3 3 Biochemical Reactions Part 2 Photosynthesis VCE

3. 3 Biochemical Reactions Part 2: Photosynthesis VCE Biology Unit 3&4 Ms Veronica Parsons 2013

Photosynthesis Veronica Parsons 2013

• the nature of biochemical processes within cells: – catabolic and anabolic reactions in terms of reactions that release or require energy – the role of ATP and ADP in energy transformation – requirements for photosynthesis – excluding differences between CAM, C 3 and C 4 plants – including: the structure and function of the chloroplast; the main inputs and outputs of the light dependent and light independent stages Veronica Parsons 2013

Energy Producers Most plants are autotrophs. Organisms which are capable of producing their own energy are called _______ Photosynthetic autotrophs (e. g. plants, algae and some bacteria) convert light energy into chemical energy. Chemosynthetic autotrophs derive their energy from inorganic sources such as sulfur or ammonia. Some bacteria are__________ Anabaena sphaerica (left) is a cyanobacterium, and is an example of an autotrophic bacteria.

Energy All organisms require energy to grow, reproduce, move and carry out fundamental maintenance and repairs. ) The Sun is the ultimate energy source for life on Earth Energy can not be created or destroyed, but it can be ________from one form to another. The ultimate source of energy is the______ Heat (thermal energy)

• Photosynthesis-An Anabolic Reaction Involves the conversion of light energy (ultimate source of energy) into chemical energy (_____-intermediate energy) which can be broken down into ______(immediate energy) during cellular respiration.

Leaf-Organ of Photosynthesis Veronica Parsons 2013

Chloroplast-Site of Photosynthesis In Eukaryotic cells- plants and photosynthetic protists, photosynthesis takes place in _______bound organelles called chloroplasts. Chloroplasts are filled with a green pigment A plant mesophyll cell with a chloroplast highlighted. called__________. This is what gives plants their _________coloring. In Prokaryotic cells-(photosynthetic bacteria) the reactions of photosynthesis take place within the ______ itself, not within a discrete organelle. Plant chloroplast. TEM X 37, 000

The Chloroplast The chloroplast is enclosed by an envelope consisting of two membranes separated by a very narrow intermembrane space. Membranes also divide the interior of the chloroplast into compartments: flattened sacs called ______which in places are stacked into structures called_______ the ________fluid) outside thylakoids. They contain _______and also__________, which are used to synthesize some of the proteins within the chloroplast.

Chlorophyll-Light Capturing Pigment • Substances that absorb visible light are called________ • Chlorophyll are light energy capturing pigment molecules found on the ________of the thylakoid discs. Gamma rays x-rays Ultra violet Infrared Microwave Radio waves Visible light 380 400 450 550 Veronica Parsons 2013 Increasing energy Wavelength (nm) 650 Increasing wavelength 750

Photosynthetic Pigments The photosynthetic pigments of plants fall into two categories: Chlorophylls, which absorb ________light. They are the main photosynthetic pigment in plants and give leaves their green color (below). Carotenoids, which absorb strongly in the ______and appear_______, yellow, or red. They are considered to be associate pigments. Carotenoids give carrots their orange color (right).

Photosynthetic Pigments Each photosynthetic pigment has its own characteristic absorption spectrum. Although only _______can participate directly in the light reactions of photosynthesis, the accessory pigments (_______and_________) can absorb wavelengths of light that chlorophyll a cannot. The accessory pigments pass the energy (photons) to chlorophyll a, thus ________the ________that can effectively drive photosynthesis. Space filling model of the chlorophyll a molecule (left). Chlorophyll has a porphyrin ring with a magnesium atom in its centre and a hydrocarbon tail. Chlorophyll a is responsible for the green coloration of plant leaves (right). Porphyrin ring Hydrocarbon tail

Absorption spectrum The absorption spectrum of different photosynthetic pigments provides clues to their role in photosynthesis, since light can only perform work if it is absorbed. Absorption spectra of photosynthetic pigments (Relative amounts of light absorbed at different wavelengths) 80 Percentage absorbance Chlorophyll b 60 Carotenoids Chlorophyll a 40 20 0 400 500 600 Wavelength (nm) 700

