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

Question 1:

Group the following as nitrogenous bases and nucleosides:

• Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Answer

Nitrogenous bases present in the list are adenine, thymine, uracil, and cytosine.

Nucleosides present in the list are cytidine and guanosine.

Question 2:

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Answer

According to Chargaff’s rule, the DNA molecule should have an equal ratio of pyrimidine (cytosine and thymine) and purine (adenine and guanine). It means that the number of adenine molecules is equal to thymine molecules and the number of guanine molecules is equal to cytosine molecules.

% A = % T and % G = % C

If dsDNA has 20% of cytosine, then according to... Continue reading "Understanding DNA: Bases, Replication, and Functions" »

Genetics: Key Concepts

Vocabulary Terms:

• Chromosome: A structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
• Gene: A unit of heredity transferred from parent to offspring, determining some of the offspring's characteristics.
• Homologous Pairs: Chromosomes containing genes for the same traits but potentially different alleles. These are usually paired during mitosis.
• Allele: One of two or more alternative forms of a gene that arise by mutation and are found at the same location on a chromosome.
• Sister Chromatid: Identical copies of a chromosome formed by DNA replication, joined by a common centromere. It's essentially half of a duplicated chromosome.
• Nucleotide: A compound

• The outer ear: it is formed by the pinna and the auditory canal.
• The middle ear: a cavity in the eardrum that reaches the oval window and the round window.
• The inner ear: formed by the membranous labyrinth.
• Sweat gland: this secretes sweat, cooling the body surface when it is necessary and removing certain waste substances.
• Sebaceous gland: these secretes substances that lubricate the skin and hair.
• Taste buds: are located inside the mouth especially on the tongue.
• Long bones: these are long and contain spongy bone tissue at either end, as well as compact bone.
• Short bones: these are rounded and mostly made up of spongy bone tissue.
• Flat bones: these are plate-shaped. Formed by an inner layer of bone tissue surrounded by two layers of compact bone

Step 1: Glycolysis - What Happens?

1 glucose molecule is split into two 3-carbon molecules called pyruvate.

Who Controls It? Enzymes. Where? Cytosol. Result? Two molecules of ATP are produced.

Step 2: Oxidative Respiration - The pyruvate molecules made during glycolysis still have a lot of potential to make more energy (ATP). What Happens? The 2 pyruvate molecules now go through oxidative respiration where they produce carbon dioxide, water, and 34 ATP! Where? Mitochondria.

Three Metabolic Pathways - Within these two systems, aerobic vs. anaerobic, there are three main metabolic pathways by which ATP energy reserves are restored.

1. The ATP-PC Pathway: Anaerobic Alactic.

2. The Glycolysis Pathway: Anaerobic Lactic.

3. Cellular Respiration: Aerobic - It is

Environmental Factors

Characteristics of the environment that affect living things are called environmental factors. They can be abiotic (related to non-living things) or biotic (related to living things).

Biotic and abiotic factors

⦁ Abiotic factors: Physical and chemical conditions that affect living things.

The main abiotic factors are water, light, temperature, soil, pH, humidity, and nutrients found in water and soil. Some abiotic factors are more important than others depending on the location they are in.

• Sunlight is essential for life on Earth to exist.
• The concentration of oxygen in the atmosphere decreases as altitude increases.
• Temperature is a decisive factor in the physiological activity of living things.
• Water is an essential substance

Core Concepts of Health and Disease

Health and Disease Definitions

• Health: A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity.
• Disease: A disorder or malfunction of the mind or body, which leads to a departure from good health. It can be a disorder of a specific tissue or organ due to a single cause.

Pathogens and Infectious Diseases

Types of Pathogens

• Fungi
• Bacteria
• Viruses

Diseases Caused by Viruses

Influenza (Flu)

Influenza is a virus that causes a severe form of respiratory tract infection with generalized bodily symptoms. While it shares cold-like symptoms, its onset is rapid and violent, often featuring:

• High fever
• Severe aches and pains, often in the back and muscles

Other common viral diseases... Continue reading "Understanding Disease, Immunity, and STIs: Core Concepts" »

Understanding Shigellosis: Causes and Treatment Challenges

What is Shigellosis?

Shigellosis is a significant public health threat in both developed and developing countries. It is an infectious disease caused by a group of bacteria known as Shigella. The genus Shigella includes four pathogenic serogroups: Shigella dysenteriae, Shigella flexneri, Shigella sonnei, and Shigella boydii. Shigellosis typically causes symptoms such as diarrhea, fever, and stomach cramps.

How is Shigellosis Contracted?

Individuals can contract shigellosis by ingesting contaminated food or water, or through direct contact with the stool of an infected person. This highlights the ease of transmission and the importance of hygiene.

Current Treatments and Emerging Resistance

Antibiotic... Continue reading "Sfin-1 Bacteriophage: A Potent Weapon Against Drug-Resistant Shigella" »

The Internal Environment

• Refers to the fluids that surround the cells.
• Temperature and composition must be stable for the correct working of cells.
• This internal environment is maintained by the organ systems of the body.
• Interstitial fluid (plasma): Surrounds and bathes the cells.
• Blood and lymph: Collect and distribute substances for the cells (O2, nutrients) and remove waste.

The Circulatory System

• Carries nutrients and oxygen throughout the body and collects waste (blood): Blood Circulatory System.
• Returns excess interstitial fluid to the blood.
• Transports fat to the blood.
• Defends the immune system (lymph): Lymphatic System.

The Lymphatic System

• Lymph capillaries:
  • Thin vessels closed at one end.
  • Collect excess interstitial fluid.
• Lymphatic vessels:

Human Body Systems

1. Respiratory System: The purpose of this system is to take in air, filter it, and take it to the tissues responsible for gas exchange. Oxygen is then transported by blood to all the tissues in the body. Carbon dioxide, a waste product, is reabsorbed and excreted from the body.
2. Skeletal System: This system forms the basic framework of the body. It supports and protects all internal organs. Bones serve as levers (with the attached muscles) for movement, produce blood cells, and store calcium salts, which can be absorbed into the blood when there is not enough calcium in the diet.
3. Endocrine System: The secretion of hormones, which regulate the body's functions chemically, is the function of this system.
4. Urinary System: This system