This organelle forms a network of intracellular canals within the cytoplasm. It exists in two forms: rough ER and smooth ER. Rough ER is ER with ribosomes attached. Here is where proteins and other biomolecules can be made and transported through the ER’s canal network to other parts of the cell and outside the cell. Smooth ER is without ribosomes and its function is less clear, although it appears that smooth ER may be the site of steroid synthesis in the testes and adrenal glands. Evidence also indicates that lipid and cholesterol metabolism occur in smooth ER of the liver cells.
The Golgi apparatus consists of stacks of tiny oblong sacs embedded in the cytoplasm of the cell near the nucleus. Research has presented convincing evidence that the Golgi sacs are responsible for synthesis of carbohydrate biomolecules (Cooper, 2000). These carbohydrates are then combined with the proteins made in the ER to form glycoproteins. Glycoproteins play an important part in the function of enzymes, hormones, antibodies, and structural proteins, among other things. As the amount of glycoprotein produced within the Golgi sac increases, the sac becomes inflated. At this point, small spheres form along the surface of the Golgi sac and break away. These globules contain the glycoproteins, which are transported to the cell membrane and then out of the cell into the bloodstream to be used by other cells.
Lysosomes are other sac-like structures whose size and shape change with the degree of their activity. They start out small, and as they become active, they increase in size. Lysosomes contain a variety of enzymes, which act as catalysts, directing all major biochemical reactions. These enzymes are capable of breaking down all of the main components of the cell, such as protein, fat, and nucleic acid. The broken-down products formed inside the lysosome can be used as raw materials for synthesis of new biomolecules or for energy. In this way, lysosomes serve to contain and isolate these important cellular digestive enzymes and thereby prevent complete digestion of the cell. They also play a limited role in the engulfing and destroying of bacteria that may enter the cell.
After the nucleus, mitochondria are probably the most known and talked about organelle in the athletic arena, due to their role in the generation of energy. Referred to as the powerhouse of the cell, mitochondria are small, complex organelles that resemble a sausage in shape. They consist of a smooth outer membrane, which surrounds an inner membrane, forming a sac within a sac. The inner membrane is folded like an accordion, and it forms a number of inward extensions called cristae.
The enzymes that are essential for making one of the most important biomolecules, adenosine triphosphate (ATP), exist in the mitochondria. It is here in the mitochondria that ATP stores energy which is used to power biological functions. Within the inner mitochondria membrane, catabolic enzymes (which are involved in breaking down of biomolecules) catalyze reactions that provide the cells with life-sustaining energy.
Nutrients such as glucose and fatty acids are made of carbon atoms linked together with chemical bonds. When these chemical bonds are broken, energy is released. Within the intricate confines of the mitochondria, this energy can be trapped and stored in the ATP molecule,
which can then make use of it. In other words, the energy from glucose is transferred to the ATP molecule, and the energy is now in a form that the body can use.
These biological structures are the main components of the cell. Some of the other structures include glycogen granules, which store glycogen and enzymes for glycogen breakdown and synthesis. Although not a structure, the cytoplasm is worth mentioning. This liquid portion of the cell is the site of many reactions, including gluconeogenesis (glucose and glycogen formation), fatty acid synthesis, activation of amino acids, and glycolysis (the first phase of breaking down glucose to make ATP molecules for energy).
glycogen granule: Structure of the cell that stores glycogen and enzymes for glycogen breakdown and synthesis.
gluconeogenesis: Chemical process that converts lactate and pyruvate back into glucose.
glycolysis: The metabolic process that creates energy from the splitting of glucose to form pyruvic acid or lactic acid and ATP.
While the cell is the fundamental unit of life, tissues are the fundamental units of function and structure for the human body. Tissues are defined as the aggregation of cells bound together working to perform a common function. For example, cells of the adrenal cortex form a glandular tissue that produces several hormones, including androgens, glucocorticoids, and mineralocorticoids. Muscle tissue is made up of special muscle fiber cells that collectively have the ability to shorten and form the basis of contractile tissue.
This section introduces you to the basic tissues that make up the body. The human body is considerably complex, yet the tissues that form it can be separated into four basic groups: epithelial, connective, muscle and nervous tissue.
Epithelial tissue is found throughout the body: as a continuous external layer over the whole body (skin), on most of the body’s inner cavities, and making up the body’s several glands. On the surface, epithelial tissue functions to protect underlying cells from bacterial invasion, adverse chemicals, and drying. On the inside, it functions as
absorbing and secreting tissue, such as in digestive system glands. Epithelial tissue is divided into four groups, which are distinguished according to the shape of the cells that comprise them. They are as follows:
- Squamous epithelium is composed of one layer of flat cells. It is located in the linings of the mouth, esophagus, and blood and lymphatic vessels. Substances can easily diffuse through this layer of cells.
- Cuboidal epithelium is made of cube-shaped cells as found in the lining of kidney tubules.
- Columnar epithelium resembles a column or pillar in shape. These cells are widespread throughout the body, forming linings in the digestive and respiratory tracts. They function as secretory cells or absorptive cells. Some also have small hairs, called cilia, which beat rhythmically and move materials out of a passage, as in the respiratory tract where cilia serve to sweep out foreign matter that may pass into the lungs.
- Glandular epithelial cells secrete mucus and hormones, such as those of the salivary and thymus glands.
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Psalm 109:4 NKJV In return for my love they are my accusers, But I give myself to prayer.
Psalm 122:6 NKJV Pray for the peace of Jerusalem: “May they prosper who love you.
Psalm 141:2 NKJV Let my prayer be set before You as incense, The lifting up of my hands as the evening sacrifice.
Psalm 143:1 NKJV Hear my prayer, O Lord, Give ear to my supplications! In Your faithfulness answer me, And in Your righteousness.
Proverbs 15:29 ESV The Lord is far from the wicked, but he hears the prayer of the righteous.
Jeremiah 29:12 ESV Then you will call upon me and come and pray to me, and I will hear you.
Matthew 6:6 ESV But when you pray, go into your room and shut the door and pray to your Father who is in secret. And your Father who sees in secret will reward you.
Matthew 6:9-13 ESV Pray then like this: “Our Father in heaven, hallowed be your name.[a] 10 Your kingdom come, your will be done,[b] on earth as it is in heaven. 11 Give us this day our daily bread,[c] 12 and forgive us our debts, as we also have forgiven our debtors. 13 And lead us not into temptation, but deliver us from evil.
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