Biology 251 Exam 1 WSU

What are the four levels of organization in the body?

Cells, Tissues, Organs, Organ Systems

What are the three major functions of cells? Cells independently carry out all life processes.

- 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?

- Sensitive to internal environment
- Communicate with other cells
- Cell growth
- Cell division; most cells

What is differentiation?

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?

A Stem Cell--not assigned a specific job yet

What are two main categories of undifferentiated cells?

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?

1) Epithelial
2) Muscle
3) Nerve
4) Connective

What is the function of Epithelial tissue?

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?

Contraction, generation of force

What is the function of Nerve tissue?

Initiate, transmit electrical impulses

What is the function of Connective tissue?

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?

Specialized organs for secretions there are EXOcrine glands and ENDOcrine glands

What is an EXOcrine gland?

ducts lead to external environment (ex. Salivary glands)

What is an ENDOcrine gland?

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?

EXOcrine glands=have ducts
ENDOcrine glands=NO ducts

What are the three types of muscles?

- skeletal muscle
- smooth muscle
- cardiac muscle

Where are the muscles found?

Attach to the skeleton, found in heart, in other internal organs.

Are muscles voluntary or involuntary?

Some muscles are under voluntary control like the skeletal muscle, while others are involuntary.

What are the purposes/functions of nerves?

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?

(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?

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 ECM made of?

ECM=gel like substance plus protein "fibers"
Elastin
Collagen

What is an organ?

Collection of TWO or more types of tissues put together into a structure that performs a specific function

What is an example of an organ?

Esophagus and Trachea

What is an organ system?

Collection of organs that work together to accomplish a particular task
We have a total of 10 (or 11) different organ systems

What is the body's external environment?

Interior of body separated from external environment by a layer of epithelial tissue.

What makes up the body's external environment?

Epithelial Tissue

Think of one example of the body's external environment. What are commonalities between the body's external environment?

The lumen(where food passes through when you swallow in the esophagus) of respiratory system, gastrointestinal system, and urinary system are part of the external environment think of them all lined by a layer of epithelium tissue that's similar to skin in function. They all secrete something via the glands.

What is the body's internal environment?

Fluid surrounding cells.

What kinds of fluid are in the body's internal environment?

Body Fluid Compartments:
- Intercellular Fluid (ISF)- fluid in cytosol
- Extracellular Fluid (ECF)

What are the three types of extra cellular fluid?(ECF)

- Interstitial fluid
- Plasma
- Other (fluid in joint capsule, intra-ocular fluid)

Approximately what ratio is the body's water ICF to ECF?

ICF is approx. ⅔ of total body water and therefore most of the body's water is inside of cells!!
ECF is approx. ⅓ of total body water

What is extracellular fluid composed of?

- Plasma
- Interstitial Fluid(ISF)

In extracellular fluid, approximately what ratio of water is in the plasma and what is in the interstitial fluid (ISF?)

3 liters water in plasma to 11 liters ISF

What is the definition of homeostasis?

The process of maintaining a stable INTERNAL environment compatible for life.

What organ system is exempt from maintaining homeostasis?

The reproductive system

What three main things does the body do to maintain ECF in order to maintain homeostasis?

1) Composition (disposing or composting kind of)
2) Temperature
3) Volume

In the step of Composition when maintaining ECF, what components does composition maintain?

a) Ionic composition (sodium, calcium, etc.)
b) Oxygen, Carbon Dioxide levels
c) pH

What is Negative Feedback Control in homeostasis?

This is the primary feedback control in maintaining homeostasis

How does Negative Feedback Control maintain homeostasis?

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?

1) Set point: desired level of regulated variable(normal)
2) Sensors: detect level of regulated variable and provide input to integrating center
3) Integrating center: compares set point to actual level of regulated variable
4) Error signal=difference between actual level and set point
5) Integrating center sends output to effectors to return regulated variable toward set point

Negative Feedback Control of Car Speed

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

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?

The barrier between cell and the internal environment (around all cells: v thin)

What is the job of the Plasma Membrane?

- 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?

Selective Permeability: lipid insoluble molecules (polar molecules) are unable to pass directly through the membrane

What 4 molecules is the plasma membrane composed of?

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?

a lipid containing a phosphate group in its molecule

What is a lipid?

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?

chain of amino acids

What is cholesterol?

Cholesterol is a waxy substance found in your blood

What is a carbohydrate?

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?

They are polar

What is the current hypothesis for the structure of the plasma membrane?

Fluid Mosaic Model

What are the five parts of the fluid mosaic model we discussed?

1) Membrane Proteins
2) Integral Membrane Proteins
3) Peripheral Membrane Proteins
4) Cholesterol
5) Carbohydrates

Where do membrane proteins fit with the lipid bilayer?

- Some extend through the entire membrane (transmembrane--think like the transcontinental railroad goes across the entire country)
- Some are inserted only into the outer half of bilayer; - Some are inserted only into inner half
- Some are attached to the surface of the membrane, both inner and outer halves of bilayer(known as peripheral membrane proteins)

Describe the tails of a Integral Membrane Protein? A word to describe this

Amphiphatic; so has both hydrophobic and hydrophilic regions can span the entire membrane.

What is an Integral Membrane Protein and what does it do in regards to transport?

Some are transmembrane proteins(carry polar molecules)
- Channels or pores that allow substances to move across the membrane
- Carrier proteins
Some on one side only
- Enzymes
- Receptors

What are the characteristics of peripheral membrane proteins?

