Basic physiology

BASIC PHYSIOLOGY

Levels of Organization:

1. Atoms are the simplest level. 2. Two or more atoms comprise a molecule. 3. Macromolecules are large, biologically important molecules inside cells. 4. Organelles are aggregates of macromolecules used to carry out a specific function in the cell. 5. Cells are the basic living unit. 6. Tissues are groups of cells functioning together. 7. Groups of tissues form organs. 8. Groups of organs function together as organ systems. 9. Organ systems functioning together make up an organism.

The human body is the sum of its parts and these parts can be studied at a variety of levels of organization.

A. Compounds that contain both hydrogen and carbon are called organic, the others are inorganic
Chemical Constituents of Cells:

1. Water a. Water is the most abundant compound in living things and makes up two-thirds of the weight of adults. b. Water is an important solvent so most metabolic reactions occur in water.

B. Inorganic Substances

2. Oxygen a. Oxygen is needed to release energy from nutrients and is used to drive the cell's metabolism. 3. Carbon Dioxide a. Carbon dioxide is released as a waste product during energy-releasing metabolic reactions.

B. Inorganic Substances

4. Inorganic Salts a. Inorganic salts are the sources of ions of sodium, chloride, potassium, calcium, magnesium, phosphate, carbonate, bicarbonate, and sulfate. b. These electrolytes play important roles in many of the body's metabolic processes.

B. Inorganic Substances

1. Carbohydrates a. Carbohydrates provide energy for cellular activities and are composed of carbon, hydrogen, and oxygen. b. Carbohydrates are made from monosaccharides (simple sugars); disaccharides are two monosaccharides joined together; complex carbohydrates (polysaccharides), such as starch, are built of many sugars.

C. Organic Substances:

a. Lipids are insoluble in water and include fats, phospholipids, and steroids. b. Fats supply energy, are composed of oxygen, carbon, and hydrogen, and are built from glycerol and three fatty acids.
2. Lipids:

c. Phospholipids contain glycerol, two fatty acids, and a phosphate group, and are important in cell structures. d. Steroids are complex ring structures, and include cholesterol, which is used to synthesize the sex hormones.
2. Lipids:

a. Proteins have a great variety of functions in the body---as structural materials, as energy sources, as certain hormones, as receptors on cell membranes, as antibodies, and as enzymes to catalyze metabolic reactions.
3. Proteins:

b. Proteins contain C, O, H, and nitrogen atoms; some also contain sulfur. c. Building blocks of proteins are the amino acids, each of which has a carboxyl group, an amino group and a side chain called the R group.
3. Proteins:


d. Proteins have complex shapes held together by hydrogen bonds. e. Protein shapes, which determine how proteins function, can be altered (denatured) by pH, temperature, radiation, or chemicals.
3. Proteins:


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a. Nucleic acids form genes and take part protein synthesis. b. They contain carbon, hydrogen, oxygen, nitrogen, and phosphorus, which are bound into building blocks called nucleotides.
4. Nucleic Acids:

4. Nucleic Acids:

Cells

A. The human body consists of 75 trillion cells that vary considerably in shape and size yet have much in common. B. Differences in cell shape make different functions possible.
Introduction:

A. A composite cell includes many different cell structures. B. A cell consists of three main parts---the nucleus, the cytoplasm, and the cell membrane. C. Within the cytoplasm are specialized organelles that perform specific functions for the cell.
A Composite Cell:

1. The cell membrane regulates the movement of substances in and out of the cell, participates in signal transduction, and helps cells adhere to other cells.
D. Cell Membrane:


2. General Characteristics a. The cell membrane is extremely thin and selectively permeable. b. It has a complex surface with adaptations to increase surface area.
D. Cell Membrane:


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3. Cell Membrane Structure: a. The basic framework of the cell membrane consists of a double layer of phospholipids, with fatty acid tails turned inward. b. Molecules that are soluble in lipids (gases, steroid hormones) can pass through the lipid bilayer.
D. Cell Membrane:

c. Embedded cholesterol molecules strengthen the membrane and help make the membrane less permeable to water-soluble substances. d. Many types of proteins are found in the cell membrane, including transmembrane proteins and peripheral membrane proteins.
D. Cell Membrane:

e. Membrane proteins perform a variety of functions and vary in shape. f. Some proteins function as receptors on the cell surface, starting signal transduction. g. Other proteins aid the passage of molecules and ions.
D. Cell Membrane:


h.Proteins protruding into the cell anchor supportive rods and tubules.i.Still other proteins have carbohydrates attached; these complexes are used in cell identification. Membrane proteins called cellular adhesion molecules (CAMs) help determine one cell’s interactions with others. D. Cell Membrane:


1. The cytoplasm consists of a clear liquid (cytosol), a supportive cytoskeleton, and networks of membranes and organelles. a. Endoplasmic reticulum is made up of membranes, flattened sacs, and vesicles, and provides a tubular transport system inside the cell.


