LECTURE 8

MEMBRANES AND MEMBRANE TRANSPORT

THE PLASMA MEMBRANE SEPARATES THE INTERNAL CONTENTS OF THE

CELL FROM THE SURROUNDING ENVIRONMENT

THE PLASMA MEMBRANE REGULATES WHAT GOES INTO AND WHAT GOES OUT OF A CELL

THE PLASMA MEMBRANE DETECTS AND RESPONDS TO EXTERNAL
CHANGES AND RECOGNIZES CHEMICAL MESSENGERS FROM OTHER
CELLS

PROPERTIES OF THE PLASMA MEMBRANE

1. LIPIDS
       a.BLOCK PASSAGE OF MOST MOLECULES EXCEPT WATER
   AND SELECTED IONS
2. PROTEIN
      a.CONTROL THE ENTRANCE AND EXIT OF SELECTED
   MATERIALS

    1. CHANNELS
   
2. TRANSPORTED

3. CARBOHYDRATES - ATTACHED TO LIPIDS (GLYCOLIPIDS)
   OR PROTEINS (GLYCOPROTEINS)
       a. ACT AS RECEPTOR SITES THAT RECOGNIZE AND BIND
              WITH CERTAIN SUBSTANCES TO ENABLE CELLS TO:
             1. RECEIVE CHEMICAL COMMUNICATIONS FROM OTHER
        CELLS
             2. DETECT CHEMICAL CHANGES IN THEIR
        SURROUNDINGS
             3. RECOGNIZE OTHER CELLS

HOW MATERIALS PASS THROUGH THE PLASMA MEMBRANE

1. PASSIVE TRANSPORT

  
MOLECULES MOVE SPONTANEOUSLY FROM AN AREA OF
   HIGH CONCENTRATION TO AN AREA OF A LOWER
   CONCENTRATION. THIS IS A CONCENTRATION GRADIENT

2. ACTIVE TRANSPORT

   NOT SPONTANEOUS. ENERGY MUST BE USED SO, THE
   ACTION
IS ACTIVE

   THINGS MOVE AGAINST A CONCENTRATION GRADIENT

TYPES OF PASSIVE TRANSPORT

1. DIFFUSION
2. OSMOSIS
3. FACILITATED DIFFUSION

THINGS THAT PASS THROUGH THE MEMBRANE PASSIVELY ALWAYS MOVE BY DIFFUSION

DIFFUSION LEADS TO THE EQUAL DISTRIBUTION OF IDENTICAL MOLECULES

DIFFUSION IS AFFECTED BY:

1. STATE OF MATTER
   
a. SLOWEST IN SOLIDS
   
b. FASTEST IN GAS
2. TEMPERATURE
   
a. HEAT ACCELERATES MOLECULAR VELOCITY 
       INCREASES THE RATE OF DIFFUSION
3. SIZE OF MOLECULE
   
a. SMALLER MOLECULES TRAVEL FASTER THAN LARGER
       MOLECULES
4. DIFFERENCE IN CONCENTRATION OF
   IDENTICAL MOLECULES BETWEEN AREAS
  
   a. THE GREATER THE DIFFERENCE IN CONCENTRATION
       BETWEEN TWO AREAS THE FASTER THE RATE OF
       DIFFUSION

OSMOSIS (SPECIAL DIFFUSION)

THE DIFFUSION OF WATER THROUGH A DIFFERENTIALLY PERMEABLE MEMBRANE

THE CONCENTRATION OF SOLUTES IN A SOLUTION IS A
PRIMARY
  FACTOR IN DETERMINING THE RATE OF DIFFUSION.
THE MORE SOLUTES IN A SOLUTION THE LESS FREE WATER.

IF A CELL IS PUT IN A SOLUTION WITH MORE SOLUTES
AND LESS FREE WATER THAN IS IN THE CELL, WATER WILL
MOVE OUT OF THE CELL. THE SOLUTION IS HYPERTONIC. THE CELL WILL SHRINK

IF A CELL IS PUT INTO A SOLUTION HAVING FEWER SOLUTES THAN INSIDE THE CELL, AND MORE FREE WATER, THE WATER MOVES INTO THE CELL. THE SOLUTION IS HYPOTONIC. THE CELL WILL SWELL AND BURST.

IF A CELL IS PUT INTO A SOLUTION HAVING THE SAME AMOUNT OF SOLUTES AND THE SAME AMOUNT OF FREE WATER THERE WILL BE NO NET MOVEMENT OF WATER. THE SOLUTION IS ISOTONIC.

WHEN WATER ENTERS AN ANIMAL CELL IT WILL BURST IF TOO MUCH WATER ENTERS

WHEN WATER ENTERS A PLANT CELL A TURGOR PRESSURE DEVELOPS BECAUSE OF THE WATER PRESSING AGAINST THE CELL WALL. WHEN TURGOR PRESSURE GETS TO A CERTAIN LEVEL WATER NO LONGER ENTERS THE CELL

WHEN A PLANT CELL IS PUT IN A HYPERTONIC SOLUTION, WATER EXITS THE CELL AND THE MEMBRANE PULLS AWAY FROM CELL WALL. THIS IS CALLED PLASMOLYSIS

FACILITATED DIFFUSION

1. CARRIER PROTEINS AID IN THE TRANSPORT OF
   MOLECULES
THROUGH THE MEMBRANE
2. CARRIER PROTEINS FORM CHANNELS THROUGH THE
   MEMBRANE AS THEY CHANGE SHAPE

   WHEN A PROTEIN PICKS UP A MOLECULE IT CHANGES
       SHAPE

3. MOLECULES TYPICALLY TRANSPORTED THIS WAY ARE
       LIPIDS, GLUCOSE, UREA

LECTURE 9

ACTIVE TRANSPORT

CARRIER PROTEINS FUNCTION TO CARRY SOLUTES ACROSS A CELL MEMBRANE AGAINST A CONCENTRATION GRADIENT

SOLUTE - WHAT IS DISSOLVED IN A LIQUID
SOLVENT - WHAT A SOLUTE IS DISSOLVED IN

CONTINUES UNTIL THE SOLUTE BECOMES MORE CONCENTRATED ON THE SIDE OF THE MEMBRANE WHERE IT IS BEING PUMPED

FACTS ABOUT ACTIVE TRANSPORT

1. ACTIVE TRANSPORT IS NOT SPONTANEOUS
2. ENERGY IS REQUIRED
   
a. ATP ENERGY

    ATP = ADENOSIE TRIPHOSPHATE
   
b. WHEN ATP DONATES ENERGY TO THE CARRIER
      PROTEIN,THE SOLUTE BINDING SITE IS ALTERED

        1. THIS MAKES IT EASIER FOR SOLUTES TO BIND
   
                    TO THE CARRIER PROTEIN
   
             2. THE PROTEIN IS THEN CARRIED ACROSS THE
   
                    MEMBRANE
   
             3. ONCE ACROSS THE PROTEIN DROPS OFF THE
   
                    SOLUTE
   
             4. ONCE THE SOLUTE IS DELIVERED, THE
           CARRIER PROTEIN REVERTS TO IT’S LESS
           ATTRACTIVE SHAPE

EXAMPLES:

