C H A P T E R 1 0

Photosynthesis

Photosynthesis -converts sunlight E to chemical E

Directly or indirectly supports almost all living world

CO2 + H2O + light O2 + C6H12O6

Autotrophs = producers

produce organic molecules from CO2 and inorganic molecules

Almost all plants

Heterotrophs = consumers

obtain organic material from other organisms

Photosynthesis converts light E to chemical E

Chloroplasts evolved from photosynthetic cyanobacteria living inside a eukaryotic cell

Chloroplast evolution

Chlorophyll = green pigment of chloroplast

Absorbs light energy

30–40 chloroplasts/cell (500,000/mm2)

Most in mesophyll - interior tissue of leaf

Stomata = microscopic

pores for gases

Open during the day

O2 out

Water vapor out

CO2 in

Chloroplast enclosed by double membrane

Mesophyll cell with chloroplasts

Within chloroplast

Thylakoids

Membranous sacs

Chlorophyll in thylakoid membrane

Thylakoid space

Granum = thylakoid stackStroma = dense fluid

Photosynthesis

6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2O

reactants products

6 CO2 + 6 H2O + Light energy C6H12O6 + 6 O2

inorganic organic

chemical E

The O2 comes from the H2O

Endergonic

2 Stages of Photosynthesis

1.Light reaction-Sun E to chemical E

-Thylakoid membrane

-Water split to form O2 and H+

- NADPH electron carrier produced

- ATP produced

Light

H2O

Chloroplast

LightReactions

NADP+

PADP

i+

ATP

NADPH

O2*NADPH

*ATP

O2

Light reactionRequires water

Visible light

Can detect with human eye

380 – 750 nm wavelength

Photons – particles have a fixed amount of energy

Visible light drives photosynthesis

Reflectedlight

Absorbedlight

Light

Chloroplast

Transmittedlight

Granum

Wavelength of light (nm)

Chlorophyll a

Chlorophyll b

Carotenoids

500400 600 700

Which wavelengths support photosynthesis?

Chlorophyll b and carotenoids are accessory pigments

Light reaction: Photosystems are protein complexes in thylakoid membrane

STROMA

e–

Pigmentmolecules

Photon

Transferof energy

Special pair ofchlorophyll amolecules

Th

yla

ko

id m

em

bra

ne

Photosystem

Primaryelectronacceptor

Reaction-centercomplex

Light-harvesting

complexes

Summary of light reaction

1. Light absorbed by pigments in photosystems I and II

2. Electron transport

3. NADPH produced

4. H2O O2

5. H+ ion gradient ATP synthase ATP

CO2, ATP and NADPH will be used in the Calvin cycle to produce sugar

2. Calvin cycle/dark reaction-Stroma (dense fluid outside thylakoids)

-Carbon fixation = CO2 from air into sugar

Series of chemical reactions powered by ATP

and NADPH

End result

Can form glucose or sucrose

Glucose used by plant

to build cellulose for cell walls

store sugar as starch roots/tubers, seeds, and fruits

for cellular respiration (mt)

Light

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

[CH2O]

(sugar)

Adaptations

C4 and CAM

Adapted to arid, hot climates

C H A P T E R 1 2

The Cell Cycle

The Key Roles of Cell Division

cell division = reproduction of cells

All cells come from pre-exisiting cells

Unicellular organisms division of 1 cell reproduces organism

Binary fission

Why cells reproduce Development/Growth

Replacement

Repair

Multicellular organisms

Cellular Organization of Genetic Material

chromosome = strand of DNA

2 sets of 23 chromosomes in humans = 46

genome = All DNA in a cell

single chromosome (prokaryotes)

many chromosomes (eukaryotes)

chromatin complex of DNA and protein

Somatic cells= body cells (2 trillion in adult)

two sets of chromosomes (pairs= diploid)

Produced by mitosis - 1 diploid cell 2 identical diploid cells

Gametes sperm and eggs

have one set = haploid

Produced by meoisis – 1 diploid cell 4 unique cells

Occurs only in ovaries, testes

Gametes

Identical cells Unique cells

Diploid Haploid

Concept check

1. start with a fertilized egg 5 cell divisions produce how an embryo of ______ cells

2. a chicken has 78 chromosomes in a somatic cell. How many chromosomes in a chicken sperm?

