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| Front | | Back | |
| Typical Cell
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- -a.k.a composite cell
- -varies in size, structure, & function
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| Cell Structure
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- 3 main structures
- Plasma Membrane (made of lipoproteins)
- Cytoplasm = contains cytosol with organelles
-Nucleus
- Each cell contains variety of membranes
- plasma membrane
- membranous organelles = canals and sacs
- nonmembranous = made of microfilaments
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| Fluid Mosaic Model
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- Theory explaning how cell membranes are constructed
- molecules of cell membrane are arranged in sheet
- mosaic of molecules is fluid; molecules are able to float around slowly
- illustrates molecules of cell membrane form continuous sheet
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| Cell Membranes
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- Chemical attractions hold them together
- Groupings of molecules form rafts that float around membrane
- rafts may pinch inward, bringing material into cell/organelle
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| Primary Structure of Cell Membrane
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- double layer of phospholipid molecules
- heads are hydrophilic
- tails are hydrophobic
- molecules arranged in bilayer in water
- cholesterol scattered among phospholipids - lets membrane funtion in body temp.
- most of membrane is hydrophobic - water cannot pass easily
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| Membrane Proteins
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- cell controls what goes in/out of membrane due to membrane proteins in phospholipid bilayer
- some membrane contains carbohydrates (glycoproteins) - act as I.D. markers
- Signal Transduction - allows a msg to be carried across membrane
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| Cytoplasm
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- gel-like substance of cells containing organelles suspended in watery fluid called cytosol
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| Rough Endoplasmic Reticulum
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- contain ribosomes on surface
- synthesizes proteins, which move toward golgi and eventually out the cell
- function in protein synthesis and intracellular transportation
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| Smooth Endoplasmic Reticulum
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- No Ribosomes
- Sythesizes lipids & carbohydrates & creates membranes for use throughout cell
- removes and stores Ca
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| Ribosomes
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- some attached to R.E.R.
- others are free in cytoplasm
- made of two subunits (large & small) - contain ribosomicRNA
- those on RER make proteins for plasma membrane
- free ones are for domestic use
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| Golgi Apparatus
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- a.k.a. golgi complex
- consists of cisternae stacked on one another
- located near nucleus
- processes protein molecules from RER
- Processed proteins leave final cisternae thru vesicle; contents then secreted outside cell
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| Lysosomes
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- Made of microscopic sacs "pinched off" from Golgi
- Digestive system of cell (act as garbage collector)
- Enzymes digest proteins of defective cell parts
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| Proteasomes
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- Hollow, protein cylinders found throughout cytoplasm
- break down abmormal/misfolded and unwanted proteins
- break down proteins one at a time by tagging with ubiquitin molecules and unfolding it as it enters proteasome.. then breaking apart peptide bonds
- proteins -> amino acides ->recycle
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| Peroxisomes
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- small membranous sacs containing enzymes that detoxifies harmful substances
- Often seen in kidney and livers
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| Mitochondria
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- made of microscopic sacs
- wall composed of inner and outter membranes separated by fluid
- enzyme molecules attached to both membranes
- "power plant" of cells. provide about 95% of energy supply
- has it's own DNA molecule - allows it to replicate copies of itself and make own enzymes
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| Nucleus
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- spherical body in center of cell
- enclosed with envelope with many pores (2 membranes)
- Contains DNA (heredity molecule)
- nondividing cells = chromatin: threads or granules
- dividing cells = chromosomes: early stages of cell division (coiled up)
- functions of nucleus = functions of molecules
- determines both function and structure of cells and heredity
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| Cytoskeleton
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- cell's internal supporting framework made up of rigid, rodlike pieces
- provide support and allow movement
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| Cell Fibers
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- Detailed arranged fivers of varying lengths that form a 3D shaped lattice
- Fivers support ER, Mitochondria, 7 "free" ribosomes
- 3 main fibers
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| Microfilaments
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- smallest cell fibers
- cell's muscles
- thin, twisted strand of protein molecule
- lie parallel to long axis of cell
- able to slide past one another, causing shortening of cell
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| Intermediate Filaments
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- twisted protein strands
- thicker than microfilaments
- form supporting framework in many cells
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| Microtibules
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- tiny, hollow tubes
- thickest of cell fibers
- made of protein subunits arranged in spiral fashion
- funtion is to move things around in cell
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| Centrosome
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- near nucleus that coordinates building and breaking of microtubules in cell
- a.k.a. microtubule-organizing center (MTOC)
- Plays important role during cell division
- location is identified by centrioles
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| Centrioles
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- tiny cylinders
- sit @ right angles to each other
- occurs when centrioles separate in preparation for cell division
- Pericentriolar material - cloud like material surrounds it
- involved in formation of microtubular cell extensions
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| Cell Extensions
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- cytoskeleton forms projections that extend plasma membrane outward to form tiny, fingerlike processes
- 3 types
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| Microvilli
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- found in epithelial cells (surface) that lines intestines and areas where absorption is important
- help increase surface area of manyfold
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| Cilia
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- have cylinders made of microtubules at the core
- short and more numerous than flagella
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| Flagella
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- have cylinders made of microtubules at the core
- found only in human sperm cells
- help sperm swim
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| Cells are held together by fibrous nets or direct connections
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- 3 types of direct connections
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| Desmosome
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- fibers on outer surface interlock with each other; anchored internally by intermediate filaments of cytoskeleton
- Spot desmosomes, connect adjacent membranes
- belt desmosomes encircle cell like collar
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| Gap Junctions
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- membrane channels of adjacent plasma membranes adhere to each other
- 2 effects
- form gaps/tunnels that join cytoplasm of 2 cells
- fuse two plasma membranes into single structure
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| Tight Junctions
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- Occur in cells joined by collars of tightly fused material
- molecules cannot go thru the cracks of tight junctions
- occur in lining of intestines and etc where it is important to control what gets thru sheet of cells
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