تورتورا , جابتر ٣

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nucleus

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chromosome (chromo- colored), a single molecule of DNA associated with several proteins, contains thousands of hereditary units called genes that control most aspects of cellular structure and function.

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The Lipid Bilayer

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About 75% of the membrane lipids are phospholipids, lipids that contain phosphorus. Present in smaller amounts are cholesterol (about 20%), a steroid with an attached OOH (hydroxyl) group, and various glycolipids (about 5%), lipids with attached carbohydrate groups.

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1 FUNCTIONS OF THE PLASMA MEMBRANE

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Helps identify the cell to other cells (e.g., immune cells).

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The lipid bilayer portion of the plasma membrane is highly permeable to nonpolar molecules such as

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oxygen (O2), carbon dioxide (CO2), and steroids;

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moderately permeable to small, uncharged polar molecules, such as

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water and urea (a waste product from the breakdown of amino acids)

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and impermeable

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to ions and large, uncharged polar molecules, such as glucose.

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water and urea

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The permeability of the lipid bilayer to water and urea is an unexpected property given that they are polar molecules. These two molecules are thought to pass through the lipid bilayer in the following way. As the fatty acid tails of membrane phospholipids and glycolipids randomly move about, small gaps briefly appear in the hydrophobic environment of the membrane’s interior. Because water and urea are small polar molecules that have no overall charge, they can move from one gap to another until they have crossed the membrane.

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oxygen molecules and sodium ions (Na

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more concentrated in the extracellular fluid than

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active processes,

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cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient.

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In diffusion, a substance moves down its concentration gradient.

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Passive transport

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emphysema/Surface area

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reduce the surface area. This slows the rate of oxygen diffusion and makes breathing more difficult.

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In pneumonia, Diffusion distance.

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fluid collects in the lungs; the additional fluid increases the diffusion distance because oxygen must move through both the built-up fluid and the membrane to reach the bloodstream.

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types of diffusion:

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simple diffusion, facilitated diffusion, and osmosis.

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simple diffusion.

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Nonpolar, hydrophobic molecules move across the lipid bilayer through the process of simple diffusion. Such molecules include oxygen, carbon dioxide, and nitrogen gases; fatty acids; steroids; and fat-soluble vitamins (A, D, E, and K). Small, uncharged polar molecules such as water, urea, and small alcohols also pass through the lipid bilayer by simple diffusion. Simple diffusion through the lipid bilayer is important in the movement of oxygen and carbon dioxide between blood and body cells, and between blood and air within the lungs during breathing. It also is the route for absorption of some nutrients and excretion of some wastes by body cells.

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In simple diffusion, a substance moves across the lipid bilayer of the plasma membrane without the help of membrane transport proteins.

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In facilitated diffusion, a substance moves across the lipid bilayer aided by a channel protein or a carrier protein.

Front 16

water and urea

Back 16

The permeability of the lipid bilayer to water and urea is an unexpected property given that they are polar molecules. These two molecules are thought to pass through the lipid bilayer in the following way. As the fatty acid tails of membrane phospholipids and glycolipids randomly move about, small gaps briefly appear in the hydrophobic environment of the membrane’s interior. Because water and urea are small polar molecules that have no overall charge, they can move from one gap to another until they have crossed the membrane.

Front 17

oxygen molecules and sodium ions (Na

Back 17

more concentrated in the extracellular fluid than

Front 18

active processes,

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cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient.

Front 19

In diffusion, a substance moves down its concentration gradient.

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Passive transport

Front 20

emphysema/Surface area

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reduce the surface area. This slows the rate of oxygen diffusion and makes breathing more difficult.

Front 21

In pneumonia, Diffusion distance.

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fluid collects in the lungs; the additional fluid increases the diffusion distance because oxygen must move through both the built-up fluid and the membrane to reach the bloodstream.

Front 22

types of diffusion:

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simple diffusion, facilitated diffusion, and osmosis.

Front 23

simple diffusion.

Back 23

Nonpolar, hydrophobic molecules move across the lipid bilayer through the process of simple diffusion. Such molecules include oxygen, carbon dioxide, and nitrogen gases; fatty acids; steroids; and fat-soluble vitamins (A, D, E, and K). Small, uncharged polar molecules such as water, urea, and small alcohols also pass through the lipid bilayer by simple diffusion. Simple diffusion through the lipid bilayer is important in the movement of oxygen and carbon dioxide between blood and body cells, and between blood and air within the lungs during breathing. It also is the route for absorption of some nutrients and excretion of some wastes by body cells.

