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The Pressure Flow Model in a Plant

By: HWC, Views: 7096

The vascular system of plants has two transport tissues, called xylem and phloem. Xylem transports water and minerals, while phloem transports a variety of dissolved substances, including sugars and amino acids, throughout the plant. Water in the xylem always moves up, in the direction from th...

Pressure Flow Model Animation

By: HWC, Views: 6989

This apparatus of beakers A and funnels simulates the flow of a sucrose solution in the phloem of a plant. The funnels and connecting tube represent a sieve tube of the phloem. Differentially permeable membranes cap the funnels at the source and sink ends, allowing water, but not sucrose, to cros...

Four Giant Convection Cells oF Earth

By: HWC, Views: 7038

Earth Has Four Giant Convection Cells Earth's climates range from dry and cold at the poles to wet and warm at the equator. These climates are dictated largely by the amount of solar radiation that a region receives. Solar radiation warms the Earth and the surrounding air, setting up convection c...

Erythropoietin (EPO)

By: HWC, Views: 7217

■ Secreted by kidney cells when blood oxygen is low. ■ Targets cells in red bone marrow that will become red blood cells. ■ Promotes increased numbers of mature red blood cells. ■ More mature red blood cells carry more oxygen so blood oxygen level is restored to normal.

T cell receptors

By: HWC, Views: 7399

• T cells are responsible for cell-mediated immunity. • Each T cell contains a unique form of T cell receptor (TCR) on its membrane. • These T cell receptors are produced through a process of genetic recombination which is able to produce millions of different variations. • Each T ce...

Cytotoxic T cell receptors, activation, proliferation, differentiation & action

By: HWC, Views: 8025

• Most cells which have CD8 on their surface become cytotoxic T cells (Tc cells). • CD8 T cells recognize a foreign antigen when it is presented in conjunction with the protein, MHC-I. • Nearly all nucleated cells in the body express MHC-I molecules. • T cells that recognize self-pe...

Cardiac conductile cells

By: HWC, Views: 7966

• In order for the heart to function properly, all of its cells must contract in a specific sequence. This sequence is determined by a pathway known as the conduction system. • Cardiac muscle cells have two attributes that enable the conduction system to work: • Connective. Action pot...

Griffith's experiments

By: HWC, Views: 4856

In the late 1920s, Fred Griffith was attempting to develop a vaccine against a bacterium that causes pneumonia. To find out why two strains of the bacteria differed in their deadliness, he injected mice with four different mixtures. Mice injected with R cells remained healthy. When Griffith ex...

Cell mediated immune response to a viral infection Animation

By: HWC, Views: 3742

Intracellular pathogens are the targets of cell-mediated immune response. The process begins when a virus infects a macrophage. Another macrophage engulfs the same virus or an antigen from it. In both cells, enzymes cleave the viral antigens into small bits. The fragments move to the cell sur...