Cellular Respiration, Photosynthesis, and lab 4

4/20/16

Announcements

• We will not be covering chapter 9: cell communication

• Today, we will finish cell respiration (ch7), photosynthesis (ch 8), and start on cell division (ch 10)

• Lab is on cell division

• Also, must prepare seeds for next lab

Cellular Respiration – oxygen present

Cellular respiration

• Glycolysis

• Kreb’s or citric acid cycle

• Electron Transport Chain

• Overall reaction:

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 38 ATP + heat

Energy carriers and electron carriers

• ATP – the main energy carrier molecule

• NADH, FADH2, and NADPH – electron carriers

GTP

The energy carrier molecule, ATP

• Three phosphate groups

• Ribose sugar

• Adenine base

Glycolysis

• Happens in cytoplasm• Convert glucose to 2 pyruvate or pyruvic acid• What are the reactants? What are the

products?

Glycolysis

• Reactants: Glucose, 2 ATP, 2 NAD+, and 4 ADP• Products: 2 pyruvate, 2 ADP, 2 NADH, 4 ATP, and H2O• Gained 2 ATP and 2 NADH

• Red blood cells get their energy here

Kreb’s or citric acid cycle

• Happens in the matrix of the mitochondria

• Citric acid is first product

• Closed loop

• What are the reactants? What are the products?

ATP

Kreb’s or citric acid cycle

• Reactants: 2 pyruvate, 8 NAD+, 2 FAD+, and 2 ADP

• Products: 6CO2, 2 ATP, 8 NADH, and 2 FADH2

• Gained 2 ATP, 8 NADH, and 2 FADH2

• Glucose catabolism complete

• So far, total of 4 ATP, 10 NADH, and 2 FADH2

ATP

Electron Transport Chain

• Only step that uses oxygen

• Relay race of e-

• Many in the inner membrane

• Oxygen and H H2O

• Leads to oxidative

phosphorylation –

Generating ATP using

chemiosmosis in

mitochondria

If there is no oxygen,

• Anaerobic bacteria, muscles, yeast

PHOTOSYNTHESIS

Energy

• Required to drive all chemical reactions that

sustain life

• Cannot be created or destroyed, so living things

must obtain it from the environment (1st law of

thermodynamics)

Trapping sunlight

• Ultimately, all living things on Earth derive energy from the sun

• Some directly by photosynthesis

– Photoautotrophs

• Others indirectly through the food chain

– Heterotrophs

Photosynthesis

• Takes place mostly in the leaves

• Why are leaves large and flat?

• They have specialized structures that allow all required components to come together

– H2O

– CO2

– Sunlight

Leaves

cuticle

upperepidermis

lowerepidermis

mesophyllcells

chloroplasts

outer membrane

inner membrane

thylakoid

stroma

stoma

stoma

bundle sheath cells

vascular bundle (vein)

channelinterconnectingthylakoids

Internal leaf structure

Mesophyll cell containing chloroplasts

Chloroplast

Leaf structure and photosynthesis

• Source of H2O: taken in through roots

• Problem: large surface area

• Solution: cuticle and stomata

– Waxy protective coating reduces water loss

– Stomata can open and close

Leaf structure and photosynthesis

• Source of CO2: air

• Problem: cuticle keeps gases out

• Solution: stomata

– Adjustable pores allow gases in (and out)

– Where the plant “breathes”

Leaf structure and photosynthesis

• Sunlight captured by chloroplasts

• Primarily in mesophyll layer of leaf

• One cell may contain 40-50 chloroplasts

cuticle

(b) Internal leaf structure

upperepidermis

mesophyllcells

lowerepidermis

outer membrane

inner membrane

thylakoid

stroma

(d) Chloroplast

(a) Leaves

(c) Mesophyll cell containing chloroplasts

Light

• Composed of tiny packets of energy called photons

• Energy of photons correspond to wavelength

– Long wavelength = low energy

– Short wavelength = high energy

Visible light

• Infinite number of wavelengths contained in sunlight

– Correspond to different colors

Light

• Three possible outcomes when photons strike an object

– Absorbed

– Reflected

– Transmitted

Reflected Absorbed Transmitted

Absorbed light

• Absorbed wavelengths generate heat, drive biological processes

Reflected light

• Reflected wavelengths reach the eye of observers

• Perceived as color

Thought question

• Why is white so bright?

