Photosynthesis

Photosynthesis

• A process in which light energy is converted to chemical energy (glucose)

– Chloroplasts (organelle)

– Leaves (plant structure)

Background Concepts

Autotroph (producer)

• Organism that uses energy from the sun to produce organic compounds – Glucose

• Plants

• Some bacteria

• Some protists

Heterotroph (consumer)

• Organism that must get energy from the food they consume

• Animals

• Fungus

• Some bacteria

• Some protists

Photosynthesis

6 Carbon dioxide + 6 water + Light Glucose + 6 Oxygen

6CO2 + 6H20 + Light C6H1206 +CO2

Plant Pigments

• Biological molecules used to absorb light

– Chlorophyll a and b

• Absorbs: red, orange, blue, indigo, violet

• Reflects: green, yellow

– Carotenoids

• Absorbs: green, blue, indigo, violet

• Reflect: red, orange, yellow

Electromagnetic Spectrum

• Plants utilize the visible portion of the electromagnetic spectrum

– ROY G BIV

Absorption Spectrum

• Shows which wavelength of the visible spectrum are absorbed by chlorophyll a and b, and carotenoids

Mystery Solved!

Stages of Photosynthesis

1. Light Reactions

2. Calvin Cycle

Light Reactions

• Absorb light energy to make ATP and NADPH

• Needs water (soil) and light (sun) to run

• Produces oxygen gas, ATP, NADPH

Calvin Cycle

• Uses the ATP and NADPH made in the light reactions to make sugar (glucose)

• Needs ATP and NADPH

• Produces glucose

Products of Light Reactions

• ADP + ATP

• NADP+ + H NADPH

• Oxygen comes from the splitting of H2O, not CO2

H2O 1/2 O2 + 2H+

(Reduced)

P(Reduced)

ATP Synthesis (Like a Dam)

• Proton Pump

• Powered by Hydrogen (Protons)

• Powers ATP synthesis.

• Located in the thylakoid membranes.

• Uses ATP synthase (enzyme) to make ATP.

• Photophosphorylation: addition of phosphate to ADP to make ATP.

Stroma

Cytoplasm

ATP Synthesis

Calvin Cycle• Carbon Fixation (light independent rxn).

• C3 plants (80% of plants on earth).

• Occurs in the stroma.

• Uses ATP and NADPH from light rxn.

• Uses CO2.

• To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.

Calvin Cycle (C3 fixation)

6CO2

6C-C-C-C-C-C

6C-C-C 6C-C-C

6C-C-C-C-C

12PGA

RuBP

12G3P

(unstable)

6NADPH 6NADPH

6ATP 6ATP

6ATP

C-C-C-C-C-CGlucose

(6C)

(36C)

(36C)

(36C)

(30C)

(30C)

(6C)

6C-C-C 6C-C-C

C3

glucose

Calvin Cycle

• Remember: C3 = Calvin Cycle

C3

Glucose

Photorespiration

• Occurs on hot, dry, bright days.

• Stomates close.

• Fixation of O2 instead of CO2.

• Produces 2-C molecules instead of 3-C sugar molecules.

• Produces no sugar molecules or no ATP.

Photorespiration

• Because of photorespiration: Plants have special adaptations to limit the effect of photorespiration.

1. C4 plants

2. CAM plants

C4 Plants

• Hot, moist environments.

• 15% of plants (grasses, corn, sugarcane).

• Divides photosynthesis spatially.

• Light rxn - mesophyll cells.

• Calvin cycle - bundle sheath cells.

CAM Plants

• Hot, dry environments.

• 5% of plants (cactus and ice plants).

• Stomates closed during day.

• Stomates open during the night.

• Light rxn - occurs during the day.

• Calvin Cycle - occurs when CO2 is present.

Question:

• Why would CAM plants close their stomatesduring the day?