1. CALCIUM PUMP - KEEPS THE CALCIUM CONCENTRATION IN
   
CELLS 1000X LOWER THAN THE CONCENTRATION OUTSIDE
2. SODIUM-POTASSIUM PUMP - (COTRANSPORT)
   
a. SODIUM BINDS TO A CARRIER PROTEIN, CHANGING
      IT’S SHAPE, MAKING IT MORE RECEPTIVE TO
      POTASSIUM BINDING
   
b. BOTH ARE CARRIED IN TOGETHER

EXOCYTOSIS AND ENDOCYTOSIS

TWO METHODS USED TO MOVE LARGE AMOUNTS ACROSS A MEMBRANE

EXOCYTOSIS = MOVEMENT FROM INSIDE TO OUTSIDE

1. CYTOPLASMIC VESICLE MOVES TO THE MEMBRANE SURFACE
       AND FUSES WITH IT
2. CONTENTS EXPELLED WHEN MEMBRANES FUSE

ENDOCYTOSIS = MOVEMENT FROM OUTSIDE TO INSIDE

1. PART OF THE MEMBRANE SINKS INWARD AND BALLOONS
   AROUND PARTICLES
2. IT SEALS UPON ITSELF TO FORM A VESICLE WHICH IS
       RELEASED INTO THE CELL

PHAGOCYTOSIS = CELL "EATING"

1. CELL WRAPS "ARMS" AROUND A PARTICLE AND ARMS JOIN
   FORMING A VESICLE

   ARMS = PSEUDOPODS

2. VESICLE GOES FURTHER INTO CELL AND FUSES WITH A
   LYSOSOME

3. VESICLE CONTENTS DIGESTED

PINOCYTOSIS = CELL "DRINKING"

1. DEPRESSION FORMS ON THE CELL SURFACE A PUSHES
   INWARD
2. A VESICLE FORMS AND MOVES INTO THE CELL

ENDOCYTOSIS MAY BE RECEPTOR MEDIATED

1. RECEPTORS LOCATED IN
SHALLOW PITS (COATED
       PITS). THEY ARE COATED WITH RECEPTORS
       a. RECEPTORS ARE SPECIFIC FOR LIPOPROTEIN
      PARTICLES
   b. WHEN LIPOPROTEINS BIND
TO THE RECEPTORS, PITS
               SINK INTO THE CYTOPLASM,FORMING ENDOCYTIC
      VESICLES

METABOLISM

METABOLISM = THE CELLS ABILITY TO ACQUIRE ENERGY AND USE IT TO BUILD, STORE, BREAK APART AND ELIMINATE SUBSTANCES

ENERGY = A CAPACITY TO MAKE THINGS HAPPEN, TO DO WORK

ENERGY - HOW MUCH EXISTS?

1. TOTAL AMOUNT OF ENERGY IN A SYSTEM REMAINS
   CONSTANT
       a. ENERGY CANNOT BE CREATED
       b. ENERGY CANNOT BE DESTROYED
       c. ENERGY CAN ONLY BE CONVERTED FROM ONE FORM TO
      ANOTHER

EXAMPLE:

1. A CORN PLANT ABSORBS ENERGY FROM THE SUN
2. SUNLIGHT ENERGY IS CONVERTED INTO STARCH
      (CHEMICAL ENERGY)
3. AN ANIMAL EATS CORN AND
CONVERTS THE CHEMICAL
   ENERGY INTO OTHER FORMS OF
ENERGY

ENERGY FACTS:

1. ENERGY IS LOST AT EACH TRANSFER
2. ENERGY GOES FROM A STATE OF ORDER TO A STATE OF
   DISORDER
3. ENERGY IS STORED IN COVALENT BONDS IN SUCH
   COMPOUNDS AS
GLUCOSE, STARCH, GLYCOGEN,FATTY
   ACIDS
4. ENERGY CAN BE EXPRESSED IN
KILOCALORIES
       a. A KILOCALORIE IS 1000 CALORIES
       b. A KILOCALORIE IS THE AMOUNT OF ENERGY
      NECESSARY TO
HEAT 1000 GRAMS FROM 14.5
               TO 15.5OC AT STANDARD PRESSURE
5. THE ENERGY CONTENT IN GLUCOSE
AND OTHER MOLECULES
   OF LIFE IS
HIGH-QUALITY ENERGY
6. THE ENERGY LOST TO THE
ENVIRONMENT IS LOW QUALITY
       ENERGY
7. THE AMOUNT OF LOW QUALITY
ENERGY IS INCREASING

THE SECOND LAW OF THERMODYNAMICS

ENERGY GOES FROM AN ORDERED TO A DISORDERED STATE
ENTROPY IS A MEASURE OF THE DEGREE OF DISORDER


LECTURE 10

ENERGY LOSSES AND ENERGY GAINS

GLUCOSE ---> CO2 + H2O

RESULTS IN A NET LOSS OF ENERGY THE REACTION IS EXERGONIC

EXERGONIC = ENERGY OUT

THE HUMAN BODY USES AN AVERAGE OF 1,200 TO 2,800 KILOCALORIES OF ENERGY A DAY

EXERGONIC REACTIONS DO NOT REQUIRE ENERGY TO BE PUT IN THE SYSTEM

WHEN LARGE MOLECULES ARE MADE UP OF SMALLER MOLECULES ENERGY IS REQUIRED TO PUT THEM TOGETHER. THERE IS A NET GAIN OF ENERGY INTO THE SYSTEM. THESE REACTIONS ARE ENDERGONIC

ENDERGONIC = ENERGY IN

REVERSIBLE REACTIONS

REACTANTS ----> PRODUCTS
                         <----

A SPONTANEOUS REACTION TENDS TOWARD CHEMICAL EQUILIBRIUM

CELLS CONTINUALLY BUILD UP AND TEAR DOWN MOLECULES UNTIL THEY DIE. WHY?

