Lecture 1

1.Introduction to Cell and Molecular Biology Lecture 1

DNA is a requirement of life

Molecules of life:As you look around the classroom, it is quite simple to determine the living from nonliving-your classmates are living while their chairs are not living. Do you know why? Both the chair and living organism contain the same fundamental units of matter called protons, electrons, and neutrons that make up atoms.

Atoms make up large molecules that are the substances of life.

DNA and the next generation: At the macromolecular level of life,

a difference starts to emerge between living and nonliving material.

DNA holds the secrets of life. Encoded in the DNA sequence is information for numerous proteins that have both structural and regulatory functions. Among the proteins found in cells are enzymes that catalyze biochemical reaction. Enzymes speed up the rate of

a reaction that allows life to continue. A simple way to think of

the flow of information from DNA to mRNA to protein is the molecular trinity that is central to all life and is known as the central dogma.

We may think of humans as individuals who enter the world abruptly and leave the same way. This is not the way it happens however, our genes existed before birth and will exist after our death if we succeed in reproduction. Cells can arise only from cells that already exist. They do this by one of life's defining features, reproduction. Parents transmit DNA to their offspring which allows their offspring to look like them. The process starts with a single cell that contains the DNA of one parent in asexual reproduction or two parents in sexual reproduction.

DNA the Molecule of life

Embryology:DNA encodes the developmental patterns for all organisms including humans. After the ovum is fertilized, the single cell divides numerous times and the cells become specialized cells known as tissue and organs, which form complete individual. The instructions for each stage were written into the DNA long before reproduction.

Energy is another requirement of life

Energy: Everything in the universe has energy, which is defined as a capacity to do work. There are many different types of energy, and absolutely nothing can happen in the universe without a complete or partial transfer of energy. Without energy organisms cannot stay alive, grow and reproduce.

Metabolism: Metabolism can be defined as:

The ability to obtain and convert energy from its surroundings (plants and animal generally do it differently), and the use of energy to maintain itself, grow, and make more cells

Living organism sense and respond to energy: Life forms sense and make changes in the environment. Organisms have receptors, which are molecules that detect specific stimuli. A stimulus is an energy change in the environment such heat, light, or sound. Cells adjust their metabolic activities in response to stimulus (or energy changes). Organisms respond to energy changes and their internal operating conditions remain within a narrow limit. We call this narrow limit of change homeostasis, that is a defining feature of life.

Levels of organization of life

Biosphere

All regions of water, land, and atmosphere in which organisms can exist

Ecosystem

A community and its physical environment

Community

The populations of all species occupying the same area

Population

A group of individuals of the same Kind occupying a defined area

Multicellular Organism

Individual with interdependent cells which are organized into tissues,

organs and organ systems

Organ Systems

Two or more organs interacting in a way that allow survival of the whole

organism

Organ

A number of tissue combined in a pattern to perform a common task

Tissue

A group of cells and surrounding substances functioning in a specialized

activity

Cell

The smallest unit that lives and reproduces

Organelle

A membrane-bound part of cell with specialized task

A fundamental substance called an element

Subatomic Particles

An electron, proton, or neutron

Interdependencies of Life

Producers: Producers are plants and all other organisms that make their own food. Generally this is done through a process called photosynthesis.

Consumers: Animals that consume plants or other animals. They depend on the energy stored in the tissues of producers or other animals.

Decomposers: Decomposers break down biological material into simple material that can be recycled. All the energy that the producers capture from the sun is returned to the environment.

The Same But Yet Different

Characteristic that all living things have:

1.They are made of the same elements.

2.They remain alive through metabolism.

3.They interact for energy and raw materials.

4.They sense and respond to environment.

5.They reproduce based on instructions found in DNA.

Diversity

You share the planet with millions of different kinds of organisms and species. Ancient scholars recognized only two kingdoms (plant and animal). Modern biologists have recognized as many as five

kingdoms, but evidence suggests there should be six:

Kingdom Archaebacteria: Form the anaerobic (oxygen-free) habitat.

They live in extreme habitats

Kingdom Eubacteria: They are the most successful and live nearly everywhere, including in and on other organisms.

Kingdom Protista: The Protistans include single-celled species as well as some multicelled forms. Most are larger than bacteria and are eukaryotic.

Kingdom Fungi: Some species of fungi are parasites and some cause diseases, but vast majority are decomposers. Without decomposers the plant would be filled with garbage.

Kingdom Plantae: Include may familiar species. Plant are

multicelled producers and most are photosynthetic.

Kingdom Animalia: Animals are multicelled consumers that eat both plants and animal.

Source of variation

Mutations are a change in the genetic material. Mutations can be harmful, have no effect, or have a survival advantage. Light colored moths survive better on light colored trees.

Evolution The DNA in the moth must change during some point in time.

The environment must select for the change and there will be gradual change in color of the moth population with time.

Natural Selection is the outcome of survival of populations with different traits. Those organism that survive were select to remain in the population and can pass on their genes to the next generation.

Scientific Method

1.Observe some aspect of nature, carefully check what other have found out about it, and

then frame a question or identify a problem related to your observation. Observation was woodrats do not die when put into a den of rattlesnakes. We found no published information. The question is are woodrats resistant to snake venom.

2.Develop hypothesis, or educated guesses, about possible answers to questions or

solutions to the problems. Possible solutions were snakes were not hungry, snake did not inject venom into the rat, or the woodrats are resistant. A good hypothesis would be that woodrats are resistant to snake venom.

https://www.wendangku.net/doc/5b15677846.html,ing the hypotheses as a guide, make a prediction. If rats are resistant then when

injected with venom they should live. There must be a control to insure that the venom was active.

4.Devise a test to measure the accuracy of the predictions. Inject 1 ml of Crotalus atrox

venom in two a 300 g woodrat.

5.If the tests do no turn out as you expected, check to see what might have gone wrong. The

test did turn out in favor of the hypothesis but we did not have proper controls.

6.Repeat the test or devise new test. Other test conducted.

7.Objectively analyze and report the test results in journals and professional meetings. The

research was published in Toxicon