Purpose of Photosynthesis

1. Plants use the sugar made through photosynthesis for energy

2. Plants use the sugars to make starch, which can be stored for energy

3. Plants use the sugars to make cellulose, which is used for building cell walls

Purpose of Photosynthesis

1. Animals and fungus use the oxygen and sugars for cellular respiration

– To make ATP

Cellular Respiration and Fermentation

Cellular Respiration• Cellular Respiration

– Transfer of energy in organic compounds to ATP– Carbohydrates, fats, and proteins can all be used as fuels– Process more efficient when oxygen is present– Carried out in the mitochondria

• Aerobic processes– Require oxygen– If oxygen is available, 40% of energy in glucose can be used

to make 38 ATP

• Anaerobic processes– Do not require oxygen– If oxygen is unavailable, 2% of the energy in glucose can be

used to make 2 ATP

Structure of Mitochondrion

Cellular Respiration

• Cellular Respiration

– Glucose is main substance converted to ATP

– Equation:

• C₆H₁₂O₆ + 6O₂ 6CO₂ + 6H₂O + energy

glucose oxygen carbon water ATP (heat + 38 ATP)

gas dioxide

Stages of Cellular Respiration

1. Glycolysis

2. Transition Reaction

3. Kreb’s Cycle

4. Electron Transport Chain

Stages of Cellular Respiration

• Glycolysis:

– Occurs in the cytoplasm

– Anaerobic

• Does not require oxygen

• 2 ATP molecules used in glycolysis, 4 ATP molecules produced in glycolysis

– Net gain of 2 ATP molecules

Stages of Cellular Respirations

• Transition Reactions

– Matrix of the Mitochondria

– 0 ATP produced

– 2 molecules of CO2

Stages of Cellular Respiration

• Krebs Cycle/Citric Acid Cycle

• Matrix of Mitochondria

• Aerobic

– Oxygen must be present

• 4 molecules of CO2

• 2 ATP molecules produced

Krebs/Citric Acid Cycle

Stages of Cellular Respiration

• Electron Transport Chain

– Inner membrane of mitochondria

– 6 H2O molecules produced

– Aerobic

• Oxygen must be present

• 6 oxygen molecules are used

– Produces up to 34 ATP molecules

Cytoplasm

2 2 34

Fermentation

• Fermentation

– Breakdown of carbs by enzymes, bacteria, yeasts, or mold in the absence of oxygen

– Anaerobic• No oxygen required

– 2 main types• Lactic acid fermentation

• Alcoholic fermentation

Lactic Acid Fermentation

• Lactic Acid Fermentation

– Produces Lactic Acid

– Anaerobic process

– Only produces 2 ATP

– Bacteria, humans (in muscles)

– Importance/Effects to humans:• Cheese and yogurt production

(bacteria)

• Muscle soreness (reduced performance)

Lactic Acid Fermentation

Alcoholic Fermentation

• Alcoholic Fermentation

– Produces ethanol and CO2

– Anaerobic process

– Only produces 2 ATP

– Yeast

– Importance to humans:• Alcoholic fermentation by yeast

produces:

– Biofuels (ethanol)

– Brewing industry

– Baking industry (rising bread)

Alcoholic Fermentation

Purpose of Cellular Respiration & Fermentation

• Both processes produce ATP that is needed to power metabolism

Mitosis

Background Concepts

• Genetic information is contained in the nucleus

• Chromosomes: structures in a nucleus made out of DNA, which contain genes

– 46 chromosomes in human cells

– Visible during cell division

• Light microscope

Background Concepts

• Chromatids: two copies of a chromosome held together at the centromere

• Chromosomes are copied to ensure each of the new cells receives a complete set of chromosomes

Cell Cycle

• The repeating sequence of growth and cell division during the life of an organism

Interphase

• Preparation for cell division

– G1: cell grows to ensure both daughter cells receive large amounts of cytoplasm

– S: cell copies its DNA so each daughter cell receives a complete set of chromosomes

