biology chapter 9

in the chemical bonds of organic compounds. Almost all of the energy in organic compounds comes from the sun.

Solar energy enters living systems which plants,algae, & certain prokaryotes use sunlight to make organic compounds from carbon dioxide & water.

-Organisms able to perform photosynthesis are autotrophs. Autotrophs make organic compounds that serve as food for them and for almost all of the other organisms on Earth.

• -Most autotrophs have a supply of food as long as sunlight is available. Organisms that make their own food must absorb food molecules made my autotrophs, by eating autotrophs or consuming
• organisms that do.

food molecules that are consumed are the fuel of cells.

it involves either using energy to build organic molecules or breaking down organic molecules in which energy is stored. Organic molecules contain carbon. Therefore, an organism's metabolism is part of earth's carbon cycle.

-The carbon cycle not only makes carbon compounds continually available in an ecosystem but also delivers chemical energy to organisms living within that ecosystem.

Photosynthesis-energy enters the ecosystem when organisms use photosynthesis. This happens in Chloroplasts.

Cellular Respiration- Organisms extract energy stored in glucose molecules. Through cellular respiration cells make the carbon in glucose into stable carbon dioxide molecules and produce energy. Thus, stable & less stable compounds alternate during the carbon cycle & provide a continuous supply of energy for life processes in an ecosystem.

"the breakdown" input:a glucose molecule & 6 oxygen molecules. Product: 6 carbon dioxide molecules & 6 water molecules. Energy is also released & used to make ATP. ATP an organic molecule that is the main energy source for cell processes.

it is gradually released in a series of chemical reactions that are assisted by enzymes.

• ATP- ATP can be used to power chemical reactions. Its is a form of energy "currency" inside cells. It can be "earned" or made, in one place & "spent" or used in another place. Its a nucleotide made of 3 phosphate groups. The chain is unstable because the phosphate groups are negatively charged and thus repel each other. When the bond of the 3rd phosphate group is broken, energy is released. This produces ADP.
• ATP----> ADP+P+energy
• the reaction requires a small amount of energy. But the energy released is far greater then the energy put in.
• ATP Synthase- an enzyme that catalyzes the synthesis of ATP. Its recycles ADP by bonding a 3rd phosphate group to the molecule. They act as both an enzyme & a carrier protein for hydrogen+ ions. The flow of H+ ions through ATP synthase powers the production of ATP. As the ions flow, ATP synthase catalyzes a reaction in which a phosphate group os added to a molecule of ADP to make ATP.
• Hydrogen Ion Pumps- The inner mitochondrial membrane allows H+ ions to diffuse through only ATP synthase. When glucose is broken down during cellular respiration NAD accepts electrons & hydrogen ions which changes NAD to NADH. NADH enters an electron transport chain, a series of molecules in the inner membrane of a mitochondria, it allows electrons to drop in energy as they are passed along & uses the energy released to pump H+ ions out of the mitochondria's inner compartment. THis increases the concentration of H+ ions in the outer compartment. THe ions then diffuse in the the inner compartment through ATP synthase,

the breaking & forming of bonds

photosynthesis

• organelles that convert light energy into chemical energy.
• It has an outer membrane & an inner membrane. Molecules diffuse easily through the outer membrane. The inner membrane is much more selective about what substances enter & leave. Both membranes allow light to past thorough.
• the space inside the inner membrane is the stroma. Within the stroma is a membrane called the thylakoid membrane. This membrane is folded in a way that produces flat, disc- like sacs called thylakoids. These sacs , which contain molecules that absorb light energy for photosynthesis, are arranged in stacks. The first stage of photosynthesis begins when light waves hit these stacks.

Electromagnetic Radiation- Energy that can travel through empty space in the form of waves, light is a form of this. The differences lie in the wavelengths. Each wavelength corresponds to a certain amount of energy. The wavelength is the distance between consecutive wave peaks. Sunlight contains all of the wavelengths of visible light.

• Pigments- a substance that absorbs certain wavelengths ( colors) of light & commonly reflects all of the others. It makes the human eye sensitive to light. In plants, light energy is harvested by pigments that are located in the thylakoid membrane of chloroplasts.
• Chlorophyll is a green pigment in chloroplasts that absorbs light energy to start photosynthesis. It absorbs mostly blue & red light & reflects green & yellow light which makes plants appear green. there are two types of chlorophyll; chlorophyll a & chlorophyll b. carotenoids,pigments also found in plants, absorb blue & green and they reflect yellow, orange, & red. carotenoids aid photosynthesis by allowing plants to absorb additional light energy. chlorophyll fades in fall then carotenoids appear.

electron carriers- when light hits a thylakoid, energy is absorbed by many pigment molecules. they all funnel the energy to a special chlorophyll molecule in a region called the reaction center, where the energy causes the electrons to become "excited" & to move to a higher energy level. These electrons are transferred quickly to other nearby molecules & then to an electron carrier.

electrons from the electron carrier are used to produce new molecules, including ATP, that temporarily store chemical energy. The carrier transfer the electrons to the first of two electron transport chains in the thylakoid membrane. During photosynthesis, one electron transport chain provides energy to make ATP, while the other provides energy to make NADPH.

• producing ATP
• 1) water splitting- During photosynthesis an enzyme splits water molecules inside the thylakoid. When water molecules are split, chlorophyll molecules take the electrons from the H atoms which leaves H+ ions. The O from the split becomes O2 which is not used & is released.
• 2) hydrogen ion pumps- A protein acts as a membrane pump. Excited electrons transfer some of their energy to pump H+ ions into the thylakoid. This process creates a concentration gradient across the thylakoid membrane.
• 3)ATP synthase- The energy form the diffusion of H+ ions through the carrier protein is used to make ATP, the carrier proteins are unusual because they function both as an ion channel & as the enzyme ATP synthase . It produces ATP which is used to power the final stages of photosynthesis.

