NUTRIENT TRANSPORT ACROSS CELLULAR MEMBRANE Flashcards
TYPICAL THICKNESS OF CELL MEMBRANE
4-10nm
WHAT DETERMINES HUMAN BLOODTYPE?
MARKER PROTEINS ON ERYTHROCYTES
THE FLUID MOSAIC MODEL OF THE PLASMA MEMBRANE DESCRIBES THE MEMBRANE AS:
FLUID COMBINATION OF PHOSPHOLIPIDS, CHOLESTEROL AND PROTEINS. CARBOH. ATTACHED TO LIPIDS (GLYCOLIPIDS) AND PROTEINS (GLYCOPROTEINS) EXTEND FROM THE OUTWARD FACING SURFACE OF THE MEMBRANE.
WHAT IS THE MOST RAPIDLY METABOLIZING ORGANELLE OF THE CELL?
MITOCHONDRION
PROPORTIONS OF PLASMA MEMBRANE COMPONENTS VARY ACCORDING TO…
CELL TYPE
MEMBRANES ACTIVELY INVOLVED IN METABOLISM CONTAIN MORE OF WHICH PLASMA MEMBRANE COMPONENT?
PROTEIN
MITOCHONDRION MEMBRANE COMPOSITION VS SCHWANN CELL MEMBRANE COMPOSITION
M: 76% PROTEIN, 24% LIPID
S: 76% LIPID, 18% PROTEIN
STRUCTURE OF PHOSPHOLIPID MOLECULES:
HYDROPHILIC HEAD (PHOSPHATE CONTAINING GROUP ATTACHED TO A GLYCEROL MOLECULE); ATTRACTS WATER BECAUSE PHOSPHATE IS NEGATIVELY CHARGED MAKING THE HEAD POLAR
AND
TWO HYDROPHOBIC TAILS (EACH CONTAINING EITHER A SATURATED OR UNSATURATED FATTY ACID); UNCHARGED AND NON POLAR
WHAT ARE AMPHIPATHIC MOLECULES?
MOLECULES THAT CONTAIN BOTH A HYDROPHILIC AND HYDROPHOBIC REGION
WHAT ROLE DO PHOSPHOLIPIDS PLAY IN THE FOOD INDUSTRY AND WHY?
THEY ACT AS EMULSIFIERS BECAUSE OF THEIR AMPHIPATHIC NATURE
WHAT IS THE MOST STABLE THERMODYNAMIC STRUCTURE?
THE PHOSPHOLIPID BILAYER
IN THE PHOSPHOLIPID BILAYER, WHICH PART IS FACING OUTWARD?
THE HYDROPHILIC HEADS
IS THE LIPID BILAYER SYMETRICAL OR ASYMETRICAL?
ASYMETRICAL (DIFFERENT PHOSPHATE CONTAINING GROUPS, DIFFERENT PROTEINS AND CARBS, OVERALL DIFFERENT LOOK OF THE INNER AND OUTER MONOLAYER)
WHICH CHARACTERISTIC OF THE LIPID BILAYER IS ESSENTIAL FOR ITS STRUCTURE AND FUNCTIONS?
FLUIDITY (IT BEHAVES AS A 2 DIMENSIONAL FLUID) AND DYNAMICS
TYPES OF MOVEMENTS POSSIBLE IN THE LIPID BILAYER + EXPLANATIONS:
ROTATION ON THE PHOSPHOLIPID AXIS AND VIBRATION (‘FLEXION’); VERY DYNAMIC, 10 -9sec
LATERAL MOVEMENT; 10 -6sec
FLIP FLOP MOVEMENT; RARE, OCCURRING CCA EVERY 28HRS (10 5sec), PHOSPHOLIPIDS SWITCH MONOLAYERS, CATALYSED BY ENZYMES, SOME REQUIRE ATP
WHERE ARE CARBOHYDRATES LOCATED IN THE PLASMA MEMBRANE AND WHERE ARE PROTEINS LOCATED?
CARBS: OUTER MONOLAYER
PROTEINS: EITHER INNER OR OUTER MONOLAYER OR INTEGRATED WITHIN THE BILAYER
WHAT IS USED TO MONITOR MOLECULAR DYNAMICS?
