what is energy?
the ability to do work
where does the energy that living things need come from?
food, originally the sun
where do autotrophs get their energy?
light energy from the sun
what is an autotroph?
Organisms such as plants, which make their own food
what is a heterotroph?
organisms, such as animals, that cannot use the sun's energy directly
where do heterotrophs get their energy?
the foods they consume
what must all organisms do with energy in order to live?
release the energy in sugars and other compounds
what are the forms energy comes in?
heat, light, electricity, chemical compounds
do living things use chemical fuels?
what is ATP?
adenosine triphosphate, one of the principal chemical compounds that cells use to store and release energy
wat does ATP consist of?
adenine, a 5-carbon sugar called ribose, and three phosphate groups
what chemical compound is used by all types of cells as their basic energy source?
wat is the difference between ADP and ATP?
ADP has two phosphates instead of three
why does the body need both ADP and ATP?
because when a cell has energy available, it can store small amounts of it by adding a phosphate group to ADP molecules, producing ATP, which can be used like a fully charged battery
what is ADP?
Adenosine diphosphate, a compound that looks almost like ATP
how is energy that is stored in an ATP molecule released?
by breaking the chemical bond between the second and third phosphates
how much can one molecule of ATP power?
a variety of cellular activities, including active transport across cell membranes, protein synthesis, and muscle contraction
what is adenine
one of the bases found in DNA and RNA
what is ribose?
a sugar molecule found in RNA
what is the adenine and ribose part of the ATP molecule called?
what are the three phosphates in ATP called?
how does ATP help carry out active transport?
Many cell membranes contain a sodium-potassium pump, a membrane protein that pumps sodium ions (Na+) out of the cell and potassium ions (K+) into it. ATP provides the energy that keeps this pump working, maintaining a carefully regulated balance of ions on both sides of the cell membrane
how does ATP produce movement?
provides the energy for motor proteins that move organelles throughout the cell
Why do most cells have only a small amount of ATP, enough to last them for a few seconds of activity?
because ATP is not good for storing large amounts of energy over a long term
how many times more chemical energy does a molecule of sugar glucose store than a molecule of ATP?
what is photosynthesis?
a series of reactions that uses light energy from the sun to convert water and carbon dioxide into sugars and oxygen
how did Jan van Helmont contribute to the idea of photosynthesis?
he concluded that plants got their mass from water because that was the only thing he had added, the hydrate part
how did Joseph Priestley contribute to the idea of photosynthesis?
he concluded that plants produce oxygen
how did Jan Ingenhousz contribute to the idea of photosynthesis?
he concluded that light was necessary for plants to produce oxygen
why is the 6 added to the photosynthesis equation?
because photosynthesis usually produces 6-carbon sugars (C6H12O6) as the final product
what is the photosynthesis equation?
6 CO2 + 6 H2O _light_ C6H12O6 + CO2 (carbon dioxide + water _light_ sugar + oxygen)
what does photosynthesis use sunlight energy for?
to convert water and carbon dioxide into high-energy sugars and oxygen
what do plants use the sugars produced in photosynthesis for?
to produce complex carbohydrates such as starches
where do plants obtain carbon dioxide from?
from the air or water in which they grow
what goes in a plant during photosynthesis and what comes out after?
water and carbon dioxide go in to produce high-energy carbohydrates—sugars and starches—and oxygen, a waste product
in addition to water and carbon dioxide, what does photosynthesis require?
light and chlorophyll, a molecule in chloroplasts
how do plants gather the sun's energy?
what are pigments?
what is chlorophyll?
the plant's main pigment
what are the types of chlorophyll?
a and b
what colors does chlorophyll absorb very well?
blue-violet and red
why do plants look green?
green light is not absorbed well and is reflected by leaves
why do plants contain red and orange pigments?
to absorb light in other regions of the spectrum
what is carotene?
an example of a red and orange pigment
why is it important for photosynthesis that light is a form of energy?
because any compound that absorbs light also absorbs the energy from that light
what happens when chlorophyll absorbs light?
much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons make photosynthesis work
what are the two stages of photosynthesis?
light dependent reactions and the calvin cycle (two parts of the photosystems)
what is the energy of sunlight in the light-dependent reaction used to do?
split the water molecules and produce the high-energy molecules (ATP and NADPH)
what are the ATP and NADPH molecules that were produced in the light-dependent reactions used to do in the Calvin cycle stage?
to convert carbon dioxide into carbohydrates
does the calvin cycle require light?
