CELLULAR TRANSPORT AND ENERGY

Cells get materials from the external environment. The cell needs to move materials into and out of the cell These include wastes, large molecules, nutrients, and other substances Materials pass through the cell membrane The membrane is selectively permeable It “chooses” what will enter and exit Certain materials are able to pass through the membrane all the time Water and gases Larger materials are not able to pass through unless the membrane allows

2 Types of Transport Passive and Active Passive transport does not require energy to move materials Active transport does require energy

Diffusion A type of passive transport (no energy needed) Materials move from areas of greater concentration to areas of less concentration Will occur until there is an equal concentration on either side of the membrane Diffusion of water is called osmosis Water will move through the membrane until there is an equal concentration on either side

Facilitated Diffusion Also passive transport (no energy needed) Diffusion with help Proteins within the cell membrane (carrier and channel proteins) bind to materials and bring them into the cell Can also move materials out of the cell Used for larger materials

Endocytosis and Exocytosis 2 types of active transport Used for large materials Endocytosis Endo=into Brings materials into the cell The cell membrane forms a vesicle around the material and brings the materials into the cell Exocytosis Exo=exit Releases materials from the cell Vesicles bind to the cell membrane and open to the external environment, releasing the materials

Cell Size and Transport The size of the cell has an impact on the efficiency of transport As the cell grows, the volume of the cell grows faster than the membrane The membrane is the only way to get materials in and out Because the membrane cannot keep up, larger cells have a difficult time getting materials in and out This limits the size that cells can be

Cells and Energy Cells need to do their jobs The energy is…energy ATP! Told you it would be back ATP is a nucleic acid that the cell uses for energy The energy is made within the cell 2 processes Cellular respiration Photosynthesis These processes are cycles Not just that, there are cycles within cycles And cycles in the cycles in the cycles

ATP Adenosine Triphosphate An Adenosine molecule (a nucleic acid) bonded to 3 phosphates (tri=3) The bonds are very high energy Energy is released from ATP when bonds between 2 of the phosphates are broken This forms ADP: adenosine diphosphate (di=2) ATP  ADP + P + Energy The ADP is now able to bond to another phosphate, repeating the cycle

Cellular Respiration Occurs in all living things Uses oxygen and sugar to produce energy, carbon dioxide, and water The first step occurs in the cytoplasm Called glycolysis Glucose (a sugar) is broken down into smaller molecules The second step occurs in the mitochondria This step requires oxygen to occur Called aerobic respiration The products from glycolysis enter a step called the Krebs Cycle Carbon dioxide and water are released A lot of ATP are produced

Equation for Cellular Respiration

If no oxygen is present, cells cannot enter aerobic respiration Anaerobic respiration The first step (glycolysis) is the same However, without oxygen, the products cannot proceed to the Kreb’s Cycle Enters Fermentation Makes less ATP Occurs in the cytoplasm

2 Types of Fermentation Lactic Acid Fermentation Produces lactic acid, which is what causes muscle cramps Alcoholic Fermentation Produces adult drinks, and also is responsible for bread rising in the presence of yeast (a fungi)

Photosynthesis Occurs only in organisms that contain chloroplasts Uses sunlight, water and carbon dioxide to produce oxygen and sugar Again, cycles in cycles A pigment in chloroplasts, called chlorophyll, absorbs sunlight

Why are plants green? Objects appear to be the color of the light that they are reflecting Plants reflect green light The other colors of light are absorbed Plants, then, absorb the rest of the colors of light except for green Black objects absorb all colors of light White objects reflect all colors of light What is hotter on a sunny day, a white shirt or a black shirt?

Reactions in Photosynthesis Step 1: Light energy breaks water down and releases oxygen and other molecules Step2: The molecules enter the Calvin Cycle, which uses the products from step 1 and carbon dioxide to form sugar Plants can then use their own sugars to make ATP by advancing them to their mitochondria Other organisms must breathe oxygen and eat foods to get the materials necessary for respiration

Comparison of Respiration and Photosynthesis Cellular Respiration: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + energy Photosynthesis: 6CO 2 + 6H 2 O + energy → C 6 H 12 O 6 + 6O 2 One way to think about this: Ask yourself, what do plants need? What do they make? Need Carbon Dioxide, water, sunlight Make Oxygen and food (sugars) Respiration is the exact opposite. You can ask yourslef, what do you need to survive? What do you make? You need food (sugar), and oxygen You make carbon dioxide, water, and energy for your cells