1. CELLS CAN ONLY USE SO MANY MOLECULES AT ANY GIVEN
   TIME
2. CELLS HAVE A LIMITED AMOUNT OF SPACE TO HOLD ANY
   EXCESS
3. IF THEY PRODUCE MORE THEY CAN USE OR STORE THE
   EXCESS
MAY CAUSE PROBLEMS

a. PKU - PHENYLKETOUREA
       DEFECTIVE CELLS CANNOT BREAK DOWN PHENYLALANINE
b. PHENYLALANINE BUILDS UP IN THE CELL
c. EXCESS PHENYALANINE ENTERS REACTIONS TO PRODUCE
   PHENYLKETONES
d. PHENYLKETONES ACCUMULATE AND CAUSE BRAIN DAMAGE

METABOLIC PATHWAYS

A METABOLIC PATHWAY IS AN ORDERLY SEQUENCE OF REACTIONS WITH SPECIFIC ENZYMES REACTING AT EACH STEP.

BIOSYNTHETIC PATHWAYS - SMALL MOLECULES ARE ASSEMBLED INTO PROTEINS, LIPIDS, AND OTHER LARGE MOLECULES.

DEGRATIVE PATHWAYS - LARGE MOLECULES ARE BROKEN DOWN INTO SMALLER MOLECULES OF LESSER ENERGY

BOTH PATHWAYS INVOLVE THE FOLLOWING COMPONENTS:

1. SUBSTRATES (REACTANTS) - SUBSTANCES ABLE TO ENTER
   REACTIONS
2. INTERMEDIATES - COMPOUNDS FORMED BETWEEN THE
   START AND THE END OF A PATHWAY
3. ENZYMES - PROTEINS THAT CATALYZE REACTIONS
4. COFACTORS - ORGANIC MOLECULES OR METAL IONS THAT
   AID ENZYMES
5. ENERGY CARRIERS - ATP, DONATES ENERGY
6. END PRODUCTS - SUBSTANCES PRESENT AT THE END OF A
   REACTION

ENZYMES

CHARACTERISTICS:

1. CATALYTIC (SPEED-UP REACTIONS)
2. DON’T MAKE ANYTHING HAPPPEN THAT WOULDN’T HAPPEN
   ON ITS
OWN
3. ENZYMES ARE NOT ALTERED OR PERMANENTLY CHANGED IN
   A
REACTION. THEY CAN BE USED OVER AND OVER AGAIN
4. EACH ENZYME IS SUBSTRATE SPECIFIC

ENZYME-SUBSTRATE INTERACTIONS

ENZYMES HAVE AN ACTIVE SITE WHERE THE SUBSTRATE BINDS TO CATALYZE A REACTION

THE FIT IS NOT QUITE PERFECT. THIS IS THE INDUCED-FIT MODEL

BONDS ARE BROKEN AND THE ENZYME ALTERS THE SUBSTRATES

SHAPE SO IT FITS BETTER IN THE ACTIVE SITE. SUBSTRATES THAT HAVE BEEN ALTERED ARE IN AN ACTIVATED OR TRANSITION STATE.

SUBSTRATES IN THE TRANSITION STATE REACT SPONTANEOUSLY

ENZYMES MUST COLLIDE WITH A MINIMUM AMOUNT OF ENERGY TO REACT SPONTANEOUSLY. THIS MINIMUM AMOUNT OF ENERGY IS THE ACTIVATION ENERGY

ENZYMES DECREASE THE AMOUNT OF ACTIVATION ENERGY NECESSARY FOR A REACTION TO OCCUR

 

 

 

 

 

 

 

 

 

 

EFFECT OF TEMPERATURE AND pH ON ENZYME ACTIVITY

EACH ENZYME HAS A TEMPERATURE AND A pH OPTIMUM

AS TEMPERATURES INCREASE, THE ENZYME SHAPE CHANGES (DENATURATION), CHANGING THE SHAPE OF THE ACTIVE SITE.

A pH THAT IS TOO LOW OR TWO HIGH WILL ALSO CAUSE A CHANGE IN THE PROTEINS THREE-DIMENSIONAL SHAPE

CONTROL OF ENZYME ACTIVITY

1. ENZYME SYNTHESIS IS CONTROLLED
2. ENZYMES STIMULATED
3. ENZYMES INHIBITED

FEED-BACK INHIBITION - THE AMOUNT OF PRODUCT CONTROLS THE AMOUNT OF ENZYME ACTIVITY

ALLOSTERIC CONTROL - SUBSTANCES BIND TO A SITE OTHER THAN THE ACTIVE SITE TO AFFECT ENZYME ACTIVITY

ENZYME HELPERS

1. COENZYME
       a. COMPLEX ORGANIC MOLECULES DERIVED FROM
      VITAMINS
              A. NAD+ (NICOTINAMIDE ADENINE DINUCLEOTIDE)
              B. FAD (FLAVIN ADENINE DINUCLEOTIDE)
       b. PICK UP HYDROGEN ATOMS THAT ARE LIBERATED
      DURING GLUCOSE BREAKDOWN
       c. TRANSPORT PROTONS TO OTHER REACTION SITES

      NAD+ + H ---> NADH
              FAD + H2 ---> FADH2

   d. NADP+ + H ---> NADPH

2. METAL IONS

Fe++ - COMPONENT OF A CYTOCHROME MOLECULE

ELECTRON TRANSFERS IN METABOLIC PATHWAYS

WHEN CHEMICALS ARE BROKEN DOWN THEY ARE BROKEN DOWN SLOWLY

SUBSTRATE --> INTERMEDIATE --> PRODUCT

WHEN SUBSTRATES ARE BROKEN DOWN, ELECTRONS ARE RELEASED

ELECTRONS ARE SENT DOWN ELECTRON TRANSPORT CHAINS

ELECTRON TRANSPORT CHANS ARE IN THE MEMBRANES OF MITOCHONDRIA AND CHLOROPLASTS

ELECTRON TRANSPORT CHAINS ARE ARRANGEMENTS OF ENZYMES AND COENZYMES THAT TRANSFER ELECTRONS ALONG A ORGANIZED SEQUENCE.