In plants and other photosynthetic eukaryotes, where does photosynthesis take place?
what are thylakoids?
saclike photosynthetic membranes inside the chloroplasts of plant and other photosynthetic eukaryotic cells
what is a grana?
stacks of thylakoids (singular: granum)
what is a photosystem?
Proteins in the thylakoid membrane which organize chlorophyll and other pigments into clusters and are the light-collecting units of the chloroplast
where do the light-dependent reactions take place?
within the thylakoid membranes
where does the Calvin Cycle take place?
in the stroma
what is the stroma?
the region outside the thylakoid membranes
what are the primary light-collecting organs of plants?
what is the structure of the chloroplast?
outer membrane, inner membrane, thylakoids, granum, stroma
what is the space inside a thylakoid called?
thylakoid space, or lumen
what happens when sunlight excites electrons in chlorophyll
the electrons gain a great deal of energy which requires a special carrier
what do cells use electron carriers for?
to transport high-energy electrons from chlorophyll to other molecules
what is a carrier molecule?
a compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule
what is the electron transport chain?
the carrier molecules themselves
what is electron transport?
when electrons are transferred along with most of their energy
what is NADP+
(nicotinamide adenine dinucleotide phosphate) a carrier molecule that accepts and holds 2 high-energy electrons along with a hydrogen ion (H+). This converts the it into NADPH
what is one way in which some of the energy in sunlight can be trapped in chemical form?
the conversion of NADP+ into NADPH
what does NADPH do?
carries high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell
what are high-energy electrons used to do?
to help build a variety of molecules the cell needs, including carbohydrates like glucose
what do light-dependent reactions use energy from light to do?
to produce ATP and NADPH
what does the light-dependent reaction do?
produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH
when does photosynthesis begin?
when pigments in photosystem II absorb light
what happens after photosystem 2 absorbs light?
The light energy is absorbed by electrons, increasing their energy level. These high-energy electrons are passed on to the electron transport chain
As light continues to shine, does the chlorophyll run out of electrons?
why does the chlorophyll not run out of electron?
The thylakoid membrane contains a system that provides new electrons to chlorophyll to replace the ones it has lost
how does the thylakoid membrane's electron system work?
new electrons come from water molecules (H2O). Enzymes on the inner surface of the thylakoid membrane break up each water molecule into 2 electrons, 2 H+ ions, and 1 oxygen atom. The 2 electrons replace the high-energy electrons that chlorophyll has lost to the electron transport chain
What happens as plants remove electrons from water?
oxygen is left behind and is released into the air
what happens to the hydrogen ions that are left behind when water is broken apart?
they are released inside the thylakoid membrane
what is energy from the electrons used by the molecules in the electron transport chain for?
to transport H+ ions from the stroma into the inner thylakoid space
what do pigments in photosystem 1 use energy from light for?
to reenergize the electrons. NADP+ then picks up these high-energy electrons, along with H+ ions, at the outer surface of the thylakoid membrane, plus an H+ ion, and becomes NADPH
what happens as electrons are passed from chlorophyll to NADP+?
more hydrogen ions are pumped across the thylakoid membrane
why are the H+ ions so important?
because the difference in charges across the thylakoid membrane provides the energy to make ATP
what is ATP synthase?
a large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP
what happens as the H+ ions pass through the ATP synthase?
the protein rotates like a turbine being spun by water in a hydroelectric power plant
what happens as the ATP synthase rotates?
it binds ADP and a phosphate group together to produce ATP
why does the light-dependent electron transport produce not only high-energy electrons but ATP as well?
because of the ATP synthase and its rotation
why are ATP and NADPH compounds important?
They provide the energy to build energy-containing sugars from low-energy compounds
what is the Calvin cycle?
reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars
what happens during the calvin cycle?
plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time
what are the steps in the calvin cycle?
1. Six carbon dioxide molecules enter the cycle from the combine with six 5-carbon molecules and result in twelve 3-carbon molecules
2. The twelve 3-carbon molecules are converted into higher-energy forms. The energy for this conversion comes from ATP and high-energy electrons from NADPH.