FRAP: FLUORESCENCE RECOVERY AFTER PHOTOBLEACHING
WHAT INFLUENCES THE FLUIDITY OF THE CELL MEMBRANE?
TEMPERATURE, PHOSPHOLIPID COMPOSITION (ESP NATURE OF FATTY ACID CHAINS) AND THE PRESENCE OF STEROLS (E.G. CHOLESTREOL)
WHAT DOES C16:0 INDICATE ABOUT A FATTY ACID?
C16 INDICATED THE NUMBER OF CARBONS, A 0 THE NUMBER OF DOUBLE BONDS
WHY ARE SATURATED FATTY ACIDS CALLED SATURATED?
BECAUSE THEY ONLY HAVE SINGLE BONDS SO EVERY CARBON HAS A BOND WITH MAXIMUM NUMBER OF HYDROGEN ATOMS
THE MOLECURAL INTERACTION BETWEEN 2 PHOSPHOLIPIDS IS STRONGER WHEN THE FATTY ACID CHAINS ARE MADE FORM WHAT TYPE OF FATTY ACIDS?
SATURATED
WHICH TYPE OF FATTY ACIDS CONTRIBUTES MORE TO MEMBRANE FLUIDITY (MAKING THE MEMBRANE LESS PACKED)?
UNSATURATED
MOLECULAR FORMULA OF CHOLESTEROL?
C27H46O
CHOLESTEROLS INTERACTIONS WITH WATER AND HYDROPHILIC MOLECULES?
CHOLESTEROL IS MOSTLY NON POLAR AND IS GENERALLY REPELLED TO WATER. BUT THE PRESENCE OF THE HYDROXYL GROUP (OH) ALLOWS IT TO WEAKLY INTERACT WITH HYDROPHILIC MOLECULES
CHOLESTEROL IS CLASSED AS A:
STEROID
HOW DOES INSERTION OF CHOLESTEROL BETWEEN THE PHOSPHOLIPIDS OF THE PLASMA MEMBRANE CHANGE ITS FLUIDITY?
BECAUSE OF ITS RIGID STRUCTURE CHOLESTEROL GENERATES SPACE, REDUCES INTERACTIONS BETWEEN THE FATTY ACID CHAINS AND INCREASES FLUIDITY.
WHEN IS CHOLESTEROL PARTICULARLY IMPORTANT FOR MAINTAINING MEMBRANE FLUIDITY?
WHEN TEMPERATURE CHANGES (IT CAN BOTH MODERATE THE INCREASE IN FLUIDITY WHEN IT’S WARMER, AND INCREASE IT)
WHAT IS THE RELATIONSHIP BETWEEN MEMBRANE FLUIDITY AND PERMEABILITY?
INCREASED FLUIDITY IS GENERALLY ASSOCIATED WITH INCREASED PERMEABILITY
WHAT DOES THE TERM ‘GLYCOCALYX’ REFER TO?
CARBOHYDRATES OF THE PLASMA MEMBRANE AS A WHOLE
MOST CARBOHYDRATES IN THE MEMBRANE ARE LINKED TO:
PROTEINS
ROLE OF CARBOHYDRATE LAYER IN THE MEMBRANE + ONE EXAMPLE FOR FUNCTION:
THE CARB LAYER ABSORBS WATER AND LUBRICATES THE OUTER LAYER OF THE MEMBRANE, THUS HELPING E.G. ERYTHROCYTES CHANGE THEIR SHAPE WHEN GOING INTO SMALL BLOOD VESSELS
+ STRUCTURAL ROLE
+ CELL RECOGNITION AND ADHESION
+ HAVE ATTACHING SITES FOR PATHOGENS
APPROXIMATE PROTEIN:LIPID RATIO IN MEMBRANES (IN TERMS OF NUMBER OF MOLECULES):
60:40
HOW MANY OF OUR GENES CODE FOR MEMBRANE PROTEINS?
