Notes, summaries, assignments, exams, and problems for Biology

Spontaneous Generation

Spontaneous generation proposes that life began from inanimate objects.

Oparin's Theory

Alexander Ivanovich Oparin developed this abiogenic theory.

1. Components of the atmosphere (methane, ammonia, hydrogen, and water vapor) reacted due to the energy of storms, solar radiation, and continuous volcanic eruptions, creating simple organic molecules.
2. The Earth cooled down, and intense rain produced primitive seas where organic molecules accumulated.
3. Organic molecules joined, creating bigger molecules; some of them were insulated from the water inside structures called coacervates.
4. Some of the coacervates developed molecules in their interior that were able to self-replicate; these were the first organisms and the origin of all cells.

Yeast

Yeast is an unicellular saprophytic fungus present in the air and on the surface of fruit. Yeast causes the spoilage of fruit, jam, honey, and is used in the production of bread, beer, and wine. It feeds on carbohydrate foods, flourishes at 25C-30C, is killed above 60C, requires moisture for growth, can live with or without oxygen, and requires time to grow. It reproduces asexually through budding, where a cell develops a bud, the nucleus moves towards the bud, the nucleus divides in two, a wall develops and divides the bud from the parent cell, and the bud separates from the cell. Yeast has granular cytoplasm, food vacuoles, vacuole, and a cell wall.

Food Preservation

Food preservation involves long term storage, preventing enzyme activity... Continue reading "Food Preservation Methods and Microbial Growth" »

Moss Theory and 2 Examples

• Growth of face happens as response to functional needs and neurotrophic influences and is mediated via soft tissues in which jaws are embedded.
• Soft tissue growth causes both bone and cartilage to react.
• Growth of cranial vault is a direct response to growth of brain.
• Growth of eyes increases size of orbit.
• Major determinant of growth of maxilla and mandible is enlargement of nasal and oral cavities, which grow in response to functional needs. Important for orthodontic treatment with functional appliances and orthopedic treatment.

Endocrine System Regulation

How is the endocrine system regulated? Endocrine gland activity is regulated by the brain. The brain manages the endocrine system through two glands: the hypothalamus and the pituitary glands. The hypothalamus directs, and the pituitary glands produce and secrete.

Neuron Structure and Classification

Neurons: These transmit messages (nerve impulses) and have a unique appearance.

• Cell body: This is where the nucleus is located; it contains most of the cytoplasm and organelles. It forms part of the grey matter.
• Dendrites: These are branched projections connected to other neurons that receive information from them.
• Axon: A long tail structure where information passes from here to the next neuron or cell. A group of axons is

In Situ Tests: Parameters, Methods, Limitations

In situ tests: Values of different parameters are obtained from theoretical interpretation of the test result. Compared with laboratory tests, in situ tests reduce some limitations such as:

• Disturbance of soil samples (matters less; no transport of the sample).
• Change in the stress state of the sample.
• Small size of laboratory samples may be unrepresentative (a larger portion of the soil is involved).

Other limitations appear:

• Some disturbance is always present.
• Less control over test conditions (in the laboratory we can control water conditions).
• If the parameters of the theoretical model are two or more, only a relationship between them is obtained (for example, E and ν, or c and φ).

Common In Situ

Nutritional Needs

D(calciferol); it helps the calcification of our bones, it is present in milk and dairy products, fish liver oil. C(ascorbic acid), antioxidant and it keeps mucus normal and healthy, it is present in citrus fruits, strawberries, and vegetables.

Structural

The most important structural nutrients are proteins, although certain lipids, cell membranes, and certain salts such as the ones that form our skeleton.

Energy Needs

Our body needs energy to perform any physical activity. Energy nutrients (carbohydrates and fats) can be obtained from proteins, this process is possible due to cell respiration.

Different Caloric Values

One gram of fat 9 kcal, one gram of carbohydrates 3.75 kcal, one gram of protein 4 kcal.

Basal Metabolic Rate and

Cooking Techniques

Moist-Heat Techniques

Methods in which heat is conducted to foods by water or other liquid or by steam:

• Simmer: To cook in water or other liquid that is bubbling gently (85-96°C). Similar to poaching, the only difference is the time.
• Steam: To cook by direct contact with steam.
• Boil: To cook in water or other liquid that is bubbling rapidly, about 100°C at sea level and at normal pressure.
• Poach: To cook gently in water or other liquid that is hot but not actually bubbling (71-82°C).
• Blanch: To cook an item partially and very briefly in boiling water or in hot fat. Usually a pre-preparation technique, as to loosen peels of vegetables, fruits, and nuts, to partially cook French fries or other foods before service, to prepare for

Human Receptors and Nervous System

Receptors: Structures that human beings use to detect stimuli.

Interoceptors

Collect information about the body’s internal conditions. Located in the internal environment.

Exteroceptors

Provide information from the body’s outside environment. Located on the surface of the body.

Proprioceptors

Inform about the relative position and condition of each of the body’s muscles. Found in the inner ear’s vestibule and locomotive system.

Eyes/Sight

Detect light stimuli. Photoreceptors

Ears/Hearing

Detect sound waves (Mechanoreceptors) and proprioception.

Nose/Smell

Detect substances dissolved in the air. Chemoreceptors

Mouth/Taste

Detects substances dissolved in liquids found in the oral cavity. Chemoreceptors

Skin/Touch

Detects... Continue reading "Human Receptors and Nervous System: An Overview" »

1. Telomerase is a ribonucleoprotein complex that consists of telomerase RNA (which contains several tandem hexanucleotide repeats complementary to the telomere repeats in the substrate) and a reverse transcriptase. This complex is able to synthesize telomeric repetitive DNA sequences at the end of linear DNA molecules. Telomerase RNA binds to the DNA strand, and complementary dNTPs are incorporated into newly synthesized, extended DNA strands by reverse transcriptase. Thus, dNTPs must also have been present during step 1 of the TRAP assay (step 1).

2. The PCR reaction mixture also contained a heat-resistant DNA polymerase (Taq polymerase).

3. Sample 3 contained cell extract isolated from immortal cells. In the presence of the telomerase, products... Continue reading "Telomerase Activity in Immortalized Cells" »

Blood Composition and Functions

Cells live immersed in a medium that provides them with all the nutrients they need. They also secrete the waste products released during metabolism into this medium. In multicellular organisms like humans, this medium is called the internal milieu and is made up of the interstitial plasma, a fluid found in the space between the cells. The interstitial plasma is renewed thanks to the blood, which continuously circulates around the whole body, providing nutrients and taking away waste products.

What is Blood?

Blood is a viscous fluid with a salty taste that flows inside the vessels that make up the circulatory system.

Blood Components

Blood is made up of cells suspended in a liquid called blood plasma.

• Blood plasma