epithelial tissue or the epithelium.
They specialize in transport in and out of the body and various organs in the body.
Forms barriers by:
- Separating body from external environment
- Lining hollow organs
- Forming glands
- *possibly specialized for transport of molecules like in the gut and kidneys
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Download Ion Transport in Cell Membrane: Glands, Proteins, and Channels and more Exams Biology in PDF only on Docsity!

1 Biology 251 Exam 1 WSU solution (15p)

updated 2024

What are the four levels of organization in the body? - ANS>> Cells, Tissues, Organs, Organ Systems What are the three major functions of cells? Cells independently carry out all life processes. - ANS>> - Perform chemical reactions that use oxygen and nutrients to produce energy

  • Produce CO2, wastes
  • Synthesize Complex Molecules What are the four common characteristics of cells? - ANS>> - Sensitive to internal environment
  • Communicate with other cells
  • Cell growth
  • Cell division; most cells What is differentiation? - ANS>> The process by which cells become specialized to perform specific functions, resulted from altered gene expression in response to locally produced molecules What is an undifferentiated cell? - ANS>> A Stem Cell--not assigned a specific job yet What are two main categories of undifferentiated cells? - ANS>> 1) Embryonic stem cells-pluripotent (can become any type of future fetus) **Totipotent cell (=zygote, first few divisions)--can become any cell including placenta
  1. Tissue-specific stem cells-partially specialized, found in many adult tissues What are the four types of tissues in the body? - ANS>> 1) Epithelial
  2. Muscle
  3. Nerve
  4. Connective What is the function of Epithelial tissue? - ANS>> Epithelial tissue or the epithelium. They specialize in transport in and out of the body and various organs in the body. Forms barriers by:
  • Separating body from external environment
  • Lining hollow organs
  • Forming glands
  • *possibly specialized for transport of molecules like in the gut and kidneys

What is the function of Muscle tissue? - ANS>> Contraction, generation of force What is the function of Nerve tissue? - ANS>> Initiate, transmit electrical impulses What is the function of Connective tissue? - ANS>> Connective tissues: Connect and support various body parts Cells plus extracellular matrix (ECM) kind of like gel Like the cytoplasm of the entire body What are Epithelial Tissue glands? - ANS>> Specialized organs for secretions there are EXOcrine glands and ENDOcrine glands What is an EXOcrine gland? - ANS>> ducts lead to external environment (ex. Salivary glands) What is an ENDOcrine gland? - ANS>> ductless and secrete hormones into blood (hormones use bloodstream as a highway to deliver messages) What is the difference between and EXOcrine gland and the ENDOcrine gland? - ANS>> EXOcrine glands=have ducts ENDOcrine glands=NO ducts What are the three types of muscles? - ANS>> - skeletal muscle

  • smooth muscle
  • cardiac muscle Where are the muscles found? - ANS>> Attach to the skeleton, found in heart, in other internal organs. Are muscles voluntary or involuntary? - ANS>> Some muscles are under voluntary control like the skeletal muscle, while others are involuntary. What are the purposes/functions of nerves? - ANS>> Nerve tissue(Neurons): Function in transmitting electrical signals. Additionally, control and regulate muscle contraction, gland secretion, sensory perception, thoughts, memory, emotions, and much more What are some examples of connective tissues? - ANS>> (Ex. Adipose (fat)--special connective tissue, blood cells(all blood), cartilage, bone) kind of like jello supporting fruit which is the cells--they are stuck and suspended in things like the extracellular matrix What is the extracellular matrix? - ANS>> Cells plus extracellular matrix (ECM) kind of like gel google def: an intricate network composed of an array of multidomain macromolecules organized in a cell/tissue-specific manner.

What is the definition of homeostasis? - ANS>> The process of maintaining a stable INTERNAL environment compatible for life. What organ system is exempt from maintaining homeostasis? - ANS>> The reproductive system What three main things does the body do to maintain ECF in order to maintain homeostasis? - ANS>> 1) Composition (disposing or composting kind of)