1/3
2 MAIN GROUPS OF PROTEINS:
INTEGRAL AND ASSOCIATED
WHICH PROTEINS ARE PERMANENT COMPONENTS OF THE MEMBRANE?
INTEGRAL PROTEINS
WHAT KIND OF PERMEABILITY DOES THE CELL MEMBRANE HAVE?
SELECTIVE
WHICH SUBSTANCES CAN MOVE UNAIDED (SIMPLE DIFFUSION!!!!) THROUGH THE LIPID BILAYER OF THE CELL MEMBRANE?
RELATIVELY SMALL AND NON POLAR SUBSTANCES LIKE OTHER LIPIDS, LIPID SOLUBLE VITAMINS, O2, CO2 AND ALCOHOL
HOW DO WATER-SOLUBLE MATERIALS LIKE GLUCOSE, AMINO ACIDS AND ELECTRICALLY CHARGED IONS CROSS THE BILAYER?
BY INTRINSIC PROTEINS THAT FORM A VARIETY OF TRANSPORT SYSTEMS ACCORDING TO THE SUBSTANCE TYPE
HOW DO WATER-SOLUBLE MATERIALS LIKE GLUCOSE, AMINO ACIDS AND ELECTRICALLY CHARGED IONS CROSS THE BILAYER?
BY INTRINSIC PROTEINS THAT FORM A VARIETY OF TRANSPORT SYSTEMS ACCORDING TO THE SUBSTANCE TYPE
WHAT ARE THE 2 MAIN TYPES OF CELL TRANSPORT?
PASSIVE AND ACTIVE
WHAT ARE THE EXAMPLES OF PASSIVE CELLULAR TRANSPORT?
SIMPLE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION
WHAT ARE THE 2 MAIN TYPES OF ACTIVE TRANSPORT + THEIR SUBTYPES?
PUMP (PRIMARY AND SECONDARY) AND VESICLE (EXOCYTOSIS AND ENDOCYTOSIS)
WHAT ARE THE TYPES OF ENDOCYTOSIS?
PINOCYTOSIS, PHAGOCYTOSIS AND RECEPTOR MEDIATED ENDOCYTOSIS
WHAT IS THE NAME FOR THE UNEQUAL DISTRIBUTION OF MOLECULES?
CONCENTRATION GRADIENT
WHAT IS DIFFUSION?
SPREAD OF PARTICLES THROUGH RANDOM MOTION FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION (DOWN THEIR CONCENTRATION GRADIENT)
CAN NON LIVING SYSTEMS EXPERIENCE DIFFUSION?
YES
02 IS TYPICALLY MORE CONCENTRATED INSIDE OR OUTSIDE THE CELL?
OUTSIDE
WHAT IS FILTRATION AND WHERE DOES IT OCCUR?
A PROCESS WHICH IS A VARIATION OF DIFFUSION. MATERIAL MOVES ACCORDING TO ITS CONCENTRATION GRADIENT THROUGH A MEMBRANE; SOMETIMES THE RATE OF DIFFUSION IS ENHANCED BY PRESSURE
–> IT OCCURS IN THE KIDNEYS (BP FORCES LARGE AMOUNTS OF WATER AND ACCOMPANYING SOLUTES OUT OF THE BLOOD AND INTO THE RENAL TUBES; THE RATE OF DIFFUSION ALMOST TOTALLY DEPENDENT ON BP); IF THE BP IS TOO HIGH IT CAN ALSO ‘SQUEEZE’ PROTEIN THROUGH, LEADING TO PROTEIN IN URINE
OSMOSIS?
SPECIFIC TYPE OF DIFFUSION; PASSAGE OF WATER FROM A REGION OF HIGHER CONCENTRATION TO A REGION OF LOWER CONC.
CLASSIC EXAMPLE TO DEMONSTRATE OSMOSIS AND OSMOTIC PRESSURE?
IMMERSING CELLS (E.G. ERYTHROCYTES) INTO SUGAR SOLUTIONS OF VARIOUS CONCENTRATIONS.
WHAT IS LYSIS?