DONATES-->ACCEPTS-->DONATES--> ACCEPTS

OXIDATION --> REDUCTION

OXIDATION = DONATES ELECTRONS

REDUCTION = ACCEPTS ELECTRONS

ATP

STRUCTURE AND FUNCTION

WHEN GLUCOSE IS BROKEN DOWN, THE ENERGY RELEASED IS HARNESSED AND CONVERTED TO ATP ENERGY

ATP CONSISTS OF:
1. ADENINE
2. RIBOSE SUGAR
3. THREE PHOSPHATES

COMPONENTS ARE HELD TOGETER BY COVALENT BONDS

WHEN THE OUTER PHOSPHATE COVALENT BOND IS BROKEN, ENERGY IS RELEASED

ATP/ADP CYCLE

ADP IS PHOSPHORYLATED TO FORM ATP

WHEN A MOLECULE IS PHOSPHORYLATED ITS STORE OF ENERGY INCREASES

LECTURE 11

ENERGY-ACQUIRING PATHWAYS

PHOTOSYNTHESIS IN HIGHER PLANTS CONSISTS OF TWO STAGES

1. LIGHT-DEPENDENT REACTIONS
       a. ENERGY FROM SUNLIGHT ABSORBED AND CONVERTED TO
      ATP ENERGY
   b. WATER MOLECULE IS SPLIT, OXYGEN, AND HYDROGEN
      AND ELECTRONS ARE LIBERATED
   c. NADP+ PICKS UP THE LIBERATED HYDROGEN AND
      ELECTRONS TO FORM NADPH

2. LIGHT-INDEPENDENT REACTIONS
       a. ATP ENERGY DONATED TO SITES WHERE GLUCOSE IS
      MADE FROM CARBON, HYDROGEN AND OXYGEN
       b. CARBON DIOXIDE PROVIDES CARBON AND OXYGEN
       c. HYDROGEN IS BROUGHT IN AS NADPH

12H2O + CO2 -> 6O2 + C6H12O6 + 6H2O

        sunlight

GLUCOSE MOLECULES COMBINE WITH EACH OTHER SIMPLE SUGARS TO FORM SUCROSE, STARCH AND OTHER CARBOHYDRATES

WHERE THE REACTIONS TAKE PLACE

BOTH REACTIONS TAKE PLACE INSIDE THE CHLOROPLAST

THE CHLOROPLAST IS SURROUNDED BY A DOUBLE MEMBRANE AND CONTAINS A SERIES OF STACKS OF FLATTENED SACS (THYLAKOID MEMBRANES) LOCATED IN THE STROMA.

THE LIGHT DEPENDENT REACTIONS OCCUR IN THE THYLAKOID MEMBRANES

THE LIGHT INDEPENDENT REACTIONS OCCUR IN THE STROMA

LIGHT TRAPPING PIGMENTS

PIGMENTS - MOLECULES THAT ABSORB LIGHT.

PHOTONS ARE PACKETS OF LIGHT ENERGY

1. CHLOROPHYLLS - ABSORB RED AND BLUE LIGHT AN
   TRANSMIT GREEN LIGHT
       a. CHLOROPHYLL a - MAIN PIGMENT
       b. CHLOROPHYLL b

2. CAROTENOIDS - ABSORB VIOLET AND BLUE AND TRANSMIT
   RED,ORANGE AND YELLOW

3. PHYCOBILINS - RED AND BLUE PIGMENTS

CHLOROPHYLL b, CAROTENOIDS AND PHYCOBILINS ARE ACCESSORY PIGMENTS THAT TRAP WAVELENGTHS OF LIGHT THAT CHLOROPHYLL a CANNOT. THEY PASS THE TRAPPED ENERGY ON TO CHLOROPHYLL a.

LIGHT-DEPENDENT REACTIONS

THREE EVENTS:

1. PIGMENTS ABSORB SUNLIGHT ENERGY AND GIVE UP
   ELECTRONS
2. ATP AND NADPH FORMATION
3. PIGMENTS THAT GAVE UP ELECTRONS GAIN ELECTRONS

PHOTOSYSTEMS

THOUSANDS OF PHOTOSYSTEMS ARE EMBEDDED IN THE THYLLAKOID MEMBRANES

EACH PHOTOSYSTEM HAS SEVERAL HUNDRED PIGMENT MOLECULES

1. LIGHT ENERGY IS ABSORBED BY THE PIGMENT MOLECULES
2. THE SUNLIGHT ENERGY BOOSTS AN ELECTRON IN A
   PIGMENT
MOLECULE TO A HIGHER ENERGY STATE
3. THE ENERGIZED ELECTRON BOUNCES AROUND IN THE
   LIGHT HARVESTING COMPLEX, LOSING ENERGY AT EACH
   BOUNCE, UNTIL THE WAVELENGTH IS THE WAVELENGTH
   NEEDED TO
ACTIVATE THE CHLOROPHYLL MOLECULE THAT
   GIVE OFF THE
ELECTRONS USED FOR PS.

ATP AND NADPH FORMATION

TRAPPED ELECTRONS ARE TRANSPORTED DOWN AN ELECTRON TRANSPORT CHAIN TO PRODUCE ATP AND NADPH

ELECTRON TRANSPORT CHAINS ARE ORGANIZED SEQUENCES OF ENZYMES AND OTHER PROTEINS BOUND TO CELL MEMBRANES

1. ELECTRONS PASS FROM PROTEIN TO PROTEIN
2. EXTRA ENERGY IS RELEASED TO DRIVE SPECIFIC
   REACTIONS

TWO KINDS OF PHOTOSYSTEMS GIVE UP ELECTRONS IN PLANTS TO MAKE ATP BY TWO DIFFERENT PATHWAYS

THESE TWO PHOTOSYSTEMS ARE:

1. PHOTOSYSTEM I
2. PHOTOSYSTEM II

THE TWO PATHWAYS PRODUCING ATP ARE:

1. CYCLIC
2. NONCYCLIC

CYCLIC PATHWAY

1. ELECTRON EXITS CHLOROPHYLL (P700) IN PHOTOSYSTEM
   I
2. EXCITED ELECTRON ACCEPTED BY AN ELECTRON ACCEPTOR
3. ELECTRON PASSED THROUGH A CHAIN OF ELECTRON
   ACCEPTORS BACK TO P700

ATP FORMED FROM ADP AND PHOSPHATE AS THE ELECTRON PASSES DOWN THE CHAIN

THE CYCLIC PATHWAY IS THE OLDEST MEANS OF ATP PRODUCTION. NOT MUCH IS PRODUCED IN THIS PROCESS

THE ELECTRONS THAT LEAVE PHOTOSYSTEM I RETURN

NONCYCLIC PATHWAY

THE ELECTRONS THAT EXIT PHOTOSYSTEM II DO NOT RETURN.

