Study Guide: Review all Quiz Answers, plus read the Chapters, and this study guide.
Chapter 10: Photosynthesis: transforming light energy (photons = electrons) into chemical energy (ATP,
NADPH & Glucose), using water and CO2 as starting materials.
Light absorbing organelles called chloroplasts carry out photosynthesis, specifically in the thylakoid
membranes of the grana stacks. In the chloroplasts, there is a fluid called stroma (not cytoplasm); and pores
called stomata where O2 expels as a waste product (CO2 comes in).
**Equation for Photosynthesis: H20 + CO2 + Light (photons) > O2 + Glucose (C6H12O6) + ATP
Know definitions of wavelength, electromagnetic spectrum; and know that we are able to see colors because all
the colors are absorbed, except green is reflected, in case of a plant.
So within the thylakoid membranes there are green pigments called Chlorophyll. Chlorophyll a specifically
deals with the light reactions and electrons. Chlorophyll b and Carotenoids help chlorophyll a by expanding the
range to more colors thus harnessing more energy (electrons) for photosynthesis. Know what are carotenoids.
Light is a photon, dense, packed energy of electrons. **The shorter the wavelength, the greater the energy
of a photon. When a photon is absorbed by a pigment, it becomes “excited;” which means the electrons have
been raised from a ground state to an excited state, however this state is very unstable so it eventually loses its
excess energy and falls back to ground state. As it falls, it can give off heat or light (fluorescence – like in the
glow stick), or some other type of energy. (I like to equate this to a sugar ‘high’ – meaning you can’t stay at the
high energy, you have to fall down to ‘dormancy.’)
There are 2 PHOTOSYSTEMS, (WATER SPLITTING & NADPH-PRODUCING,) And CALVIN CYCLE.
PHOTOSYSTEM I: in the thylakoid membranes (remember location is important), chlorophyll antenna
pigments absorb photons (light); also H20 is introduced via veins of the plant (from rainfall). So the inputs are
photons and H20. The H20 splits into H and O2, where the O2 (waste byproduct) escapes via the stomata pores;
the H (electrons) and photons, at ground state, jump from chlorophyll to chlorophyll till it hits a chlorophyll a.
While they are jumping, they are gaining more energy, thus the electrons become “excited” and go to the
primary electron acceptor. **(chlorophyll a + primary electron acceptor = reaction center.) The electrons
fall down because they are unstable, & when they fall down they go thru the ATP synthase rotor. Thus making
ATP via Electron Transport Chain & the ATP synthase rotor. Outputs are O2 and ATP.
**You must know the link between Photosystem I and II. It is the ETC!!!!
PHOTOSYSTEM II: Inputs ATP and light (photons again) hit another chlorophyll a & become excited going
to the primary electron acceptor again, falling down to make the output NADPH. **You must know the link
between Photosystem II and Calvin Cycle. It is the molcules ATP & NADPH!!!
The NEXT STEP: CALVIN CYCLE. Inputs NADPH & ATP add to CO2 (from air) to enter the Calvin Cycle.
The cycle turns 6 times to make outputs ATP and Glucose (G3P). This cycle repeats over and over.
LOOK AT THE FIGURES FOR THIS CHAPTER 10!
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CHAPTER 11: CELL COMMUNICATION
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A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted
into a specific cellular response
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Signal transduction pathways convert signals on a cell’s surface into cellular responses
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The below figure on the left is: gap junctions in animal cells. The right is plasmodesmata in plant cells.
And the bottom shows receptor cell-cell communication.
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In many other cases, animal cells communicate using local regulators, messenger molecules that travel
only short distances
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In long-distance signaling, plants and animals use chemicals called hormones FIGURE 11.5 SHOWS
PARACRINE AND ENDOCRINE SIGNALING! **
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Cells receiving signals go through three processes: FIGURE 11.6!! MUST GO OVER THIS FIG**
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STEP 1: Reception
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The binding between a signal molecule (ligand) and receptor is highly specific
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A shape change in a receptor is often the initial transduction of the signal
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Most signal receptors are plasma membrane proteins (INTEGRAL PROTEINS)
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There are three main types of membrane receptors
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G protein-coupled receptors: G-protein-coupled receptor (GPCRs) are the
largest family of cell-surface receptors. A GPCR is a plasma membrane receptor
that works with the help of a G protein. The G protein acts as an on/off switch: If
GDP is bound to the G protein, the G protein is inactive. FIGURE 11.7B SLIDE
22 ***(GTP IS FUNCTIONALLY THE SAME AS ATP)!!!
