CHAPTER 3

PART 1: C

ELLULAR

PROCESSES

A N A T O M Y AN D P

H Y S I OL O G Y

An adult human body consists of about 75 trillion cells.

There are at least 260 varieties of cells.

Cells differentiate considerably in size, shape, and function.

Cells have different, distinctive shapes that make possible their functions.

INTRODUCTION

Late 1600’s, Robert Hooke was looking through a primitive microscope at some plant tissue (cork).

Saw cube-like structure that reminded him of monk’s rooms (cells) so he named the structure cells.

HISTORY

OVERVIEW OF THE CELLULAR BASIS OF LIFECells are made up of 4 elements primarily: Carbon,

Oxygen, Hydrogen, and Nitrogen.

The other elements are important for cell functions:

Calcium- blood clotting and other things. Iron- necessary to make hemoglobin (carries oxygen in

the blood. Iodine is required to make the thyroid hormone that

controls metabolism. Calcium, potassium, and sodium- carry electrical

impulse. Electrolytes. Sodium and Potassium: nerve impulse and muscle

contractions.

OVERVIEW OF THE CELLULAR BASIS OF LIFE

Cells are about 60% water.Interstitial fluid- all the cells of the body are

constantly bathed in a dilute saltwater solution. Comes from the blood. All exchanges between cells and blood are made

through this fluid.Cell size: 2micrometers (1/12000th of an inch) to over 1 meter (3

feet)Long cells are nerve cells to your feet.

OVERVIEW OF THE CELLULAR BASIS OF LIFE

Cell structure reflects the job.Disk shaped - red blood cellsThreadlike extensions - nervesToothpick shaped - smooth muscle cellsCube-like - epithelial cellsWhite blood cells - wander freely through the body tissue. And protect the body by destroying bacteria and other foreign substances.

All cells have three main regions: nucleus, cytoplasm, and plasma membrane.

Nucleus- usually located near the center of the cell

Cytoplasm- semifluid in the cell

Plasma membrane- forms the outer cell boundary.

ANATOMY OF A GENERALIZED CELL

NUCLEUSDNA- contains the blueprint that contains all the

instructions needed for building the whole body Instructions for building proteins. If a cell ejects its nucleus it is programmed to die.Nucleus usually forms to the cell shape so not

always round. Nucleus has three distinct regions:Nuclear envelopeNucleoliChromatin

Double membrane barrierBetween the two layers is fluid-

filled moat. At various points the two layers

of the nuclear envelope approach each other and fuse- nuclear pores penetrate through the fused regions

Selectively permeable but much freer than else where because of large pores.

Encloses a jellylike fluid called nucleoplasm in which nucleoli and chromatin are suspended.

NUCLEAR ENVELOPE

NUCLEOLIOne or more small, dark

staining, essentially round bodies.

Ribosomes are assembled here

Then the ribosomes are released into the cytoplasm.

Ribosomes do protein synthesis.

CHROMATINLoose network of

bumpy threadsWhen a cell is dividing

to form two daughter cells the chormatin threads coil and condense to form dense, rodlike bodies called chromosomes

Fragile transparent barrier that contains the cell contents and separates them from the surrounding environment.

Consists of 2 lipid layers arranged “tail to tail” in which protein molecules float.

Most of the lipid portion is phospholipids with a substantial amount of cholesterol.

The heads are polar (hydrophilic)

The tails are nonpolar (hydrophobic). These tails make the cell relatively impermeable to most water-soluble molecules.

PLASMA MEMBRANE

CELL MEMBRANE

PLASMA MEMBRANESome proteins are enzymesMany proteins mounted on the cell exterior are

receptors for hormones or other chemical messengers.

Most proteins are for transport functions. Glycoproteins- are a sugar protein. The cell

surface is a fuzzy, sticky area. Determine your blood typeChanges in glycoproteins occur in cells that are being transformed into cancer cells

SPECIALIZATIONS OF THE PLASMA MEMBRANEMicrovilli- tiny fingerlike projections that

greatly increase the cell’s surface area for absorption so that the process occurs more quickly.

Membrane junctions- vary structurally depending on their roles.

Tight junctions- impermeable junctions that bind cells together into leakproof sheets that prevent substances from passing through the extracellular space between cellsKeep digestive enzymes from seeping into the blood stream.

SPECIALIZATIONS OF THE PLASMA MEMBRANE

Membrane junctionsDesmosomes- anchoring junctions that prevent cells subjected to mechanical stress (skin cells) from being pulled apart.

Gap junctions- commonly seen in the heart and between embryonic cells, function mainly to allow communication.Connexons- connected to neighboring cells.

CYTOPLASMThe cellular material outside the nucleus and

inside the plasma membrane. Site of most cellular activity. Factory area3 major elements: cytosol, organelles, and

inclusions. Cytosol is semitransparent fluid that suspends the

other elements. Organelles are the metabolic machinery of the cell. Inclusions are not functioning units but are chemical

substances that may or may not be present Include fat droplets, glycogen granules, pigments

such as melanin, mucus and other secretory products and various crystals.

CYTOPLASMIC ORGANELLESMitochondria- sausage-shaped organelles Squirm, lengthen and change shape almost continuously.

Outer membrane is smooth but inner membrane has shelves called cristae.

Carry out reactions in which oxygen is used to break down foods.

Captured and used to form ATP moleculesPowerhouse of the cellLiver cells and muscle cells have lots of mitochondria

Unfertilized egg has few mitochondria

CYTOPLASMIC ORGANELLESRibosomes- tiny round, dark bodies

made of proteins and one variety of RNA called ribosomal RNA.

