Endoplasmic Reticulum: Key Cellular Functions

Rough ER: Exportable Protein Synthesis

Proteins destined for export enter the Rough Endoplasmic Reticulum (RER) lumen through a channel. The signal peptide is cleaved by a signal peptidase, leaving the mature protein ready for further processing and export.

Smooth ER: Lipid Synthesis and Metabolism

Lipid synthesis and metabolism primarily occur in the Smooth Endoplasmic Reticulum (SER), although some fatty acids and phospholipids are synthesized in mitochondria. The SER is crucial for synthesizing:

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Human Blood: Components and Functions

Blood

The human body contains several extracellular fluids that constitute the internal environment. These include the interstitial fluid of the intercellular matrix and circulating fluids such as blood and lymph. These fluids act as intermediaries between the highly variable external environment and the intracellular environment, where metabolic reactions occur.

Blood is a liquid tissue, part of the internal environment, that circulates through blood vessels.

Blood performs a wide variety of functions:

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Mollusk and Annelid Characteristics & Classes

Mollusks: Diverse Invertebrates

Mollusks are a diverse group of invertebrates, including snails, clams, squids, and octopuses. They have soft bodies, often protected by a shell, and exhibit a wide range of adaptations.

Mollusk Body Plan

  • Head-foot: Includes the sensory organs and movement structures.
  • Visceral mass: Contains internal organs like the heart, digestive system, and reproductive organs.
  • Mantle: Secretes the shell and forms the mantle cavity, housing gills or lungs.
  • Radula: A specialized feeding
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Evolutionary Biology: Darwin, Wallace, and Evidence of Evolution

Evolution and Natural Selection

Evolution occurs through mutations. Individuals do not change; they pass changes to their offspring, leading to population change.

Alfred Russell Wallace and Darwin’s Contemporary

Alfred Russell Wallace was a naturalist who independently conceived the theory of natural selection, similar to Darwin’s. Although they corresponded by letters, they never met in person. Wallace’s contributions were not as widely recognized as Darwin’s for several reasons. Wallace mistakenly

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Human Circulatory and Excretory Systems Explained

Blood Components and Function

Blood is a red liquid that circulates through blood vessels, carrying oxygen, nutrients, carbon dioxide, and collected waste products. It consists of plasma (55%) and blood cells (45%), totaling approximately 5 liters in the average adult.

Plasma Composition

Plasma is a yellowish liquid containing water, salts, minerals, hormones, and proteins.

Blood Cells: Types and Roles

Blood cells are formed in the bone marrow.

Red Blood Cells (Erythrocytes)

These are the most abundant

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Defining Life: Core Characteristics and Cellular Basis

Core Characteristics of Living Things

All living things share fundamental characteristics:

  • Life Cycle: They have a life cycle that includes birth (origin) and death.
  • Chemical Composition: They share a similar chemical composition, primarily based on organic matter.
  • Cellular Structure: They are composed of one or more basic units called cells. Cells are the smallest microscopic units considered to be alive.
  • Life Functions: They perform essential life functions:

Nutrition

Nutrition is the set of processes

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