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In simple diffusion, a substance moves across the lipid bilayer of the plasma membrane without the help of membrane transport proteins.

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In facilitated diffusion, a substance moves across the lipid bilayer aided by a channel protein or a carrier protein.

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carrier-mediated facilitated diffusion

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Glu

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Glucose

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عنده ٥ ترانسبورتات

١

٢

٣

٤

٥

الاهم هو ٤الي موجود بالعضلات و الخلايا الدهنيه

وهذا هو الوحيد الي يحتاج انسولين حت يفتح

اما البقيه فلا تحتاج انسولين

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diabetes mellitus

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An inability to produce or utilize insulin is

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diabetes mellitus

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An inability to produce or utilize insulin is

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hypotonic solution (

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water molecules enter the cells faster than they leave, causing the RBCs to swell and eventually to burst. The rupture of RBCs in this manner is called hemolysis

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water molecules move out of the cells faster than they enter, causing the cells to shrink. Such shrinkage of cells is called crenation

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hypertonic solution

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hypertonic solution such as mannitol (sugar alcohol) is useful to treat

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patients who have cerebral edema, excess interstitial fluid in the brain.

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given either orally or through an IV, can be used to treat people who are dehydrated.

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Hypotonic solutions,

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poison cyanide

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are lethal because they shut down active transport in cells throughout the body. A typical body cell expends about 40% of the ATP it generates on primary active transport.

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Digitalis

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often is given to patients with heart failure, a condition of weakened pumping action by the heart. Digitalis exerts its effect by slowing the action of the sodium–potassium pumps, which lets more Na accumulate inside heart muscle cells. The result is a decreased Na concentration gradient across the plasma membrane, which causes the Na –Ca 2 antiporters to slow down. As a result, more Ca 2 remains inside heart muscle cells. The slight increase in the level of Ca 2 in the cytosol of heart muscle cells increases the force of their contractions and thus strengthens the force of the heartbeat. •

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the concentration of calcium ions (Ca2) is low in the cytosol

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because Na–Ca 2antiporters eject calcium ions.

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help regulate the cytosol’s pH (H concentration) by expelling excess H .

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Na –H antiporters

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Na –glucose and Na –amino acid symporters

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dietary glucose and amino acids are absorbed into cells that line the small intestine

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Degradation in lysosomes. /LDL

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vesicles, which contain the LDL particles, bud off the endosome and soon fuse with a lysosome. Lysosomes contain many digestive enzymes. Certain enzymes break down the large protein and lipid molecules of the LDL particle into amino acids, fatty acids, and cholesterol. These smaller molecules then leave the lysosome. The cell uses cholesterol for rebuilding its membranes and for synthesis of steroids, such as estrogen. Fatty acids and amino acids can be used for ATP production or to build other molecules needed by the cell.

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Viruses and Receptor-

Mediated Endocytosis

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Although receptor-mediated endocytosis normally imports needed materials, some viruses are able to use this mechanism to enter and infect body cells. For example, the human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), can attach to a receptor called CD4. This receptor is present in the plasma membrane of white blood cells called helper T cells. After binding to CD4, HIV enters the helper T cell via receptormediated endocytosis. •

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Exocytosis

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(1) secretory cells that liberate digestive enzymes, hormones, mucus, or other secretions and (2) nerve cells that release substances called neurotransmitters

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Cytosol

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The cytosol (intracellular fluid) is the fluid portion of the cytoplasm that surrounds organelles and constitutes about 55% of total cell volume.

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Tay-Sachs disease

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Some disorders are caused by faulty or absent lysosomal enzymes. For instance, Tay-Sachs disease (TA¯-SAKS), which most often affects children of Ashkenazi (eastern European Jewish) descent, is an inherited condition characterized by the absence of a single lysosomal enzyme called Hex A. This enzyme normally breaks down a membrane glycolipid called ganglioside G M2 that is especially prevalent in nerve cells. As the excess ganglioside GM2 accumulates, the nerve cells function less efficiently. Children with Tay-Sachs disease typically experience seizures and muscle rigidity. They gradually become blind, demented, and uncoordinated and usually die before the age of 5. Tests can now reveal whether an adult is a carrier of the defective gene. •

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Peroxisomes/oxidized

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remove hydrogen atoms from) various organic substances

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The two types of cell division

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somatic cell division and reproductive cell division

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nuclear division called

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mitosis

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cytoplasmic division called

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cytokinesis

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Cancer

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cell division.

When cells in a part of the body divide without control, the excess tissue that develops is called a tumor or neoplasm

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carcinomas

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malignant tumors that arise from epithelial cells