The cell cycle = time from new cell to when it divides

Interphase –90% of time

Mitosis 4o min

S(DNA synthesis)

G1

G2

Cell Division

Mitosis = division of the nucleus

Cytokinesis = division of cytoplasm

INTERPHASE

G1 phase – cell grows, gets ready

S phase – DNA replicates

G2 phase – cell grows, gets ready

G2

Signs of interphase?

S phase of Interphase

Chromosomes (DNA) replicate

Sister chromatids = 2

Centromere = constricted region

0.5 µm Chromosomes

Chromosomeduplication(including DNAsynthesis)

Chromosome arm

Centromere

Sisterchromatids

DNA molecules

Separation ofsister chromatids

Centromere

Sister chromatids

Chromosomes condense

Mitotic spindle forms from centromeres

Nuclear membrane breaks apart

MITOSIS I. Prophase

The mitotic spindle (formation begins in prophase)

ProphaseG2 of Interphase

AsterCentrosomes

Aster = radial array of microtubules

II. Prometaphase

Spindle microtubules attach to kinetochores

of chromosomes

Chromosomes pulled towards center of cell

III. Metaphase

chromosomes (sister chromatids) line up at the metaphase plate

midway between spindle’s two poles

IV. Anaphase

sister chromatids separate

microtubules shorten – depolymerize to move chromosomes toward opposite ends of cell

V. Telophase

Identical nuclei form at opposite ends of cell

Chromosomes less condensed

Cytokinesis

Division of cytoplasm

animal cells

cleavage furrow

plant cells

cell plate

The cell cycle is regulated by a molecular controls

Short length – ex. skin cell divides frequently

Longer length – ex. neurons may not divide at all

Cytoplasmic Signals

Specific signal molecules in cytoplasm

cell cycle control system

internal and external controls coordinate

checkpoints - cell cycle will not proceed until go signal

Why?

Has DNA been copied correctly?

Are chromosomes moving correctly?

How is the mitotic spindle?

Is the cell big enough?

SG1

M checkpoint

G2M

Controlsystem

G1 checkpoint

G2 checkpoint

G1 checkpoint

most important

If no go signal, cell G0 phase (non-dividing)

Most cells

Can re-enter cell cycle

Heart muscle Nervous tissue

Cell Cycle

Regulatory proteins in cell cycle control:

1. Cdks

Phosphorylate other molecules

Always present

2. Cyclins

Attach to Cdk to give “go” signal

Concentration cycles

3. growth factors (>50 types)

External signals

Petriplate

Scalpels

Cultured fibroblasts

Without PDGFcells fail to divide

With PDGFcells prolifer-ate

10 µm

PDGF stimulates fibroblasts to divide

PDGF mechanism

PDGF made by platelets at wound site

Fibroblasts have PDGF receptors on cell membrane

Signal pathway cells pass G1 checkpoint

Cells divide

Cancer cells lose control of the cell cycle

Lose density-dependent inhibition

crowded cells SHOULD stop dividing

Lose anchorage dependence

Cells normally attached to a substratum in order to divide

Anchorage dependence

Density-dependent inhibition

Density-dependent inhibition

(a) Normal mammalian cells (b) Cancer cells

25 µm25 µm

May not need growth factors

May make own growth factor

Transformed Immortal

Abnormal chromosomes

Tumor mass of abnormal cells

Benign tumor – abnormal cells do not invade other tissues

Malignant tumors - invasive

can metastasize and form secondary tumors

Angiogenesis - tumor gets a blood supply

Metastasis – tumor spreads to other locations

Treatments

Radiation destroys fast growing cells (target site)

Chemotherapy (systemic toxins)

Excision

Cancer results from gene mutation

Plant Structure, Growth, and Development

C H A P T E R 3 5

PLANTS

developmental plasticity = ability of plant to alter form to respond to environment

Biological heirarchy

Cell – basic unit of life

Tissue – group of cells perform a common function

Organ – multiple tissue types with a common function

Organ system – multiple organs with common function

Organism – all of above

Example

Parenchyma cells

Plant epidermis

Leaf

Shoot system

Plant

ORGAN SYSTEMS

1. Root System Root (organ)

Anchors plant

Absorbs minerals and water

Stores food

Root hairs

Absorb water and

minerals

Large surface area

Renewed continually

Radish seedling

A. Taproot system

Taproot = main vertical root, deep

Stores sugar, starch

Why harvest carrots before they

flower?

