Content Summary:

This section comprises Chapter 3 which discusses cell structure and genetic control, and Chapter 6 which discusses interactions between cells and the extracellular environment. Both chapters detail how complicated cells are despite their invisibility to us without the use of an electron microscope.



Summary #1
Cellular composition involves many types of cells that have distinct shape, size and function but share common characteristics with each other. All have a plasma membrane which surrounds and shapes the cell and is involved in intercellular communication. Within the plasma membrane is an aqueous cytoplasm that holds all the organelles. The nucleus of the cell contains DNA (deoxyribonucleic acid) which is the genetic material of the cell and directs all it's activities, and one or more nucleoli which produce ribosomes, the synthesizers of proteins.
mitochondria.jpg

Summary #2
Mitochondria are organelles within the cell that are the site of energy production. Numbers within cells range from a hundred to a few thousand and they come in various sizes and shapes but have the same basic structure. Mitochondria have an inner membrane with many folds called cristae, an outer membrane and their own DNA.



Summary #3

Osmosis is the net diffusion of water across a cell membrane. Three things are needed for this to occur: 1) the cell membrane must be selectively permeable, 2) there must be a difference in the concentration levels of the solute on both sides of the membrane, and 3) the membrane must be impermeable to the solute. When a solute can not pass through a membrane, it is osmotically active. Water must be more concentrated on one side of the membrane than the other for osmosis to occur.



Application:
Cell composition is important to my profession in that my patients will be dealing with illnesses that are due to a change in cell physiology. If cell physiology is not working properly, a patient will be dealing with the illness that has been caused because of it. As an OTA, my patients will have illnesses that will keep them from performing ADL as they once did. My job is to know and understand the outcomes of those illnesses and provide treatment to the patient to help them perform ADL the best that they can.


Essential Questions;
Cells are considered the basic structure and function of the human body because we are composed of cells and all the processes of life occur within them. There are about 75 trillion cells within us, each highly specialized with a specific function. The structure of a cell determines what its function is. Similar types of cells are grouped together to make up specific tissues, two or more tissues comprise an organ, and groups of organs make up systems with the body.

Passive transport is the net movement of molecules and ions from higher to lower concentration across a membrane and does not require energy. Active transport is the net movement of molecules and ions from a lower to higher concentration across a membrane that does require energy. The differences are: 1) energy used in active transport and no energy used in passive transport, and 2) active transport moves against the concentration gradient while passive moves down a concentration gradient. The similarities are that both tranport molecules to be used within cells. Examples of passive transport are transport of glucose by GLUT carriers where it is always transported down its concentration gradient, transport of urea within renal tubules and dialysis, which is simple diffusion. Examples of active transport are transport of Na+ and glucose from the extracellular fluid in the lumen of the intestines, re-absorption of glucose and amino acids, and kidney tubules across the epithelial cell's membrane, and the transport of polypeptides and proteins through the cell membrane. Cells need to bring molecules in because they are needed for functions that the cell is responsible for, as well as nutrients for cell health. Molecules are released out cells because they are no longer needed, they may be waste or may be hormone secretions.

Cells communicate through a process called cell signaling. There are three types of signaling: 1) endocrine, 2) paracrine and 3) synaptic. Chemical signals go to a target cell which needs a receptor protein to pass the message on. A cell will only receive the message if its specific receptor protein brings it. A cell can have a million receptor proteins. Receptor proteins may be located on the cell membrane, or intracellularly within the cytoplasm or nucleus. The location depends on whether the regulatory molecule can penetrate the plasma membrane of the target cell.

References: Human Physiology by Stuart Ira Fox, Anatomy and Physiology by Stanley E Gunstream