THEY ARE CARRIED AWAY AS PART OF NADPH

1. LIGHT HITS A CHLOROPHYLL MOLECULE(P680)IN
   PHOTOSYSTEM II
2. CHLOROPHYLL GIVES UP AN ELECTRON AND A WATER
   MOLECULE
SPLITS INTO OXYGEN, HYDROGEN IONS AND
   ELECTRONS
3. THE EXCITED ELECTRON IS ACCEPTED BY AN ELECTRON
       ACCEPTOR AND THE ELECTRONS FROM THE WATER
   MOLECULE REPLACE THE EXCITED ELECTRONS
4. THE ELECTRONS FROM P680 ARE PASSED ALONG AN
   ELECTRON TRANSPORT CHAIN TO P700 WHERE THEY ARE
   REACTIVATED
5. ACTIVATED ELECTRONS ACCEPTED BY ANOTHER ELECTRON
   ACCEPTOR
6. ELECTRONS PASSED DOWN ANOTHER ELECTRON TRANSPORT
   CHAIN
7. TWO ELECTRONS ALONG WITH A HYDROGEN ION COMBINE
   WITH NADP+ TO FORM NADPH

ATP FORMATION IN CHLOROPLASTS

MADE ALONG THE ELECTRON TRANSPORT SYSTEM

1. ELECTRONS FLOW THROUGH THE MEMBRANE-BOUND
   TRANSPORT
SYSTEM
2. THE ELECTRONS PICK UP H+ IONS OUTSIDE THE
   THYLAKOID
MEMBRANE AND DUMP THEM OFF IN THE
   INSIDE (LUMEN) SETTING UP A H+ CONCENTRATION AND
   AN ELECTRIC GRADIENTS ACROSS THE MEMBRANE
3. H+ IONS FROM WATER BEING SPLIT IN THE LUMEN ADD
   TO THE CONCENTRATION OF IONS
4. IONS FLOW OUT OF THE LUMEN ACROSS THE MEMBRANES
   CAUSING AN ENERGY FLOW
5. ENERGY USED TO BIND PHOSPHATE TO ADP FORMING ATP

LECTURE 12

LIGHT-INDEPENDENT REACTIONS

SYNTHESIS PART OF PHOTOSYNTHESIS

USES ATP AND NADPH FROM THE LIGHT REACTION ALONG WITH CO2 TO FORM CARBOHYDRATES

CAPTURING CARBON

CARBON DIOXIDE FIXATION

1. CO2 DIFFUSES INTO THE AIR SPACES IN A LEAF
2. CO2 DIFFUSES ACROSS THE PLASMA MEMBRANE AND INTO
   THE STROMA OF A CHLOROPLAST
3. CO2 ATTACHES TO RuBP (RIBULOSE BISPHOSPHATE)
       BUILDING GLUCOSE SUBUNITS

CALVIN-BENSON OR CALVIN CYCLE - PRODUCES A SUGAR-PHOSPHATE MOLECULE AND REGENERATES RuBP

NAMED IN HONOR OF MELVIN CALVIN WHO DISCOVERED THE CYCLE

CO2 + RuBP ---> UNSTABLE 6-C MOLECULE

6-C MOLECULE ---> 2PGA

(PGA=PHOSPHOGLYCERATE; EACH PGA HAS 3 CARBONS)

PGA + ATP + H+ + e- ---> PGAL

(PGAL = PHOSPHOGLYCERALDEHYDE)

THE ABOVE REACTION OCCURS SIX TIMES TO MAKE A 6-C MOLECULE AND 12 PGAL’s

TWO PGAL’s COMBINE TO FORM A 6-CARBON SUGAR PHOSPHATE WHICH GOES INTO MORE REACTIONS

THE OTHER 10 PGAL’s ARE REARRANGED TO FORM MORE RuBP TO REPLACE THE ONES USED (6)

THE ADP, NADP+, AND PHOSPHATES THAT ARE LEFT OVER DIFFUSE BACK TO THE SITES OF THE LIGHT-DEPENDENT REACTIONS WHERE THEY ARE NEEDED AND CONVERTED BACK TO ATP AND NADPH

THE 6-C MOLECULE PRODUCED IS A BUILDING BLOCK FOR SUCROSE, STARCH OR CELLULOSE

HISTORY

THREE PATHWAYS OF CARBON FIXATION

1. C3 - FIRST PRODUCT OF CO2 FIXATION IS A 3 CARBON
   COMPOUND
2. C4 - FIRST PRODUCT OF CO2 FIXATION IS A 4 CARBON
   COMPOUND
3. CAM - CRASSULACEAN ACID METABOLISM

C3 PLANTS ARE CAPABLE OF PHOTORESPIRATION.

RuBisCO - ENZYME THAT ADDS CO2 TO RuBP TO FORM AN
UNSTABLE 6-C COMPOUND

CAN ALSO ADD O2 TO RuBP MAKING IT UNAVAILABLE FOR CARBON FIXATION

THIS MAKES FOR A LESS PRODUCTIVE PLANT

C4 METABOLISM

1. OCCURS IN MANY GRASSES AND WEEDS
2. HAS A STABLE 4-C COMPOUND AS IT’S FIRST PRODUCT
       a. OAA (OXALOACETATE)
3. CLOSES STOMATES DURING TIMES OF WATER STRESS
       a. C4 PHOTOSYNTHESIS OCCURS IN MESOPHYLL CELLS
      AND OAA IS PRODUCED
       b. OAA IS TRANSPORTED TO BUNDLE SHEATH CELLS
      WHERE CO2 IS RELEASED AND FIXED AGAIN BY THE
               C3 PATHWAY
4. 80% OF ALL PLANT SPECIES THAT EVOLVED IN FLORIDA
   ARE
C4 PLANTS.

CAM PLANTS

FIX CARBON AT NIGHT AND USE IT BY DAY

FOUND PREDOMINANTLY IN PLANTS GROWING IN SEVERELY DRY ENVIRONMENTS SUCH AS DESERTS

STOMATES ARE CLOSED DURING THE DAY AND OPEN AT NIGHT.

