Cellular Transportation & Respiration Passive Transport • A cell membrane is semiperamble, which means that it allows only certain substances to enter or leave a cell. • Passive transport is the movement of substances through a cell membrane without using the cell’s energy. Diffusion • Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration. • Usually diffusion continues through a membrane until the concentration of a substance is the same on both sides of the membrane. Osmosis • Osmosis is the diffusion of water molecules only through a cell membrane. • If the concentration of water in the air surrounding a plant is less than the concentration of water inside the plant’s vacuoles, water will diffuse into the air until the concentration of water is equal. • Facilitated diffusion occurs when molecules pass through a cell membrane using special proteins called transport proteins. • Carrier proteins are transport proteins that carry large molecules through the cell membrane. • Channel proteins are transport proteins that form pores through the cell membrane. Active Transport • Active transport uses the cell’s energy to move substances through a cell membrane. • Active transport moves substances from areas of lower concentration to areas of higher concentration. Active Transport • A cell uses endocytosis to take in a substance too big to pass through the cell membrane. • A cell’s vesicles release their contents outside the cell during exocytosis. Cell Size and Transport • For a cell to survive, its surface area must be large compared to its volume. • As a cell grows, its volume increases faster than its surface area. diffusion osmosis endocytosis exocytosis Facilitated diffusion Cellular Respiration • All living things need energy to survive. • Cellular Respiration is the process in which organisms break down food to release energy. Cellular Respiration • The first step of cellular respiration, called glycolysis, occurs in the cytoplasm of all cells. • During glycolysis glucose, a sugar, is broken into smaller molecules. • The second step of cellular respiration occurs in the mitochondria of eukaryotic cells. This step requires oxygen. Cellular Respiration • During the 2nd step of cellular respiration, the smaller molecules made during glycolysis are broken down. Large amounts of usable energy, called ATP, are produced. • Water and carbon dioxide (CO2) are two waste products that are given off during the 2nd step of cellular respiration. Fermentation • Fermentation is the process that releases energy without using oxygen. • Eukaryotic and prokaryotic cells use fermentation to obtain energy from food when oxygen levels are low. • Fermentation occurs in the a cell’s cytoplasm. Fermentation • Lactic-acid fermentation converts glucose into ATP and a waste product called lactic acid. • Some types of bacteria and yeasts make ATP during alcohol fermentation. The process produces alcohol/ethanol and CO2 Photosynthesis • Plants and some unicellular organisms obtain energy from light. • Water, carbon dioxide (CO2), and chlorophyll are involved in photosynthesis. • In plants, light energy is absorbed by pigments such as chlorophyll. Photosynthesis • The chemical reactions of photosynthesis occur in chloroplast, the organelles in plant cells that convert light energy into food. • Photosynthesis uses CO2 that is released during cellular respiration to make food energy and release oxygen (waste product). • When an organism eats plant material, it takes in food energy. An organism’s cells use oxygen released during photosynthesis. carbon reactions in reactions in dioxide cytoplasm mitochondria water carbon dioxide reactions in chloroplasts oxygen light energy.