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Download 7th Grade Cells and Heredity (Module A)
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7th Grade Cells and Heredity (Module A) Unit 1: Cells Lessons 5 & 6 Homeostasis & Cell Processes Photosynthesis & Cell Respiration Homeostasis Maintaining a constant internal state (staying in BALANCE) in a changing environment What makes an environment change? Cells need to be able to do 4 things 1. obtain and use energy 2. make new cells 3. exchange materials 4. eliminate wastes (examples?) (process?) (examples?) (examples?) 1. Obtain and use energy Plants, algae and some bacteria use photosynthesis to make their own food These organisms are called producers because they produce their own food Happens in the chloroplasts Capture light energy from the sun and change it to chemical energy in sugars Use green pigment called chlorophyll Do pg. 70-71 1. Obtain and use energy (con’t) Animals get their energy from consuming other organisms, so we call them consumers To get this energy out of the organism they consume (eat!) they must break down the sugar stored This process is called cellular respiration – the process of breaking down food to produce ATP (adenosine triphosphate) More about Cellular Respiration Both plants and animals do cellular respiration – in mitochondria and cell membrane Even prokaryotic cells (like bacteria) do it! – in cytoplasm and cell membrane Read and do pgs. 72-73 Photosynthesis and Cellular Respiration are the reverse process of each other! Read and do pg. 74 Q: What are the starting materials of photosynthesis? A: carbon dioxide and water Q: What are the products of photosynthesis? A: Glucose and oxygen Q: What are the starting materials of cellular respiration? A: glucose and oxygen Q: What are the products of cellular respiration? A: carbon dioxide and water 2. Cells make new cells! All cells grow, divide and die Some more often than others ex. Skin cells constantly divide, nerve cells can’t divide once they are fully formed GROWTH occurs when new cells are added Mitosis (part of the cell cycle) 1. DNA is copied (inside nucleus) 2. DNA organizes into chromosomes 3. chromosomes separate & nucleus splits (We will study mitosis in more depth later in the year) 3. Cells exchange materials (Like what? Read page 56 1st pgh) cell membranes are semi-permeable – some particles can go in and out Passive transport – movement across cell membrane without using energy Diffusion – movement of molecules from high concentration to low concentration Ex. Tea in tea bag Osmosis – diffusion of WATER through semi-permeable membrane If molecule is too large to diffuse, may use protein channels (facilitated diffusion) 3. Cells exchange materials (con’t) Active transport – movement from areas of low concentration to high concentration – REQUIRES ENERGY Some other examples are endocytosis and exocytosis 3. Cells exchange materials Endocytosis – cell surrounds particle, encloses it, and brings it in to cells (con’t) Amoebas use this to eat! Exocytosis – (reverse of endocytosis) – particle gets enclosed in a vesicle Vesicle fuses to cell membrane Particles released outside of cell SO, how do organisms maintain homeostasis (during temperature changes? When some organisms (like YOU and ME) get cold ________________ Behavioral adaptations: Some reptiles ______________________________ Some mammals ____________________________ When it’s cold, some trees _____________________ amount of water loss to reduce the Some trees also ______________________ because chlorophyll (the green pigment) breaks down