1. COLLECT CO2 AT NIGHT WHEN STOMATES ARE OPEN AND
       STORE IT IN THE VACUOLE
2. USE STORED CO2 DURING THE DAY WHEN THE STOMATES
   ARE
CLOSED
3. CARBON IS FIXED IN THE SAME TISSUES AT DIFFERENT
   TIMES
4. GROW SLOWLY

CHEMOSYNTHESIS

1. CONDUCTED BY SOME BACTERIA CALLED CHEMOAUTOTROPHS
       a. ENERGY FROM AMMONIUM IONS, IRON OR SULFUR
              COMPOUNDS

AUTOTROPHS - ORGANISMS CAPABLE OF PRODUCING THEIR OWN FOOD

HETEROTROPHS - ORGANISMS NOT CAPABLE OF PRODUCING THEIR OWN FOOD (ANIMALS)


LECTURE 13

ENERGY-RELEASING PATHWAYS

HOW CELLS MAKE ATP

1. BY BREAKING COVALENT BONDS OF CARBOHYDRATES,
   LIPIDS AND PROTEINS

THREE TYPES OF ENERGY-RELEASINGPATHWAYS

1. AEROBIC RESPIRATION
       a. MAIN ENERGY-RELEASING PATHWAY
       b. REQUIRES OXYGEN

2. FERMENTATION (ANAEROBIC)
       a. OCCURS IN THE ABSENCE OF OXYGEN

3. ANAEROBIC RESPIRATION
       a. OCCURS IN THE ABSENCE OF OXYGEN

ALL THREE ENERGY-RELEASING PATHWAYS START WITH THE SAME REACTION: GLYCOLYSIS

1. EACH GLUCOSE MOLECULE SPLITS AND REARRANGES
   ITSELF TO FORM 2 PYRUVATE 
MOLECULES

2. OXYGEN IS NOT REQUIRED

3. OCCURS IN THE CYTOPLASM

AEROBIC RESPIRATION

1. OCCURS INSIDE A MITOCHONDRION
2. OXYGEN IS THE FINAL ELECTRON ACCEPTOR
3. ALL REACTION STEPS ARE
CATALYZED BY ENZYMES
4. PRODUCE THE MOST ATP FOR EACH GLUCOSE MOLECULE;
   36 OR MORE

GLUCOSE + 6O2 ---> 6CO2 + 6H2O

THERE ARE THREE STAGES OF REACTIONS MAKING UP AEROBIC RESPIRATION

STAGE 1 - GLYCOLYSIS

STAGE 2 - KREB CYCLE

      a. PYRUVATE IS BROKEN DOWN COMPLETELY TO
   
               CO2

STAGE 3 - ELECTRON TRANSPORT PHOSPHORYLATION

   
       a. YIELDS MANY ATP MOLECULES BY PASSING
         ELECTRONS
DOWN THE CHAIN
      b. OXYGEN ACCEPTS THE "SPENT" ELECTRONS

GLYCOLYSIS

1. GLUCOSE PHOSPHORYLATED (2 PHOSPHATE MOLECULES
   ADDED FROM 2 ATP MOLECULES)

2. GLUCOSE MOLECULE SPLITS APART TO FORM 2 PGAL
   MOLECULES

3. EACH PGAL MOLECULE FORMS UNSTABLE INTERMEDIATES
   THAT GIVE UP PHOSPHATE MOLECULES TO FORM
       4 ATP MOLECULES

4. ELECTRONS GIVEN UP TO NAD+ TO FORM NADH

5. NET PRODUCTS; 2 ATP, 2 NADH, 2 PYRUVATE MOLECULES

THE PYRUVATE PRODUCED IN GLYCOLYSIS IS PREPARED TO ENTER
THE KREB CYCLE INSIDE THE MITOCHONDRION

PREPARATORY STEPS

1. A CARBON ATOM IS TAKEN FROM EACH PYRUVATE
   MOLECULE LEAVING AN ACETYL GROUP

2. THE ACETYL GROUP IS PICKED UP BY A COENZYME A TO
   FORM
ACETYL CoA

KREB’S CYCLE

SERVES THREE FUNCTIONS:

1. HYDROGEN AND ELECTRONS ARE TRANSFERRED TO NAD+
   AND FAD
TO FORM NADH AND FADH2 (6 NADH AND 2 FADH2
   PER CYCLE CoA)

2. 2 ATP’s ARE PRODUCED

3. INTERMEDIATES ARE REARRANGED TO FORM OXALOACETATE

KREB’s CYCLE NAMED FOR HANS KREBS WHO FIGURED OUT THE STEPS OF THE CYCLE

ALSO CALLED THE CITRIC ACID CYCLE BECAUSE THE FIRST PRODUCT FORMED IS CITRIC ACID

OAA +ACETYL-CoA ---> CITRIC ACID

ELECTRON TRANSPORT PHOSPHORYLATION

1. OCCURS ACROSS THE CRISTAE OF THE MITOCHONDRION

2. THE ELECTRONS FROM NADH AND FADH2 ARE PASSED
   ACROSS THE MEMBRANE INTO THE OUTER COMPARTMENT
   (SPACE BETWEEN THE CRISTAE AND THE OUTER
   MEMBRANE) OF THE MITOCHONDRION SETTING UP AN
   ELECTRON GRADIENT.

       FADH2 = 2 ATP
       NADH = 3 ATP

3. HYDROGEN IONS FLOW BACK INTO THE INNER
   COMPARTMENT (MATRIX) DRIVING THE FORMATION OF ATP
   FROM ADP AND FREE PHOSPHATE

TRACKING THE ENERGY

            NADH    FADH2    ATP

GLYCOLYSIS    2       0      2 
PREP STEP     2

KREB’S CYCLE  6       2      2 

ELECTRON TRANSPORT

10NADH ---> 30 ATP

2FADH2 ---> 4 ATP

TOTAL ATP’s = 38

ANAEROBIC ROUTES

FERMENTATION PATHWAYS

1. LACTATE FERMENTATION

2. ALCOHOLIC FERMENTATION

WHAT ORGANISMS GROW UNDER ANAEROBIC CONDITIONS?

ORGANISMS THAT LIVE IN BOGS,MARSHES, SEWAGE TREATMENT PONDS, CANNED FOODS....

