Bio 183, Jacquet Exam 2 Material

Photosynthesis

CO2 + H2O = C6H12O6 + H2O + O2

_____ _______- internal membrane
Contains chlorophyll and other photosynthetic pigments
-Pigments clustered into photosystems

Thylakoid membrane

____ - stacks of flattened sacs of thylakoid membrane

Grana

_____ ______ - connect grana

Stroma lamella

______ - semiliquid surrounding thylakoid membranes

Stroma

Made up of thylakoid membrane, grana, and stroma

Chloroplast

Brings water up from the roots

Cohesion

Opening at bottom of leaf
Moves gases in and out of leaves

Stoma(ta)

Two stages of photosynthesis

Light-dependent and light-independent reactions

-Require light
-Capture energy from sunlight
-Make ATP and reduce NADP+ to NADPH

Light-dependent reactions

-Does not require light
-Use ATP and NADPH to synthesize organic molecules from CO2

Light-independent reactions

Molecules that absorb light energy in the visible range

Pigments

Particle of light

Photon

Removal of an electron from a molecule by light

Photoelectric effect

Range and efficiency of photons molecule is capable of absorbing

Absorption spectrum

Only two general types of pigments are used in green plant photosynthesis
_________ and ____________

Chlorophylls, Carotenoids

-Main pigment in plants and cyanobacteria
-Only pigment that can act directly to convert light energy to chemical energy
-Absorbs violet-blue and red light

Chlorophyll a

-Accessory pigment or secondary pigment absorbing light wavelengths that chlorophyll a does not absorb

Chlorophyll b

Structure of chlorophyll
________ _________
(Complex ring structure with alternating double and single bonds; Magnesium ion at the center of the ring)

porphyrin ring

Carbon rings linked to chains with alternating single and double bonds
Can absorb photons with a wide range of energies
Also scavenge free radicals - antioxidant

Carotenoids

Important in low-light ocean areas

Phycobiloproteins

Photosystem Organization:
__________ ___________
-Hundreds of accessory pigment molecules
-Gather photons and feed the captured light energy to the reaction center
-Also called light-harvesting complex
-Captures photons from sunlight and channels them to the reaction center chlorophylls

Antenna complex

Photosystem Organization:
_________ __________
-1 or more chlorophyll a molecules
-Passes excited electrons out of the photosystem
-Transmembrane protein-pigment complex

Reaction center

-When a chlorophyll in the reaction center absorbs a photon of light, an electron is excited to a _______ energy level

higher

-Light-energized electron can be transferred to the primary electron acceptor, ___________ it

reducing

Oxidized chlorophyll then fills its electron "hole" by oxidizing a __________ __________

donor molecule

Light Dependent Reaction stages:
1. ______ ______
Photon of light is captured by a pigment molecule
2. _________ __________
Energy is transferred to the reaction center; an excited electron is transferred to an acceptor molecule
3. _______ _______
Electrons move through carriers to reduce NADP+
4. ___________
Produces ATP

Primary photoevent
Charge separation
Electron transport
Chemiosmosis

Chloroplasts have ____ connected photosystems

two

Functions like sulfur bacteria (P700)

Photosystem I

Can generate an oxidation potential high enough to oxidize water (P680)

Photosystem II

Working together, the two photosystems carry out a __________ transfer of electrons that bis used to generate both ATP and NADPH

noncyclic

Photosystem I transfers electrons ultimately to NADP+, producing

NADPH

Electrons lost from photosystem I are replaced by

electrons from photosystem II

Photosystem II oxidizes water to

replace the electrons transferred to photosystem I

2 photosystems connected by

cytochrome/ b6-f complex

Who hates this class?

Me!