3. Two of the twelve 3-carbon molecules are removed from the cycle. The plant cell uses these molecules to produce sugars, lipids, amino acids, and other compounds needed for plant metabolism and growth.
4. The remaining ten 3-carbon molecules are converted back into six 5-carbon molecules. These molecules combine with six new carbon dioxide molecules to begin the next cycle
what does the calvin cycle use 6 molecules of carbon dioxide for?
to produce a single 6-carbon sugar molecule
what does a plant use the sugars from the calvin cycle for?
to meet its energy needs and to build more complex macromolecules such as cellulose that it needs for growth and development
what are some factors that affect photosynthesis?
water amount, temperature, intensity of light
why does photosynthesis only work in a certain temperature?
it depends on enzymes that function best between 0°C and 35°C. Temperatures above or below this range may damage the enzymes, slowing down the rate of photosynthesis
what does food provide living things with?
the building blocks they need to grow and reproduce, a source of raw materials from which the cells of the body can synthesize new molecules, a source of energy
how much energy does one gram of sugar glucose produce when burned in the presence of oxygen release?
3811 calories of heat energy
what is a calorie?
amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius
what is a Calorie?
a kilocalorie (1000)
what do cells do with glucose?
they gradually release the energy from glucose and other food compounds
what is glycolysis?
first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid
does glycolysis release a large amount of energy?
no, only a little
what happens when oxygen is present in glycolysis?
it leads to two other pathways that release a great deal of energy (Krebs cycle and electron transport chain)
what happens when oxygen is not present in glycolysis?
it is followed by fermentation
what is cellular respiration?
process that releases energy by breaking down glucose and other food molecules in the presence of oxygen (glycolysis, the krebs cycle, and the electron transport chain)
what is the equation for cellular respiration?
6 O2 + C6H12O6 ____ 6 CO2 + 6 H2O + energy (oxygen + glucose ____ carbon dioxide + water + energy)
what would happen if cellular respiration took place in just one step?
all of the energy from glucose would be released at once, and most of it would be lost in the form of light and heat
how is the energy from cellular respiration stored?
where does glycolysis take place?
what does glycolysis do?
breaks each molecule of glucose into two molecules of pyruvate, energizes two electron carrier molecules, and produces 2 molecules of ATP
what is the cytosol?
the jelly-like part of the cytoplasm
where does the krebs cycle and electron transport chain take place?
what happens to pyruvate when it enters the mitochondrion?
it is modified and enters the krebs cycle
what do the reactions of the krebs cycle do?
breaks down pyruvate acid into into carbon dioxide, creates 2 more molecules of ATP, and energizes more electron carrier molecules
what do the electron carriers that were energized by the krebs cycle do?
they deliver electrons and hydrogen ions to the to the electron transport chain
what happens as the electrons are passed down the electron transport chain?
energy is released and used to make ATP
how many molecules of ATP does the electron transport chain produce?
as many as 32 from each molecule of glucose
how does glycolysis get started?
with two molecules of ATP
how many ATP molecules do you have when glycolysis is complete?
what is the net gain of ATP molecules for glycolysis?
what is NAD+
(nicotinamide adenine dinucleotide) electron carrier involved in glycolysis, accepts a pair of high-energy electrons
what is NADH
an electron carrier that holds electrons until they can be transferred to other molecules, helps to pass energy from glucose to other pathways in the cell
how fast is glycolysis?
so fast that cells can produce thousands of ATP molecules in just a few milliseconds
does glycolysis require oxygen?
no, it can supply chemical energy to cells when oxygen is not available
why is it bad when a cell generates large amounts of ATP from glycolysis?
In just a few seconds, all of the cell's available NAD+ molecules are filled up with electrons
what happens to the cell without NAD+?
the cell cannot keep glycolysis going, and ATP production stops
what is fermentation?
process by which cells release energy in the absence of oxygen (the combined process of the anaerobic pathway and glycolysis)
what happens during fermentation?
cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid
why is it important for fermentation to turn NADH back into the electron carrier NAD+?
because it allows glycolysis to continue producing a steady supply of ATP
what are the two main types of fermentation?
alcoholic and lactic acid
what organisms use alcoholic fermentation?
