Cell Notes Part 4

How do cells use energy? o All of the activities of an organism involve chemical reactions in some way. The total of all chemical reactions is called metabolism. o Cells need enzymes for these chemical reactions to occur. Enzymes are special proteins that regulate how fast chemical reactions occur.

How do cells use energy? o Living things are divided into two groups, Producers and Consumers, based on how they obtain food. 1. Producers make their own food. 2. Consumers need to obtain food from an outside source. o The three processes that cells use to release stored energy are photosynthesis, respiration, and fermentation.

Photosynthesis 1. During photosynthesis, producers such as plants use light energy from the sun to make sugars, which can be uses as food. - photosynthesis begins in plant cells with chlorophyll located inside chloroplasts. The sun’s energy is stored in these pigments and used to power the chemical reactions. - The cells then use water(H 2 O) and carbon dioxide(CO 2 ) and the stored energy from the sun to make sugars that the cells use for energy to carry out cell function.

Photosynthesis cont’d - the water in soil enters the plants through the roots and moves up the stem to the leaves and inside the chloroplasts where the stored energy from the sun fuels the following chemical reaction: 6CO 2 + 6H 2 O + light energy  C 6 H 12 O 6 + 6O 2 Carbon dioxide + Water + sunlight  (chlorophyll) Sugar (glucose) + oxygen

Photosynthesis cont’d 6CO 2 + 6H 2 O + light energy  C 6 H 12 O 6 + 6O 2 Carbon dioxide + Water + sunlight  (chlorophyll) Sugar (glucose) + oxygen - The materials on the left side of the equation, which you start with are called reactants. - The materials at the end of the equation are called the products. The oxygen is a waste product emitted into the air and the glucose is used by the plant to carry out its functions. ReactantsProducts

Respiration 2. During respiration, cells break down simple food molecules such as glucose(C 6 H 12 O 6 ) and release the energy they contain. It is the process by which cells “withdraw” energy from glucose. We call it cellular respiration so it is not confused with breathing respiration.

Respiration cont’d o In the first stage of respiration, which takes place in the cytoplasm, the glucose molecules are broken down into smaller molecules where only a small amount of energy is released. o In the second stage of respiration, the mitochondria use oxygen to break down the glucose molecules into even smaller molecules to release even more energy. When this occurs, water and carbon dioxide are released as waste products of the reaction.

Respiration cont’d o The carbon dioxide and water diffuse out of the cell and are released into the air when animals breathe out. o The following equation represents this chemical reaction inside the cell: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy Sugar (glucose) + oxygen  Carbon dioxide + Water + energy Plants make their own glucose while animals get it from food. Oxygen comes from the air. ReactantsProducts

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Fermentation 3. During fermentation cells are able to obtain energy from food without using oxygen. The amount of energy released during fermentation, however is much lower than respiration. - Fermentation begins in the cytoplasm where glucose molecules are broken down into smaller molecules. - Unlike respiration, the molecules do not move into the mitochondria. Instead more chemical reactions keep occurring in the cytoplasm.

Fermentation cont’d - Depending on the type of cell, the waste products may be lactic acid or alcohol and carbon dioxide. * When your muscle cells use fermentation, lactic acid is a waste product that builds up and makes muscles sore. * Some bacteria that use fermentation to release energy release lactic acid are used to make things like yogurt and cheese. The acid gives the food some of its flavor. * When yeast cells use fermentation they produce alcohol and carbon dioxide as a waste product. This is used to make bread rise. This type of fermentation is also how ancient peoples learned to make the first alcoholic beverages.

Fermentation cont’d - The following equation represents fermentation: C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2 + Energy Glucose  Ethanol + Carbon dioxide + energy ReactantsProducts