NPB 101- Exam 1

Plasma membrane

Thin membrane enclosing each cell
Composed of phospholipid bilayer

Membrane proteins

-channels and carriers to transport molecules and ions
-receptors to signal responses
-form adhesions and junctions

Nucleus

Membrane bound organelle containing the genetic material

deoxyribonucleic acid (DNA)

-genes are blueprints for protein synthesis
-DNA is replicated during cell division

riboncleic acid (RNA)

Carries out protein synthesis

Messenger RNA

DNA's genetic code is transcribed to mRNA and the message leaves the nucleus

Ribosomal RNA

Participates in reading the message and translates it into the appropriate protein sequence

Transfer RNA

Transfers the appropriate amino acids from the cytoplasm to their designed site in the proteins being constructed

Cytoplasm

Portion of cells interior, NOT occupied by the nucleus

Organelles

-Membrane-enclose structures that carry out specific functions
-5 main types

Endoplasmic Reticulum (ER)

-continuous fluid filled network of membranous tubules
-2 types

Rough ER

ER membrane covered w/ ribosomes (sites of protein synthesis)

Smooth ER

ER membrane lacking ribosomes

Golgi complex

Processes raw material into finished products and directs products to their destination

Exocythosis

Fusion of vesicles w/ plasma membrane to secrete contents

At which 2 locations in the cell can you find ribosomes?

-rough ER
-Free floating

The Golgi can sort proteins to one of which 3 locations?

-outside the cell (secretion)
-plasma membrane
-lysosomes

Why can a protein made in the ER not end up in the cytoplasm?

Proteins cannot cross a lipid bilayer

Lysosomes

-membrane-enclosed sacs containing hydrolytic enzymes
-material to be digested by lysosomes enters the cell via endocytosis

Pinocytosis

-"cell drinking"
-invagination of the membrane to form a pouch and internalize extra cellular fluid

receptor-mediated endocytosis

binding of ligands to receptors triggers vesicle formation

Phagocytosis

-"cell eating"
-invagination of the plasma membrane to form a large vesicle and internalize large particles such as bacteria or tissue debris

Peroxisomes

Membrane-enclosed sacs containing oxidative enzymes which act to remove hydrogen from toxic molecules

Catalase

Antioxidant enzyme converting H202 into H20 and O2

Mitochondria

Responsible for aerobic metabolism and the production of cellular energy

Cellular respiration

The process of burning nutrients using O2 to free up energy and yielding CO2

What are two main forms in which cells store energy?

Carbohydrates (glycogen); fat

In what organelle is energy stored?

Cytosol

Which cells are specialized to store nutrients?

Muscle & liver

Cytosol

Semiliquid portion of the cytoplasm

functions of cytosol

- Enzymatic regulation of intermediary metabolism
- Ribosomal protein synthesis
- Storage of fat and carbohydrates

Cytoskeleton

Protein network for structural support, transport, and cellular movement

3 components of cytoskeleton

-microtubules
-microfilaments
-intermediate filaments

Microtubules

-Maintain cell shape and control axonal transport, movement of cilia, flagella and chromosomes
-formed by small, globular tubulin molecules

Axonal transport

Bidirectional movement of large molecules and vesicles along the axon of neurons

Cilia

-Motile, hair-like protrusions on cell surface
-Ex: respiratory pathway

Flagella

-Motile appendage enabling cellular movement
-Ex: sperm

Microfilaments

Function in cellular contraction and mechanical support

Intermediate filaments

Provide structural support for components subject to mechanical stress

Tissue

-Aggregate of cells and extracellular material
- 4 main types: muscle, nervous, connective, epithelial

Muscle

-specialized for contraction
3 types: skeletal, cardiac, smooth

Nervous

-specialized for electrical and chemical signaling
-central & peripheral

Connective

-specialized for structural support
-tendons, bones, blood

Epithelial

-specialized for exchange
-epithelial sheets
-glands

Epithelial sheets

Form boundaries

Glands

-Specialized in secretion
-two types: exocrine (external) & endocrine (internal)

Sweat from the sweat glands in our skin is what type of secretion?

Exocrine

Insulin from pancreatic beta cells in what type of secretion?

Endocrine

Organ

Two or more primary tissues organized to perform a function
Ex: stomach

Homeostasis

-Dynamic maintenance of a stable internal (extracellular) environment w/in the organism
-essential to survival of each cell

Homeostasis pt.2

-requires continual exchange of material between the intracellular and extracellular spaces
-each organ system contributes by counteracting changes of internal environment

Homeostasis is maintained by control systems..