Action Spectrum Rate of photosynthesis (as percent of rate at 670 nm) An action spectrum profiles the effectiveness of different wavelength light in fueling photosynthesis. It is obtained by plotting wavelength against some measure of photosynthetic rate (e. g. CO 2 production). 100 Action spectrum for photosynthesis (Effectiveness of different wavelengths in fueling photosynthesis) 80 60 40 20 The action spectrum closely matches the absorption spectrum for the photosynthetic pigments. 0 400 500 Wavelength (nm) 600 700

Photosynthesis There are two phases in photosynthesis: The light dependent phase (D), which occurs in the ________of a chloroplast. The light independent phase (I), which occurs in the_______ of chloroplasts. D I Diagrammatic representation(top) and false colored electron micrograph (left) of a plant chloroplast showing the sites of the light dependent and light independent phases of photosynthesis.

What happens in Light Dependent Stage Veronica Parsons 2013 http: //www. gtac. edu. au/site/gcasts/UNIT 3/photosynthesis/inde x. html

What happens in Light independent Stage Veronica Parsons 2013 http: //www. gtac. edu. au/site/gcasts/UNIT 3/photosynt hesis/index. html

A Summary of Photosynthesis Water Raw materials Carbon dioxide ADP Light Dependent Phase Solar energy ATP Process: Energy Capture Location: Grana Light Independent Phase Process: Carbon fixation via the Calvin cycle NADP. H 2 NADP By-products Location: Stroma Main product Glucose

Factors Affecting Photosynthetic Rate The rate at which plants can make food (the photosynthetic_____) is dependent on environmental factors. Some factors have a greater effect than others. These include: the amount of _______available. the level of _______(CO 2). The____________

Factors Affecting Photosynthetic Rate of photosynthesis (mm 3 CO 2 cm-2 h-1) Light intensity vs photosynthetic rate The effect of light intensity on photosynthetic rate is shown in this experiment using 90 cucumber plants. 80 The experiment was carried out at a constant temperature and constant carbon dioxide 70 level. 60 The rate of photosynthesis _______exponentially with light intensity until a maximum rate is achieved. At 50 this point increasing the light intensity has no effect on photosynthetic rate and the rate of 40 1 2 3 4 5 6 Units of light intensity (arbitrary scale) 7 photosynthesis reaches a_______

Factors Affecting Photosynthetic Rate This graph shows how temperature and CO 2 Light intensity, CO 2, and temperature vs photosynthetic rate plants. Photosynthetic rate increases as the _________increases. At high concentrations, the rate of photosynthesis begins to slow as limiting factors other than CO 2 become important. An increase in ________increases photosynthetic rate because of its effect on enzyme activity. However, temperatures exceeding the _______will eventually decrease photosynthetic rates because of the detrimental effects of heat on enzyme structure. Rate of photosynthesis (mm 3 CO 2 cm-2 h-1) levels affect photosynthetic rate in cucumber High CO 2 at 30°C 240 200 High CO 2 at 20°C 160 120 Low CO 2 at 30°C 80 40 Low CO 2 at 20°C 1 2 3 4 5 6 Units of light intensity (arbitrary scale) Increasing the temperature when CO 2 is limiting has little effect on photosynthetic rate. 7

Rubisco • Very large enzyme made up of ______polypeptide chains. • It has many active sites requiring _____as a________ • Most abundant protein on planet. • Ru. Bis. CO is important biologically because it catalyzes the primary chemical reaction by which ________enters the _________ • Implications for biotechnology. Veronica Parsons 2013

• Measuring Photosynthesis Processes like photosynthesis and respiration can be measured by either: • o ______of substrate. o ________of products The rate of photosynthesis can therefore be measured by: • Depletion of substrate which includes measuring how much carbon dioxide has been used or how much water is used. • Accumulation of product which might include measuring how much oxygen is produced or organic molecules (biomass) produced.

Measuring Photosynthesis • In this simple experiment the accumulation of oxygen is measure of rate of reaction. • Independent variable: • Dependent variable • Method : • Specimen: http: //www. youtube. com/watch? v=w. Ivz 6 v. H Yvsw