BIOL 600 Study Guide - Summer 2018, Comprehensive Midterm Notes - Wireless Access Point, Oxygen, Protein
12 Oct 2018
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BIOL 600
MIDTERM EXAM
STUDY GUIDE
Fall 2018
AP Bio Chapter 10 Photosynthesis
Lecture Outline
Overview: The Process That Feeds the Biosphere
Life on Earth is solar powered.
The chloroplasts of plants use a process called photosynthesis to capture light energy
from the sun and convert it to chemical energy stored in sugars and other organic
molecules.
Plants and other autotrophs are the producers of the biosphere.
Photosynthesis nourishes almost all the living world directly or indirectly.
o All organisms use organic compounds for energy and for carbon skeletons.
o Organisms obtain organic compounds by one of two major modes: autotrophic
nutrition or heterotrophic nutrition.
Autotrophs produce their organic molecules from CO2 and other inorganic raw materials
obtained from the environment.
o Autotrophs are the ultimate sources of organic compounds for all heterotrophic
organisms.
o Autotrophs are the producers of the biosphere.
Autotrophs can be separated by the source of energy that drives their metabolism.
o Photoautotrophs use light as a source of energy to synthesize organic compounds.
Photosynthesis occurs in plants, algae, some other protists, and some
prokaryotes.
Chemoautotrophs harvest energy from oxidizing inorganic substances,
such as sulfur and ammonia.
Chemoautotrophy is unique to prokaryotes.
Heterotrophs live on organic compounds produced by other organisms.
o These organisms are the consumers of the biosphere.
o The most obvious type of heterotrophs feeds on other organisms.
Animals feed this way.
o Other heterotrophs decompose and feed on dead organisms or on organic litter,
like feces and fallen leaves.
Most fungi and many prokaryotes get their nourishment this way.
o Almost all heterotrophs are completely dependent on photoautotrophs for food
and for oxygen, a by-product of photosynthesis.
Concept 10.1 Photosynthesis converts light energy to the chemical energy of food
All green parts of a plant have chloroplasts.
However, the leaves are the major site of photosynthesis for most plants.
o There are about half a million chloroplasts per square millimeter of leaf surface.
The color of a leaf comes from chlorophyll, the green pigment in the chloroplasts.
o Chlorophyll plays an important role in the absorption of light energy during
photosynthesis.
find more resources at oneclass.com
find more resources at oneclass.com
Chloroplasts are found mainly in mesophyll cells forming the tissues in the interior of the
leaf.
O2 exits and CO2 enters the leaf through microscopic pores called stomata in the leaf.
Veins deliver water from the roots and carry off sugar from mesophyll cells to
nonphotosynthetic areas of the plant.
A typical mesophyll cell has 30–40 chloroplasts, each about 2–4 microns by 4–7 microns
long.
Each chloroplast has two membranes around a central aqueous space, the stroma.
In the stroma is an elaborate system of interconnected membranous sacs, the thylakoids.
o The interior of the thylakoids forms another compartment, the thylakoid space.
o Thylakoids may be stacked into columns called grana.
Chlorophyll is located in the thylakoids.
o Photosynthetic prokaryotes lack chloroplasts.
o Their photosynthetic membranes arise from infolded regions of the plasma
membranes, folded in a manner similar to the thylakoid membranes of
chloroplasts.
Evidence that chloroplasts split water molecules enabled researchers to track atoms
through photosynthesis.
Powered by light, the green parts of plants produce organic compounds and O2 from
CO2 and H2O.
The equation describing the process of photosynthesis is:
o 6CO2 + 12H2O + light energy --> C6H12O6 + 6O2+ 6H2O
o C6H12O6 is glucose.
Water appears on both sides of the equation because 12 molecules of water are
consumed, and 6 molecules are newly formed during photosynthesis.
We can simplify the equation by showing only the net consumption of water:
o 6CO2 + 6H2O + light energy --> C6H12O6 + 6O2
The overall chemical change during photosynthesis is the reverse of cellular respiration.
In its simplest possible form: CO2 + H2O + light energy --> [CH2O] + O2
o [CH2O] represents the general formula for a sugar.
One of the first clues to the mechanism of photosynthesis came from the discovery that
the O2 given off by plants comes from H2O, not CO2.
o Before the 1930s, the prevailing hypothesis was that photosynthesis split carbon
dioxide and then added water to the carbon:
Step 1: CO2 --> C + O2
Step 2: C + H2O --> CH2O
o C. B. van Niel challenged this hypothesis.
o In the bacteria that he was studying, hydrogen sulfide (H2S), not water, is used in
photosynthesis.
o These bacteria produce yellow globules of sulfur as a waste, rather than oxygen.
o Van Niel proposed this chemical equation for photosynthesis in sulfur bacteria:
CO2 + 2H2S --> [CH2O] + H2O + 2S
He generalized this idea and applied it to plants, proposing this reaction for their
photosynthesis:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The chloroplasts of plants use a process called photosynthesis to capture light energy from the sun and convert it to chemical energy stored in sugars and other organic molecules. Plants and other autotrophs are the producers of the biosphere. Photosynthesis nourishes almost all the living world directly or indirectly: all organisms use organic compounds for energy and for carbon skeletons, organisms obtain organic compounds by one of two major modes: autotrophic nutrition or heterotrophic nutrition. Autotrophs produce their organic molecules from co2 and other inorganic raw materials obtained from the environment: autotrophs are the ultimate sources of organic compounds for all heterotrophic organisms, autotrophs are the producers of the biosphere. Autotrophs can be separated by the source of energy that drives their metabolism: photoautotrophs use light as a source of energy to synthesize organic compounds. Photosynthesis occurs in plants, algae, some other protists, and some prokaryotes. Chemoautotrophs harvest energy from oxidizing inorganic substances, such as sulfur and ammonia.
