Physiology : The Cell Physiology : The Cell & General Physiology& General Physiology

By : aRif WRBy : aRif WR

Human PhysiologyHuman Physiology

► In human physiology, we attempt to explain the specific In human physiology, we attempt to explain the specific characteristics and mechanisms of the human body that make it a characteristics and mechanisms of the human body that make it a living being. living being.

► The very fact that we remain alive is almost beyond our control, for The very fact that we remain alive is almost beyond our control, for hunger makes us seek food and fear makes us seek refuge. hunger makes us seek food and fear makes us seek refuge. Sensations of cold make us look for warmth. Other forces cause us to Sensations of cold make us look for warmth. Other forces cause us to seek fellowship and to reproduce. seek fellowship and to reproduce.

► Thus, the human being is actually an automaton, and the fact that Thus, the human being is actually an automaton, and the fact that we are sensing, feeling, and knowledgeable beings is part of this we are sensing, feeling, and knowledgeable beings is part of this automatic sequence of life; these special attributes allow us to exist automatic sequence of life; these special attributes allow us to exist under widely varying conditions. under widely varying conditions.

Cells as the Living Units of the Body Cells as the Living Units of the Body

► The basic living unit of the body is the cell. Each organ is an The basic living unit of the body is the cell. Each organ is an aggregate of many different cells held together by aggregate of many different cells held together by intercellular supporting structures. intercellular supporting structures.

► Each type of cell is specially adapted to perform one or a few Each type of cell is specially adapted to perform one or a few particular functions. For instance, the red blood cells, particular functions. For instance, the red blood cells, numbering 25 trillion in each human being, transport oxygen numbering 25 trillion in each human being, transport oxygen from the lungs to the tissues. from the lungs to the tissues.

► Although the red cells are the most abundant of any single Although the red cells are the most abundant of any single type of cell in the body, there are about 75 trillion additional type of cell in the body, there are about 75 trillion additional cells of other types that perform functions different from cells of other types that perform functions different from those of the red cell. The entire body, then, contains about those of the red cell. The entire body, then, contains about 100 trillion cells. 100 trillion cells.

► Although the many cells of the body often differ markedly from one another, all Although the many cells of the body often differ markedly from one another, all of them have certain basic characteristics that are alike. For instance, in all of them have certain basic characteristics that are alike. For instance, in all cells, oxygen reacts with carbohydrate, fat, and protein to release the energy cells, oxygen reacts with carbohydrate, fat, and protein to release the energy required for cell function. Further, the general chemical mechanisms for required for cell function. Further, the general chemical mechanisms for changing nutrients into energy are basically the same in all cells, and all cells changing nutrients into energy are basically the same in all cells, and all cells deliver end products of their chemical reactions into the surrounding fluids. deliver end products of their chemical reactions into the surrounding fluids.

► Almost all cells also have the ability to reproduce additional cells of their own Almost all cells also have the ability to reproduce additional cells of their own kind. Fortunately, when cells of a particular type are destroyed from one cause kind. Fortunately, when cells of a particular type are destroyed from one cause or another, the remaining cells of this type usually generate new cells until the or another, the remaining cells of this type usually generate new cells until the supply is replenished. supply is replenished.

► About 60 per cent of the adult human body is fluid, mainly a water solution of About 60 per cent of the adult human body is fluid, mainly a water solution of ions and other substances. Although most of this fluid is inside the cells and is ions and other substances. Although most of this fluid is inside the cells and is called intracellular fluid, about one third is in the spaces outside the cells and is called intracellular fluid, about one third is in the spaces outside the cells and is called extracellular fluid.called extracellular fluid.

► In the extracellular fluid are the ions and nutrients needed by the cells to In the extracellular fluid are the ions and nutrients needed by the cells to maintain cell life. Thus, all cells live in essentially the same environment—the maintain cell life. Thus, all cells live in essentially the same environment—the extracellular fluid. For this reason, the extracellular fluid is also called the extracellular fluid. For this reason, the extracellular fluid is also called the internal environment of the bodyinternal environment of the body

CELLULAR CELLULAR

cells are the cells are the basic structural basic structural and functional and functional units of the units of the human body & human body & there are many there are many different types different types of cells (e.g., of cells (e.g., muscle, nerve, muscle, nerve, blood, and so blood, and so on) on)

