BIOL 145 - Week 4 - Simpson college

Anabolism

Forming chemical bonds to build molecules

Catabolism

Breaking chemical bonds

Cellular respiration reactions

Release energy held in chemical bonds by breaking down carbohydrates, producing carbon dioxide and water

Photosynthesis-respiration cycle involves?

Transfer of energy via oxidation-reduction reactions

Oxidation

Loss of electron

Reduction

Gain of electrons

Essence of photosynthesis

Adenosine triphosphate (ATP) gives cellular activity. Plants make it by using light as energy.

Carbon dioxide reaches chloroplast in mesophyll cells by

Diffusing through stomata into leaf interior

Three fates of light absorbed:

Photochemical, non-photochemical, and emission

Less than 1% of all water absorbed by plants is used in…

Photosynthesis

Most of water is used for?

Transpiration and other plant materials

PAR definition (for spectrum of colors)

Photosynthetic active radiation

Different colors =

Different wavelengths of light

Each pigment has its own distinctive pattern of light absorption =

Pigment absorption spectrum

If light and temp too high

Ratio of carbon dioxide to oxygen inside leaves may change

If light intensity is too high

Photooxidation occurs, which results destruction of chlorophyll

Several types of chlorophyll molecules

Magnesium end captures light. Lipid tail anchors into thylakoid membrane. Contain chlorophyll a (blue-green) and chlorophyll b (yello-green)

Chlorophyll b transfers

Energy from light to chlorophyll

Other photosynthetic pigments include

Carotenoids, phycobilin’s, and several types of chlorophyll

Two phases of photosynthesis

Light-dependent reaction and light-independent reactions

Light-dependent reactions

In thylakoid membranes of chloroplasts. Water molecules split apart, releasing electrons and hydrogen ions; oxygen gas released. Electrons pass along electron transport system. ATP produced. NADP is reduced, forming NADPH (used in light-independent reactions)

Light-independent reactions

In stroma of chloroplasts. Utilize ATP and NADPH to form sugars. Calvin cycle

Calvin cycle

Carbon dioxide combine RuBP (ribulose bisphosphate) and then combined molecules are converted to sugars (glucose). Energy furnished from ATP and NADPH produced during light-dependent reactions

Chlorophyll fluorescence II

When electrons are not able to be processed, energy must be dissipated. Heat or fluorescence.

Fluorescence as a measure of light stress:

Measure of fluorescence when reaction centers are all open (Fo) vs when all reaction centers are closed (Fm) The difference is Fm-Fo= Fv

Fv/Fm used as a measure of the efficiency of PSII and an indicator of the health of photosynthesis

Photosystem I =

Chlorophyll a, small amount of chlorophyll b, carotenoid pigment, and p700

( Photosystem I) P700 =

Reaction-center molecule - Only one that actually can use light energy

(Photosystem I) Remaining pigments =

antenna pigments

Photosystem II =

Chlorophyll a, B-carotene, small amounts of chlorophyll b, and reaction-center molecule: P680

(Photosystem II) Pheophytin (Pheo)

Primary electron acceptor

Light Dependent & Independent Reactions

Both work in tandem. Calvin cycle (aka Independent Reactions) do not necessarily need active light (photosynthesis) to continue metabolic processes

Photorespiration

Competes with carbon-fixing role of photosynthesis

Photorespiration forms

CO2, and PGA that can reenter Calvin cycle. No ATP formed

C4 plants can manage higher temps due to

Efficiency of photosynthesis because of higher internal CO2 levels

CAM (Crassulacean Acid Metabolism) photosynthesis

Often do not have well defined palisade mesophyll. Chloroplasts resemble the mesophyll cell chloroplasts of C3 plants. Organic acids accumulate at night (stomata open)

CAM Photosynthesis

Most water efficient

Factors Affecting the Rate of Respiration

Temperature, Water, and Oxygen

Factors Affecting the Rate of Respiration: Temperature

When air temperature rises from 20C to 30C, respiration rates double or triple

Factors Affecting the Rate of Respiration: Water

Low water levels decrease respiration. Water acts as a medium for enzymatic reactions

Factors Affecting the Rate of Respiration: Oxygen

Flooding can reduce the oxygen supply to roots

Growth

Irreversible increase in mass due to division and enlargement of cells

Determinate growth

Plant grows, stops growing and dies in one season

Indeterminate growth

Plant or parts of plant grow and continue to be active for several to many years

Differentiation

Cells develop different forms adapted to specific functions

Development

Coordination of growth and differentiation of a single cell into tissues and organs

Nutrients

Furnish elements and energy for plant growth and maintenance. Obtained from air and soil

Vitamins

Organic molecules that participate in catalyzed reactions, mostly by functioning as electron acceptors or donor. Synthesized in cell membranes and cytoplasm. Required in small amounts for normal growth and development

Plant hormones definition

Compounds which are synthesized in one part of the plant and translocated to another part where they influence growth or other processes

Plant Hormones movement is

Either upwards in the sap from the roots in the xylem tissue or moves with sugar and other solutes in the phloem

Plant Hormones five groups

auxins , gibberellins , cytokinins , abscisic acid , ethylene

Plant Hormones act by

Chemically binding to specific receptors. Triggers series of biochemical events, including turning genes on and off

Biochemical events =

Signal transduction

Plant Hormones: Auxins (to grow)

Formed in vegetative growing points, expanding leaves, and in growing seeds

Auxin production occurs mainly in

apical meristems, buds, young leaves and actively growing parts of plants

Effects of Auxins

Inhibit lateral branching. Promote cell enlargement and stem growth, cell division in the cambium, and initiation of roots, and differentiation of cell types

Gibberellins (GA)

Dramatically increases stem growth. Cell Division/Cell Elongation

Gibberellins (GA) site of action is

Before the pathway enters into the Endoplasmic Reticulum

Cytokinins

Speed up the transition to mitosis from the G2 phase, if auxin is present. Synthesized in root tips and germinating seeds

Abscisic Acid (ABA)

Has inhibitory effect on stimulatory effects of other hormones. Helps leaves respond to excessive water loss

Abscisic Acid (ABA) Interferes with

Transport or retention of potassium ions in guard cells, causing stomata to close

Ethylene

Produced by fruits, flowers, seeds, leaves and roots. Produced from amino acid methionine. Causes leaf abscission

Positive Phototropism

Toward light

Phototropism

Growth movement toward or away from light

Negative phototropism

Away from light

Gravitropism

Growth responses to stimulus of gravity

Primary roots

Positively gravitropic

Shoots

Negatively gravitropic

Thermotropism

Temperature

Turgor movements

Result from changes in internal water pressures and often initiated by contact with objects outside of plant

Solar tracking

Heliotropism-Leaves often twist on their petioles in response to illumination and become perpendicularly oriented to light source. Blades oriented at right angles to sun

Taxes (taxic movement)

Movement that involves entire plant or reproductive cells

Photoperiodism

Length of day (night) directly related to onset of flowering

Phytochromes

Pigments that control photoperiodism

Cryptochromes

Blue, light-sensitive pigments that play a role in circadian rhythms and interact with phytochromes to control reactions to light. Also important for maintaining stability of CO proteins involved in flower induction

Phytochromes two stable forms

Pr & Pfr

Pr

Absorbs red light

Pfr

Absorbs far-red light

Dormancy

Period of growth inactivity in seeds, buds, bulbs, and other plant organs even when temperature, water, or day length would typically cause growth

Quiescence

State in which seed cannot germinate unless environmental conditions normally required for growth are present

Stratification

Artificially breaking dormancy