Energy in a Cell

Chapter 9Chapter 9

Goals

• How cells get energyHow cells get energy

• PhotosynthesisPhotosynthesis

• Cellular RespirationCellular Respiration

ATP

• Adenosine Adenosine TriTriphosphatephosphate

• Energy = ATPEnergy = ATP

• Made up of:Made up of:• AdenosineAdenosine

• Ribose – sugarRibose – sugar

• 3 – phosphates – positively charged particles3 – phosphates – positively charged particles

ATP

• Energy of ATP is stored in Energy of ATP is stored in the bonds the bonds between the phosphatesbetween the phosphates

• Phosphate bonds break = energy is releasedPhosphate bonds break = energy is released

• ADPADP

ADP

• Adenosine Adenosine DiDiphosphatephosphate

• Made of Made of • AdenosineAdenosine

• RiboseRibose

• 2 phosphates2 phosphates

Forming & breaking down ATP

• Adenosine – PAdenosine – P = little energy= little energy

• Adenosine – P – PAdenosine – P – P = more energy= more energy

• Adenosine – P – P – PAdenosine – P – P – P= Tremendous = Tremendous EnergyEnergy

Cells need energy for:

• Making new molecules = EnzymesMaking new molecules = Enzymes

• Maintain HomeostasisMaintain Homeostasis– Break down food moleculesBreak down food molecules

• Send Nerve ImpulsesSend Nerve Impulses

• ReproductionReproduction

• Movement = Cilia & FlagellaMovement = Cilia & Flagella

9.2 Photosynthesis

• Plants trapping sunlight energy to make Plants trapping sunlight energy to make sugar/glucosesugar/glucose

• Converting sunlight energy to chemical Converting sunlight energy to chemical energyenergy

Photosynthesis

• 6CO6CO22 + 6H + 6H22O + Sun O + Sun → C→ C66HH1212OO66 + 6O + 6O22

• Takes place in Takes place in ChloroplastChloroplast

Chloroplast

Chloroplast

• ChlorophyllChlorophyll – Pigment that absorbs specific – Pigment that absorbs specific wavelengths of sunlightwavelengths of sunlight

• Chlorophyll a & b absorb all wavelengths Chlorophyll a & b absorb all wavelengths of sunlight exceptof sunlight except

• PigmentsPigments – molecules that absorb specific – molecules that absorb specific wavelengthswavelengths

2 phases of Photosynthesis

1.1. Light – dependent rxnLight – dependent rxn

- Energy to make glucose- Energy to make glucose

2. Light – independent rxn2. Light – independent rxn

- Make glucose- Make glucose

Light – Dependent Rxn

• Converts sunlight energy into chemical Converts sunlight energy into chemical energyenergy

Light – Dependent Rxn

• How does it work?How does it work?

1.1. Sunlight energy excites electrons in the Sunlight energy excites electrons in the chlorophyllchlorophyll

2.2. Excited electrons pass from chlorophyll to Excited electrons pass from chlorophyll to Electron Transport Chain (ETC)Electron Transport Chain (ETC)

Electron Transport Chain (ETC)

• Series of proteins in the thylakoid Series of proteins in the thylakoid membranemembrane

• Each step of ETC small amounts of energy Each step of ETC small amounts of energy are lostare lost

• Energy lost used to make ATP from ADP & Energy lost used to make ATP from ADP & pump Hpump H++ ions back to thylakoid membrane ions back to thylakoid membrane

ETC

• Electrons move down ETC then transferred Electrons move down ETC then transferred to Stroma where NADPto Stroma where NADP+ + accepts the accepts the electronelectron

• NADPNADP++ - Nicatinamide adenine - Nicatinamide adenine dinucleotide phosphatedinucleotide phosphate

NADP+

• Electron carrier moleculeElectron carrier molecule

• Becomes NADPH when it accepts electrons Becomes NADPH when it accepts electrons (end of ETC)(end of ETC)

NADPH

• Provides energy to form carbohydrates or Provides energy to form carbohydrates or glucoseglucose

• PhotolysisPhotolysis – Splitting of water to replace – Splitting of water to replace electrons = oxygen we breatheelectrons = oxygen we breathe