Plants use photosystems II and I in series to produce both ATP and NADPH
Path of electrons not a circle
Photosystems replenished with electrons obtained by splitting water
Z diagram

Noncyclic photophosphorylation

-Resembles the reaction center of purple bacteria
-Core of 10 transmembrane protein subunits with electron transfer components and two P680 chlorophyll molecules
-Reaction center differs from purple bacteria in that it also contains four manganese atoms
-Essential for the oxidation of water

Photosystem II

Proton pump embedded in thylakoid membrane

b6-f complex

-Reaction center consists of a core transmembrane complex consisting of 12 to 14 protein subunits with two bound P700 chlorophyll molecules
-accepts an electron from plastocyanin into the "hole" created by the exit of a light-energized electron
-Passes electrons to NADP+ to form NADPH

Photosystem I

-Electrochemical gradient can be used to synthesize ATP
-Chloroplast has ATP synthase enzymes in the thylakoid membrane
-Allows protons back into stroma

Chemiosmosis

Stroma contains enzymes that catalyze the reactions of carbon fixation

Calvin cycle reaction

Noncyclic photophosphorylation generates ______, ________
Building organic molecules takes more energy than that alone so cyclic photophosphorylation is used to produce additional ATP

NADPH
ATP

Cyclic photophosphorylation used to produce additional ATP
-Short-circuits photosystem I to make a larger _______ ________ to make more ATP

proton gradient

The Calvin Cycle-
to build carbohydrates, cells use energy in the form of ATP (from light-dependent rxns, and cyclic and noncyclic photophosphorylation; drives endergonic rxn)

Carbon fixation

NADPH from photosystem I
Source of protons and energetic electrons

Reduction potential

C3 photosynthesis

Calvin Cycle

The key step of the Calvin Cycle is the attachment of ____ to _________ to form PGA

CO2, RuBP

The Calvin Cycle uses the enzyme _______ ___________/_________ or _________

bisphosphate carboxylase/oxygenase, rubisco

3 phases of Calvin Cycle
1. _____ ____
- RuBP + CO2 --> PGA
2. _________
- PGA is reduced to G3P
3. ________ __ _______
- PGA is used to regenerate RuBP

Carbon fixation
Reduction
Regeneration of RuBP

During the 3 phases of the Calvin Cycle, ____ turns incorporate enough carbon to produce anew G3P
6 turns incorporate enough Carbon for ___ glucose(s)

3, 1

a 3 Carbon sugar

G3P

_____ is not a direct product of the Calvin Cycle

Glucose

G3P is used to form ____ and make _____

sucrose, starch

Sucrose is a ____ ________ _______ in plants (disaccharide made of fructose and glucose)

major transport sugar

Starch is stored for later use. It is an insoluble _______ __________

glucose polymer

Photosynthesis uses the products of _______as starting substrates

respiration

Respiration uses the products of _________ as starting substrates

photosynthesis

Production of glucose from G3P even uses part of the ancient glycolytic pathway, run in _______
-Principal proteins involved in electron transport and ATP production in plants are evolutionarily related to those in mitochondria

reverse

Rubisco has 2 enzymatic activities
- _________
- _________

Carboxylation
Photorespiration

Addition of CO2 to RuBP
Favoured under normal conditions

Carboxylation

Oxidation of RuBP by the addition of O2
Favoured when stoma are closed in hot conditions
Creates low CO2 and high CO2

Photorespiration

CO2 and O2 compete for the active site on ______

RuBP

When it is hot, leaves _____ water through stomata

lose

The stomata ______ to conserve water but this results in O2 build up inside the leaves and CO2 cannot enter

close

Types of photosynthesis
___
___ and ___

C3, C4, CAM

Types of photosynthesis
Plants that fix carbon using only the Calvin Cycle

C3

Types of photosynthesis
Add CO2 to PEP to form 4 carbon molecule
Use PEP carboxylase
Greater affinity for CO2, no oxidase activity
------spatial solution

C4

Types of photosynthesis
Add CO2 to PEP to form 4 carbon molecule
Use PEP carboxylase
Greater affinity for CO2, no oxidase activity
------temporal solution

CAM

C4 plants produce __________, converted to malate, transported to bundle-sheath cells

oxaloacetate

corn, sugarcane, sorghum, and a number of other grasses
Initially fix carbon using PEP carboxylase in mesophyll cells

