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

Genetic Disorders and Their Causes

Genetic disorders: Most genetic disorders are caused by mutations in one or more genes or by abnormal numbers of chromosomes.

Genetic Disorders Caused by Mutations

Some disorders are caused by mutations in autosomal genes. In the table below, there is a list of genetic disorders caused by a mutation in a single gene.

Inorganic biomolecules

Essential for non-living things.

• Water: The most abundant substance found in living things. It makes up about 65% of the human body.
• Mineral salts: Substances that can be found in living things in the form of dissolved ions, such as sodium ion.

Organic biomolecules

Unique to living things. Structures made up of carbon.

• Carbohydrates: Made of carbon and water.
• Lipids: Fats, phospholipids, and cholesterol.
• Proteins: Chains of amino acids.
• Nucleic acids: Groups of nucleotides.

The cell: Functions

• Structural
• Functional
• Basic
• Biological

Prokaryotic cell

• No nucleus
• Organelles: Ribosomes
• Bacteria are prokaryotes
• Membranes: Cell membrane, cell wall, and bacterial capsule (not always)
• Flagella and Fimbriae

Eukaryotic cell

• Nucleus
• Cell membrane: two

Cell Organelles

Mitochondria: Oval-shaped organelles with two membranes. Through cellular respiration, mitochondria produce energy for the cell.

Vesicles: Small, rounded organelles that store, transport, or digest cellular substances. Lysosomes are rounded vesicles produced by the Golgi body.

Endoplasmic Reticulum: A network of interconnected membranous sacs and channels. There are two types:

• Rough ER: Connected with the nuclear envelope and ribosomes.
• Smooth ER: This type has no attached ribosomes.

Golgi Body: Flat, membranous sacs arranged in layers. Secretory vesicles transport substances out of the cell.

Centrosome: Consists of two centrioles: perpendicular cylindrical structures composed of microtubules. They are surrounded by other microtubules... Continue reading "Cell Organelles and Food Preservation Techniques" »

Human Reproduction: Fundamental Processes

Human reproduction is sexual, meaning that both the mother and father contribute genetic material to their offspring via gametes. Offspring will have a mix of their parents' characteristics, and each person obtains their own unique genetic make-up.

The female gametes, ovules, and the male gametes, sperm, fuse together in the process called fertilisation, inside the female reproductive system, to form a zygote.

The embryo develops from the zygote inside the mother's uterus, undergoing repeated cell divisions. The new cells created specialise to form tissues and organs.

Sexual Characteristics and Puberty

Boys and girls are born with different reproductive organs, which constitute the so-called primary sexual

Cellular Division: Meiosis and Mitosis

Meiosis has two rounds of genetic separation and cellular division, while mitosis only has one of each.

Key Differences

• Meiosis: Homologous chromosomes separate, leading to daughter cells that are not genetically identical.
• Mitosis: The daughter cells are genetically identical to the parent cell, as well as to each other.

Male Reproductive System

Primary Sex Organs

A pair of testes (singular: testis) lying outside the abdominal cavity, enclosed in a sac called the scrotum.

Secondary Sex Organs and Accessory Structures

Seminiferous Tubules

These tubules unite to form a long, coiled structure called the epididymis. They are involved in sperm production.

Epididymis

A long, coiled structure that acts as the main storage

All cells in your body are surrounded by a liquid environment. They depend on it to stay alive. The internal environment is made up of the interstitial fluid and the circulating fluids. Lymph is the fluid that flows through the lymphatic vessels. It is formed from the remaining interstitial fluid. Blood is the fluid in charge of transporting substances through the inside of blood vessels. Interstitial fluid is the fluid that surrounds every cell. Cells extract nutrients, oxygen and release into the waste and carbon dioxide produced in cell metabolism. The circulatory system connects the system involved in the nutrition function with the interstitial fluid that surrounds the cells in the body. It has 2 systems: the cardiovascular system through... Continue reading "Understanding the Circulatory System and Its Functions" »

How Scientists Work with DNA

It always starts with the sequence. Once the sequence is known, specific regions can be isolated, cloned, amplified, and then used to help us.

Biotechnology Methods and Applications

Biotechnology is the use of technology to change the genetic makeup of living things for human purposes. Generally, the purpose of biotechnology is to create organisms that are useful to humans or to cure genetic disorders.

Biotechnology uses a variety of techniques to achieve its aims. Two commonly used techniques are gene cloning and the polymerase chain reaction.

The Four Steps of Gene Cloning

Gene cloning is the process of isolating and making copies of a gene. Gene cloning involves four essential steps:

1. Isolation: In isolation, an enzyme

Organization of Life

Atoms: smallest unit of an element that still retains the element's properties.

Molecules: two or more joined atoms of the same or different elements.

Cell: smallest unit of life that can live and reproduce on its own or as part of a multicellular organism.

Multicellular organisms: made of specialized, interdependent cells that are often organized into:

• Tissues
• Organs
• Organ systems

Population: consists of individuals of the same species in a specified area.

Community: consists of all populations occupying the same area.

Ecosystem: a community interacting with its physical and chemical environment.

Biosphere: includes all regions of Earth's atmosphere, waters, and land where we find living organisms.

DNA is inherited.

Inheritance: an... Continue reading "Organization of Life and Enzymes: An Overview" »

The Digestive System

Liver

The liver, the largest internal organ, contains ducts called hepatocytes. These hepatocytes collect bile secreted by liver cells. The liver plays a crucial role in the metabolism of carbohydrates, lipids, and proteins.

Gallbladder

The gallbladder is a pear-shaped structure located under the liver. Its primary function is to store bile.

Pancreas

The pancreas is a long, narrow gland with two ducts, located on the left side of the abdomen.

Small Intestine

The small intestine starts at the pylorus and ends at the ileocaecal valve, where it joins the large intestine. It has two main parts:

• Duodenum: Secretes bile and pancreatic juice into this section.
• Jejunum and Ileum: Form the rest of the intestine. The small intestine is covered

Energy: Capacity for Change

Potential Energy: Stored energy.

Kinetic Energy: Energy from motion.

Conservation of Energy: Energy cannot be created or destroyed.

Heat: A usually random form of energy.

Entropy: A measure of disorder or randomness.

Chemical Energy: Energy stored in chemical bonds, such as food.

ATP Molecule

Draw a molecule of ATP: Adenosine-P-P-P

Metabolism

Metabolism: The total of all chemical reactions in an organism, requiring enzymes.

ATP and Cellular Work

ATP energy helps cells perform three types of work:

1. Chemical: Assists chemical reactions.
2. Transport: Performs transport work.
3. Mechanical: Moves muscle fibers, for example.

Enzyme Assistance

How do enzymes assist in chemical reactions?

1. Enzymes provide an active site specific to a substrate