Notes, abstracts, papers, exams and problems of Biology

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

Wood Structure and Properties

Sapwood and Heartwood

Sapwood

• Width varies with species, growth rate, and tree age.
• Typically represents 20-50% of the total radius (except in very young trees).

Heartwood

• Formed from former sapwood cells.
• Acidity increases, extractives form, and color changes.
• Resistance to fungal and insect attack increases.
• Many timbers develop gums and resins in the heartwood.

Functions of Cells in a Growing Tree

• Primary function: Conduction of water and dissolved minerals from roots to leaves.
• Secondary function: Mechanical support of the tree.
• Tertiary function: Food storage for spring growth.

Characteristic Differences between Softwoods and Hardwoods

• Hardwoods: Water-conducting elements distributed throughout the annual ring.
• Softwoods:

Understanding Digestion

What is Digestion?

Digestion is the process by which food is transformed into simpler substances (nutrients) so they can be used by our cells. It involves two main processes:

• Mechanical Process: Chewing and the muscular action of organs crush and mix foods with digestive juices.
• Chemical Process: Digestive enzymes in digestive juices cause chemical reactions that break food into simple substances.

Mechanical vs. Chemical Digestion

The digestive system employs both mechanical and chemical digestion:

• Mechanical: Mouth
• Chemical: Stomach, liver, small and large intestine

Swallowing: The Process

Swallowing allows substances to pass from the mouth to the pharynx. It involves three main stages:

1. The bolus is moved to the oral cavity as

Human Nutrition

The cells of all organisms require nutrients to grow and function. Heterotrophic organisms, like humans, cannot produce their own nutrients, so they obtain them from food. Multicellular organisms have many organs grouped into systems, such as the digestive and respiratory systems.

Digestive System

Like all animals, humans obtain proteins, fats, and sugars from food through the digestive system. Food processing involves three phases: digestion, absorption, and waste expulsion. Food moves through the digestive tract via peristaltic movements—muscle contractions in the tract walls that narrow the tube.

Respiratory System

Besides nutrients from digestion, our cells need oxygen for cellular respiration, the process that converts glucose... Continue reading "Human Nutrition and Respiration: A Comprehensive Guide" »

Cellular Respiration

Glycolysis

• Enzymes break down a 6-carbon glucose molecule into two 3-carbon pyruvate molecules.
• A small amount of ATP is synthesized through substrate-level phosphorylation, an enzyme-catalyzed reaction transferring a phosphate group from a substrate to ADP.

Oxidative Phosphorylation

• High-energy electrons are delivered to oxygen through a series of electron carriers in the electron transport system.
• The free energy released by electron flow generates an H+ gradient via chemiosmosis.
• ATP synthase utilizes the H+ gradient as the energy source for ATP production.

Reaction Locations

• Glycolysis: Occurs in the cytosol.
• Pyruvate oxidation and citric acid cycle: Take place in the mitochondrial matrix.
• Electron transfer system and ATP synthase