TISSUE

a tissue is a group a tissue is a group of cells that perform of cells that perform a specific function a specific function and the basic types and the basic types of tissues in the of tissues in the human body include human body include epithelial, muscle, epithelial, muscle, nervous, and nervous, and connective tissues connective tissues

►ORGAN ORGAN :: an organ consists of 2 or more an organ consists of 2 or more tissues that perform a particular function tissues that perform a particular function (e.g., heart, liver, stomach, and so on)(e.g., heart, liver, stomach, and so on)

►SYSTEM SYSTEM :: an association of organs that an association of organs that have a common function; the major have a common function; the major systems in the human body include systems in the human body include digestive, , nervous, , endocrine, , circulatory, , respiratory, , urinary, and , and reproductive

Type of CellsType of Cells

► There are two main types or categories of cells: There are two main types or categories of cells: prokaryotic cells and and eukaryotic cells. Both of these types of cells have several . Both of these types of cells have several things in common. All cells are surrounded by a things in common. All cells are surrounded by a plasma plasma membranemembrane, which is made of a double layer (a , which is made of a double layer (a bilayerbilayer) of ) of phospholipids. Within this membrane, is the phospholipids. Within this membrane, is the cytoplasm which is which is composed of the fluid and composed of the fluid and organelles of the cell. of the cell.

► Bacteria (Kingdom Monera) are Bacteria (Kingdom Monera) are prokaryotesprokaryotes. They do have . They do have DNA, , but it is not organized into a true nucleus with a nuclear envelope but it is not organized into a true nucleus with a nuclear envelope around it. Also, they lack many other internal organelles such as around it. Also, they lack many other internal organelles such as mitochondria and chloroplasts. mitochondria and chloroplasts.

► TThe he Organisms in the other four kingdoms are Organisms in the other four kingdoms are eukaryoteseukaryotes. Their . Their DNA isDNA isTT organized into a true organized into a true nucleusnucleus surrounded by a surrounded by a nuclear nuclear envelopeenvelope which consists of two bilayer membranes. The nucleus which consists of two bilayer membranes. The nucleus of eukaryotic cells contains the genetic material which chemically of eukaryotic cells contains the genetic material which chemically directs all of the cell’s activities. Usually this is in the form of long directs all of the cell’s activities. Usually this is in the form of long strands of strands of chromatin made of DNA and affiliated proteins. made of DNA and affiliated proteins.

Organization of CellOrganization of Cell

► A typical cell, as seen by the light microscope, is shown in A typical cell, as seen by the light microscope, is shown in Figure below.Figure below.

► It’s two major parts are the nucleus and the cytoplasm. It’s two major parts are the nucleus and the cytoplasm. ► The nucleus is separated from the cytoplasm by a nuclear The nucleus is separated from the cytoplasm by a nuclear

membrane, and the cytoplasm is separated from the membrane, and the cytoplasm is separated from the surrounding fluids by a cell membrane, also called the plasma surrounding fluids by a cell membrane, also called the plasma membrane.membrane.

► The different substances that make up the cell are collectively The different substances that make up the cell are collectively called protoplasm. called protoplasm.

► Protoplasm is composed mainly of five basic substances: Protoplasm is composed mainly of five basic substances: water, electrolytes, proteins, lipids, and carbohydrates.water, electrolytes, proteins, lipids, and carbohydrates.

Physically Structure of The Physically Structure of The CellCell

► The cell is not merely a bag of fluid, enzymes, and The cell is not merely a bag of fluid, enzymes, and chemicals; it also contains highly organized chemicals; it also contains highly organized physical structures, called intracellular organelles. physical structures, called intracellular organelles.

► The physical nature of each organelle is as The physical nature of each organelle is as important as the cell’s chemical constituents for cell important as the cell’s chemical constituents for cell function. For instance, without one of the function. For instance, without one of the organelles, the mitochondria, more than 95 per organelles, the mitochondria, more than 95 per cent of the cell’s energy release from nutrients cent of the cell’s energy release from nutrients would cease immediately.would cease immediately.

Cell MembraneCell Membrane

StructureStructure

► primary building blocks include protein (about primary building blocks include protein (about 60% of the membrane) and lipid, or fat (about 60% of the membrane) and lipid, or fat (about 40% of the membrane). 40% of the membrane).

► The primary lipid is called The primary lipid is called phospholipid, and , and molecules of phospholipid form a 'phospholipid molecules of phospholipid form a 'phospholipid bilayer' (two layers of phospholipid molecules).bilayer' (two layers of phospholipid molecules).

