Cell Energy: Photosynthesis & Respiration

Today’s Learning Goals In plants, chlorophyll (found in chloroplasts) captures energy from the sun in order to make food during photosynthesis Cells release energy from food through either cellular respiration or fermentation Why it matters: Understanding how plants & animals get energy to grow & develop is an important part of biology.

How Does a Plant Make It’s Own Food? Plants use carbon dioxide (CO2), water (H2O), and sun’s energy to make food. This is called “photosynthesis” The food gives plants energy Animals get the energy stored in plants when they eat them.

How Do Plants Get Energy From Sun? Plants have pigments that absorb energy from light Chlorophyll (found in chloroplasts) is the pigment used in photosynthesis

What “Food” do Plants Make? The “food” plants make is a sugar called glucose (C6H12O6). Glucose and oxygen (O2) are made during photosynthesis.

Inside a Chloroplast where Photosynthesis Occurs Stroma-space between grana Granum-stacks of thylakoids Thylakoids-structures that contain chlorophyll

Light Reactions and the Calvin Cycle Green-Light Rxns Blue-Calvin Cycle (Light Independent Rxns) GlucoseC6H12O6 Chloroplast

How Do Organisms Get Energy From Food? Animals cannot make their own food like plants can. But, BOTH plants and animals must break down (digest) food in order to get energy from it (so they can live, grow, & develop) Cells do this 2 ways: cellular respiration and fermentation

Cellular Respiration & Fermentation Cellular Respiration uses oxygen (O2) to break down food Fermentation does not use oxygen Cellular respiration releases more energy from food than fermentation (38 ATP per molecule glucose vs. 2 ATP) So most eukaryotes (plants, fungi, protists & animals) get their energy through cell respiration

Where Cellular Respiration Occurs Cellular Respiration is a chemical process that happens in cells In prokaryotes, it happens in the cell membranes In eukaryotes, it happens mostly in the mitochondria

Process of Cellular Respiration Food (glucose) is broken down into CO2 and H2O and energy is released C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy (ATP) This energy can be used for: Keeping a constant body temperature Storage (ATP) - to be used later for metabolic processes (growth, development, reproduction, etc…)

Cell Respiration Occurs in the Mitochondria

The Three Stages of Cell Respiration Glycolysis-”sugar spliting”, glucose is broken down into two pyruvate (pyruvic acid) molecules in the cytoplasm. Two ATP molecules are formed.

When Oxygen is Present (aerobic) 2. Kreb’s Cycle, or the Citric Acid Cycle-pyruvate enters the mitochondron. Through a series of reactions, the carbon atoms in pyruvate are rearranged to form more ATP and NADH, and FADH2 (energy) molecules. Carbon dioxide is released.

Finally…the third stage 3. The Electron Transport Chain-electrons, e-, and hydrogen ions, H+, produced in the Kreb’s Cycle, move through the inner mitochondrial membranes. This movement allows enzymes to make ATP.

What Do You Notice?

Check It Out! Did you notice that cellular respiration is just the opposite of photosynthesis?

When Oxygen Is Not Present (anaerobic) Fermentation Happens when cells cannot get the oxygen they need for cellular respiration, or in anaerobic conditions Fermentation is a way to get energy when oxygen isn’t available Two Types: Alcoholic Fermentation & Lactic Acid Fermentation 1. Alcoholic Fermentation in yeast + 2ATP 2. Lactic Acid Fermentation in muscle cells

Pop Quiz 1) Plants use carbon dioxide (____), water (____), and the sun’s energy to make food. CO2 and H2O 2) What type of cell has chloroplasts? PLANT CELL 3) BOTH plants and animals must break down food in order to get ________from it. ENERGY 4) How are respiration and photosynthesis related? THEY ARE THE REVERSE (OPPOSITE) OF EACH OTHER. 5) Fermentation is a way to get energy when ______ isn’t available. OXYGEN

Today’s Learning Goals In plants, chloroplasts capture energy from the sun in order to make food during photosynthesis Cells release energy from food through either cellular respiration of fermentation Why it matters: Understanding how plants & animals get energy to grow & develop is an important part of biology.