Chapter 7 Photosynthesis

They produced their own food by photosynthesis. The sun gives them solar energy which the autotrophs convert into usable energy.

A chloroplast is an organelle which carries out photosynthesis once water and carbon dioxide diffuse into it. The chloroplast has a double membrane and and a semifluid interior which is called the STROMA. Within the stroma there are flattened sacs called THYLAKOIDS, which are stacked to form a GRANA. Within the grana the thylakoids each have a space called the THYLAKOID SPACE.

Heterotrophs release carbon dioxide when they respire, then the carbon dioxide enter autotrophs through leaves (through the STOMA, small openings where carbon dioxide enters) and are converted into carbohydrate. CARBOHYDRATE in the form of glucose is is the chief source of chemical energy for most organisms.

The three major groups of photosynthetic organisms are land plants, algae, and cyanobacteria.

The thylakoid which contains CHLOROPHYLL absorbs energy in the chloroplast. The STROMA contains an enzyme-rich solution which forms a carbohydrate in the chloroplast.

Autotrophs- include plants, algae, and cyanobacteria and are photosynthetic organisms. Heterotrophs- are consumers that get energy by feeding on autotrophs. Both use organic molecules produced by photosynthesis as a source of building blocks for growth and repair and as a source of chemical energy for cellular work.

6CO₂ + 12H₂O →(solar energy) 6CH₂) + 6H₂O + 6O₂
Photosynthesis consists of an Oxidation (the loss of electrons) and a Reduction (the gain of electrons.) In Photosynthesis, carbon dioxide is reduced and water is oxidized. Solar energy is used to generate the ATP needed to reduce the carbon dioxide to a carbohydrate. have two types of reactions, the light reactions and the Calvin Cycle reactions.

The input of a light reaction is the solar energy, and the output is the converted energy into ATP and NADPH.

In the Calvin Cycle, the carbon is reduced to a carbohydrate and then later converted into glucose.

Redox reactions are when atoms such as hydrogen are lost.

Enzymes need to be involved in the reduction of carbon dioxide to a carbohydrate.

As the wavelength gets shorter, the energy increases.

Pigment molecules absorb wavelengths of light, but only some pigments absorb certain lights, so they either reflect or transmit other wavelengths. So, the chloroplast makes pigments that are capable of absorbing various portions of visible light , called ABSORPTION SPECTRUM.

ATP is made in the mitochondria from oxygen which was made when water molecules were split by replacement electrons. NADPH is made when each NADP+ accepts two electrons and H+ to become reduced and form NADPH.

The electromagnetic spectrum is light that we cannot see with the naked eye, vs. visible light which are colors that we can see roygbiv.

Low energy electrons within chlorophyll in Photosystem II are excited to a higher energy state by sunlight. (happens during redox reactions in ETC), it creates a proton gradient across thylakoid membrane. E- are excited again to a higher energy state by Photosystem I.

The three carbon cycles are (1) carbon dioxide fixation, (2) carbon dioxide reduction, and (3) regeneration of RuBP.

RuBP carboxylase enzyme is significant because it makes up to 20-50% of the protein content in the chloroplast. Even though it is slow, processing only a few molecules of substrate per second, there is a lot of it so it work out.

Glycerade-3-phosphate produced other plant molecules by reforming the RuBP molecules so that the RuBP and create important proteins.

The three major steps of the Calvin Cycle are Carbon fixation, carbon reduction, and regeneration of RuBP.

It takes 3 turns of the Calvin Cycle to produce 1 G3P because for every three turns of the Calvin cycle, five molecules of G3P are used to re-form three molecules of RuBP.

Photosynthesis is in the mesophyll of C₃ and C₄ plants.

CAM stands for crassulacean-acid metabolism, it’s a family of succulent (water containing) plants that live in warm, dry regions. Whereas a C₄ plant represents partitioning in space, carbon dioxide fixation occurs in mesophyll cells while the Calvin cycle occurs in bundle sheath cells.

Photosynthesis is essential for life on earth, so different organisms adapted to different environments to sustain life.

CAM plants such as cacti, orchids, ferns, pineapple, and agave.

In dry hot climates, the net photosynthetic rate of C₄ plants is amour two to three times that of C₃ plants. C₄ plants enjoy this because they can avoid photorespiration.

A C₃ plant uses the enzyme RuBP carboxylase to fix CO₂ to RuBP in mesophyll cells. C₄ is an adaptation photosynthesis which enables some plants to avoid photorespiration.

The oxygen given off by photosynthesis comes from H₂O.

The function of the light reaction is to convert light energy into a usable form of chemical energy

In order for the earth to to work, there must be sunlight for the plants to get energy from and there must be plants for the animals to get their energy from.

The Calvin cycles retains produce carbohydrate, convert one form of chemical energy into a different form of chemical energy, regenerate more RuBp, and use the products of the light reactions.

C₄ photosynthesis occurs in plants whose bundle sheath cells contain chloroplasts and is an advantage when the weather is hot and dry.

The final acceptor of electrons during the noncyclic electron pathway is NADP+.

The NADPH and ATP from the light reactions are used for converting 3PG to G3P.

CAM photosynthesis is prevalent in desert plants that close their stoma during the day.