1. What is life? How is it defined?

2. Organized structures

3. Homeostasis = maintaining internal balance

4. Requires energy Nutrients

5. Grow Reproduce

6. Reproduction passes DNA

7. Basic Properties of Life 1. Cellular organization  all living things are comprised of at least one cell 2. Metabolism  all living things process energy which is used to power other processes 3. Homeostasis  all living things maintain stable internal environments to optimize conditions for metabolism and other processes 4. Growth and reproduction  all organisms have the capacity for growth and reproduction 5. Heredity  all organisms pass genetic information across generations from parents to offspring

8. Living things function and interact with each other on many levels

11. Levels of organization Biosphere Ecosystem

12. Atoms: elements all matter is made up of atoms Cannot be broken down or changed 92 elements in nature (total = 116) Can combine to make compounds Most common elements in life: Oxygen (O) Carbon (C) Hydrogen (H) Nitrogen (N)

13. Nucleus: Neutrons, Protons (+) Electrons (-): Move around nucleus in shells Helium

14. Isotopes are unstable = radioactive Unstable because nucleus decays and releases particles and energy PET scan – application with radioactive isotope (example of use of isotopes)

15. Molecules Atoms combine to form molecules When combining with another atom, atoms will share an electron or give up an electrons to the other

16. (slightly negative) (slightly positive) Water (H 2 O) is a polar molecule

17. Water Water is essential for life (life in Mars?), has Unique Properties 1. Heat Storage: temperature changes slowly and holds temperature well 2. High Heat of Vaporization: requires tremendous energy to vaporize 3.Ice Formation: less dense as it freezes 4. Water molecules are sticky

18. cohesion – when one water molecule is attracted to another water molecule adhesion – when polar molecules other than water stick to a water molecule

19. 5. The bond within a water molecule breaks spontaneously H 2 O  OH - + H + Water Hydroxide Hydrogen

20. The amount of ionized hydrogen from water in a solution can be measured as pH  pH in most living cells and their environments is close to 7  Organisms use buffers to minimize pH disturbances pH = -log[H + ]

21. The pH scale

22. Energy in Living Cells Energy is the ability to do work There are many forms of energy but all of them can be converted to heat, which is the most convenient form of energy to measure

23. ATP The Energy Currency of the Cell The energy from the sun or from food sources must be converted to a form that cells can use: adenosine triphosphate (ATP) ATP is an energy carrier

24. endmost phosphate group is broken off and energy is released ATP  ADP + Pi + energy ATP cycle: 1.photosynthesis Plant cells convert energy from the sun into ATP and to make sugar 2.cellular respiration cells break down the energy in sugars and convert it ATP

25. Scientific Investigation The scientific process has six stages 1. Observation: of natural phenomena 2. Hypothesis: make an educated guess that might be true 3. Predictions: if a hypothesis is correct, then specific consequences can be expected 4. Testing: scientists conduct experiments to attempt to verify predictions made by hypotheses 5. Controls: experiments usually employ a parallel design 6. Conclusion: a hypothesis that has been tested and not rejected is tentatively accepted

26. Review Questions 1. The smallest particle into which a substance can be divided and still retain all of its chemical properties is: A) matter.B) an atom.C) a molecule.D) mass. 2. The source of immediate, or "ready cash" energy in the body is _______________

27. 3. The attraction of water molecules to other water molecules is called A) cohesion.B) capillary action.C) solubility.D) adhesion 4. The ability to do work is the definition for: A) thermodynamics.B) radiation.C) energy.D) entropy.