- Easily dissociated from membrane
- Most located on cytosolic side
- Most are part of cytoskeleton

In the structure of the plasma membrane, what is the function of cholesterol?

- Cholesterol molecules are tucked amongst the phospholipid tails in the bilayer interior (have to have or membrane won't function normally)
- Adds fluidity to membrane
- Decreases permeability of membrane to water

Why are carbohydrates important in plasma membranes and what kinds of bonds do they form?

- Carbohydrates are important for cell to cell recognition--other cells will only interact if there is sugar inside
- Carbohydrates are covalently bound to membrane lipids or proteins like glycolipids or glycoprotiens

What is selective permeability?

Movement can occur across a membrane ONLY IF the membrane is permeable to the molecule

What molecules can move directly across a semi-permeable membrane?

Non-polar and small polar molecules can directly cross membrane
Ex. O2, CO2, fatty acids, water

What ions can't move directly across a semi-permeable membrane?

Large Hydrophilic molecules and ions can't cross (require transport proteins=transporters)
Ex. Glucose, ions

What are the four factors affecting membrane permeability?

1)Lipid-solubility of molecule
a) Hydrophobic vs. Hydrophilic
b)Carries an electrical charge: ex. ions=lipid insoluble
2) Presence or absence of Transport proteins
3) Molecular weight and shape of molecule (for lipid soluble molecules)
4) Membrane thickness (for lipid soluble molecules)

What are the two categories of Membrane Transport?

passive and active

What is Active Transport?

- From low concentration to high concentration
- Requires metabolic energy like ATP along with pumps like integral membrane proteins and transporters

What is passive transport?

- 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?

1) Simple Diffusion: Passive transport directly through the lipid bilayer
2) Diffusion Through Ion Channels (membrane proteins; a type of mediated transport)
3) Facilitated Diffusion: Passive Transport through carrier proteins in membrane a type of mediated transport

What are general properties of active transport?

1) Move molecules against a concentration gradient
2) Requires metabolic energy
3) 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?

1) Primary Active Transport
2) Secondary Active Transport

What is Primary Active Transport?

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?

*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?

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?

- 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?

1) An ion moves down its concentration gradient causing another molecule or ion to move against its concentration gradient
2) Most common ion=sodium
3) ATP needed to maintain gradient for sodium (ion gradient maintained by primary active transport, ex. Na+/K+ pump)
4) Ion acts as modulator-changes affinity of carrier for molecule to be transported

What two factors affect rates of active transport?

1) Rate of transport by individual pumps (Nature of pump like fast vs. slow)
2) Number of pumps in the membrane

What are the general characteristics of Passive Transport?

- From high concentration to low concentration
- No energy required, simple diffusion or mediated transport via transport proteins

What types of passive transport are there?

1) Simple Diffusion
2) Diffusion through ion channels
3) Facilitated Diffusion

Describe simple diffusion

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)

A type of mediated transport
Ion channels are TRANSMEMBRANE PROTIENS that allow diffusion of specific ion(s) across the membrane
a) Amphipathic-contains both hydrophilic and hydrophobic regions
b) Form a water filled pore that is shielded from the hydrophobic portion of lipid bilayer
Ions pass through pore
Some ion channels interact (bind) with the ion as it passes through pore (allow some selectivity)

What is the rate of transport through ion channels dependent on?

a) Concentration gradient(there has to be one)
b) Number of channels in the membrane
c) Binding interactions between ion and channel(interacting with proteins for ex. Within a pore would slow down the process)
*Some allow 100,000's of ions to pass per second; others less

What are the two main kinds of ion channels?

Most ion channels can exist in two configurations: an open state and a closed state
* Leak Channels: constantly open; constantly allow passage of ions
* Gated Channels: remain closed until stimulated to open. 3 main types

What are the 3 ion channels and how are they stimulated?

- Ligand (chemical) gated: closed until a specific chemical binds to channel--opens the channel
- Voltage-gated: closed until membrane potential reaches certain voltages, then opens
- Mechanical-gated: mechanical force causes the ion channel to open

What is Facilitated Diffusion? What is a good analogy for it? What is the affinity of the Facilitated Diffusion carrier proteins?

Facilitated Diffusion: Passive Transport or mediated transport in which the molecule moves passively across the membrane with the aid of a carrier protein. Protein flips like revolving door to let things in and out.
**Affinity(binding strength of something) of carrier for molecule is same on both sides of membrane.

What factors affect rates of facilitated diffusion?

1)Transport rate of individual carriers
- Chemical or Electrochemical gradient
- Affinity for transported substance
2) Number of carriers in the membrane

What is the importance of the concentration gradient?

It is the chemical driving force for passive diffusion

What is the Net flux and how does it relate to the concentration gradient?

The net flux is the number of molecules that cross the membrane in a specific time period. The greater the concentration gradient, the greater the net flux.

What are the two main mechanisms of Intercellular communication?

1) Direct Communication through Gap Junctions
2) Indirect Communication through Chemical Messengers

What is a Gap junction? Where is it common?

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?

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?

Mode of Action and Functional Class

What are the three modes of Action?

Autocrines, Praracrines, Endocrines

What is an autocrine mode of action?

Autocrines(auto=self) so a cell-communicating with itself

What is a paracrine mode of action?

Paracrines (para=nearby) adjacent to or close to other cells--in same neighborhood

What is an endocrine mode of action?

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?

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:

Nervous System

What is a neurohormone?

Just a specialized type of secretory hormone relating to neurons

What is a cytokine? Is released by:

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