ETC

Chloroplast

Light Independent RXN

• Also known as Calvin CycleAlso known as Calvin Cycle

• Does not require sunlightDoes not require sunlight

Calvin Cycle

• Series of rxns that use COSeries of rxns that use CO22 to build to build

carbohydrates or glucosecarbohydrates or glucose

• Takes place in stroma of chloroplastsTakes place in stroma of chloroplasts

Calvin Cycle

1.1. Carbon fixation – 1 carbon atom from Carbon fixation – 1 carbon atom from COCO22 is added to a is added to a 5 carbon sugar5 carbon sugar

2.2. 6 carbon sugar from #1 splits in two 6 carbon sugar from #1 splits in two molecules of PGA (phosphoglyceric acid)molecules of PGA (phosphoglyceric acid)

3.3. Several rxns take place = 2 molecules Several rxns take place = 2 molecules PGAL form by using ATP & NADPH PGAL form by using ATP & NADPH from light rxnfrom light rxn

Calvin Cycle

4.4. Several cycles = 2 PGAL leave to form Several cycles = 2 PGAL leave to form GlucoseGlucose

5.5. Some PGAL reform 5 carbon sugar that Some PGAL reform 5 carbon sugar that we started withwe started with

- Ready for a new Calvin Cycle to start- Ready for a new Calvin Cycle to start

9.3 Cellular Respiration

• Process which mitochondria breaks down Process which mitochondria breaks down food to produce ATPfood to produce ATP

• CC66HH1212OO66 + 6O + 6O22 → 6CO→ 6CO22 + 6H + 6H22O + EnergyO + Energy

• Takes place in Takes place in MitochondriaMitochondria

3 Stages of Cellular Respiration

• AnaerobicAnaerobic – without O – without O22

1.1. GlycolysisGlycolysis – series of rxns that breakdown – series of rxns that breakdown glucose (6 carbon) into 2 molecules of glucose (6 carbon) into 2 molecules of Pyruvic acid (3 carbon)Pyruvic acid (3 carbon)

Glycolysis

• Takes place in cytoplasm of cellTakes place in cytoplasm of cell

• 2 ATP used to start2 ATP used to start

• 4 ATP produces4 ATP produces

• Net gain = 2 ATPNet gain = 2 ATP

• NADNAD++ electron carrier molecule electron carrier molecule

3 Stages of Cellular Respiration

• AerobicAerobic – with O – with O22

2.2. Citric acid cycleCitric acid cycle – (Krebs cycle) – (Krebs cycle)– Series of rxns breakdown carbohydrates or glucoseSeries of rxns breakdown carbohydrates or glucose

– Opposite of Calvin cycleOpposite of Calvin cycle

– 2 ATP produced2 ATP produced

– 3 NADH + H3 NADH + H++ produced = 1 NADH = 3 ATP produced = 1 NADH = 3 ATP

– 2FADH produced = 1 FADH = 2 ATP2FADH produced = 1 FADH = 2 ATP

– 2 CO2 CO22 produced produced

3 Stages of Cellular Respiration

• AerobicAerobic

3.3. ETCETC– Takes place in MitochondriaTakes place in Mitochondria

– NADH & FADH pass electrons along releasing small NADH & FADH pass electrons along releasing small amounts of energyamounts of energy

– Pump HPump H++ back to center of mitochondria back to center of mitochondria

– Final electron acceptor = OFinal electron acceptor = O22

– Without OWithout O22 chain becomes blocked chain becomes blocked

– 32 ATP produced32 ATP produced

ETC – cellular respiration

Fermentation

• Without OWithout O22

• Allows our cells to continue to make ATP Allows our cells to continue to make ATP w/o Ow/o O22 after glycolysis for a short period after glycolysis for a short period

of timeof time

Fermentation

1.1. Lactic acidLactic acid – 2 lactic acid molecules are – 2 lactic acid molecules are byproducts of producing just 2 ATPbyproducts of producing just 2 ATP

– Occurs in muscle cellsOccurs in muscle cells

Fermentation

2.2. AlcoholicAlcoholic – ethyl alcohol is formed as a – ethyl alcohol is formed as a byproduct to produce 2 ATPbyproduct to produce 2 ATP

– Occurs in yeast cells and bacteriaOccurs in yeast cells and bacteria

Comparing ATP productionProcessProcess ATP ATP

producedproducedATP usedATP used Net gainNet gain

GlycolysisGlycolysis 44 22 22

Citric acid Citric acid cyclecycle

22 00 22

ETCETC 3232 00 3232

Lactic acid Lactic acid 22 00 22

AlcoholicAlcoholic 22 00 22