human biology instructor terry wiseth cell structure & function

Human Biology

Instructor Terry Wiseth

CELL CELL STRUCTURE & STRUCTURE &

FUNCTIONFUNCTION

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CELL MEMBRANECell membrane made up

of:

1) Phospholipids1) Phospholipids

2) Sterols2) Sterols

3) Proteins3) Proteins

4) Glycoproteins4) Glycoproteins

PHOSPHOLIPIDScell membrane - semi-permeable lipid

bilayertwo layers of Phospholipids

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STEROLS

common sterols of cell membranesCholesterol (animal cells)

prevent packing of lipid cells in the cell membrane

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PROTEINS

Proteins are embedded into the cell membraneThese proteins serve a variety of cell

membrane functions

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GLYCOPROTEINSproteins are embedded in the bilayer

glycoproteins - sugar-protein combinations

sugars extend out to the extracellular fluid

CELL MEMBRANE

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FLUID MOSAIC MODEL

membrane bilayer shows fluid behaviormolecules of the bilayer are in constant

motion

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FLUID MOSAIC MODEL

membrane is composite of molecules allowing a “mosaic description”

cell survival depends on fluidity characteristics of the cell membrane

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FLUID MOSAIC MODEL

extracellular fluid temperature decreases cause a stiffening of the cell membranedisrupts membrane protein function

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CELL THEORYSmallest entity that retains the

characteristics of life1) Complex organization2) Metabolic activity3) Reproduction

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CELL SIZE

Most cannot be seen without the aid of a microscopeLarger cells

”Yolk” of bird eggsFish eggs “caviar”

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CELL SIZEHuman eyes able to see about 100

microns

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LIGHT MICROSCOPE

The light microscope has a limit of resolution of about 200 nm (0.2 microns)

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TEMThe Transmission Electron Microscope

(TEM) has a limit of resolution of about 2 nm

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SEMThe Scanning Electron Microscope (SEM) also has a limit of 2 nm

Bronchiole cilia

WBC engulf bacteria

Sperm & Egg

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GENERALIZATIONS OF CELL THEORY

Cells vary in size, shape and activitiesAll cells have:

1) Plasma membrane2) DNA region3) Cytoplasm4) Organelles

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PLASMA MEMBRANEOuter membrane

maintains the integrity of the cell

Membrane does not however isolate the cell

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PLASMA MEMBRANECell membrane

“Lipid bilayer”Boundary that bars free passage of water

soluble substances in and out of the cell

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NUCLEUSDNA is localized in the cell nucleus

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CYTOPLASMEverything enclosed by the plasma

membrane except the DNA semi-fluid

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CYTOPLASMIC STREAMING

Cytoplasm is not stagnant but rather is constantly moving (streaming)

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ORGANELLESOrganelles--internal sacs which have a

specific metabolic functionEssential in keeping chemical reactions in

the cytoplasm separate from each other

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CELL MACHINERY

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CELL MACHINERY

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NUCLEUSNucleus sequesters DNA

1) Separates DNA from chemical reactions in cytoplasm

2) Nuclear membranes control access between nuclear material and cytoplasm

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NUCLEUSNuclear envelope has pores to allow

passage of messenger units of nucleic acid

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NUCLEUS

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NUCLEOLUS1) AssemblyAssembly of RNA and

ribosomes2) StorageStorage of RNA and

ribosomes

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DNAInstructions for building proteins (enzymes)

are contained in DNAInstructions of heredity are distributed in

several DNA molecules of various lengthsHumans = 46 DNA molecules

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DNADNA is threadlikeprior to cell division the DNA molecules

duplicate

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CHROMOSOMESDNA folds and twists into condensed

structures called chromosomes

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CYTOMEMBRANE SYSTEM

Series of organelles through which lipids and proteins, produced on cytoplasmic ribosomes, pass through in becoming packaged for export

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CYTOMEMBRANE SYSTEM

1) Endoplasmic reticulum (ER)

2) Golgi bodies3) Vesicles4) Lysosomes

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ENDOPLASMIC RETICULUM

1) Rough endoplasmic reticulumRibbon like structure with ribosomes

attachedArranged as flat, stacked sacs

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ENDOPLASMIC RETICULUM

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RIBOSOMESRibosomes are small spherical shaped

structuresServe as the “working table” for

assembling proteins

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RIBOSOMES

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ENDOPLASMIC RETICULUM

2) Smooth endoplasmic reticulumLacks ribosomes

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SMOOTH ENDOPLASMIC RETICULUM

Appears like a system of pipes1) Lipid synthesis

Ex: endocrine glands produce steroid hormones

2) Inactivate harmfulby-products ofmetabolism and drugsEx: liver cells

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GOLGI BODIES

Resemble stacks of pancakes

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GOLGI BODIES

Flattened sacs in which lipids and protein molecules are modified

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GOLGI BODIESModifications allow for sorting and

packaging for transport

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GOLGI MODIFICATIONS

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GOLGI MODIFICATIONS

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VESICLESSacs which transport or store enzymes,

lipids and proteins1) Peroxisomes2) Lysosomes (microbodies)

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VESICLES1) Peroxisomes

Contain enzymes to break down fatty acids and amino acids

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VESICLES2) LysosomesVesicles of intracellular digestionContain enzymes which can break down

any polysaccharide, protein, nucleic acid and some lipids

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LYSOSOMESImportant in proper function of white

blood cells (immunity)

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LYSOSOMES

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CYTOMEMBRANE SYSTEM

Raw materials (amino acids and lipids) are dissolved in the cytoplasm

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CYTOMEMBRANE SYSTEM

Under the instructions of the DNA molecule polypeptide chains of proteins are assembled from the dissolved raw materials

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CYTOMEMBRANE SYSTEM

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MITOCHONDRIAContains a series of inner membranes

folded repeatedly (cristaecristae)Increases the total surface area available

for reactions

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MITOCHONDRIAUse oxygen to assist in liberating energy

stored in sugars (aerobic respiration)

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MITOCHONDRIAEnergy is used to form ATP molecules

which is used for protein synthesis and transport

ATP-molecule is able to store and transport energy for short periods of time

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MITOCHONDRIAMost numerous in high energy demanding

cellsEx: muscles, liver

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MITOCHONDRIA

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CYTOSKELETONInterconnected system of bundled fibers,

threads and lattices

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CYTOSKELETONExtend from the cell membranes, organelles

and nucleus

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CYTOSKELETON

Supply internal organization, shape, ability to move, reinforce the cell membrane and hold proteins in place

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CELL SURFACE SPECIALIZATIONS

Gap Junctionschannels of exchange in animal cells

ex: liver, heart

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CELL SURFACE SPECIALIZATIONS

Junction Proteinshold cells together in forming tissues

ENDEND

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