Cell Biology Exam 2 SH
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- Membrane Functions
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Cell Communication
Import/Export of molecules
Movement
- What makes up phospholipids and most abundant
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Polar Head
-Phosphate
-Glycerol
-Choline
Fatty acid tails
Phosphotidylcholine - Phospholipid Bilayer
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Assymetric (not same # on opposite sides)
Move by:
-Lateral Diffusion
-Flipflop
-Rotation - Flippases
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Synthesize the bilayer
Move phospholipids to opposite side of bilayer with enzymes
Macrophages take away dying cells - Membrane Protein Functions
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Transport nutrients
Anchor membrane to macromolecules
Receptors to detect signals
Work as enzymes to catalyze reactions
Hemotaxis-move toward chemical signals - How proteins move within the membrane
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Cytoskeletal confinement
Directed motion
Transient confinement(spontaneous)
Random diffusion - How can proteins be removed from the bilayer
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Detergents
-remove integral proteins - Integral Proteins
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Scan the lipid bilayer
-Glycophorin-RB cells (a-helix)
-Bacteriordopsin-proton pump
-Porin-nonselective channel - Peripheral Proteins
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Removed by interupting protein/protein interactions
Cross bilayer by a-helix (20AA)
Hydopathy Index-determines how many AA needed to cross layer - Detergents
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Disrupt Protein/Bilayer interaction
SDS-Sodium Dodecyl Sulfate - Parts of Microscope
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Lens
Light source
Object - Image and its properties
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2-D representation of a 3-D object
Intensity-brightness
Contrast-object from background
Resolution-object from other objects - Types of Light Microscopy
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Bright-field-outline of cell and nucleus
Phase Contrast-halo
Differential-interference-3-D image - Fluorescence Microscopy
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Dyes that stain certain parts of cell
Epifluorescence-light source and sample image go through same lens - Confocal Microscopy
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Looks inside the cell
-Uses LASER and PINHOLE
-Blurred background -
Scanning Electron Microscope
(SEM) - Gives 3-D image
- Transmission Electron Microscope(TEM)
- Looks at cell detail
- 2 Classes of cell membrane transport proteins
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Transporter-transfer small molecules by changing shape (Active or Passive Transport)
Channels-tiny hydrophilic pores (Passive transport)
- Channel regulation
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Permeable dependent on SIZE and CHARGE
-if ion is small enough and carries right charge then it can pass through open channel - Transporter regulation
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Permeable to molecules that fit into binding site
Transfers by conforming shape - Passive/Active Transport
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Passive-moves WITH the concentration gradient
(Facilitated diffusion)
Active-moves against concentration gradient
(Pumps) - Membrane Potential
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difference in electrical charges on each side of membrane
Cytoplasmic side has (-) charge - Electrochemical Gradient
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Net force driving a charged solute across the membrane
Determines direction of passive transport
Due to: CONCENTRATION GRADIENT AND VOLTAGE
Na=high EG
K=Low EG
- Active Transporters (examples)
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Na-K Pump-uses ATP to pump Na out of cell and K into cell (against gradient)
-also an enzyme-ATPase
-called "Na+K+ATPase"
Ca2+Pumps-keeps Ca concentration mostly outside cell
-ATP-driven Ca2+Pumps
-maintains free calcium concentration - Glucose Transport
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1.Epithelial cells(lumen) transfer glucose across lining by "Glucose-Na+ Symport"
-Apical surface-contains symport
2.Basal surface has PASSIVE GLUCOSE UNIPORTS to release glucose down concentration gradient
-Tight Junctions keep transporters separate - How do ion channels differ
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1.Ion Selectivity-type of ions