GLYCOLYSIS IS THE FIRST STEP IN ANAEROBIC RESPIRATION. 2 ATP, 2 NADPH MOLECULES AND 2 PYRUVATE MOLECULES FORM

LACTATE FERMENTATION

PYRUVATE IS CONVERTED TO LACTATE

LACTIC ACID IS WHAT FORMS IN YOUR MUSCLES WHEN THEY ARE OXYGEN STARVED

ALCOHOLIC FERMENTATION

PYRUVATE CONVERTED TO ACETALDEHYDE, CO2 IS LIBERATED
AND ACETALDEHYDE IS CONVERTED TO ETHANOL

USED BY YEAST:

1. MAKE BREAD DOUGH RISE

2. PRODUCE ALCOHOL FOR CONSUMPTION

ALCOHOL IS LETHAL TO YEAST AT A CONCENTRATION OF GREATER THAN 14%

ALCOHOL IS LETHAL TO WILD YEAST AT CONCENTRATIONS OF GREATER THAN 4%. BIRDS GET DRUNK EATING FERMENTING BERRIES

NET PRODUCTION 2 ATP’s FROM GLYCOLYSIS

ANAEROBIC ELECTRON TRANSPORT

ELECTRONS TAKEN FROM OTHER SOURCES SUCH AS SULFUR OR NITROGEN ARE SENT THROUGH ELECTRON TRANSPORT CHAINS

ENERGY FROM FATS

1. ENZYMES IN FAT CELLS BREAK APART GLYCEROL AND
   FATTY ACIDS

2. GLYCEROL IS CONVERTED TO PGAL WHEN IT REACHES THE
   LIVER

3. PGAL IS CONVERTED TO ACETYL CoA TO ENTER THE KREB
   CYCLE

4. FATS PRODUCE MORE ATP THAN CARBOHYDRATES

ENERGY FROM PROTEINS

EXCESS PROTEINS ARE NOT STORED

1. PROTEINS SPLIT INTO AMINO ACIDS

2. AMINE GROUPS SPLIT OFF OF THE AMINO ACIDS

3. CARBON BACKBONE THAT REMAINS CONVERTED TO FATS OR
   CARBOHYDRATES OR ENTER THE KREBS CYCLE FOR ATP
   FORMATION.

4. AMINO GROUPS CONVERTED TO UREA AND EXCRETED IN
   URINE


Lecture 14

CELL DIVISION AND MITOSIS

WHEN CELLS DIVIDE, PARENT CELLS MUST PROVIDE THEIR DAUGHTER CELLS WITH HEREDITARY INSTRUCTIONS (DNA) AND CYTOPLASMIC MACHINERY TO START UP THEIR OWN OPERATION

DNA = THE BLUEPRINT OF LIFE

CELLS DIVIDE THEIR DNA BY THE PROCESSES OF MITOSIS AND MEIOSIS

CYTOPLASM IS DIVIDED BY A PROCESS CALLED CYTOKINESIS

MITOSIS OCCURS IN SOMATIC OR BODY CELLS WHILE MEIOSIS OCCURS IN THE GERM CELLS OR SEX CELLS.

MEIOSIS PRECEDES THE FORMATION OF SPERM AND EGG

CHROMOSOMES

CONSISTS OF A STRAND OF DNA AND ATTACHED PROTEINS

PRIOR TO MEIOSIS THE CHROMOSOME UNDERGOES DUPLICATION

THE TWO CHROMOSOMES (NOW CALLED SISTER CHROMATIDS) STAY TOGETHER UNTIL THE LATER STAGES OF MITOSIS

SISTER CHROMATIDS ARE ATTACHED TO EACH OTHER AT THE CENTROMERE

MITOSIS AND CHROMOSOME NUMBER

ALL MEMBERS OF THE SAME SPECIES HAVE THE SAME TOTAL NUMBER OF CHROOMOSOMES IN THEIR SOMATIC CELLS

EACH ORGANISM RECEIVES ONE SET OF CHROMOSOMES FROM EITHER PARENT

HUMANS = 46 CHROMOSOMES (2N)

23 PAIRS (1N)

DIPLOID = 2N

HAPLOID = 1N

IN MITOSIS A DIPLOID PARENT CELL PRODUCES TWO DIPLOID DAUGHTER CELLS

N = NUMBER OF DIFFERENT CHROMOSOMES IN A CELL

MITOSIS AND THE CELL CYCLE

THE CELL CYCLE STARTS AT THE TIME NEW CELLS ARE PRODUCED AND ENDS WHEN THEY END THEIR OWN DIVISION

THE PHASES OF THE CELL CYCLE:

M = MITOSIS; NUCLEAR DIVISION AND CYTOPLASMIC

DIVISION

G1 = GAP BEFORE ONSET OF DNA REPLICATION

S = SYNTHESIS OF DNA AND ASSOCIATED PROTEINS

G2 = GAP BETWEEN COMPLETION OF DNA REPLICATION AND
  
    THE ONSET OF MITOSIS

G1, S AND G2 = INTERPHASE

THE CELL CYCLE LASTS FOR DIFFERENT AMOUNTS OF TIME FOR DIFFERENT CELLS

THE STAGES OF MITOSIS

THERE ARE FOUR STAGES TO MITOSIS

1. PROPHASE

a. PROMETAPHASE

2. METAPHASE

3. ANAPHASE

4. TELOPHASE

CHROMOSOMES ARE MOVED BY A SPINDLE APPARATUS

A SPINDLE APPARATUS CONSISTS OF TWO SETS OF MICROTUBULES EXTENDING FROM OPPOSITE POINTS TO THE CENTROMERE OF THE SISTER CHROMATIDS


PROPHASE: MITOSIS BEGINS

1. CHROMOSOMES START CONDENSING AND BECOME VISIBLE

2. THE SPINDLE STARTS FORMING.
   SPINDLE FIBERS MADE OF THE PROTEIN, TUBULIN.

3. KINETOCHORES ATTACH TO THE CENTROMERE

4. CENTRIOLES MOVE TO OPPOSITE POLES TO SET UP THE
   SPINDLE

PROMETAPHASE

1. NUCLEAR ENVELOPE BREAKS UP

2. MICROTUBULES ATTACH TO THE

KINETOCHORES

METAPHASE

1. CHROMOSOMES ALIGN ON THE EQUATORIAL PLATE (HALF
   WAY
BETWEEN THE POLES)

ANAPHASE

1. TWO SISTER CHROMATIDS SEPARATE FROM EACH OTHER
   AND MOVE TOWARD OPPOSITE POLES

2. EACH CHROMATID IS REFERRED TO AS A CHROMOSOME AT
   THIS POINT

TELOPHASE

1. BEGINS WHEN CHROMOSOMES REACH THE POLES

2. CHROMOSOMES RELAX AND UNWIND

3. NUCLEAR ENVELOPE REFORMS ENDING MITOSIS

DIVISION OF THE CYTOPLASM

CYTOPLASMIC DIVISION = CYTOKINESIS

PLANT CELL CYTOKINESIS:

