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October, 2006
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Vacuoles: Any spaces or cavities within a cell. They may function in digestion, storage, secretion, or excretion.

C4 Pathway and CAM

JoVE 10754

Some plants, like sugar cane and corn, that grow in hot conditions, use an alternative process called the C4 pathway to fix carbon. The cycle begins with CO2 from the atmosphere entering mesophyll cells where it is used to generate oxaloacetate—a four-carbon molecule—from phosphoenolpyruvate (PEP). Oxaloacetate is then converted to malate and transported to bundle sheath cells, where the oxygen concentration is low. There, CO2 is released from malate and enters the Calvin Cycle where it is converted into sugars. The CAM pathway is carried out in plants like cacti that also need to conserve water during the day. CAM plants let CO2 into the leaves at night and produce malate that is stored in vacuoles until the following day. The malate is then released from vacuoles and processed in the Calvin Cycle. The C4 pathway separates the different processes locally, while the CAM pathway separates them chronologically. Some plants, like corn and sugarcane, have evolved alternative ways to fix carbon that help avoid water loss in hot, dry environments. One such method is the C4 pathway. In the first step, CO2 enters mesophyll cells, and the enzyme phosphoenolpyruvate (PEP) carboxylase adds it to the 3-carbon compound PEP to form the 4-carbon compound oxaloacetate. Oxaloacetate is then converted

 Core: Biology

Cell Structure- Concept

JoVE 10587


Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, multicellular organisms like elephants and giant redwood trees. In the mid 19th century, the Cell Theory was proposed to define a cell, which states:

Every living organism is made up of one or more cells.
The cells…

 Lab Bio

Tonicity in Plants

JoVE 10703

Tonicity describes the capacity of a cell to lose or gain water. It depends on the quantity of solute that does not penetrate the membrane. Tonicity delimits the magnitude and direction of osmosis and results in three possible scenarios that alter the volume of a cell: hypertonicity, hypotonicity, and isotonicity. Due to differences in structure and physiology, tonicity of plant cells is different from that of animal cells in some scenarios. Unlike animal cells, plants thrive when there is more water in their surrounding extracellular environment compared to their cytoplasmic interior. In hypotonic environments, water enters the cell via osmosis and causes it to swell because there is a higher concentration of solutes inside plant cells than outside. The force, that is generated when an influx of water causes the plasma membrane to push against the cell wall, is called turgor pressure. In contrast to animal cells, plant cells have rigid cell walls that limit the osmosis-induced expansion of the plasma membrane. By limiting expansion, the cell wall prevents the cell from bursting and causes plants to stiffen (i.e., become turgid). Turgidity allows plants to hold themselves upright instead of wilting. Plants wilt if they cannot take up sufficient water. In such a scenario, their extracellular surrounding becomes hypertonic, causing water to leave the

 Core: Biology


JoVE 10709

Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells envelop the particles in spherical membranes called vesicles or vacuoles. Vesicles that transport material into the cell are built from the cell membrane. These vesicles encapsulate external molecules and transport them into the cell in a process called endocytosis. Pinocytosis (“cellular drinking”) is one of three main types of endocytosis. In pinocytosis, the cell repeatedly takes in fluid from the surrounding environment using tiny vesicles. Pinocytosis occurs in many cell types. In the small intestine, bristle-like protrusions called microvilli use pinocytosis to absorb nutrients from food. Egg cells use pinocytosis to obtain nutrients before fertilization. In pinocytosis and other forms of endocytosis, vesicles form when sections of the cell membrane sink inward, creating tear-shaped pockets that surround the material being taken into the cell. In pinocytosis, the imported material consists of fluid and other molecules. As the membrane reconnects, the vesicles pinch off, separating from the membrane. In the process, the vesicles enter the cell, taking the enclosed substances with them. Specific characteristics distinguish pinocytosis from the other forms of endocytosis&mdash

 Core: Biology

Cell Structure - Prep Student

JoVE 10631

Visualizing Onion and Cheek Cells
Immediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and cut the onion in half with a knife. Pull apart the layers of the onion. The thin, nearly transparent film layers within the onion will be used by the students.
Place the onion film into a Petri…

 Lab Bio

An Introduction to Cell Death

JoVE 5649

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as cell injury, low nutrient levels, or signaling proteins. Whereas necrosis is considered to be an “accidental” or unexpected form of cell death, evidence exists that apoptosis and autophagy are both programmed…

 Cell Biology
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