– G2: cell grows more

Cell Division

• Mitosis: division of the nucleus

– Prophase

– Metaphase

– Anaphase

– Telophase

• Cytokinesis: division of the cytoplasm

Cell Division

• Prophase

• Nuclear envelope breaks down

• Chromosomes coil

• Spindle forms

• Moves chromosomes during cell division

Cell Division

• Metaphase

• Chromosomes are at the equator of the cell

Cell Division

• Anaphase

• Chromosomes are pulled apart and moved to the poles

Cell Division

• Telophase

• Nuclear envelope forms

• Chromosomes uncoil

• Spindle breaks down

• Cytokinesis: division of the cytoplasm

Result Mitosis and Cytokinesis• Two Genetically Identical Daughter Cells

Cytokinesis in Plant Cells

• Cell Plate: splits cytoplasm in half

Importance of Cell Division

1. Allows organisms to reproduce

– yeast cells

2. Allows organisms to repair damaged tissue

– Wound healing

3. Allows organisms to replace cells that die

– Red blood cells

– skin

Background Concepts

• Haploid Cell: cell (nucleus) that has only one set of unpaired chromosomes

– Gametes

– 23 chromosomes (in humans)

• Diploid Cell: cell that contains two sets of chromosomes

– Somatic cells

– 46 chromosomes (in humans)

Somatic Cells vs Gametes

• Somatic Cells: body cells (other than eggs and sperm)– Diploid

– 46 chromosomes

• Gametes: haploid reproductive cells that unite with another haploid cell to form a zygote– Haploid

– 23 chromosomes

Homologous Chromosomes

• Pair of chromosomes

• Must be same length, have centromere location, and carry the same genes

Autosomes vs Sex Chromosomes

• Autosomes: any chromosome that is not a sex chromosome– Contains genes for 1,000s of traits

– Somatic cells contain 44 autosomes

• Sex Chromosomes: one of the pair of chromosomes that determine the sex of an individual– Contains genes to determine gender

– Somatic cells contain 2 (XX=female, XY=male)

Life Cycles

• The entire span in the life of an organism, from one generation to the next

– Meiosis: type of cell division that produces gametes

– Gametes: haploid sex cells (egg and sperm cells)

– Fertilization: joining of egg and sperm cells

– Zygote: single diploid cell, results from fertilization

Meiosis

• Interphase:

– G1: cell grows

– S: cell copies its DNA

– G2: cell grows more

Meiosis

• Meiosis 1:

– Prophase 1 (crossing over occurs)

– Metaphase 1 (independent assortment occurs)

– Anaphase 1

– Telophase 1

– Cytokinesis (results in 2 daughter cells)

Meiosis

• Meiosis 2:

– Prophase 2

– Metaphase 2

– Anaphase 2

– Telophase 2

– Cytokinesis

• Results in 4 genetically different, haploid cells

• Daughter cells develop into eggs or sperm (gametes)

Mechanisms of Genetic Variation

• Crossing Over: two chromosomes, in a homologous pair, exchange sections

– Prophase 1

– Genetic variation in gametes

Mechanisms for Genetic Variation

• Independent Assortment: random distribution of homologous chromosomes at the equator of the cells

– Occurs during metaphase 1

– Genetic variation in gametes

Mechanisms of Genetic Variation

• Random Fertilization: unpredictable nature of fertilization

– Occurs after meiosis is complete

– Results in genetic variation in a zygote

Karyotype

• Photograph of an individual’s chromosomes

– Chromosomes organized from largest to smallest homologous pair

– Last pair always includes the sex chromosomes

– May indicate if an unborn child has a genetic disorder

• Trisomy 21 (Down Syndrome)

Purpose of Meiosis

• Produces haploid gametes with genetic variation

• Haploid gametes can join, through fertilization, to produce a zygote with genetic variation

• If a species lacks genetic variation, many individuals would not survive in a changing environment