BREAKDOWN OF A CELL
WHAT STOPS HYDROPHILIC MOLECULES, CHARGED IONS AND RELATIVELY LARGE MOLECULES LIKE GLUCOSE FROM CROSSING THE MEMBRANE AND HOW DO THEY OVERCOME THAT?
ALTHOUGH THERE IS A CONCENTRATION GRADIENT FOR ALL THESE MOLECULES BUT THEY ARE REPELLED BY HYDROPHOBIC PARTS OF THE MEMBRANE. THEY USE FACILITATED TRANSPORT PROTEINS TO SHIELD THEM FROM THE REPULSIVE FORCE OF THE MEMBRANE.
CHANNEL (AND PORES) PROTEINS?
- INTEGRAL TRANSMEMBRANE PROTEINS CONTAINING HYDROPHILIC PASSAGES
- CHANNELS ARE SPECIFIC FOR THE SUBSTANCE BEING TRANSPORTED (DIFFERENT DIAMETERS)
- ALWAYS PASSIVE MOVEMENTS SINCE IONS MOVE THROUGH BY GRADIENT CONCENTRATION
- CAN BE VOLTAGE DEPENDENT, LIGAND DEPENDENT, MECHANOSENSORY, THERMORECEPTOR CHANNELS ETC, DEPENDING ON WHICH STIMULI REGULATES THEM
WHAT ARE AQUAPORINS, WHY ARE THEY IMPROTANT AND HOW MANY OF THEM ARE THERE IN HUMANS?
WATER HAS A FREE PASSAGE THROUGH THE MEMBRANE VIA OSMOSIS, BUT THAT IS NOT ALWAYS FAST ENOUGH SO SOME CELLS HAVE DEVELOPED A MORE SOPHISTICATED AND RAPID WATER TRANSPORT SYSTEM VIA CHANNEL PROTEINS (AQUAPORINS)
- THEY ARE HIGHLY EXPRESSED IN KIDNEYS
- 11 MAMMALIAN AQPs HAVE BEEN IDENTIFIED
APART FROM WATER, WHICH OTHER MOLECULES CAN PASS THE CELL MEMBRANE VIA AQUAPORINS?
CO2, GLYCEROL, UREA, PURINES, PYRIMIDINES AND NUCLEOSIDES
WHICH PROTEINS HAVE A HIGHER TRANSPORT SPEED, CHANNEL OR CARRIER PROTEINS?
CHANNEL PROTEINS (10S OF MILLIONS OF MOLECULES PER SEC VS THOUSAND TO A MILLION MOLECULES PER SEC)
CARRIER PROTEINS AKA TRANSPORTERS?
- TRANSMEMBRANE PROTEINS THAT USE ELECTROCHEM GRADIENTS TO MOVE MOLECULES ACROSS MEMBRANES
- VERY DIVERSE AND ABUNDANT, >100 FAMILIES
- CAN BE FOUND IN ALL CELL MEMBRANES
- BEFORE CROSSING THE MEMBRANE, A MOLECULE IS FIRST RECOGNIZE BY A TRANSPORTER, WHICH INCLUDES A CONFORMATIONAL CHANGE OF THE TRANSPORTER, ALLOWING THE TRANSFER OF THE MOLECULE ACROSS THE MEMBRANE
WHAT ARE THE TYPES OF TRANSPORTERS + EXPLANATIONS OF EACH TYPE?
- UNIPORT TRANSPORT: ONE TYPE OF MOLECULE IS MOVED
- CO-TRANSPORT: 2 TYPES OF MOLECULES TRANSPORTED SIMULTANEOUSLY, CAN BE ANTIPORT/ COUNTER TRANSPORT (MOLECULES MOVING IN OPPOSITE DIRECTIONS) OR SYMPORT TRANSPORT
HOW MANY TYPES OF GLUTs ARE THERE
14
IS GLUCOSE POLAR OR NON POLAR?
POLAR
WHAT ARE PUMPS?
