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

Protein Synthesis: From DNA to Protein

1. Transcription: Copying the Genetic Message

Transcription is the process of copying part of the genetic message from DNA to RNA so that it can be used to synthesize a specific protein.

Stages of Transcription:

• The double helix of DNA unwinds.
• Complementary nucleotides position themselves opposite one of the two strands.
• Only one of the DNA strands is copied.
• An RNA strand is produced with a sequence of bases that is complementary to the DNA bases.

2. Translation: Building the Protein

Stages of Translation:

• The message copied as RNA is identical to the message in the DNA (except it contains uracil instead of thymine).
• This RNA, known as messenger RNA (mRNA), is a single-chain molecule that can leave the nucleus.

The Pancreas

Long, greyish-white organ behind and underneath the stomach. Functions: Produces hormones (insulin & glucagon) that regulate the amount of glucose in the bloodstream. Secretes pancreatic juice which contains digestive enzymes & sodium bicarbonate.

How Digestion Works

Most digestive processes take place in the small intestine. Digestion produces nutrients that cells need:

• Monosaccharides (simple sugars): obtained from complex carbohydrates.
• Glycerol & fatty acids: obtained from fats.
• Amino acids: obtained from proteins.

Nutrient Absorption

Nutrients pass from the small intestine into the bloodstream through absorption and then are delivered to cells by the blood. The inside wall of the small intestine is covered in folds that... Continue reading "Understanding the Pancreas and Respiratory System" »

1. Sequence of Life's Emergence

What is the correct sequence of events representing how life may have emerged?

Answer: Monomers formed — Polymers formed — Membrane-bound "sacs" emerged — Metabolism and self-replication — RNA produced.

2. Identifying Extinct Species

Which species are extinct?

Answer: Species A and E.

3. Common Ancestor Location

In a phylogenetic tree, the common ancestor for both species C and E could be at position number:

Answer: 4.

4. Science of Classification

The area of science that classifies and names organisms is called:

Answer: Taxonomy.

5. Correct Binomial Nomenclature

Which of the following is correctly written using the binomial nomenclature system?

Answer: Canis lupus.

6. Definition of Binomial Nomenclature

Binomial nomenclature... Continue reading "Key Concepts in Biology: Life's Origins & Classification" »

The Nervous System: Communication Network

Neurons: The Building Blocks of the Nervous System

• Neurons: Specialized cells that conduct electrical impulses throughout the body. They are elongated cells with a cell body and a thin axon.
• Dendrites: Thin projections that extend from the cell body and connect with other neurons to allow electrical impulses to pass through.
• Myelin Sheath: An insulating lipid layer that surrounds some axons, speeding up impulse transmission.
• Nerve: A bundle of nerve fibers enclosed within a protective sheath.
• Nerve Fibers: Long axons of neurons together with any associated tissue.

Types of Neurons

The nervous system is comprised of three specialized types of neurons:

• Sensory Neurons: Transmit messages from receptors (e.g., eyes,

DNA and RNA: The Nucleic Acids

What are DNA and RNA?

DNA and RNA belong to the group of molecules called nucleic acids.

Functions of DNA and RNA

DNA

• Stores genetic information
• Provides instructions for protein synthesis
• Passes genetic code to daughter cells

RNA

Carries out instructions from DNA for protein synthesis.

Types of RNA and Their Functions

• mRNA (messenger RNA): Makes a copy of DNA and carries this copy from the nucleus to the cytoplasm for protein synthesis.
• tRNA (transfer RNA): Transfers amino acids to ribosomes for protein synthesis.
• rRNA (ribosomal RNA): Controls ribosome formation in the cytoplasm.

Structure of Nucleic Acids

Monomers and Components

The monomer that makes up nucleic acids is called a nucleotide. Each nucleotide consists of:

• Phosphate

The Circulatory System

1. The circulatory system is responsible for transporting nutrients to and from the cells in the body. It is made up of the heart, blood vessels, and the blood.

2. The function of the internal environment is to give nutrients needed to cells. It is located in the interstitial fluid.

3. Blood carries nutrients that go from the blood vessels to the interstitial fluid. Cells found in tissues exchange substances with the interstitial fluid.

4. Cells get rid of waste products with the help of the interstitial fluid that collects this.

5. Cells would not obtain nutrients.

6.1. It transports nutrients and oxygen to the cells. 2. It removes waste: CO2, urea, salts. 3. Defends the organism against infections. 4. Helps to control body... Continue reading "Understanding the Circulatory System" »

The heart: double circulatory system

Vena cava - body to the heart (DO), pulmonary artery heart to lungs (DO), pulmonary vein - lungs to heart (O), aorta - heart to body (O). Arteries take blood away from the heart, veins take it towards the heart, Pulmonary means lungs. Valves make sure blood flows in a one way direction. Blood goes from heart to lungs to be oxygenated via the pulmonary artery. The now oxygenated blood goes back to the heart via the pulmonary vein to be pumped around the body via the aorta. Once the blood has been round the body, it is pumped to the heart via the vena cava to be sent to the lungs again for oxygenation then the cycle repeats.

Coronary heart disease

The coronary artery supplies blood to the heart (the heart is... Continue reading "Understanding the Human Heart and Immune System" »

3.3 The Nervous System

Receives information from the receptors, processes and coordinates it, and generates orders for the effectors. It is made up of the central nervous system or CNS, and the peripheral nervous system or PNS.

3.4 The Central Nervous System or CNS

Coordinates all the body's functions. It is formed by the encephalon and the spinal cord.

The Encephalon

Protected by the skull or cranium and by three membranes, the meninges, between which a liquid called the cerebrospinal fluid circulates. This liquid protects the encephalon from knocks and blows. Divided into three parts:

• The brain is divided into two hemispheres, which are separated by a fissure. Its surface, the cerebral cortex, is full of folds and furrows, known as circumvolutions.

Regulation of Enzyme Activity

Enzymes are the workhorses of cells, catalyzing the thousands of biochemical reactions that keep cells alive and functioning. The activity of enzymes is carefully controlled to ensure that the proper amount of product is produced at the right time.

Why Regulate Enzyme Activity?

There are several reasons why cells need to regulate enzyme activity. First, the concentration of substrates and products can vary widely within the cell. If enzyme activity were constant, the rate of the reaction would also vary wildly, depending on the availability of substrates. Regulation allows the cell to adjust the rate of the reaction to match the needs of the cell.

Second, the cell needs to coordinate the activities of different enzymes... Continue reading "Enzyme Regulation: Mechanisms and Examples" »