Thought question

• Why are our pupils black?

Photosynthesis

• Sunlight is captured by pigments in chloroplasts

• Primarily chlorophyll

– Others (example: carotenoids)

• What colors does chlorophyll absorb? Reflect?

Chlorophylabsorbs

mainly blue and red light

Vitamin A

• Beta-carotene

– Plant pigment that gives orange vegetables their color

• Converted to vitamin A in animals

• Forms light-absorbing pigments in eye

– Blue and near-ultraviolet light

Photosynthesis

• Overall chemical reaction:

6 CO2 + 6 H2O + light energy C6H12O6 + 6 O2

Photosynthesis - VIPs

• Chloroplast

– Thylakoid

• Granum

• Lumen

– Stroma

Light reactions

• Light strikes chlorophyll and electrons are moved from PSII to ETC to PSI

• High energy electrons release energy to make

– ATP

– NADPH

• Low pH in thylakoid

lumen

• Leads to

photophosphorylation –

Generating ATP using

chemiosmosis in

chloroplast

Calvin cycle

• ATP and NADPH go on to fuel the Calvin cycle

• Light-independent reactions of photosynthesis

• Still in the chloroplast, just a different part(Light reactions) (Calvin cycle)

Where does carbon come from?

• Carbon in biomolecules of plants comes from CO2 in the air

• Carbon is “fixed” into larger organic molecules through the Calvin cycle

Energy

CO2

Calvin cycle -VIPs

• Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), ribulose bisphosphate (RuBP), CO2, glycerate 3-phosphate (3-PGA), glyceraldehyde 3-phosphate (G3P)

Products

• Products of photosynthesis: sugars, oxygen

• What happens to these products?

– Some sugar turned into tissues, stored for later use

– Oxygen and most sugars used to fuel cellular respiration in mitochondria

Reactants and products

• Light reactions– Reactants: Light energy, water

– Products: oxygen, ATP, NADPH

• Calvin cycle– Reactants: CO2, ATP, NADPH

– Products: Glucose

• Overall chemical reaction:

6 CO2 + 6 H2O + light energy C6H12O6 + 6 O2

Summary

• Photosynthesis

– Where: in chloroplast

– Uses: light, water, CO2

– Produces: sugar, O2, ATP, NADPH

LAB 4 – MITOSIS AND MEIOSIS

3 Parts to Lab 3

• Part 1: modeling mitosis– show:

• Starting chromosomes• Alignment of chromosomes in metaphase• Ending chromosomes

• Part 2: modeling meiosis– show:

• Starting chromosomes• Crossing over• Alignment of chromosomes in metaphase 1 • Alignment of chromosomes in metaphase 2• Ending chromosomes

• Part 3: observing mitosis onion root cells

• Extra: Prepare plates for next week’s lab

Learning Goals for Today:

• Describe the outcome of mitosis– Number of cells produced– Genetics of new cells compared to original

• Describe the outcome of meiosis– Number of cells produced– Genetics of new cells compared to original

• Observe and draw mitotic chromosomes from actual specimens (onion root tips)

Definitions

• Mitosis: cell division of a mother cell into two daughter cells, genetically identical to each other and to their parent cell

• Meiosis: a specialized type of cell division that reduces the chromosome number by half– DNA replication two rounds of cell division

– Mother cell 4 genetically distinct daughter cells

Cell Division is Only Part of the Cell Cycle

Fig. 9-7

G2: cellgrowthand preparationfor celldivision; organellesare duplicated

S: synthesisof DNA;chromosomesare duplicated

G1: cell growth andpreparation for synthesis

replication

mitosis

centromere

2 daughter cells

1 chromosome

1 duplicated chromosome

Chromosomes Are Copied Before Cell Division

Original cell

Each has 1 chromosome

Why do Cells Need to Divide?

