Photosynthesis and Cellular Respiration Unit

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2 Photosynthesis and Cellular Respiration Unit

3 All cellular activities require energy. Directly or indirectly nearly all energy for life comes from the sun. Autotrophs: organisms that can make their own food. Plants convert light energy from the sun into chemical energy. Hetertrophs: organisms that need to ingest food to obtain energy.

4 All of the chemical reactions in a cell are referred to as the cell s metabolism. Photosynthesis is a pathway in which light energy from the Sun is converted to chemical energy for use by the cell. CO 2 + H 2 O + light C 6 H 12 O 6 + O 2 Cellular respiration is a pathway in which organic molecules are broken down to release energy for use by the cell. C 6 H 12 O 6 + O 2 CO 2 + H 2 O + about 38 ATP

5 Adenosine triphosphate ATP- is the most important biological molecule that provides chemical energy. ATP is the most abundant energy-carrier molecule in cells and is found in all types of organisms. ATP is made of an adenine base, a ribose sugar, and three phosphate groups. Adenosine = Adenine + ribose sugar Triphosphate 3 phosphate groups Where energy is found ATP releases energy when the bond between the second and third phosphate groups is broken forming a molecules called adenosine diphosphate- ADP

6 Cells use ATP to perform 3 types of work Chemical, mechanical, and transport ATP is continuously converted to ADP as cells do work ADP can be converted back to ATP

7 Organisms break down carbon-based molecules to produce ATP. Carbohydrates are the molecules most commonly broken down to make ATP. not stored in large amounts up to 36 ATP from one glucose molecule tri=3 adenosine triphosphate adenosine diphosphate di=2

8 Photosynthesis and Cellular Respiration Unit

9 Photosynthesis occurs in two phases. Phase 1(Light reactions): light-dependent reactions, light energy is absorbed and then converted into chemical energy in the form of ATP and NADPH. Phase 2 (Calvin Cycle): light independent reactions, the ATP and NADPH that were formed in phase one are used to make glucose. Once glucose is produced, it can be jointed to other simple carbohydrates and form larger molecules = STARCH!

10 6CO 2 + 6H 2 O + light C 6 H 12 O 6 + 6O 2 Two steps in the process of photosynthesis Phase 1: Light Reactions Phase 2: Calvin Cycle

11 Chloroplasts-large organelles that capture light energy in photosynthetic organisms (mainly found in leaf cells) Two main compartments essential for photosynthesis: #1: Thylakoids- flattened saclike membranes that are arranged in stacks. Light-dependent reactions take place within the thylakoids. Thylakoids form stacks called grana. #2: Stroma- the fluid-filled space that is outside the grana. Light-independent reactions in phase 2 of photosynthesis occur here. chloroplast grana (thylakoids) stroma

12 Pigment: light-absorbing colored molecules found in the thylakoid membranes of chloroplasts. Pigments differ in their ability to absorb specific wavelengths of light. Major light-absorbing pigments in plants are chlorophylls. Chlorophyll absorbs red & blue light and reflects green light. This is why leaves appear green! Also contain accessory pigments which allow plants to trap additional light energy from other areas of the visible spectrum. Carotenoids reflect yellow, orange, and red. Give carrots and sweet potatoes their color. Also visible in fall when leaves are changing colors. chloroplast leaf cell leaf

13 The light-dependent reactions capture energy from sunlight take place in thylakoids water and sunlight are needed Water molecule is split using captured energy chlorophyll absorbs energy energy is transferred along thylakoid membrane then to lightindependent reactions oxygen is released H + ion is used later in Calvin Cycle


15 The light-independent reactions make sugars Occurs in the Stroma Uses CO 2 absorbed from atmosphere Uses ATP and H + from Light reactions to build sugar Forms sugars (glucose) (C 6 H 12 O 6 )


17 Photosynthesis and Cellular Respiration Unit

18 The function of cellular respiration is to harvest electrons from carbon compounds such as glucose, and use that energy to make ATP. Occurs in mitochondria Structure of mitochondria aids with this process Inner and outer membrane (many folds) Lots of surface area allows for many reactions to occur at once C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP

19 2 main parts to cellular respiration: Glycolysis- is an anaerobic process Anaerobic= NO OXYGEN REQUIRED Aerobic respiration- includes the Krebs cycle and electron transport. Aerobic= REQUIRES OXYGEN

20 Step 1: Glycolysis (splitting sugar) Breakdown of glucose Takes place in the cytoplasm Must use 2 ATP molecules to start Electrons are passed to carriers NAD + & NADH 4 ATP molecules produced Pyruvic Acid molecule is produced Most of the energy is still in this Glucose + 2 ATP 4 ATP + 2 Pyruvic Acid + 2 NADH

21 Step 2 The Krebs Cycle (TCA Cycle) Finishes the breakdown of glucose Occurs inside the mitochondria Pyruvic Acid is broken down using an enzyme (Acetyl CoA) Followed quickly by the Electron Transport Chain (O 2 is used) 2 Acetyl CoA + O 2 6 NADH + 2 FADH 2 + 2ATP


23 The electron transport chain uses NADH and FADH 2 to make ATP. high-energy electrons enter electron transport chain energy is used to transport hydrogen ions across the inner membrane hydrogen ions flow through a channel in the membrane

24 The breakdown of one glucose molecule produces up to 38 molecules of ATP. ATP synthase produces ATP oxygen picks up electrons and hydrogen ions water is released as a waste product


26 After glycolysis, if O 2 is not present, fermentation will occur Fermentation process of making ATP without oxygen No extra ATP is produced Only what is made in glycolysis Fermentation is Anaerobic Anaerobic = without oxygen 2 common types of fermentation Both break down the 2 Pyruvic Acids left over from glycolysis

27 Lactic Acid Fermentation Commonly done by fungi & bacteria Produces some food (cheeses, yogurt, bread, soy sauce) Can be done in the human body Produces Lactic Acid Sore muscles after hard work? Alcoholic Fermentation Commonly done by yeasts Produces many foods that we eat Produces Alcohol & CO 2

28 Food is Digested Glucose extracted, sent to cells Anaerobic (no O 2 ) Fermentation Lactic Acid Fermentation Lactic Acid Glycolysis Breaks down Glucose Alcoholic Fermentation Alcohol & CO 2 4 ATP + 2 Pyruvic Acid Aerobic (O 2 ) Krebs Cycle 6 NADH + 2 FADH 2 + 2ATP

29 Equation for cellular respiration is the opposite of photosynthesis.