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Receptor tyrosine kinases: Receptor tyrosine kinases (RTKs) are membrane
receptors that attach phosphates to tyrosines. REMEMBER THE DIMER!
**FIGURE 11.7C SLIDE 24
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Ion channel receptors: A ligand-gated ion channel receptor acts as a gate when
the receptor changes shape. When a signal molecule binds as a ligand to the
receptor, the gate allows specific ions, such as Na+ or Ca2+, through a channel in
the receptor. FIG 11.7D SLIDE 26
•
•
•
LOOK AT FIG 11.9-5 SLIDE 31
STEP 2: Transduction
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Transduction: Cascades of molecular interactions relay signals from receptors to target
molecules in the cell. Signal transduction usually involves multiple steps
•
Multistep pathways can amplify a signal: A few molecules can produce a large cellular
response
•
Like falling dominoes, the receptor activates another protein, which activates another,
and so on, until the protein producing the response is activated
•
**Phosphorylation and Dephosphorylation FIG 11.10 SLIDE 37
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In many pathways, the signal is transmitted by a cascade of protein
phosphorylations
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Protein kinases transfer phosphates from ATP to protein, a process called
phosphorylation (BASICALLY TURNING ON THE PROCESS)
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Protein phosphatases remove the phosphates from proteins, a process called
dephosphorylation (TURNING OFF)
•
This phosphorylation and dephosphorylation system acts as a molecular switch,
turning activities on and off or up or down, as required
•
Second messengers are small, nonprotein, water-soluble molecules or ions that
spread throughout a cell by diffusion (BASICALLY THEY ARE HELPERS)
•
Cyclic AMP (FIG 11.12 SLIDE 42) and calcium ions are common
second messengers
•
Pathways leading to the release of calcium involve inositol triphosphate
(IP3) and diacylglycerol (DAG) as additional second messengers FIG
11.13-4 SLIDE 48
STEP 3: Response
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Response: Cell signaling leads to regulation of transcription or cytoplasmic
activities. The cell’s response to an extracellular signal is sometimes called the “output
response”
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2 TYPES OF RESPONSES POSSIBLE: Nuclear and Cytoplasmic Responses: FIG
11.15 SLIDE 51
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Signaling pathways can also affect the overall behavior of a cell, for example, changes in
cell shape FIG 11.17 SLIDE 55: LOOK AT THE RESULTS, HOW THE SHAPE
CHANGES.
** (MOST IMPORTANT EXAMPLE: FIGHT OR FLIGHT, SIGNAL MOLECLE IS EPI &
RESPONSE: GLUCOSE INTO CELLS > INCREASE IN ATP).
Fine-Tuning of the Response (CAN BE CONSIDERED THE 4TH STEP)
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There are four aspects of fine-tuning to consider
o Amplifying the signal (and thus the response): Enzyme cascades amplify the cell’s response
at each step, the number of activated products is much greater than in the preceding step
o Specificity of the response FIG 11.18 SLIDE 59
o Overall efficiency of response, enhanced by scaffolding proteins: Scaffolding proteins are
large relay proteins to which other relay proteins are attached. Scaffolding proteins can
increase the signal transduction efficiency by grouping together different proteins involved in
the same pathway FIG 11.19 SLIDE 61
o Termination of the signal: Inactivation mechanisms are an essential aspect of cell signaling.
Unbound receptors revert to an inactive state. (You have to stop the process, otherwise you
are wasting energy)
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Apoptosis is programmed or controlled cell suicide. Components of the cell are chopped up and
packaged into vesicles that are digested by scavenger cells. Apoptosis prevents enzymes from leaking
out of a dying cell and damaging neighboring cells
•
•
Apoptosis can be triggered by 3 things:
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An extracellular death-signaling ligand
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DNA damage in the nucleus
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Protein misfolding in the endoplasmic reticulum
Apoptosis may be involved in some diseases (for example, Parkinson’s and Alzheimer’s);
interference with apoptosis may contribute to some cancers
!!!MAKE SURE YOU KNOW HOW TO LABEL THIS ABOVE FIGURE. LAST SLIDE IN CH11