What is life?

How is it defined?

Organized structures

Homeostasis =

maintaining internal

balance

Requires energy

Nutrients

Grow

Reproduce

Reproduction passes DNA

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

Living things function and interact with each other on many levels

Levels of organization

BiosphereEcosystem

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)

Nucleus: Neutrons, Protons (+) Electrons (-): Move around

nucleus in shells

Helium

Isotopes are unstable = radioactive

Unstable because nucleus decays and releases particles

and energy

PET scan – application with radioactive isotope

(example of use of isotopes)

Molecules

Atoms combine to form molecules

When combining with another atom, atoms will

share an electron or give up an electrons to the

other

(slightly negative)

(slightly positive)

Water (H2O) is

a polar molecule

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

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

5. The bond within a water molecule breaks spontaneously

H2O OH- + H+

Water Hydroxide Hydrogen

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+]

The pH scale

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

ATPThe 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

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 respirationcells break down the energy in

sugars and convert it ATP

Scientific InvestigationThe 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

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 _______________

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.