  1. Temperature
  2. Volume In the step of Composition when maintaining ECF, what components does composition maintain? - ANS>> a) Ionic composition (sodium, calcium, etc.) b) Oxygen, Carbon Dioxide levels c) pH What is Negative Feedback Control in homeostasis? - ANS>> This is the primary feedback control in maintaining homeostasis How does Negative Feedback Control maintain homeostasis? - ANS>> External change→ triggers change in regulated variable in internal environment→ triggers reaction to oppose the change and return regulated variable toward normal (set point) What steps are involved in negative feedback control mechanisms? - ANS>> 1) Set point: desired level of regulated variable(normal)
  3. Sensors: detect level of regulated variable and provide input to integrating center
  4. Integrating center: compares set point to actual level of regulated variable
  5. Error signal=difference between actual level and set point
  6. Integrating center sends output to effectors to return regulated variable toward set point Negative Feedback Control of Car Speed - ANS>> Car travels at set point of 60mph→ Speed decreases, error signal increases→ Gas flow to engine increases→ Speed increases, error signal decreases→ Car travels at set point of 60mph Negative Feedback Control of Body Temperature Loop - ANS>> Body temperature normal→ Body temperature rises; error signal increases→ Regulatory mechanism activated→ Body temperature decreases; error signal decreases→

Body temperature normal What is the definition of a plasma membrane? - ANS>> The barrier between cell and the internal environment (around all cells: v thin) What is the job of the Plasma Membrane? - ANS>> - Forms the boundary of cells

  • Separates the intracellular compartment (where ICF is stored) from extracellular compartment (where ECF is stored) What kind of permeability does the plasma membrane barrier have? What kinds of molecules cannot pass directly through? - ANS>> Selective Permeability: lipid insoluble molecules (polar molecules) are unable to pass directly through the membrane What 4 molecules is the plasma membrane composed of? - ANS>> The Plasma Membrane is composed of phospholipids(most abundant) arranged in a bilayer, proteins, cholesterol, a small amount of carbohydrates aka. sugar (attached to proteins and to lesser extent the phospholipids) What is a phospholipid? - ANS>> a lipid containing a phosphate group in its molecule What is a lipid? - ANS>> any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids. What is a protein? - ANS>> chain of amino acids What is cholesterol? - ANS>> Cholesterol is a waxy substance found in your blood What is a carbohydrate? - ANS>> A carbohydrate is a biomolecule consisting of carbon, hydrogen and oxygen atoms, usually with a hydrogen Why can't lipid insoluble molecules pass through the selectively permeable plasma membrane? - ANS>> They are polar What is the current hypothesis for the structure of the plasma membrane? - ANS>> Fluid Mosaic Model What are the five parts of the fluid mosaic model we discussed? - ANS>> 1) Membrane Proteins
  1. Integral Membrane Proteins
  2. Peripheral Membrane Proteins
  3. Cholesterol
  4. Carbohydrates

What ions can't move directly across a semi-permeable membrane? - ANS>> Large Hydrophilic molecules and ions can't cross (require transport proteins=transporters) Ex. Glucose, ions What are the four factors affecting membrane permeability? - ANS>> 1)Lipid-solubility of molecule a) Hydrophobic vs. Hydrophilic b)Carries an electrical charge: ex. ions=lipid insoluble

  1. Presence or absence of Transport proteins
  2. Molecular weight and shape of molecule (for lipid soluble molecules)
  3. Membrane thickness (for lipid soluble molecules) What are the two categories of Membrane Transport? - ANS>> passive and active What is Active Transport? - ANS>> - From low concentration to high concentration
  • Requires metabolic energy like ATP along with pumps like integral membrane proteins and transporters What is passive transport? - ANS>> - From high concentration to low concentration
  • No energy required, simple diffusion or mediated transport via transport proteins What are the 3 types of passive transport? - ANS>> 1) Simple Diffusion: Passive transport directly through the lipid bilayer
  1. Diffusion Through Ion Channels (membrane proteins; a type of mediated transport)
  2. Facilitated Diffusion: Passive Transport through carrier proteins in membrane a type of mediated transport What are general properties of active transport? - ANS>> 1) Move molecules against a concentration gradient
  3. Requires metabolic energy
  4. Affinity (binding strength) greater facing one side of the membrane, usually the side facing the low concentration of solute What are two types of active transport? - ANS>> 1) Primary Active Transport
  5. Secondary Active Transport What is Primary Active Transport? - ANS>> Needs, ATP=direct energy source. Two ways it is activated:
  • Carrier protein=ATPase (enzyme that releases a phosphate from ATP); known as ion pumps
  • Phosphorylation=covalent modulation What does phosphorylating a pump change in Primary Active Transport? - ANS>> *Adding phosphate group changes affinity of pump Ex. Na+/K+ pump, Ca2+ pump, H+/K+ pump

How does Potassium ATPase work and what is it a PRIME example of? - ANS>> Example of Primary Active Transport Sodium/Potassium ATPase:

  1. Present in nearly all cells of body
  2. Transports 3 sodium out of cell and 2 potassium into cell per ATP
  3. Electrogenic (net +1 charge out of cell)
  4. Creates Concentration gradients for sodium and potassium across cell membrane What is Secondary Active Transport? - ANS>> - Indirectly uses energy from ATP
  • Transport is secondary to a primary active transporter
  • Requires an ion gradient (usually sodium)
  • Co-transporters
  • Secondary active transporter can move the molecule being pumped across the membrane in the same (sym=same) direction as the ion=symporter
  • Or, molecule can be transported in teh opposite direction of the ion=antiporter What is the process of secondary active transport? - ANS>> 1) An ion moves down its concentration gradient causing another molecule or ion to move against its concentration gradient
  1. Most common ion=sodium
  2. ATP needed to maintain gradient for sodium (ion gradient maintained by primary active transport, ex. Na+/K+ pump)
  3. Ion acts as modulator-changes affinity of carrier for molecule to be transported What two factors affect rates of active transport? - ANS>> 1) Rate of transport by individual pumps (Nature of pump like fast vs. slow)
  4. Number of pumps in the membrane What are the general characteristics of Passive Transport? - ANS>> - From high concentration to low concentration
  • No energy required, simple diffusion or mediated transport via transport proteins What types of passive transport are there? - ANS>> 1) Simple Diffusion
  1. Diffusion through ion channels
  2. Facilitated Diffusion Describe simple diffusion - ANS>> Passive transport or movement of molecules directly through a membrane's lipid bilayer
  • These molecules HAVE TO BE lipid-soluble ex. small, non-polar molecules
  • These molecules can interact with the hydrophobic portions of the lipid bilayer and pass directly through the membrane Describe Diffusion through ion channels(describe ion channels) - ANS>> A type of mediated transport

What are the two main mechanisms of Intercellular communication? - ANS>> 1) Direct Communication through Gap Junctions

  1. Indirect Communication through Chemical Messengers What is a Gap junction? Where is it common? - ANS>> Gap Junctions are special membrane proteins that make channels between two cells via connexons forming a passage way from one cell to its neighboring cell. Common in smooth and cardiac muscle What is the general process of Indirect communication? - ANS>> One cell is a communicator or a secretory cell and it releases a chemical messenger that goes to a receptor cell or target cell. The receptor is a protein that may be a membrane protein or cytoplasmic protein. What two ways chemical messengers are classified? - ANS>> Mode of Action and Functional Class What are the three modes of Action? - ANS>> Autocrines, Praracrines, Endocrines What is an autocrine mode of action? - ANS>> Autocrines(auto=self) so a cell- communicating with itself What is a paracrine mode of action? - ANS>> Paracrines (para=nearby) adjacent to or close to other cells--in same neighborhood What is an endocrine mode of action? - ANS>> Endocrine=messangers, in this case hormones enter into bloodstream (capillaries the smallest blood vessels) and can be transported long ways What is the simple definition of a neurotransmitter? - ANS>> Neurotransmitters: Chemical messengers released by neurons--they grow out and grow to other types of cells. More to come in upcoming lectures. Neurotransmitters are considered the messengers of the: - ANS>> Nervous System What is a neurohormone? - ANS>> Just a specialized type of secretory hormone relating to neurons What is a cytokine? Is released by: - ANS>> Cytokines: General term for any messenger molecule released by cell--usually consist of peptides but act in a paracrine type of way affecting cells nearby. Is released by most cell types Describe the process of signal transduction mechanisms - ANS>> The process by which messenger binding receptor produces a response in target cell.

*Note that receptors=proteins with specific binding sites for messengers. Most receptors (R) are specific for one type of messenger (M) What affects the magnitude of the response for a target cell to a messenger? - ANS>> Magnitude of response depends on number of receptors with messenger bond (that is most important but also the concentration of messanger, number of receptors present on target cell, affinity of receptor for messanger. What triggers down regulation in receptors and what happens when it occurs? - ANS>> Down Regulation can occur when excess messenger is present

  • Target cell decreases number of receptors for messanger
  • Develop tolerance What triggers up regulation and what happens when it occurs? - ANS>> Up- Regulation can occur when too little messenger is present
  • Target cell increases number ofreceptors for messenger
  • Develop Hypersensitivity What are Receptor Agonists and Antagonists? - ANS>> Agonist: any other chemical that can binds to a receptor mimicking normal response when it should not be the messenger for this receptor Antagonist: binds to a receptor producing no response
  • Competes with normal messenger Name one example of an agonist or antagonist - ANS>> Beta- endorphhin=endogenous opiate
  • Beta-endorphin binds to opiate receptors producing analgesia (pain reduction) Morphine=opiate receptor agonist
  • Administration of morphine produces analgesia Naloxone=opiate receptor antagonist
  • Administration of naloxone blocks opiate action (antidote for morphine, heroin overdose) Name the two receptors/responses in Signal Transduction mechanisms - ANS>> - Intracellular Receptor-Mediated Responses
  • Membrane-bound receptor-Mediated Responses *Some receptors are located inside the cell, others are membrane proteins Where is an intracellular receptor located? - ANS>> In the cytoplasm or nucleus What are the two types of signal transduction mechanisms? Where are they located? - ANS>> 1) Intracellular Receptor-Mediated Responses
  1. Membrane-bound receptor-Mediated responses Some receptors are located inside the cell, others are membrane proteins.