Yeasts and a few other microorganisms
what does alcoholic fermentation do?
forms ethyl alcohol and carbon dioxide as wastes
what is the equation for alcoholic fermentation?
pyruvic acid + NADH ___ alcohol + CO2 + NAD+
what happens to the small amount of alcohol produced by alcoholic fermentation?
what causes bread dough to rise?
what happens when yeast in the dough runs out of oxygen?
it begins to ferment, giving off bubbles of carbon dioxide that form the air spaces you see in a slice of bread
what can the pyruvic acid that accumulates as a result of glycolysis be converted into?
what does lactic acid fermentation do?
regenerates NAD+ so that glycolysis can continue
what is the equation for lactic acid fermentation?
pyruvic acid + NADH ___ lactic acid + NAD+
what are the steps in glycolysis?
1. the cell gives a 6-carbon molecule 2 ATP
2. then the 6-carbon molecule splits into 2 3-carbon molecules
3. each 3-carbon molecule loses 2 electrons to 2 NAD+ molecules, turning them into 2 NADH molecules
4. then the 3-carbon molecules lose more energy to 4 ADP molecules, turning them into 4 ATP molecules
5. these two 3-carbon molecules are now 2 molecules of pyruvic acid
when is lactic acid produced?
during rapid exercise when the body cannot supply enough oxygen to the tissues
why do muscles feel sore after an intense workout?
because the buildup of lactic acid causes a burning sensation
what are the steps in lactic acid fermentation?
1. 2 molecules of pyruvate acid are turned into 2 molecules of lactic acid, generating 2 molecules of NAD+
2. the two NAD+ molecules allow glycolysis to continue, producing 2 ATP molecules
3. the process continues, and the lactic acid fermentation stage gives the glycolysis stage a continuous supply of NAD+ for ATP
how do unicellular organisms produce lactic acid?
as a waste product of fermentation
what happens at the end of glycolysis?
about 90 percent of the chemical energy that was available in glucose is still unused, locked in the high-energy electrons of pyruvic acid
what does the cell do to extract the leftover oxygen from glycolysis?
turns to one of the world's most powerful electron acceptors—oxygen
what is the krebs cycle?
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
why is the krebs cycle also known as the citric acid cycle?
Because citric acid is the first compound formed in this series of reactions
where does the krebs cycle and electron transport chain take place?
the mitochondrion (the matrix)
what are the steps in the krebs cycle?
1. the 2 3-carbon pyruvate molecules pass through the mitochondrion's outer membrane and into the outer compartment
2. the pyruvate molecule then passes through the inner membrane and into the matrix
3. the pyruvate molecule is split into a 2-carbon (which enters the krebs cycle) and a carbon (which attaches to 2 oxygen molecules)
4. as the pyruvate acid is in the cycle, ADP, NAD+, and FAD is turned into ATP, NADH, and FADH2. carbon dioxide molecules are also made and they leave the body when we exhale
how many electrons does it take for a NAD+ molecule to turn into an NADH molecule?
what happens to the pyruvate molecule before it enters the krebs cycle?
1. it is split into a 2-carbon molecule and one of its carbon's attaches to 2 oxygens to make carbon dioxide
2. the 2-carbon loses 2 electrons to make a NADH
3. then the 2-carbon attaches to a molecule called CoA (coenzyme a), which then forms Acetyl-CoA
4. Acetyl-CoA enters the Krebs cycle and becomes linked with a 4-carbon compound
5. the result is a 6-carbon molecule called citric acid
6. one carbon is then removed with 2 oxygen atoms
7. the 5-carbon molecule continues to the krebs cycle and gives off 2 electrons to produce NADH
8. the 5-carbon compound gives off another carbon and 2 more electrons are given to produce NADH
9. the 4-carbon molecule gives energy to create an ATP molecule
10. two electrons are then transferred to form FADH2
11. then two more electrons are given off to form another NADH
12. the remaining de-energized 4-carbon molecule is used to restart the krebs cycle
what is Acetyl-CoA?
a highly reactive molecule that is made when CoA and the 2-carbon molecule of ex-pyruvate combine
what is the acetyl part of acetyl-CoA made up of?
2 carbon atoms, 1 oxygen atom, and 3 hydrogen atoms
what happens to the energized molecules after the krebs cycle?
they power the electron transport chain phase
what is the electron transport chain?
a series of proteins in which the high-energy electrons from the Krebs cycle are used to convert ADP into ATP
what are the steps in the electron transport chain with NADH electron carriers?
