Molecular Biology

Characteristics of Life All living things share the following characteristics: Cells Sensitivity Growth Homeostasis Reproduction Metabolism Adaptation

Cells Cells make up all living things Multicellular organisms have many cells Unicellular organisms have only one cell Cells can divide and grow to produce more cells

Sensitivity Organisms respond to changes in the environment Plants can respond by growing toward light sources or shedding leaves in the winter Animals can respond by hibernating or fleeing from predators

Growth Organisms change over their lifetime (not evolve!) They can get bigger in size and develop new structures or behaviors. All organisms show an increase in physical and mental maturity the closer they get to adulthood (even you!)

Homeostasis Organisms must maintain an internal environment that is appropriate for life Homeostasis is the ability of an organism to keep a steady internal state (maintaining the correct amount of fluids, salts, hormones, food sources) in order to survive.

Reproduction All living things must have the ability to reproduce Can be sexual or asexual Sexual: between two organisms Asexual: one organism creates offspring

Metabolism Organisms must get energy from the environment and use the energy they obtain to live. Metabolism is the sum of all chemical reactions within an organism Metabolism is how organisms are able to get and use energy (from food)

Adaptation Over time organisms become specially suited to their particular environment Adaptations occur slowly, over time

Cell Theory and Structure The cell is the basic structural and functional unit of all organisms. Cell theory forms the basis for the way biologists study organisms. Cell theory states: All living things are made out of cells All cells come from living cells of the same kind Cells are the basic unit of all living things

Prokaryotic vs. Eukaryotic Prokaryote Eukaryotic Cell does not have true nucleus Not surrounded by a membrane No membrane bound organelles More primitive Example: bacteria Has a true nucleus that is surrounded by a membrane Has several membrane-bound organelles Tend to be larger and more complex Examples: plants and animals

Energy Organisms get energy by oxidizing their food, releasing some of its energy as thermal energy. Organisms must eat or be eaten by others for food. Matter is transferred from organisms to the physical environment when molecules from food react with oxygen to produce carbon dioxide and water in a process called cellular respiration

Energy Energy can change from one form to another in living things Animals get energy from oxidizing their food, releasing some of its energy as heat Almost all food energy comes originally from sunlight

Cellular Respiration Cells convert energy (as glucose) to a more usable form of energy called ATP (adenosine triphosphate, but you can just call it ATP) The energy stored in ATP provides the means by which cells are able to carry out their functions

Summary Matter moves within individual organisms through a series of chemical reactions in which food is turned into energy Chemical energy is transferred from one organism to another for food The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of it.