What is resting membrane potential? - ANS>> - 70mV What are the types of potential changes? - ANS>> Action Potentials and Graded Potentials Action Potentials are ___ and communicate over__ whereas Graded Potentials are ___ and communicate over ___ - ANS>> APs are large and communicate over long distances, GPs are small and communicate over short distances and can give rise to action potentials What is an action potential? - ANS>> large, rapid (10-15 msec) changes in membrane potential used for communication How is action potential produced? - ANS>> By sodium and potassium due to opening of voltage gated channels What is the threshold voltage typically? - ANS>> - 55 mV What triggers depolarization to threshold? - ANS>> Rapid opening of sodium channels (more positive inside neuron) and the slow opening of potassium channels What occurs during repolarization? - ANS>> 1-2 msec after Na+ channels close, voltage gated K+ channels open and K+ diffuses out of cell making inside less positive so Vm can return to resting membrane potential What is the amplitude? and what is it for all action potentials? - ANS>> Amplitude is the change in membrane potential and is 100 mv for all action potentials What is a frequency in regard to action potentials? - ANS>> The number of action potentials per second What constitutes the propagation(start of transmission) of Action Potentials? - ANS>> Action potentials can be propagated as waves of depolarization/repolarization of membrane potential that pass over the axon of neurons What two mechanisms does propagation depend on? - ANS>> The absence or presence of myelin What is myelin? - ANS>> Acts as "insulator" like covering of phone charger, but covers axons of some neurons What are the nodes of Ranvier? - ANS>> Spaces in between myelin sheaths What are the two myelin-forming cells? - ANS>> 1) Oligodendrocytes

  1. Schwann cells Where are oligodendrocytes found? - ANS>> Central nervous system (CNS): Brain and spinal cord Where are Schwann cells found? (think spirally) - ANS>> The Peripheral nervous system. In the Central nervous system, one oligodendrocyte can form... - ANS>> myelin sheath segments around several different axons How long can axons be? This is useful because action potentials must be propagated over great distances - ANS>> They can be 3-4 feet long just in skeletal muscles in foot, longer from spinal cord to food Where is action potential initiated? - ANS>> The axon hillock (the first part of the ion) Where does positive charge in the cell diffuse when a chunk is undergoing action potential - ANS>> The positive charge diffuses into region adjacent to area undergoing an action potential. The adjacent region reaches threshold and Na+ channels open starting action potential. repeated down axon. Myelinated axons conduct action potential ___ x faster than unmyelinated axons of equal size. MS is... - ANS>> 50 times faster and MS is a condition where the body destroys myelin What is a refractory period? - ANS>> Period of decreased excitability following an action potential What is the difference between absolute refractory periods and relative refractory periods? - ANS>> Absolute immediately follows action potential and no second action potential is possible. Relative follows absolute refractory period and action potential is possible with stronger stimulus Consequences of Refractory periods means - ANS>> Unidirectional or one way propagation of action potentials What are the three confirmation states of the absolute refractory period due to the nature of voltage gated Na+ channels? - ANS>> a) closed and available to open b) open c) closed and "locked" (unavailable to open until resting state which takes time) What is the difference in Na+ channels for Absolute RP and Relative RP? - ANS>> Absolute: Na channels inactivated Relative: Some Na channels still inactivated but some are able to open
  1. neurotransmitter diffuses and binds to receptors on post-synaptic cell
  2. ***response is terminated by removing neurotransmitter from synaptic cleft (additional clean up steps: degradation from enzyme, reuptake, diffusion away) How long is synaptic delay between the arrival of action potential and change in post- synaptic Vm? - ANS>> 1-5 msec, caused by the changes in Ca2+ and release of neurotransmitter What is postsynaptic potential? - ANS>> Change in membrane potential in response to neurotransmitter binding to receptor, produces graded potential What is the difference between Excitatory and inhibitory synapses? - ANS>> Excitatory: most-likely to have action potential, depolarization, voltage moves towards threshold. Inhibitory: less likely to have action potential, hyperpolarization, moves voltage away from threshold and involved in membrane stabilization.