Lateral roots

deep

Radish, mustard, carrot,

B. Fibrous root system

Begins with Adventitious roots

Roots arise from stems or leaves

Maize:Prop roots are adventitious

From stem on bottom of bulb canary island date palm

Fibrous root system: root form mat below surface, shallowno main root

ferns

grass

scallion

grasses

fern

2. Shoot system

Stem (organ)

Nodes = points at which leaves are attached

Internodes= stem segments between nodes

Axillary bud can form a lateral shoot, or branch

Apical bud near shoot tip for elongation

Apical bud is dominant

axillary bud allows tip to grow toward light

Pinch off apical bud plant grows laterally

Stem adaptations:

Rhizome of iris is modified stem (shoot below surface)

Tubers = enlarged rhizome endsEye is cluster of axillary buds (can plant)

Leaves (organs) Photosynthesis

Blade

Petiole

stalk joins leaf to node of stem

Simple compound doubly compound

Leaf veins = vascular tissue of leaves

parallel veins

ex. lily, orchid, grass, palm

branching veins

Ex. apple, maple, dandelion

Grape (Vitis)daylily mint

Plant tissues

1. Dermal tissue system outer protection

Water loss

Disease protection

epidermis (non-woody plants)

Covered by a waxy cuticle on leaves and stems

periderm (woody plants) from epidermis

On older stems and roots (cork, bark)

Specialized epidermis

Trichomes

Grow from shoot epidermis

Reduce water loss, reflect excess sunlight

May secrete sticky or toxic fluids

Very hairy pod

(10 trichomes/

mm2)

Slightly hairy pod

(2 trichomes/

mm2)

Bald pod

(no trichomes)

Very hairy pod:

10% damage

Slightly hairy pod:

25% damage

Bald pod:

40% damage

EXPERIMENT

RESULTS

2. vascular tissue system long-distance transport from roots to shoots

composed of parenchyma cells Thin

Synthesize and store organic materials

Fleshy tissue of fruits

Least specialized, can differentiate

Parenchyma cells in Elodea leaf,

with chloroplasts (LM)

vascular tissues

Xylem

transports water and dissolved minerals from roots to shoots

older xylem is wood

Phloem

transports nutrients from leaves to where needed

3. ground tissue system Storage

Photosynthesis

Support

Parenchyma cells

pith internal to vascular tissue

cortex external to vascular tissue

Other plant cell types

Collenchyma cells

Thick cell walls

Resilient strands (ex. celery) grow in response to mechanical stress

Flexible support

Sclerenchyma cells

• Rigid support- thick secondary walls have lignin

• Most dead at maturity (old)

Xylem

Water-Conducting Cells

Phloem

Sugar-Conducting Cells of Phloem

Sieve-tubeelement

Plasmodesma

Sieveplate

Nucleus ofcompanioncells

Sieve-tube elements:longitudinal view Sieve plate with pores (SEM)