• Make more cells

• Grow a larger organism

• Repair damage to organism

• Reproduction of the organism

Definitions

• Genome: A cell’s entire DNA, packaged as a double-stranded DNA molecule

• Chromosome: a double-stranded linear DNA molecule

– Human body (somatic) cells have 46 chromosomes (23 pairs)

– Human gametal cells have 23 chromosomes

Definitions

• Ploidy: number of sets of chromosomes in a cell

– Human somatic cells are diploid

– Human gametal cells are haploid

Definitions

Singlechromosome

DuplicatedChromosome,

“sister chromatids”

Homologous pair ofChromosomes

1A1B

1A 1A1A

1A 1B

2B2A

Homologous

Non homologous

Homologous

Sister chromatids

centromere

1A 1B

2B2A

sexchromosomes

Humans Have 23 Pairs of Chromosomes

1 set came from female parent1 set came from male parent

We are diploids (2 copies of each chromosome)

Often given number/letter names

chromosome 1Achromosome 1B

Chromosomes 1A and 1B are homologous chromosomes

Chromosomes with different numbers (like 1A and 4A) are non-homologous chromosomes

A

Copyright © 2011 Pearson Education, Inc.

The human life cycle

meiotic cell

division in

testes

meiotic cell

division in

ovaries

adults (2n)

egg (n)zygote (2n)

haploid (n)

diploid (2n)fusion of gametes

sperm (n)

embryo (2n)

baby (2n)

mitotic cell division,

differentiation, and growth

mitotic

cell division,

differentiation,

and growth

mitotic cell division,

differentiation,

and growth

Summary of Mitosis

• Prophase: chromosomes become visible

• Metaphase: chromosomes line up

• Anaphase: chromosomes move apart

• Telophase: two distinct cells form

Number of cells formed?

Cells same as original cell?

Prophase

Duplicatedchromosome

MITOSIS

Chromosomeduplication

Parent cell

2n 6

Metaphase

AnaphaseTelophase

2n 2n

Daughter cellsof mitosis

Introduction to Meiosis: the Big Picture

Starts with 1 original cell

Homologous chromosomes cross over

Ends with 4 non-identical cellsEach has half the DNA of the original cell

Meiosis is Essential for Sexual Reproduction

meioticcell division

fertilization

diploidparentalcells

diploidfertilizedegg

haploidgametes

2n

2n

2n n

n

Meiosis Allow For Genetic Recombination

• Genetic recombination is why most siblings are not identical

– Exception: identical twins

Genetic Recombination by Crossing Over of Homologous Chromosomes

Figure 13.8a

Prophase I Metaphase I Anaphase I Telophase I andCytokinesis

Centrosome(with centriole pair)

Sisterchromatids

Chiasmata

Spindle

Homologouschromosomes

Fragmentsof nuclearenvelope

Duplicated homologouschromosomes (red and blue)pair and exchange segments;2n 6 in this example.

Centromere(with kinetochore)

Metaphaseplate

Microtubuleattached tokinetochore

Chromosomes line upby homologous pairs.

Sister chromatidsremain attached

Homologouschromosomesseparate

Each pair of homologous chromosomes separates.

Cleavagefurrow

Two haploid cells form; each chromosomestill consists of two sister chromatids.

Figure 13.8b

Prophase II Metaphase II Anaphase IITelophase II and

Cytokinesis

Sister chromatidsseparate

Haploid daughtercells forming

During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing unduplicated chromosomes.

Figure 13.9a

Prophase

Duplicatedchromosome

MITOSIS

Chromosomeduplication

Parent cell

2n 6

Metaphase

AnaphaseTelophase

2n 2n

Daughter cellsof mitosis

MEIOSIS

MEIOSIS I

MEIOSIS II

Prophase I

Metaphase I

Anaphase ITelophase I

Haploidn 3

Chiasma

Chromosomeduplication Homologous

chromosome pair

Daughter cells of

meiosis I

Daughter cells of meiosis II

n n n n