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

Muscle spindles stimulate stretch, while Golgi tendon organs stimulate muscle contraction. Cerebellar tremor is characterized by low frequency. Motor pathways begin in the cerebral cortex and brainstem. Lower spinal cord motoneurons innervate skeletal muscles, including extrafusal and intrafusal fibers. Stimulation of muscle spindles or Golgi tendon organs is accomplished through the reticulospinal tract.

Muscle Tone and Movement Disorders

• Hypotonia: Decreased muscle tone
• Dyskinesia: Atypical, unconscious muscle movement
• Hypertonia: Increased muscle tone
• Spasticity: Hyper-contraction of muscles
• Akinesia: Atypical unconscious posture

Cortical Control of Movement

Layer V contains pyramidal neurons. The primary motor cortex contains smaller and fewer... Continue reading "Motor Control: Pathways, Neurons, and Muscle Function" »

Replication

AAGGCCTAGC-TTCCGGATCG

Transcription

AAGGCCTAGC

Translation

How to Read the RNAm to Make Proteins After the Transcribing DNA as RNAm

It exists from the nucleus to the cytoplasm. There, ribosomes are waiting for the RNAm, and the two subunits look for the first codon AUG. The RNAm is read by triplets. All the possible combinations of codons and its corresponding amino acids are called genetic code. Mutation is the alteration of the DNA sequence that can be transmitted to the offspring (if it occurs in gametes).

Addition:

A nucleotide is added

Deletion:

A nucleotide is removed

Substitution:

A nucleotide is changed

1. Fungi obtain nutrients through absorption.
2. The body of most fungi consists of threadlike hyphae, which form a network called a mycelium.
3. Some fungal species live in plants and can kill herbivores that feed on the plant. What type of relationship does this fungus have with its host? Mutualistic
4. What sexual processes in fungi generate genetic variation? Karyogamy and meiosis
5. Almost all of the members of this phylum form arbuscular mycorrhizae in a mutualistic partnership with plants. Glomeromycota
6. From the human perspective, which of the following kinds of fungi would be considered the least useful or beneficial? Rusts
7. Which of the following best describes the physical relationship of the partners involved in lichens? Photosynthetic cells are

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