► This bilayer forms because the two 'ends' of This bilayer forms because the two 'ends' of phospholipid molecules have very different phospholipid molecules have very different characteristics: one end is polar (or hydrophilic) characteristics: one end is polar (or hydrophilic) and one (the hydrocarbon tails below) is non-and one (the hydrocarbon tails below) is non-polar (or hydrophobic)polar (or hydrophobic)..

FunctionFunction

► supporting and retaining the cytoplasm being a selective supporting and retaining the cytoplasm being a selective barrier barrier

► The cell is separated from its environment and needs to get The cell is separated from its environment and needs to get nutrients in and waste products out. Some molecules can nutrients in and waste products out. Some molecules can cross the membrane without assistance, most cannot. Water, cross the membrane without assistance, most cannot. Water, non-polar molecules and some small polar molecules can non-polar molecules and some small polar molecules can cross. Non-polar molecules penetrate by actually dissolving cross. Non-polar molecules penetrate by actually dissolving into the lipid bilayer. Most polar compounds such as amino into the lipid bilayer. Most polar compounds such as amino acids, organic acids and inorganic salts are not allowed entry, acids, organic acids and inorganic salts are not allowed entry, but instead must be specifically transported across the but instead must be specifically transported across the membrane by proteins. membrane by proteins.

► transport ► Many of the proteins in the membrane function to help carry Many of the proteins in the membrane function to help carry

out selective transport. These proteins typically span the out selective transport. These proteins typically span the whole membrane, making contact with the outside whole membrane, making contact with the outside environment and the cytoplasm. They often require the environment and the cytoplasm. They often require the expenditure of energy to help compounds move across the expenditure of energy to help compounds move across the membrane membrane

► communication (via communication (via receptors) )

CytoplasmaCytoplasma

► Cytoplasm consists of a gelatinous solution and Cytoplasm consists of a gelatinous solution and contains contains microtubules (which serve as a cell's (which serve as a cell's cytoskeleton) and organelles (literally 'little organs') ) and organelles (literally 'little organs')

► Cells also Cells also contain a contain a nucleus within within which is found which is found DNA DNA (deoxyribonucl(deoxyribonucleic acid) in the eic acid) in the form of form of chromosomes plus plus nucleoli (within which (within which ribosomes are ribosomes are formed) formed)

DNA (Deoxyribonucleic acid)

►controls cell function via transcription controls cell function via transcription and translation (in other words, by and translation (in other words, by controlling protein synthesis in a cell) controlling protein synthesis in a cell)

Centrioles

►paired cylindrical structures located paired cylindrical structures located near the nucleas near the nucleas

►play an important role in cell divisionplay an important role in cell division

Endoplasmic Reticulum

►comes in 2 forms: smooth and rough; comes in 2 forms: smooth and rough; the surface of rough ER is coated with the surface of rough ER is coated with ribosomes; the surface of smooth ER is ribosomes; the surface of smooth ER is not not

►functions include: mechanical support, functions include: mechanical support, synthesis (especially proteins by rough synthesis (especially proteins by rough ER), and transport ER), and transport

Golgi Complex

►consists of a series of flattened sacs consists of a series of flattened sacs (or cisternae) (or cisternae)

►functions include: synthesis (of functions include: synthesis (of substances likes phospholipids), substances likes phospholipids), packaging of materials for transport packaging of materials for transport (in vesicles), and production of (in vesicles), and production of lysosomeslysosomes

Lysosomes

►membrane-enclosed spheres that membrane-enclosed spheres that contain powerful digestive enzymes contain powerful digestive enzymes

►functions include destruction of functions include destruction of damaged cells (which is why they are damaged cells (which is why they are sometimes called 'suicide bags') & sometimes called 'suicide bags') & digestion of phagocytosed materials digestion of phagocytosed materials (such as bacteria)(such as bacteria)

MitochondriaMitochondria

►have a double-membrane: outer membrane & have a double-membrane: outer membrane & highly convoluted inner membrane highly convoluted inner membrane

►inner membrane has folds or shelf-like inner membrane has folds or shelf-like structures called cristae that contain structures called cristae that contain elementary particles; these particles contain elementary particles; these particles contain enzymes important in ATP production enzymes important in ATP production