Protein synthesisSome float free in the cytoplasm and others attach to membranes.

Rough endoplasmic reticulum has ribosomes attached to it.

CYTOPLASMIC ORGANELLESEndoplasmic Reticulum- is a system of fluid-

filled cisterns that coil and twist through the cytoplasm.

Mini circulatory system for the cell Carries substances - mostly proteinsRough ER has ribosomes (export proteins)Smooth ER continuation of the rough variety. Does not do protein synthesis. It does cholesterol synthesis and breakdown (fat and detoxification of drugs) found in the liver and testes

CYTOPLASMIC ORGANELLESGolgi Apparatus- appears as a stack of

flattened membranous sacs, associated with swarms of tiny vesicles.

Traffic director of the cellModify and package proteinsSends proteins out of the cell.Secretory vesicles pinch off and go to the cell membrane and fuse with the membrane. The membrane then ruptures to the outside of the cell.Mucus and digestive enzymes are packaged this way.

CYTOPLASMIC ORGANELLESLysosomes- breakdown bodies, appear in

different sizes and are membrane bags containing powerful digestive enzymes.

Eat nonusable or worn-out cell structures and foreign substances that enter the cell.

Demolition site.Abundant in white blood cells Homeostatic Imbalance: If the lysosomal membrane becomes fragile when a cell is injured or deprived of oxygen and when excessive amounts of vitamin A are present the cell self digests.

CYTOPLASMIC ORGANELLESPeroxisomes- membranous sacs containing powerful

oxidase enzymes that use molecular oxygen (O2) to detoxify a number of harmful or poisonous substances (alcohol and formaldehyde)

Disarm dangerous free radicals: highly reactive chemicals with unpaired electrons that can scramble the structure of proteins and nucleic acids.

Convert free radicals into hydrogen peroxideCatalase converts excess hydrogen peroxide into water. Liver and kidney cells which both are very active in detoxification

CYTOPLASMIC ORGANELLESCytoskeleton- elaborate network of

protein structures extends throughout the cytoplasm.

Act as cell’s bones and musclesDetermines cell shape Intermediate filaments- help form desmosomes - provide internal guy wires to resist pulling forces

Microfilaments- cell motility and in producing changes in cell shape

Microtubles- tubelike, distribution of organelles and are very important during cell division

CYTOPLASMIC ORGANELLES

Centrioles- paired lie close to the nucleus

Rod-shaped bodies that lie at right angles to each other

Made up of fine microtubulesMitotic spindle

CYTOPLASMIC ORGANELLESCilia- whip-like cellular extensions that move substances along the cell surface.

Flagella- sperm tail that helps with movement.

CELL PHYSIOLOGYMembrane Transport- Solution- homogeneous mixture of 2 or more components.

Solvent- dissolving medium (body has water)Solutes- substances that are present in smaller amounts.

Intracellular fluid- solution containing small amounts of gases (oxygen and carbon dioxide) nutrients, and salts, dissolved in water.

Interstitial fluid- continuously bathes the exterior of our cells

Selective permeability- means that a barrier allows some substances to pass through it while excluding others.

PASSIVE TRANSPORT PROCESSES: DIFFUSION AND FILTRATION

Diffusion- the process by which molecules tend to scatter themselves throughout the available space.

The speed of diffusion is affected by the size of the molecules (the smaller the faster and the warmer the faster).

Molecules move passively through the membrane if: They are small enough to pass through its pores They can dissolve in the fatty portion of the membrane.

Simple diffusion- unassisted diffusion of solutes through the plasma membrane. Lipid-soluble or small enough to pass through the

membrane pores. Osmosis- diffusion of water through a selectively permeable

membrane Facilitated diffusion- means for certain needed substances

(glucose) to enter the cell.

FILTRATION

The process by which water and solutes are forced through a membrane by fluid.

Pushes a fluid from a high pressure to a low pressure.

KidneysNot selective process

ACTIVE TRANSPORT PROCESSESSolute pumping- similar to facilitated

diffusion Uses ATP to energize its protein carriers instead of kinetic energy.

Solute pumps pump the ATP to the molecules

Amino acids and some sugars and most ionsNerve cell transmissions

ACTIVE TRANSPORT PROCESSESBulk Transport- Exocytosis- out of the cell

Secretes hormones, mucus, and other cell productsPackaged before released into a vesicle

Endocytosis- into the cellReleased into the cytoplasm.PhagocytosisBulk-phase endocytosis- the cell forms a tiny pit and then its edges fuse around the droplet of extracellular fluid unlike phagocytes this is routine activity for a cell.

CELL DIVISION2 major periods: interphase and cell

divisionInterphase is really metabolic phase not resting phase.

Events of cell division:Mitosis: 1st is division of nucleus and 2nd cytokinesis is division of the cytoplasm (happens when mitosis is nearly completed)

CYTOKINESISOccurs during late anaphase and completes

during telophase.At the end two daughter cells exist. Genetically identical to the mother cellCarry out normal cell activity until it is their turn to divide.

Sometimes the cytoplasm does not divide. This leads to binucleate or multinucleate cells. Fairly common in the liver.

Mitosis gone wild is the basis for tumors and cancers.

http://www.ba-education.com/for/science/dnaphotos/dnaphoto.html

METABOLISM AND T3 AND T4 HORMONESThe sum total of the chemical reactions

that occur in the bodyT3 and T4 are thyroid hormones that are

required for normal development of brain tissue. Also normal metabolism of the body.

Too little you have lack of concentration and focusCan also cause infertility.

Too much leads to anxiety disorders. Iodine required for normal thyroid activity.