10 µm

Plant growth

Mature plant containsEmbryonic cells

Developing organs

Mature organs

Life cycles

Annuals complete life cycle in <year

Germinate grow flower seed

Biennials require two growing seasons

foxglove thistle sweet william

Perennials live for many years

PLANT GROWTH

Determinant growth

Some organs grow to certain size

Leaves

Flowers

Indeterminate growth

Plant grows throughout life

Meristems = embryonic tissue

Apical meristems for primary growth Tips of roots, flowers, shoots, leaves

New cells either remain as meristematic or differentiate

Lateral meristems• secondary growth = increase thickness

• woody plants

Primary Growth of Roots

root cap covers root tip

protects apical meristem as root pushes through soil

Growth occurs just behind the root tip, in three zones of cells: cell division

elongation

maturation

Primary Growth of Shoots

Leaves from leaf primordia

Note: Axillary buds

Organization of Leaves

stomata

In epidermis

allow CO2 in

guard cells

regulate stomata opening and closing

mesophyll

ground tissue of leaf

Key

to labels

Dermal

Ground

VascularCuticle Sclerenchyma

fibersStoma

Bundle-

sheath

cell

Xylem

Phloem

(a) Cutaway drawing of leaf tissues

Guard

cells

Vein

Cuticle

Lower

epidermis

Spongy

mesophyll

Palisade

mesophyll

Upper

epidermis

Secondary growth

girth in woody plants

stems and roots (not leaves)

1. vascular cambium

• Secondary xylem = wood

Ex. gymnosperms

2. Cork Cambium

Periderm

Bark

• all tissues external to vascular cambium

C H A P T E R 3 7

Soil and Plant Nutrition

Plants obtain most water and minerals from upper layers of soil

Living organisms play an important role

Complex ecosystem

Essential elements for plants

~80% of plant is water

Almost all dry mass is from CO2, water organic molecules

Carbohydrate (CHO)

N, S, P

Soil factors

pH

Compaction

Organic components

Inorganic components

Fertilizers

Organic – compost, manure

Inorganic – N,P, K

Agriculture

Erosion

Irrigation/water depletion

Macronutrients and Micronutrients

>50 chemical elements in plants

Macronutrients Needed in large amounts

C, O, H, N, P, S, K, Ca, Mg

Micronutrients

Cl, Fe, Mn, B, Zn, Cu, N, Mb

Most are enzyme cofactors

Genetic Engineering of Plants

Resistance to Aluminum Toxicity

Aluminum in acidic soils

damages roots

reduces crop yields

Roots that can secrete citric acid resistant

Citric acid binds to Al ions

Engineer citrate synthase genes into plant DNA plants secrete citric acid

Transgenic papaya

Flood Tolerance

Waterlogged soils

deprive roots of oxygen

buildup of ethanol and toxins from bacterial fermentation

Transgenic rice

new gene

encodes alcohol dehydrogenase

plants break down ethanol

Transgenic rice resists flooding damage

No phosphorusdeficiency

Beginningphosphorusdeficiency

Phosphorusdeficiency

Smart Plants

inform of a nutrient deficiency before damage

blue tinge indicates when these plants need

P-containing fertilizer

Arabidopsis

Plant nutrition often involves relationships with other organisms

Plants and soil microbes mutualistic

Dead plants provide energy for microorganisms

Secretions from roots support microbes

Bacteria

Up to 10 million per gram soil

Bacillus – what does it produce?

Azotobacteria –what does it do?

Nematodes

What are they?

What do nematodes do?

Earthworms

What is a macrofauna?

What do earthworms do?

Fungi

Examine the root tip for mycorrhizae hyphae

How do they benefit the root?

Soil Bacteria and Plant Nutrition

Located in

Rhizosphere - layer of soil bound to plant roots

Decomposing leaves (humus)

Inside roots

Roots secrete sugars, amino acids, and organic materials to benefit bacteria

Rhizobacteria

Rhizobacteria

Located in rhizosphere (20% of plants photosynthesis may be used to support bacteria)

Various species:

make hormones to stimulate plant growth

Make antibiotics to protect roots

Absorb toxic metals

Make nutrients available to roots

Inoculation of seeds with rhizobacteria can increase crop yields

Scanning electron micrograph of wheat root-

colonizing Pseudomonas fluorescens

Bacteria in the Nitrogen Cycle

Nitrogen is a limiting nutrient for plant growth

nitrogen cycle transforms nitrogen and nitrogen-containing compounds

Most soil nitrogen comes from actions of soil bacteria

Ammonifying bacteria

Decomposers in humus breakdown organic materials

Release ammonia (NH3)

Nitrogen-fixing bacteria

Convert N2 to NH3

NH3 converted to NH4+ (ammonium)

Nitrogen-fixing bacteria

N2

Ammonifyingbacteria

NH3

(ammonia)

Organic material (humus)