►primary function is production of adenosine primary function is production of adenosine triphosphate (ATP)triphosphate (ATP)

RibosomesRibosomes

►composed of rRNA (ribosomal RNA) & composed of rRNA (ribosomal RNA) & protein protein

►may be dispersed randomly throughout may be dispersed randomly throughout the cytoplasm or attached to surface of the cytoplasm or attached to surface of rough endoplasmic reticulum rough endoplasmic reticulum

►often linked together in chains called often linked together in chains called polyribosomes or polysomes polyribosomes or polysomes

►primary function is to produce proteins primary function is to produce proteins

Flagella & ciliaFlagella & cilia

►hair-like projections from some human hair-like projections from some human cells cells

►cilia are relatively short & numerous cilia are relatively short & numerous (e.g., those lining trachea) (e.g., those lining trachea)

►a flagellum is relatively a flagellum is relatively `̀long and long and there's typically just one (e.g., sperm)there's typically just one (e.g., sperm)

VilliVilli

► projections of cell projections of cell membrane that membrane that serve to increase serve to increase surface area of a surface area of a cell (which is cell (which is important, for important, for example, for cells example, for cells that line the that line the intestine) intestine)

Functional System of The CellFunctional System of The Cell

Synthesis & Formation Cellular Structure Synthesis & Formation Cellular Structure by Endoplasmic Reticulum & Golgi by Endoplasmic Reticulum & Golgi

AparatusAparatus

► The extensiveness of the endoplasmic reticulum and the Golgi The extensiveness of the endoplasmic reticulum and the Golgi apparatus in secretory cells has already been emphasized. apparatus in secretory cells has already been emphasized. These structures are formed primarily of lipid bilayer These structures are formed primarily of lipid bilayer membranes similar to the cell membrane, and their walls are membranes similar to the cell membrane, and their walls are loaded with protein enzymes that catalyze the synthesis of loaded with protein enzymes that catalyze the synthesis of many substances required by the cell. many substances required by the cell.

► Most synthesis begins in the endoplasmic reticulum. The Most synthesis begins in the endoplasmic reticulum. The products formed there are then passed on to the Golgi products formed there are then passed on to the Golgi apparatus, where they are further processed before being apparatus, where they are further processed before being released into the cytoplasm. But first, let us note the specific released into the cytoplasm. But first, let us note the specific products that are synthesized in specific portions of the products that are synthesized in specific portions of the endoplasmic reticulum and the Golgi apparatus. endoplasmic reticulum and the Golgi apparatus.

Ingestion by the Cell—EndocytosisIngestion by the Cell—Endocytosis

► If a cell is to live and grow and reproduce, it must obtain If a cell is to live and grow and reproduce, it must obtain nutrients and other substances from the surrounding fluids. Most nutrients and other substances from the surrounding fluids. Most substances pass through the cell membrane by diffusion and substances pass through the cell membrane by diffusion and active transport. active transport.

► Diffusion involves simple movement through the membrane Diffusion involves simple movement through the membrane caused by the random motion of the molecules of the caused by the random motion of the molecules of the substance; substances move either through cell membrane substance; substances move either through cell membrane pores or, in the case of lipid-soluble substances, through the pores or, in the case of lipid-soluble substances, through the lipid matrix of the membrane. lipid matrix of the membrane.

► Active transport involves the actual carrying of a substance Active transport involves the actual carrying of a substance through the membrane by a physical protein structure that through the membrane by a physical protein structure that penetrates all the way through the membrane. These active penetrates all the way through the membrane. These active transport mechanisms are so important to cell function.transport mechanisms are so important to cell function.

► Very large particles enter the cell by a specialized function of Very large particles enter the cell by a specialized function of the cell membrane called endocytosis.the cell membrane called endocytosis.

Pynocytosis & PhagocytosisPynocytosis & Phagocytosis

► Very large particles enter the cell by a specialized function of Very large particles enter the cell by a specialized function of the cell membrane called endocytosis. The principal forms of the cell membrane called endocytosis. The principal forms of endocytosis are pinocytosis and phagocytosis. endocytosis are pinocytosis and phagocytosis.

► Pinocytosis means ingestion of minute particles that form Pinocytosis means ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm.inside the cell cytoplasm.

► Phagocytosis means ingestion of large particles, such as Phagocytosis means ingestion of large particles, such as

bacteria, whole cells, or portions of degenerating tissue. bacteria, whole cells, or portions of degenerating tissue.