E. Cytoplasm:

1a1. With ribosomes, endoplasmic reticulum (ER) is rough ER, and functions in protein synthesis. 1a2. Without ribosomes, it is smooth ER, and functions in lipid synthesis.
E. Cytoplasm: (cont.)


b. Ribosomes are found with ER and are scattered throughout the cytoplasm. They are composed of protein and RNA and provide a structural support for the RNA molecules that come together in protein synthesis.
E. Cytoplasm: (cont.)

E. Cytoplasm: (cont.)

e. Lysosomes are the "garbage disposals" of the cell and contain digestive enzymes to break up old cell components and bacteria. f. Peroxisomes contain enzymes that function in the synthesis of bile acids, breakdown of lipids, degradation of rare biochemicals, and detoxification of alcohol.
E. Cytoplasm: (cont.)


F. Cell Nucleus: 1. The fairly large nucleus is bounded by a double-layered nuclear membrane containing relatively large nuclear pores that allow the passage of certain substances.
E. Cytoplasm: (cont.)

A. The cell membrane controls what passes through it. Mechanisms of movement across the membrane may be passive, requiring no energy from the cell (diffusion, facilitated diffusion, osmosis, and filtration) or active mechanisms, requiring cellular energy (active transport, endocytosis, and exocytosis).


Movements Through Cell Membranes

C. Passive Mechanisms 1. Diffusion a. Diffusion is caused by the random motion of molecules and involves the movement of molecules from an area of greater concentration to one of lesser concentration until equilibrium is reached.
Movements Through Cell Membranes (cont.)

C1b. Diffusion enables oxygen and carbon dioxide molecules to be exchanged between the air and the blood in the lungs, and between blood and tissue cells.
Movements Through Cell Membranes (cont.)

C2. Facilitated Diffusion a. Facilitated diffusion uses membrane proteins that function as carriers to move molecules (such as glucose) across the cell membrane. b. The number of carrier molecules in the cell membrane limits the rate of this process.

Movements Through Cell Membranes

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C3. Osmosis a. Osmosis is a special case of diffusion in which water moves from an area of greater water concentration (where there is less osmotic pressure) across a selectively permeable membrane to an area of lower water concentration (where there is greater osmotic pressure).
Movements Through Cell Membranes


A solution with the same osmotic pressure as body fluids is called isotonic; one with higher osmotic pressure than body fluids is hypertonic; one with lower osmotic pressure is hypotonic.
Movements Through Cell Membranes


C4. Filtration a. Because of hydrostatic pressure, molecules can be forced through membranes by the process of filtration. Blood pressure is a type of hydrostatic pressure.
Movements Through Cell Membranes


D. Active Mechanisms 1. Active Transport a. Active transport uses ATP to move molecules from areas of low concentration to areas of high concentration through carrier molecules in cell membranes. b. As much as 40% of a cell's energy supply may be used to fuel this process.
Movements Through Cell Membranes

D1c.The union of the specific particle to be transported with its carrier protein triggers the release of cellular energy (ATP), which in turn alters the shape of the carrier protein, releasing the particle to the other side of the membrane.
Movements Through Cell Membranes (cont.)

D1d. Particles that are actively transported include sugars, amino acids, and sodium, potassium, calcium, and hydrogen ions, as well as nutrient molecules in the intestines.

Movements Through Cell Membranes (cont.)

D2. Endocytosis and Exocytosis a. In endocytosis, molecules that are too large to be transported by other means are engulfed by an invagination of the cell membrane and carried into the cell surrounded by a vesicle. b. Exocytosis is the reverse of endocytosis.
Movements Through Cell Membranes (cont.)


D2c.Three forms of endocytosis are pinocytosis, phagocytosis, and receptor-mediated endocytosis. i.Pinocytosis is a form of endocytosis in which cells engulf liquids. ii.Phagocytosis is a form of endocytosis in which the cell takes in larger particles, such as a white blood cell engulfing a bacterium. iii.Receptor-mediated endocytosis allows the cell to take in very specific molecules (ligands) that pair up with specific receptors on the cell surface.
Movements Through Cell Membranes (cont.)