C4 plants

Within the bundle-sheath of C4 plants, malate is decarboxylated to produce ______ and ______

Pyruvate, CO2

Carbon fixation is started by __________ which starts the Calvin Cycle

rubisco

In C4 pathways, to produce a single glucose requires ____ additional ATP compared with the Calvin cycle alone
(C4 photosynthesis is advantageous in hot dry climates where photorespiration would remove more than half of the carbon fixed by the usual C3 pathway alone)

12

Many succulent (water-storing) plants such as cacti, pineapples, and some members of about two dozen other plant groups
Stomata open during the night and close during the day (reverse of most plants)
Fix CO2 using PEP carboxylase during the night and store in vacuoles

CAM plants

When stomata closed during the day, organic acids are decarboxylated to yield _____ _____ __ ____ which drive the Calvin cycle and minimize photorespiration

high levels of CO2

Compare C4 and CAM:
Both use C3 and C4 pathways
___ - two pathways occur in different cells
____ - C4 pathways at night and the C3 pathway during the day

C4
CAM

Signaling molecule

ligand

molecule to which the receptor binds to

receptor protein

interaction of ligand and receptor protein initiate the process of _______ ______, which converts info in the signal into a cellular response

signal transduction

There are four basic mechanisms for cellular communication
1.
2.
3.
4.

Direct contact
Paracrine signaling
endocrine signaling
synaptic signaling

Some cells send signals to themselves

autocrine signaling

Molecules on the surface of one cell are recognized by receptors on the adjacent cell
Important in early development
Gap junctions

Direct contact

Hormones released from a cell travel through circulatory system to affect other cells throughout the body
Both animals and plants use this mechanism extensively

endocrine signaling

-Occurs in animals
-Nerve cells release the signal (neurotransmitter) which binds to receptors on nearby cells
-Association of neuron and target cell is a chemical synapse

Synaptic signaling

Events within the cell that occur in response to a signal
When a ligand binds to a receptor protein, the cell has a response
Different cell types can have similar response to the same signal (Glucagon example)
Different cell types can respond differently to the same signal (Epinephrine example)

Signal transduction

A common way to change the activity of a protein
(addition of phosphate group)
- A cell's response to a signal often involves activating or inactivating proteins

Phosphorylation

an enzyme that adds a phosphate to a protein

Protein kinase

an enzyme that removes a phosphate from a protein

Phosphatase

a type of receptor located within the cell

intracellular receptor

located on the plasma membrane to bind a ligand outside the cell
-transmembrane protein in contact with both the cytoplasm and the extracellular environment

Cell surface receptor/membrane receptor

channel-linked receptor that open to let a specific ion pass in response to a ligand

chemically gated ion channels

receptor is an enzyme that is activated by the ligand
-almost all are protein kinases

Enzymatic receptor

A G-protein (bound to GTP) assists in transmitting the signal from receptor to enzyme (effector)

G protein-coupled receptor

Intracellular Receptors
_________ _______
-common nonpolar, lipid-soluble structure
-Can cross the plasma membrane to an intracellular steroid receptor
-Binding of the hormone to the receptor causes the complex to shift from the cytoplasm to the nucleus
-Act as regulators of gene expression

Steroid hormones

1. Hormone-binding domain
2. DNA-binding domain
3. Domain that interacts with coactivators to affect level of gene transcription

Steroid receptor's 3 functional domains

In its inactive state, a ______ _____ typically cannot bind to DNA because an inhibitor protein occupies the DNA binding site
-Binding of ligand changes conformation

steroid receptor

-Target cell's response to a lipid-soluble cell signal can vary enormously, depending on the nature of the cell
-Even the same type of cell may have different responses
-Depends on coactivators present

coactivators

_________ has different effects in uterine tissue than mammary tissue
Regulation is not by presence or absence of receptor
Instead presence or absence of coactivator

Estrogen

all cells have 2 main phases they can regulate that allow them to split

Receptor Kinases