1. CELL PLATE FORMATION

a. VESICLES FILLED WITH CELL WALL BUILDING
       MATERIALS COMBINE WITH SPINDLE FIBER DEBRIS

b. PLATE FORMS BETWEEN TWO NEW NUCLEI

c. CELLULOSE DEPOSITS COAT THE VESICLES AND DEBRIS
        FORMING A WALL

ANIMAL CELL CYTOKINESIS

1. DIVIDE BY PINCHING IN TWO (CLEAVAGE)

a. SHALLOW DEPRESSION FORMS AROUND THE CELL

b. MICROFILAMENTS ATTACH, SLIDE PAST ONE ANOTHER,
       AND CUT THE CELL IN HALF

QUESTIONS AT THE END OF THE CHAPTER

 

LECTURE 15

MEIOSIS

THERE ARE TWO TYPES OF REPRODUCTION:

1. ASEXUAL - ONLY ONE PARENT PASSES ON A
   DUPLICATE OF ALL ITS GENES TO ITS OFFSPRING.
       a. OCCURS IN THE ABSENCE OF SEX.
       b. THE OFFRSPRING IS/ARE GENETICALLY IDENTICAL TO
      THE PARENT.
       c. ASEXUALLY PRODUCED OFFSPRING ARE CLONES

2. SEXUAL REPRODUCTION
      a. TWO PARENTS PASS A SET OF GENES TO THEIR
     OFFSPRING
      b. OFFSPRING ARE GENETICALLY SIMILAR TO BOTH
     PARENTS BUT, NOT GENETICALLY IDENTICAL TO
     EITHER PARENT
      c. EACH HOMOLOGOUS CHROMOSOME HAS GENES FOR THE
     SAME CHARACTERISTIC SO THE OFFSPRING WILL
     INHERIT TWO GENES FOR THE SAME TRAIT (ie, HAIR
     COLOR, EYE COLOR, WEIGHT)

EACH FORM OF THE SAME GENE IS AN ALLELE

ALLELES RECOMBINE TO FORM AN INDIVIDUAL THAT IS UNIQUE

OVERVIEW OF MEIOSIS

1. MEIOSIS DIVIDES THE CHROMOSOMES IN THE NUCLEUS
   TWICE PRIOR TO CELL DIVISION

2. THE ULTIMATE GOAL OF MEIOSIS IS THE FORMATION OF
   GAMETES (EGG AND SPERM)

3. GAMETES ARISE FROM GERM CELLS

a. GERM CELLS ARE 2N

b. THEY HAVE 2 OF EACH TYPE OF CHROMOSOME

    1. THESE ALIKE CHROMOSOMES ARE HOMOLOGOUS
       CHROMOSOMES

4. GAMETES ARE HAPLOID

KEY EVENTS DURING MEIOSIS I

GOAL OF MEIOSIS I - REDUCTION OF THE CHROMOSOME NUMBER BY HALF AND THE PRODUCTION OF NEW COMBINATIONS OF ALLELES

THE PHASES

OCCUR AFTER INTERPHASE WHERE DNA IS DUPLICATED

PROPHASE I - THE TIME OF MAJOR GENE SHUFFLING

1. HOMOLOGOUS CHROMOSOMES ARE DRAWN CLOSE TO ONE
       ANOTHER BY A PROCESS CALLED SYNAPSIS

2. CROSSING-OVER OCCURS - PIECES OF CHROMOSOME ARE
       EXCHANGED BETWEEN HOMOLOGS, MIXING UP ALLELES TO
   CREATE
DIFFERENT COMBINATIONS OF ALLELES

METAPHASE I

HOMOLOGOUS CHROMOSOMES, STILL ATTACHED, MOVE TO THE EQUATORIAL PLATE

THEY ARE RANDOMLY ARRANGED SO THAT THE MATERNAL CHROMOSOMES AREN’T ALL GOING TO ONE POLE AND THE PATERNAL CHROMOSOMES AREN’T ALL GOING TO THE OTHER

HOW MANY COMBINATIONS ARE POSSIBLE?

EXAMPLE: 4 CHROMOSOMES

24 = 2 X 2 X 2 X 2 = 16

HUMANS HAVE 23 CHROMOSOME PAIRS

223 = 8,388,608 COMBINATIONS

ANAPHASE I

HOMOLOGOUS CHROMOSOMES SEPARATE AND MOVE TOWARD OPPOSITE POLES

TELOPHASE I

CHROMOSOMES AT OPPOSITE POLES. THE NUCLEI ARE NOW 1N
TELOPHASE FOLLOWED BY CYTOKINESIS

PROPHASE II

SPINDLE APPARATUS FORMS

METAPHASE II

CHROMOSOMES POSITION THEMSELVES ALONG THE EQUATORIAL PLATE

ANAPHASE II

SISTER CHROMATIDS SEPARATE AND ARE PULLED TO OPPOSITE POLES

TELOPHASE II

NUCLEAR ENVELOPES REFORM AROUND THE CHROMOSOME MASSES

CYTOKINESIS OCCURS, GIVING FOUR GENETICALLY DIFFERENT HAPLOID CELLS

FORMATION OF GAMETES

GAMETE FORMATION IN ANIMALS

1. MALES

a. SPERMATOGENESIS

- OCCURS INSIDE THE MALE REPRODUCTIVE SYSTEM

1. DIPLOID CELL ENLARGES (PRIMARY SPERMATOCYTE)

2. MEIOSIS OCCURS FOLLOWED BY CYTOPLASMIC DIVISION

3. FOUR HAPLOID DAUGHTER CELLS DEVELOPE INTO
       SPERMATIDS

4. SPERMATIDS CHANGE IN FORM, DEVELOPE TAILS AND
   BECOME
SPERM

2. FEMALES

a. OOGENESIS

- OCCURS IN THE OVARY

1. EACH DIPLOID GERM CELL DEVELOPS INTO AN
       IMMATURE EGG (OOCYTE)

2. AN OOCYTE CONTAINS MORE CYTOPLASMIC COMPONENTS
   THAN THE OTHER DAUGHTER CELLS

3. WHEN AN OOCYTE DIVIDES AFTER 1 DIVISION ONE CELL
   (SECONDARY OOCYTE) GETS NEARLY ALL THE CYTOPLASM.
   THE OTHER
CELL IS A POLAR BODY

4. DURING MEIOSIS II THE SECONDARY OOCYTE DIVIDES
   UNEQUALLY GIVING RISE TO AN OVUM OR EGG AND A
       POLAR BODY

5. THE OTHER POLAR BODY DIVIDES, GIVING RISE
       TO TWO POLAR BODIES

OOGENESIS RESULTS IN 1 EGG AND 3 POLAR BODIES. THE 3 POLAR BODIES SERVE NO PURPOSE AND DEGENERATE

GENE SHUFFLING AT FERTILIZATION