1.) Intrinsic
-local control systems built into an organ
ie: increased CO2 production leads to relaxation of smooth muscle & dilation of blood vessels
2.) Extrinsic
-external control system outside of an organ permitting coordinated regulation of several organs

negative feedback

Change in a controlled variable triggers a response that opposes the change

Sensor

Mechanism to detect the controlled variable

Set point

The desired value of the variable

Integrator

Compares the sensors input w/ the set point

Effector

Adjusts the value of the controlled variable

postive feedback

Reinforces the change in a controlled variable, occurs relatively rarely
Ex: giving birth, stronger contractions

Feedforward control

Response occurring in anticipation of a change in a control variable

Homeostasis is one of the most important concepts in physiology. Which of the following statements is correct?

-Homeostasis is the dynamic maintenance of a stable internal environment w/in the organism
-each organ system contributes to homeostasis by counteracting changes to the stable internal environment
-homeostasis relies primarily on negative feedback
-homeostasis control may be archived by intrinsic and/or extrinsic control systems

Which of these parameters is under homeostatic control?

-calcium concentration in the plasma
-body temp
-the concentration of glucose in our blood

Types of Intercelluar Communication

-gap junctions
-direct contact
-extracellular chemical messengers

Gap junctions

Proteinaceous tunnels that permit free diffusion of small molecules from one cell to the other

Direct contact

-Transient direct contact via cell surface receptors
-can be linked to intracellular cascades

Extracellular chemical messengers

paracrine secretion, neurotransmitter secretion, hormonal secretion, neurohormone secretion

Paracrine secretion

Signaling molecules released by a cell only affects target cells in close proximity to other neighboring cells

Hormonal secretion

Spatial range is body wide

Neurotransmitter secretion

neuron sends electrical signal to local target cell

neurohormone secretion

Neuron secretes hormone through blood to target cell

The body's two major control systems

-endocrine
-nervous

Endocrine system

-specialized for slower-acting, longer-lasting signals
-based on diffuse, indirect connections via bloodstream

functions of the endocrine system

Homeostasis, growth & development, reproduction & modulation of behavior

Nervous system

-specialized to process rapid, short-acting signals
-a network of precise, direct connections between cells

Ligand-Receptor Interactions

-ligand activates the receptor
4 types: nuclear receptors, GPCRS, enzyme-linked receptors, ionotropic receptors

nuclear receptors

-Protein inside a eukaryotic cell that, on binding to a signal molecule, enters the nucleus and regulates transcription
-activates gene expression

GPCRs

-binding w/exogenous or endogenous agonists induces GPCRS into a active conformational state which influences intracellular binding of G-proteins

Enzyme-linked receptors

transmembrane proteins that bind a hormone signal and directly catalyze a reaction inside the cell

ionotropic signaling

Activation of ion channels by direct binding of extracellular chemical messenger

Neurons

Cells specialized for electrical and chemical signaling
-electrical signals including action potentials are happening w/in neurons

Transporter proteins

-carrier-mediated transport
-used to escort molecules across the membrane that can't diffuse unassisted; has solute-binding site

Two types of transporter proteins

-facilitated diffusion
-membrane pump

Transporters

-have binding sites specific for their ligand
-can be saturated; max flux of molecules/unit of time

facilitated diffusion (passive transport)

-results in net movement downhill; from high to low concentration
-requires no ATP

facilitated diffusion pt.2

-binding site has a fixed affinity for the molecule to be transported
-binding triggers the binding site to flip to the opposite side of the membrane

Membrane pumps (active transport)

-pump results in a uphill movement; against the concentration gradient
-requires ATP

Membrane pump pt. 2

-binding site has variable affinity
-carrier undergoes two separate conformational rearrangements; affinity & orientation

What is an example of a membrane pump?

Na+/K+ ATPase pump

What are the main function of the Na+/K+ pump?

-establish & maintain concentration gradients for Na+/K+ ions

Ion channels (protein channels)

-permeable to specific ions such as Na+ or K+
-has a pore that allows ions to diffuse

The Na+/K+ ATPase

-sodium is being pushing OUT of the cell & potassium INTO the cell
-potassium is low affinity; sodium sites will be more likely to be occupied
-switches places; & affinity for potassium increases

What are the three differences in ion channels?

-selectivity, gating & permeability

Ligand gated channel

An ion channel that is stimulated to open by the binding of a small molecule such as a neurotransmitter.

Voltage gated channel

-Opens when changes in the membrane potential
-voltage allows it to open

Mechanically gated channel

The "gate: is tethered to another structure and can be pulled open or closed

Ungated channels

-always open
-two types: leak channels for Na & K

Diffusion (chemical driving force)

-down a concentration gradient; from area of high to low
-due to thermal motion which results in random collisions

The greater the concentration of solute in regard to diffusion..

The greater the likelihood of collision

Diffusion through a membrane

-larger concentration gradient> faster initial rate of diffusion
-higher permeability of the membrane> faster rate of diffusion

The electrical driving force

-movement of charged particles along an electrical gradient due to repulsion or opposite charges
-particles DO NOT need to be in physical contact

Resting Membrane Potential (RMP)

-part of the electrical driving force
-the voltage difference across the plasma membrane (Vm)