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

Factors Affecting Enzyme Activity

pH Effects on Enzyme Function

Enzymes exhibit an optimum pH at which their activity is maximal, characterized by a low K_m (substrate concentration) and maximum velocity. Small variations around this optimum pH value cause a sudden drop in activity. This can be due to the appearance or disappearance of electrostatic forces that alter the spatial structure of the active site, or changes in the charges of the active center and substrate, which affect their binding capacity. If the pH change is very high, the enzyme is denatured and ceases to be functional.

Temperature's Role in Enzyme Kinetics

In general, an increase in temperature increases the rate of chemical reactions. In the case of enzyme-catalyzed reactions,... Continue reading "Enzyme Activity: Factors, Inhibition, and Metabolic Control" »

Fertilization Process

Ovulation occurs about fourteen days before menstruation. The egg released from the Graafian follicle is propelled along the fallopian tube to the uterus, taking over a week for this journey.

The egg can be fertilized for only 24 hours after ovulation while traveling along the fallopian tube.

Intercourse, or the sexual act, is the introduction of the penis into the vagina. At ejaculation, sperm are released inside the vagina.

Unlike the egg, sperm are very fast. They ascend through the vagina, traverse the cervix and uterus, and reach both fallopian tubes in a few hours. They can also survive for three to five days, so if intercourse occurs in the days before ovulation, the probability of pregnancy is very high.

If the egg... Continue reading "Fertilization and Early Pregnancy Stages" »

Fundamentals of Amino Acids and Protein Structure

Defining Amino Acids (AA)

Amino acids (AA) are organic compounds characterized by the presence of both an amino group (-NH₂) and a carboxyl group (-COOH). There are 20 standard amino acids. We cannot metabolize the essential amino acids, meaning they must be obtained through the diet.

Classification of Amino Acid Side Chains

Amino acids are classified based on the properties of their side chain (R group):

• Nonpolar (Hydrophobic): R group is hydrophobic and typically located on the exterior in aqueous environments.
• Polar Ionizable: R group is polar and located internally.
• Polar Acids: R group contains an additional carboxyl group, located internally.
• Polar Basic: R group contains an additional amino

DNA Replication

DNA replication begins with the double helix unwinding, separating like a zipper. Each strand serves as a template for creating a new complementary strand. DNA polymerase enzymes add nucleotides one by one, matching adenine with thymine and guanine with cytosine. This process creates two identical DNA molecules, each with one original and one new strand. Errors during replication can lead to mutations, which can be harmless, cause diseases, or contribute to evolution.

The Importance of Base Complementarity

Base complementarity is crucial for accurate DNA replication, ensuring that genetic information is passed correctly from parent to daughter cells. It also forms the basis of many molecular biology techniques.

Gene Expression:

Understanding Diet and Health Conditions

Essential Dietary Concepts

• Balanced Diet: Consuming the correct nutrients in the appropriate proportions for optimal health.
• Malnutrition: A condition occurring when either too much or too little of a nutrient is consumed, leading to health problems.
• Kwashiorkor: A severe form of malnutrition caused by insufficient protein intake, primarily affecting children and leading to poor growth and development.
• Myocardial Infarction (Heart Attack): Occurs when a part of the heart's wall dies due to lack of blood supply.

Obesity and Associated Health Risks

• Causes of Obesity: Primarily results from consuming too much fat and calories.
• Health Complications: Obesity is a significant health problem, contributing to conditions

Antibiotics

They test substances for chemical, biological, or synthetic origin that kill bacteria or prevent their multiplication. After years of research, we succeeded in isolating the substance that prevented the development of bacteria. It was the first antibiotic known as penicillin, discovered by Alexander Fleming. Other antibiotics have been discovered and manufactured in the laboratory; these synthetic antibiotics have a similar effect.

Antiviral

Antivirals act on bacteria; however, they have no effect on other infectious agents. For bacterial infectious diseases, other drugs should not be used.

The importance of certain viral diseases (such as AIDS) has forced pharmaceutical companies to put their efforts into development. It is not easy... Continue reading "Understanding Antibiotics and Antivirals: Key Insights" »

What is Atherosclerosis?

Atherosclerosis, literally meaning hardening of the arteries, is a degenerative disease characterized by narrowing of the arteries. Deposits of lipids, fibrous cells, muscle cells, cholesterol crystals, and calcium build up on the artery walls. This process develops slowly.

When narrowing of the arteries prevents blood flow, it leads to ischemia (lack of blood supply to the tissues).

Understanding Atherosclerosis Development

• Atherosclerosis is a widespread condition, although there are notable differences in incidence based on geography, race, and sex.
• Although the term "atherosclerosis" is relatively modern, traces of artery hardening have been found in mummies from the Fifteenth Dynasty of Egyptian pharaohs (dating back

1. Health and Disease

1.1. Definitions

Health: A state of complete physical, mental, and social well-being, not merely the absence of disease.

Disease: A change in health status, i.e., a temporary or permanent loss of physical, mental, and social well-being.

Quality of Life: The comfort level, happiness, and satisfaction in a person that allows them to act and feel positively about their lives. This depends on their physical and mental health, their level of independence, and social relationships. One of the main indicators is life expectancy at birth.

1.3. Genes, Lifestyle, and Health

There are genetic diseases due to alterations in the genome (e.g., Down syndrome, hemophilia, or certain types of diabetes).

In other cases, the genotype determines... Continue reading "Health, Disease, and Infectious Diseases: A Comprehensive Overview" »

Uric Acid Stones: Causes, Treatment, and Diet

Uric acid stones are associated with the production of acidic urine.

Treatment for Uric Acid Stones

• Increase fluid intake.
• Increase urine pH to 6.0-6.5.
• Adopt a diet rich in alkaline-forming foods, supplemented with citrate or bicarbonate.

Dietary Considerations for Uric Acid Stones

Acid-Forming Foods (Potentially Acidic Residue)

• Meat: Beef, fish, game, seafood.
• Dairy: Eggs, cheese.
• Fats: Bacon, walnuts, Brazil nuts, hazelnuts.
• Grains & Baked Goods: Flour, bread (especially whole wheat), cereal, biscuits, pasta, rice, cakes.
• Vegetables: Corn, lentils.
• Fruits: Blueberries, plums.

Alkaline-Forming Foods (Potentially Basic Residue)

• Dairy: Milk and milk products, cream, whey.
• Fats: Almonds, chestnuts, coconut.
• Vegetables:

Types of Illness

There are several types of illness:

• Physical illness: Caused by injury, infection, or a degenerative process of the organism.
• Mental illness: May result from a malfunction of the brain.
• Social diseases: Can be caused by the existence of a violent social environment.

Defining Health and Illness

Health is a state of complete physical, mental, and social well-being. Illness is the state in which a person's health is disturbed.

Violence: Impact on Health and Society

Violence is a detrimental social issue, often originating in childhood. It negatively influences health, potentially harming or causing the death of loved ones, family members, or neighbors.

Understanding Infectious Diseases

Infectious diseases are caused by pathogens (such as... Continue reading "Foundations of Health: Diseases, Risks, and Well-being" »