2.Gating-conditions that influence opening and closing - Gated Channels and Regulations
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VoltageGated-controlled by membrane potential(charge)
-used in neurons
LigandGated-controlled by binding of a ligand on inside or outside of membrane
MechanicalGated(StressGated)-controlled by mechanical force
-hairs in ear canals - K+/Na+ Channels
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Resting State(cytosolic face negative)-Na channel closed and K channel partly open
Depolarized State(cytosolic face positive)-Na channel open and K channel open - K+ Leak Channels
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Negative charges on inside cell are regulated by K+ channels
-MAJOR ROLE IN GENERATING MEMBRANE POTENTIAL
-Opens when Na+ channels close - Resting Membrane Potential
- flow of +/- ions across a membrane is balanced
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Concentration Gradients
(Na, K, Ca, Cl-) -
Na=12-fold difference
K=40-fold difference(inside)
Ca=free calcium is not good
Cl=35-fold difference - Nernst Potential
- Ca2+ K+ Positive Negative
- Graph about Resting Potential
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Depolarized-MP is higher than resting potential
Repolarized-MP is falling closer to resting potential
(Na and Ca stop moving through membrane)
Hyperpolarization-MP is below resting potential - Neurons
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Receive, conduct, and transmit signals
-Stimulated by a signal-this signal changes membrane potential at that site
Parts-Cell body, Axon, Dendrites(nerve terminal)
- Neurotransmitters
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Resting Nerve Terminal-Ca2+ channel is closed
Activated Nerve Terminal-Ca2+ channel opens and transmits chemical signal
Activated Nerve Terminal-TransmitterGated channel accepts neurotransmitters
Active Synapse-chemical signal is changed to electrical signal - Action Potential
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Traveling wave of electrical impulse
Triggered by rapid change in membrane potential
1.Fastest communication in body
2.Ca, K, and Na are crucial
3.Action potential alterations result in arrhythmias or epilepsy - 3 Channels involved in Action Potential
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1.VoltageGated Na+ channels
2.VoltageGated K+ channels
3.K+ Leak Channels - VoltageGated Na+ channels
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Open during depolarization to allow ions into cell
-Form into 3 conformations:
- VoltageGated Ca2+ Channels
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Convert electrical signals into chemical signals at nerve terminals
-transports neurotransmitter - TransmitterGated Channels
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Convert chemical signals back into electrical signals in target cells
-Changes membrane potential - VoltageGated K+ Channels
- In nerve axon-return membrane to resting potential after Na+
- 3 Stages food is broken down
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1.Digestion-enzymatic breakdown of food(catabolism)
2.Glycolysis-converts glucose into 2 pyruvate, 2ATP, and NADH
3.Oxidative Breakdown in mitochondria-Acetyl CoA goes through Citric Acid cycle to produce water, CO2, and NADH - Glycolysis facts
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ANAEROBIC process-Oxidation still occurs with NAD+ and NADH
-Occurs in cytosol
-Cleaves into 2 pyruvate molecules
-Synthesis of ATP(Phosphorylation)
-Energy is harvested in steps 6&7
-AlphaGlucose is used - Pyruvates location during glycolysis
- Junction between Aerobic and Anaerobic metabolism
- Fermentation
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Allows ATP to form without Oxygen
-How pyruvate breaks down
-NAD+ is regenerated by either producing lactate, ethanol, or CO2 as waste - CoEnzyme-A Facts
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Pyruvate is oxidized to form CoA, NADH, and CO2 by PYRUVATE DEHYDROGENASE COMPLEX
Fatty acids and sugars are also formed into Acetyl CoA in mitochondria - Citric Acid Cycle (Krebs or Tricarboxylic acid cycle)
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8 Reactions
-Requires Oxygen to turn NADH into NAD+ so cycle can continue
Generates 3 NADH, FADH2, GTP, and CO2 waste - Precursors formed by Glycolysis/Citric Acid Cycle
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Pyruvate--alanine(AA)
Others: amino acids, fatty acids, lipids, and nucleotides - Sleeping Sickness
- Trypanozome-cannot do electron transport so it eats Glucose in the bloodstream which takes all ATP (no energy)