Use of Intracellular Vesicles to Use of Intracellular Vesicles to Replenish Cellular Membranes.Replenish Cellular Membranes.

► Some of the intracellular vesicles formed by the Golgi Some of the intracellular vesicles formed by the Golgi apparatus fuse with the cell membrane or with the apparatus fuse with the cell membrane or with the membranes of intracellular structures such as the membranes of intracellular structures such as the mitochondria and even the endoplasmic reticulum. mitochondria and even the endoplasmic reticulum.

► This increases the expanse of these membranes and thereby This increases the expanse of these membranes and thereby replenishes the membranes as they are used up. For instance, replenishes the membranes as they are used up. For instance, the cell membrane loses much of its substance every time it the cell membrane loses much of its substance every time it forms a phagocytic or pinocytotic vesicle, and the vesicular forms a phagocytic or pinocytotic vesicle, and the vesicular membranes of the Golgi apparatus continually replenish the membranes of the Golgi apparatus continually replenish the cell membrane.cell membrane.

Extraction of Energy from Nutrients— Extraction of Energy from Nutrients— Function of the Mitochondria Function of the Mitochondria

► The principal substances from which cells extract energy are The principal substances from which cells extract energy are foodstuffs that react chemically with oxygen—carbohydrates, foodstuffs that react chemically with oxygen—carbohydrates, fats, and proteins.fats, and proteins.

► In the human body, essentially all carbohydrates are In the human body, essentially all carbohydrates are

converted into glucose by the digestive tract and liver before converted into glucose by the digestive tract and liver before they reach the other cells of the body. Similarly, proteins are they reach the other cells of the body. Similarly, proteins are converted into amino acids and fats into fatty acids. converted into amino acids and fats into fatty acids.

► Inside the cell, the foodstuffs react chemically with oxygen, Inside the cell, the foodstuffs react chemically with oxygen, under the influence of enzymes that control the reactions and under the influence of enzymes that control the reactions and channel the energy released in the proper direction.channel the energy released in the proper direction.

Locomotion of The CellLocomotion of The Cell

Ameboid Movement Ameboid Movement ► Ameboid movement is movement of an entire cell in relation Ameboid movement is movement of an entire cell in relation

to its surroundings, such as movement of white blood cells to its surroundings, such as movement of white blood cells through tissues. through tissues.

► Typically, ameboid locomotion begins with protrusion of a Typically, ameboid locomotion begins with protrusion of a pseudopodium from one end of the cell. The pseudopodium pseudopodium from one end of the cell. The pseudopodium projects far out, away from the cell body, and partially secures projects far out, away from the cell body, and partially secures itself in a new tissue area. Then the remainder of the cell is itself in a new tissue area. Then the remainder of the cell is pulled toward the pseudopodium.pulled toward the pseudopodium.

Cilia and Ciliary Movements Cilia and Ciliary Movements ► A second type of cellular motion, ciliary movement, is a A second type of cellular motion, ciliary movement, is a

whiplike movement of cilia on the surfaces of cells.whiplike movement of cilia on the surfaces of cells.

Genetic Control of Protein Synthesis, Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction Cell Function, and Cell Reproduction

► Virtually everyone knows that the genes, located in the nuclei Virtually everyone knows that the genes, located in the nuclei of all cells of the body, control heredity from parents to of all cells of the body, control heredity from parents to children, but most people do not realize that these same children, but most people do not realize that these same genes also control day-today function of all the body’s cells. genes also control day-today function of all the body’s cells.

► The genes control cell function by determining which The genes control cell function by determining which substances are synthesized within the cell—which structures, substances are synthesized within the cell—which structures, which enzymes, which chemicals. which enzymes, which chemicals.

► A nucleic acid called deoxyribonucleic acid (DNA), A nucleic acid called deoxyribonucleic acid (DNA), automatically controls the formation of another nucleic acid, automatically controls the formation of another nucleic acid, ribonucleic acid (RNA); this RNA then spreads throughout the ribonucleic acid (RNA); this RNA then spreads throughout the cell to control the formation of a specific protein. cell to control the formation of a specific protein.

► Because there are more than 30,000 different genes in each Because there are more than 30,000 different genes in each cell, it is theoretically possible to form a very large number of cell, it is theoretically possible to form a very large number of different cellular proteins. different cellular proteins.

Thank youThank you