TRANSMEMBRANE PROTEINS THAT ALLOW IONAS AND SMALL MOLECULES TO MOVE IN OUR OUT OF THE CELLS AGAINST THEIR CONCENTRATION GRADIENT, WHICH REQUIRES AN ENERGY SOURCE, USUALLY ATP –> TYPE OF PRIMARY ACTIVE TRANSPORT
EXAMPLE OF A PUMP (PRIMARY ACTIVE TRANSPORT)
Na+/K+ pump
WHAT PERCENTAGE OF THE TOTAL CELLULAR ATP OF ANIMAL CELLS DOES THE NA+/K+ PUMP USE?
25%
MECHANISM AND FUNCTION OF NA+/K+ PUMP:
MOVES 2 K+ INTO THE CELL AND 3 NA+ OUT OF THE CELL.
GAINS ENERGY THROUGH ATP HYDROLYSIS.
ENSURES THE INTERIOR OF THE CELL IS ALWAYS SLIGHTLY MORE NEGATIVE THAN THE EXTERIOR, WHICH CONTRIBUTES TO THE MEMBRANE POTENTIAL (ENABLES NEURONAL EXCITABILITY, CELL MUSCLE CONTRACTION, DIGESTED MOLECULE ABSORPTION..).
SECONDARY ACTIVE TRANSPORT EXAMPLE?
SGLT1 AND SGLT2 (GLUCOSE TRANSPORT COUPLED WITH NA+ TRANSPORT, ENERGY GAINED THROUGH NA+K+ATPase
WHAT IS ENDOCYTOSIS?
THE PROCESS OF A CELL IMPORTING MATERIAL BY ENVELOPING IT IN A PORTION OF ITS CELL MEMBRANE
WHAT IS EXOCYTOSIS?
THE PROCESS OF A CELL EXPORTING MATERIAL USING VESICULAR TRANSPORT.
WHAT IS PHAGOCYTOSIS?
- TYPE OF ENDOCYTOSIS
- USED FOR TRANSPORT OF LARGE MOLECULES
- MANY IMMUNE CELLS ENGAGE IN PHAGOCYTOSIS OF INVADING PATHOGENS
- WHEN THE VESICLE IS FULLY IN THE CELL, IT MERGES WITH A LYSOSOME FOR BREAKDOWN OF THE IMPORTED MATERIAL
WHAT IS CLATHRIN?
A PROTEIN THAT COATS A PIECE OF MEMBRANE WHICH WILL ENVELOP A MOLECULE UNDERGOING PHAGOCYTOSIS
– ALSO USED IT RECEPTOR MEDIATED ENDOCYTOSIS
WHAT IS PINOCYTOSIS?
- TYPE OF ENDOCYTOSIS
- FOR FLUIDS AND SOLUTES
- THE CELL MEMBRANE INVAGINATES CREATING A POUCH AND SURROUNDS A SMALL VOLUME OF FLUID/AND SOLUTES AND THEN PINCHES OFF
DIFFERENCES BETWEEN PHAGOCYTOSIS AND PINOCYTOSIS?
- TYPE OF MOLECULES THEY TRANSFER
- PINOCYTOSIS RESULTS IN MUCH SMALLER VESICLE
- THE VESICLE IN PINOCYTOSIS DOESN’T MERGE WITH A LYSOSOME
FAMILIAL HYPERCHOLESTEROLEMIA IS RELATED TO WHICH FORM OF ACTIVE TRANSPORT AND HOW?
LDL IS USUALLY REMOVED FROM BLOOD BY RECEPTOR-MEDIATED ENDOCYTOSIS. IN FAMILIAL HYPERC. THE LDL RECEPTORS ARE DEFECTIVE OR MISSING ENTIRELY WHICH IS WHY PEOPLE END UP HAVING LIFE THREATENING LEVELS OF PLASMA CHOLESTEROL
5 STAGES OF EXOCYTOSIS:
VESICLE TRAFFICKING VESICLE TETHERING VESICLE DOCKING VESICLE PRIMING VESICLE FUSION
EXAMPLES OF EXOCYTOSIS:
SECRETION OF NEUROTRANSMITTERS INTO THE SYNAPTIC CLEFT, SECRETION OF ECM PROTEINS, SECRETION OF ENZYMES, PEPTIDE HORMONES, AND ANTIBODIES!!!!!!!!
