Cells and Energy for middle school life science

Cells and Energy
life science

1. Cells and Energy

2. Objectives Understand how cells obtain energy Explain the importance of respiration, fermentation and photosynthesis

3. Cellular Respiration ( 세포호흡 ) Series of chemical reactions that convert the energy in food molecules into a usable form of energy called ATP. ATP (adenosine triphosphate): Molecule in mitochondria that contains energy. ATP is the fuel for cellular processes Eg. growth, cell division, and material transport. Cellular respiration occurs in two parts of a cell: the cytoplasm and the mitochondria.

4. Reactions in the cytoplasm The first step, called glycolysis, occurs in cytoplasm. Glycolysis ( 당 분해 ) : a process by which glucose, a sugar, is broken down into smaller molecules. Glucose ( 포도당 ) enters the cell → goes through chemical reactions → glucose is broken down into smaller molecules. Notice that ATP is used to break down the glucose, and ATP is also produced by this process.

5. Reactions in the mitochondria Glucose + Oxygen → Water + Carbon dioxide + ATP C6H12O6 + 6O2 → 6H2O +6CO2 + ATP (energy) Water and carbon dioxide are waste products. The CO2 released by cells is used by plants in photosynthesis.

6. Fermentation ( 발효 ) Reaction that cells can use to obtain energy from food when oxygen levels are low Eg. happens after you exercise, and your cells don’t have enough oxygen to make ATP through respiration Because no oxygen is used, less ATP is produced Occurs in cytoplasm, not in mitochondria

7. Photosynthesis ( 광합성 ) Series of chemical reactions that convert light energy, water, and CO2 into food energy molecule glucose and give off oxygen. Chlorophyll ( 엽록소 ) , pigment in chloroplast ( 엽록체 ) , absorbs light energy used in photosynthesis.

8. Reactions in chloroplasts

9. Importance of photosynthesis Humans and animals eat glucose as our food source. Humans and animals use oxygen during cellular respiration!