Nitrogen-Fixing Bacteria

Air 79% N2 (plants cannot use N in this form)

Nitrogen fixation N2 NH3

NH3 is used to make amino acids xylem transport

Ex. Mutualism: Rhizobacterium and legume roots

Roots form nodules with internal Rhizobacterium/bacteroids

Nodules

Roots

(a) Pea plant root (b) Bacteroids in a soybean root

nodule

5 µm

Bacteroidswithinvesicle

Fungi and Plant Nutrition

Mycorrhizae = mutualistic associations of fungi and roots

Most plant species

Two Types of Mycorrhizae

1. Ectomycorrhizae Mycelium over root

Hyphae increase surface area for water and mineral absorption

Plant does not need root hairs

Fungi benefit :

Sugar from plant

2. Arbuscular mycorrhizae

microscopic hyphae penetrate into root epidermis and cortex

Epiphytes, Parasitic, Carnivorous Plants

Non-mutualistic relationship

Epiphyte grows on another plant

obtains water and minerals from rain

Staghorn fern

Mistletoe, a photosynthetic parasite

Parasitic plants

absorb sugars and minerals from their living host plant

Mistletoe on oak tree

Venus flytrap

Carnivorous plants

photosynthetic but obtain nitrogen by killing and digesting insects

Angiosperm Reproduction

C H A P T E R 3 8

Angiosperms

Most advanced vascular plants

Flowering

Gymnosperms

Male gametophyte = pollen grain

Microspores

haploid

4 produced by microsporocyte mother cells in pollen sacs of anther

Each microspore 2 sperm cells and 1 tube cell

Female Gametophyte = embryo sac

megaspores

haploid

produced by megasporocyte mother cells in ovules

1 megaspore survives

multicellular female gametophyte (embryo sac)

Female gametophyte

1 Ovum

Fuses with 1 sperm to form zygote

2 Polar nuclei

Fuse with 1 sperm to make endosperm (3n)

Abiotic Pollination by Wind

Hazel staminate flowers(stamens only)

Hazel carpellate flower(carpels only)

Wind

Ex. grasses

Pollination by Bees

Common dandelion undernormal light

Common dandelion underultraviolet light

Insects65% of angiosperms

Pollination by Moths and Butterflies

Moth on yucca flower

Anther

Stigma

Pollination by Flies

Blowfly on carrion flower

Fly egg

Hummingbird drinking nectar of poro flower

Pollination by Birds

Birds

Long-nosed bat feeding on cactus flower at night

Pollination by Bats

Fertilization

pollen lands on stigma

1 tube cell produces pollen tube

Double fertilization = 2 sperm released

Endosperm (3n)

Zygote (2n)

Stigma

Pollen tube

2 sperm

Style

Ovary

Ovule

Micropyle Egg

Pollen grain

Polar nuclei

Ovule

Polar nuclei

Egg

Synergid

2 sperm

Endospermnucleus (3n)(2 polar nucleiplus sperm)

Zygote (2n)(egg plus sperm)

Anther

Pollen tube

Germinated pollen grain (n)(male gametophyte)

Ovary

Ovule

Embryo sac (n)(female gametophyte)

Egg (n)

Sperm (n)

Zygote

(2n)

Seed

Seed

Embryo (2n)(sporophyte)

Simple fruit

Germinatingseed

Mature sporophyte

plant (2n)

(b) Simplified angiosperm life cycle

Key

Haploid (n)

Diploid (2n)

FERTILIZATION

Endosperm Development

Stores nutrients for seedling

Ex.

• Wheat endosperm flour

• Coconut milk and meat

Mature Seeds

Seed coat - hard protection around embryo

Seed is dehydrated

Germination

when conditions for growth are favorable

Fruit forms from ovary

protects seeds

aids in seed dispersal

Dry

Nuts, legumes

Fleshy

Simple fruits

One seed (stone)

Ex. Nectarine, cherry, apricot, plum

StamenCarpels

Carpel(fruitlet)

Raspberry flower

Stigma

Ovary

Stamen

Raspberry fruit

(b) Aggregate fruit

Aggregate Fruit

raspberry

Fruit dispersal mechanisms include: Water

Wind

Animals