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

Muscle Fiber

Elongated cells that make up skeletal muscle tissue

Striation

Light and dark stripes in which skeletal muscle fibers are grouped

Fascicle

Dense bundles in which skeletal muscle fibers are grouped

Voluntary Muscle

Muscle that are consciously controlled

Involuntary Muscle

Smooth muscles that cannot be consciously controlled

Myofibril

Thread-like structures found in skeletal muscle fiber

Myosin

Thick filaments that make up myofibril

Actin

Thin filaments that make up myofibril

Z Line

Structure to which actin filaments are anchored

Sarcomere

The region from one Z line to the nerve

Tendon

Fibrous connective tissue that attaches muscles to bone

Flexor

Muscle that bends a joint

Extensor

Muscle that straightens a joint

Muscle Fatigue

Physiological inability of a

The Pupil Reflex and Light Intensity

The pupil reflex occurs when the eye adjusts the light intensity (the amount of light) entering through to the retina. Pupil size alters according to the light intensity:

• Pupil widens (dilates): Occurs when there is less light available.
• Pupil constricts: Occurs when there is more light available.

Muscle Control of the Pupil

The pupil is controlled by two types of muscles:

• Circular muscles: These circle around the pupil. When they contract, the pupil constricts.
• Radial muscles: These run outwards from the edge of the pupil. When they contract, the pupil dilates.

Photoreceptors: Rods and Cones

The retina contains two main types of photoreceptors:

• Rods: Sensitive to dim light and used for night vision. A lack of Vitamin

Lymphatic System: Components and Functions

The lymphatic system is composed of lymph, lymphatic vessels, lymphatic organs, lymphatic tissues, and lymph nodes.

Key Components of the Lymphatic System

Lymph

Lymph is a transparent liquid composed of lymphocytes and interstitial plasma that is formed when blood plasma is filtered as it travels to the tissues.

Lymphatic Vessels

Lymphatic vessels are closed at one end. Lymphatic capillaries are found in tissues, and they join into bigger conduits known as lymphatic veins that eventually connect with blood veins.

Lymphatic Organs and Tissues

Lymphatic organs and tissues perform several functions, such as producing and maturing lymphocytes and purifying blood. The most important lymphatic organs are the spleen... Continue reading "Human Body Systems: Lymphatic, Excretory, and Urinary Functions" »

The Cell Cycle

The cell cycle is a repetitive sequence of events that occurs from the time of a cell's formation until its division is completed.

Interphase

The control of cell division resides in the subphases of interphase. During this stage, the cell assembles the carbohydrates, lipids, and proteins needed for internal use and export. Subsequently, the DNA is copied, and protein synthesis drives the cell toward mitosis. Most of a cell's existence is spent in interphase.

Mitosis and Chromosome Number

All somatic cells of a particular species possess the same number of chromosomes.

Mitosis

• Prophase: Chromosomes become visible as rod-like units. Microtubules move one pair of centrioles to opposite poles of the cell, and the nuclear envelope begins

Core Principles of Photosynthesis

The Light-Dependent Reactions

1. When oxygen is released during photosynthesis, what is it a direct by-product of?

   It is a direct by-product of splitting water molecules.

2. What is the role of pigment molecules in a light-harvesting complex?

   Within the thylakoid membranes, they absorb and transfer light energy to the reaction-center chlorophyll.

3. What is directly associated with photosystem I?

   It is directly associated with receiving electrons from the thylakoid membrane's electron transport chain.

4. How can one detect the lack of photosystem II in certain photosynthetic organisms?

   The most effective method is to test for the liberation of O2 in the presence of light, as photosystem II is responsible for splitting water to

Infectious Diseases: Causes, Symptoms & Prevention

Common Infectious Conditions

• CP (Common cold): virus - headache, loss of appetite. Keep hydrated.
• Influenza: virus - high fever, pains in back and muscles. Rest.
• Measles: virus - vomiting, diarrhea, sweating. MMR vaccine.
• Tuberculosis: bacteria - weight loss, fever. Antibiotics.
• Bubonic plague: Yersinia pestis (bacterium) - muscle cramps, chills.
• Cholera: bacterial infection - leg cramps, vomiting, diarrhea. Antibiotics.
• Tetanus: bacteria - stiffness. Vaccination or antitoxin.
• Malaria: protozoa - fever, muscle pain, diarrhoea. Medicines.
• Sleeping sickness: protozoa - fever, itchiness. Different medications.
• Athlete's foot: fungus - infection of the skin. Pharmacy creams.
• Ringworm: fungus - a red rash

Fundamental Knowledge Challenge

Earth Science & Geology

Formation of Smooth Stones

Which of these is the best explanation of how a smooth, round stone becomes smooth? It was in a stream for a long time.

Key Processes of the Water Cycle

Processes of the water cycle include: Evaporation, condensation, sublimation, and so on.

Formation of Water Droplets

The process by which water droplets form is: Condensation.

Astronomy & Physics

Defining Astronomical Bodies

Any astronomical body that revolves around a larger body is called a: Satellite.

Understanding Friction

Friction is the force that: Opposes motion between two surfaces.

Measuring Liquid Resistance to Flow

When scientists measure a liquid's resistance to flow, they are measuring its: Viscosity.

Biology

Transcription: From DNA to RNA

Steps of Transcription

Initiation

• Transcription begins when transcription factors bind to a specific nucleotide sequence of DNA known as the promoter region or the "TATAA box."
• These transcription factors signal RNA polymerase II to attach to the DNA at the promoter.

Elongation

• Once attached to the DNA, RNA polymerase synthesizes a single-stranded RNA molecule in a 5’ → 3’ direction.
• RNA nucleotides are added to the growing polymer, which are complementary to the DNA template.

Termination

• Eventually, RNA polymerase will reach a termination sequence in the DNA.
• This causes RNA polymerase to release the newly synthesized mRNA and to dislodge from the DNA.

Note: The template strand is also known as the antisense strand,

Cellular Processes and Plant Adaptations

41. CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they fix CO2 into organic acids during the night.

Basics of Reproduction and Chromosomes

42. Asexual reproduction requires 1 individual.

43. Eukaryotic chromosomes differ from prokaryotic chromosomes in that they are housed in a membrane-enclosed nucleus.

44. Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called sister chromatids.

The Cell Cycle and Mitosis

45. The genetic material is duplicated during the S phase.

46. Which of the following occurs during interphase? Cell growth and duplication of the chromosomes.

Cancer and Cell Regulation

1. The out-of-control... Continue reading "Essential Biology Concepts: Cell Division and Genetics" »