• Producing NADPH
• The 2nd transport chain is to the right of the 2nd cluster of pigment molecules.
• 4) reenergizing- the excited electrons are passed on to the 2nd chain. THey are replaced by the de-energized electrons from the first transport chain.
• 5) making NADPH - excited electrons combine w/ H+ ions & an electron acceptor called NADP+ to form NADPH. NADPH is an electron carrier that provides the high-energy electrons needed to store energy in organic molecules.

BOth NADPH & the ATP made during the1st stage of photosynthesis will be used to provide the energy to carry out the final stage of photosynthesis.

on light because light energy is used to make ATP & NADH

In the final stage of photosynthesis ATP & NADH are used to produce energy-storing sugar molecules from the carbon in carbon dioxide.

• the most common method of carbon dioxide fixation is the Calvin Cycle.
• 1) Carbon Fixation- an enzyme adds a molecule of carbon dioxide to a 5-carbon compound. This occurs 3x to make 3 six-carbon molecules.
• 2)transferring energy- each 6-carbon compound splits into 2 3-carbon compounds. Phosphate groups from ATP & electrons from NADPH are added to the 3-carbon compounds to form higher energy 3-carbon sugars.
• 3) making sugars- one of the resulting 3-carbon sugars leaves the cycle & is used to make organic compounds-including glucose,sucrose,& starch- in which energy is stored for later use by the organism.
• 4) Recycling-the remaining 5 3-carbon sugars are rearranged. Enzymes use energy to reform three molecules of the initial 5 carbon compound. This completes the cycle & the reformed compounds are used to begin the cycle again.

carbon dioxide fixation or carbon fixation. The reactions that fix carbon dioxide are light independent reactions, sometimes called dark reactions. There are several ways in which carbon dioxide is fixed.

light intensity, carbon dioxide concentration, & temperature are three environmental factors the affect photosynthesis.

in general, the rate of photosynthesis increases as light intensity increases until all of the pigments in a chloroplast are used. At this saturation point, the rate of photosynthesis levels off because the pigment cannot absorb more light.

once a certain concentration of carbon dioxide is present , photosynthesis cannot proceed any faster.

unfavorable tempts. may inactivate certain enzymes so that reactions cannot take place.

glucose, which is formed when carbs such as starch & sucrose are broken down. If too few is available other molecules can make ATP. such as fats & proteins& nucleic acid

• in the 1st stage of CR glucose is broken down in the cytoplasm by glycolysis. In glycolysis enzymes break down one-six carbon molecule of glucose onto 2 3-carbon pyruvate molecules.
• 1) breaking down glucose - a phosphate group is +ed to the 6-carbon compound. This makes the molecule reactive so that an enzyme can break it into 2 3-carbon sugars, each w/ a phosphate group.
• 2)NADH production- 3-carbon compounds react w/ another phosphate group(not ATP). Hydrogen atoms are transferred to two molecules of NAD+ which produces 2 molecules of the electron carrier NADH. NADH is used later in other cell processes, where it is recycled to NAD+
• 3)Pyruvate Production- In a series of 4 reactions, each 3-carbon sugar is converted into a 3-carbon molecule of pyruvate. This process produces 4 ATP molecules. A net gain of 2 ATP molecules

• anaerobic- takes place w/o oxygen. i.e glycolysis
• aerobic- metabolic processes that require oxygen

krebs cycle -a series of reactions that produce electron carriers, breaks down pyruvate. The electron carriers enter an electron transport chain, which powers ATP synthase. Up to 34ATP molecules can be produce from 1 glucose molecule through aerobic respiration.

the 1st stage of the Krebs cycle. a 6-carbon compound is created. Its releases 1 carbon dioxide molecule & the another. Energy is released each time, forming an electron carrier NADH. Te remaining 4-carbon compound is converted to the four-carbon compound that began the cycle. This conversion produces ATP & FADH2 & NADH. THe 4-carbon compound combines w/ a new 2-carbon unit from pyruvate to continue the cycle.

1ATP, 3 NADH, & 1FADH2. electron carriers transfer energy through the electron transport chain, which ultimately powers ATP synthase.

• the 2nd stage of aerobic respiration takes place in the inner membranes of the mitochondria.
• 1) the electrons that are carried by NADH & FADH2 pass thru this chain. Energy is transferred into each molecule thru which the electrons pass. 2) energy from the electrons is used to actively transport H+ out of the inner mitochondrial compartment. As H+ ions accumulate in the outer compartment, a concentration gradient across the inner membrane is created.
• 3) ATP synthase is also present so ATP is produced.
• 4)oxygen combine w/ 2H+ = water. if oxygen is stopped then so does the krebs cycle & ATP is produced solely by glycolysis

process in which carbohydrates are broken down in the absence of oxygen. it recycles the NAD+ that is needed to continue making ATp thru glycolysis. It enables glycolysis to continue supplying a cell w/ ATP in anaerobic conditions.

Lactic acid- pyruvate is converted to lactic acid in a process called lactic acid fermentation. During vigorous exercise cells function w/o oxygen. for glycolysis to continue NAD+ is recycled by lactic acid fermentation. causes soreness in muscles.

Alcoholic Fermentation- an enzyme removes carbon dioxide fromthe 3-carbon pyruvate to form a 2-carbon molecule. then, a 2nd enzyme adds electrons & hydrogen from NADH to the molecule to form ethanol in a process called alcoholic fermentation. In this process NAD+ is recycled & glycolysis can continue to produce ATP.