1. electron carriers transfer their electrons to proteins in the inner membrane of the mitochondria
2. two electrons from NADH are given to the first ion pump and 2 hydrogen ions are pushed into the outer compartment
3. the electrons move through the chain and onto the two other ion pumps to pump out four more hydrogen ions total
4. the 2 low-charged electrons combine with 2 hydrogens and an oxygen ion to form a water molecule
what are the electron carriers in the electron transport chain?
large proteins arrayed side by side
what are ion pumps?
three of the electron carriers in the electron transport chain which use electrons to transfer hydrogen ions out of the inner membrane
what are the steps in the electron transport chain with FADH2 electron carriers?
1. an FADH2 molecule gives off 2 electrons to the second ion pump and it transfers 2 hydrogen ions outside of the inner membrane
2. the two electrons go to the last ion pump and transfer 2 more hydrogen ions
3. the 2 low-charged electrons are mixed with hydrogen and oxygen to form a water molecule
what happens after the NADH and FADH2 have transfered the hydrogen ions into the outer compartment?
1. the hydrogen ions diffuse back into the matrix through the ATP synthase, energizing the synthase
2. the energy from the synthase is then transferred into many ATP
how much chemical energy does cellular respiration yield from a single molecule of glucose when there is no oxygen?
how much chemical energy does cellular respiration yield from a single molecule of glucose when there is oxygen?
what ATP sources does the body use in a race?
To obtain energy, the body uses ATP already in muscles and new ATP made by lactic acid fermentation and cellular respiration. All three ATP sources, but stored ATP and lactic acid fermentation can only supply energy for a limited time
what happens after 15-20 minutes of physical activity?
your body begins to use fats for energy
what is a photon?
a light energy unit
is ATP good at energy storage?
where is chlorophyll a found?
all plants, algae, and cyanobacteria
where does chlorophyll a participate?
in the Light Reactions
how does chlorophyll b act indirectly to photosynthesis?
transfers the light it absorbs to chlorophyll a
which chlorophyll is lighter?
what is the primary pigment in photosystem 1?
what is the primary pigment in photosystem 2?
a and b are equal
what is phosphorylation?
As H+ ions passed through thylakoid membrane, enzyme brings them to ADP
how many turns of the Calvin Cycle are required to make one molecule of glucose
what is ribulose biphosphate?
a carbon molecule used to regenerate the Calvin cycle (RuBP), causes carbon fixation
what is carbon fixation?
Carbon from the outside joining with a five carbon to make a six carbon
what is rubisca?
an enzyme that helps to fix carbon
what is plant pigment chromatography?
a technique used for separating and identifying pigment and other molecules from cell extracts
what is Beta carotene?
the most abundant carotene in plants (orange), the most soluble
what is xanthophyll?
is carotene with oxygen (yellow-brown), second most soluble
how does the solvent move up the paper in pigment chromatography?
capillary action, and it carries substances dissolved with it
why are the pigments in a plant carried along at different rates in pigment chromatography?
they are not equally soluble and make hydrogen bonds to different degrees
what are waves?
electromagnetic energy that travels through space
what are wavelengths?
the distance between the crests of waves
what does a prism do?
separates light into a visible form
what is porphyrin?
a ring in the chlorophyll molecule which has a magnesium center
what is chemiosmosis?
ions moving across a membrane
explain van helmont's experiment
\determined the mass of a pot of dry soil and a small seedling. Then, he planted the seedling in the pot of soil. He watered it regularly. At the end of five years, the seedling, which by then had grown into a small tree, had gained about 75 kg. The mass of the soil, however, was almost unchanged
explain priestley's experiment
Priestley took a candle, placed a glass jar over it, and watched as the flame gradually died out. Something in the air, Priestley reasoned, was necessary to keep a candle flame burning. When that substance was used up, the candle went out. That substance was oxygen. Priestley then found that if he placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and would remain lighted for a while. The mint plant had produced the substance required for burning
what is the final acceptor for hydrogen?
What affect would cyanide have on the electron transport chain and the production of atp?
cyanide blocks oxygen to combine with hydrogen which stops the electron transport chain which stops the production of energy