Download Ch. 3- Cells, The Living Units Theory Cell

Ch. 3- Cells, The Living Units
_________________ Theory
* Cell - structural and functional unit of life
* All living things are composed of _____________
* New cells are produced from existing cells
Cell Diversity
* Over 200 different types of human cells
* Types differ in ______________, shape, subcellular components, and functions
Generalized Cell
* All cells have some common structures and ________________________
* Human cells have three basic parts:
* ____________________ membrane—flexible outer boundary
* Cytoplasm—intracellular fluid containing organelles
* Nucleus—__________________ center
Membrane Lipids
* _____________ phospholipids (lipid bilayer)
* Phosphate heads: polar and _________________
* Fatty acid tails: nonpolar and hydrophobic (Review Fig. 2.16b)
* 5% _______________________
* Lipids with polar sugar groups on outer membrane surface
* 20% cholesterol
-Increases membrane stability
There are two distinct populations of membrane proteins:
______________________ proteins are transmembrane proteins that span the entire width of the
membrane and are involved with transport as channels or carriers.
______________________ proteins are not embedded in the plasma membrane, but attach to
integral proteins or to phospholipids, and may function as enzymes or in mechanical functions of
the cell.
Six Functions of Membrane Proteins
1 ______________________
2 Receptors for signal transduction
3 Attachment to cytoskeleton and extracellular matrix
4 Enzymatic activity
5 Intercellular joining
6 Cell-cell ___________________
The Glycocalyx
* "Sugar covering" at cell surface
* Lipids and proteins with attached carbohydrates (sugar groups)
* Every cell type has different pattern of sugars
* Specific biological markers for cell to cell recognition
*
*
Allows immune system to recognize "self" and "non self"
Cancerous cells change it continuously
Cell Junctions
* Some cells "free"
* e.g., blood cells, sperm cells
* Some bound into communities
* Three ways cells are bound:
* __________________ junctions
* Desmosomes
* __________________ junctions
______________ Membrane
* Cells surrounded by interstitial fluid (IF)
* Contains thousands of substances, e.g., amino acids, sugars, fatty acids, vitamins,
hormones, salts, waste products
* Plasma membrane allows cell to obtain from IF exactly what it needs, exactly when it is
__________________
* Keep out what it does not need
Membrane ______________________
* Plasma membranes selectively __________________
* Some molecules pass through easily; some do not
* Two ways substances cross membrane
* Passive processes
* ______________ processes
Types of Membrane Transport
* Passive processes
-No cellular ____________________ (ATP) required
-Substance moves down its concentration gradient
* Active processes
-Energy (___________) required
-Occurs only in living cell membranes
Passive Processes
* Two types of passive transport
* Diffusion
-Simple diffusion
-Carrier- and channel-mediated facilitated diffusion
-Osmosis
* Filtration
-Usually across _________________ walls
-Driven by hydrostatic pressure (force of a fluid pushing against a surface), movement of
Molecules through a membrane from high hydrostatic pressure to ____________ hydrostatic
pressure
Isotonic solutions:
- Cells retain their normal size and shape in isotonic solutions (same solute/water
concentration as inside cells; water moves in and out).
Hypertonic solutions:
- Cells lose water by osmosis and shrink in a hypertonic solution (contains a higher
concentration of solutes than are present inside the cells).
Hypotonic solutions:
- Cells take on water by osmosis until they become bloated and burst (lyse) in a hypotonic
solution (contains a lower concentration of solutes than are present inside cells).
Active Transport
* Requires carrier proteins (solute pumps)
* Moves solutes against concentration gradient
* Requires energy
Active Transport: Two Types
* Primary active transport
-Required energy directly from ATP hydrolysis
* Secondary active transport
-Required energy indirectly from ionic gradients created by primary active transport
Cytoplasm
* Located between plasma membrane and nucleus
– Composed of
* __________________
- Water with solutes (protein, salts, sugars, etc.)
* __________________
- Metabolic machinery of cell; each with specialized function; either membranous or
nonmembranous
* __________________
- Vary with cell type; e.g., glycogen granules, pigments, lipid droplets, vacuoles, crystals
Cytoplasmic Organelles
• Membranous
–
–
–
–
–
Mitochondria
Peroxisomes
Lysosomes
Endoplasmic reticulum
Golgi apparatus
• Nonmembranous
 Cytoskeleton
 Centrioles
 Ribosomes
• Membranes allow crucial compartmentalization
Mitochondria
* Double-membrane structure with inner shelflike ________________
* Provide most of cell's ATP via aerobic cellular _______________________
* Requires _______________
* Contain their own DNA, RNA, ribosomes
* Similar to bacteria; capable of cell division called fission
Ribosomes
* Granules containing protein and ____________
* Site of ___________________ synthesis
* Free ribosomes synthesize soluble proteins that function in cytosol or other organelles
* Membrane-bound ribosomes (forming rough ER) synthesize proteins to be incorporated
into membranes, lysosomes, or exported from cell
Endoplasmic Reticulum (ER)
* Interconnected tubes and parallel membranes enclosing cisterns
* Continuous with outer nuclear membrane
* Two varieties:
- Rough ER
- Smooth ER
Rough ER
* External surface studded with ____________________
* Manufactures all secreted proteins
* Synthesizes membrane integral proteins and ______________________
* Assembled proteins move to ER interior, enclosed in vesicle, go to Golgi apparatus
Smooth ER
* Network of tubules _______________________ with rough ER
* Its enzymes (integral proteins) function in
– Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids of
lipoproteins
– Absorption, synthesis, and transport of __________
– Detoxification of drugs, some pesticides, carcinogenic chemicals
– Converting glycogen to free glucose
– Storage and release of __________________
Golgi Apparatus
* Stacked and flattened membranous sacs
* Modifies, concentrates, and packages proteins and lipids from __________________ ER
* Transport vessels from ER fuse with convex cis face; proteins modified, tagged for
delivery, sorted, packaged in vesicles
– Vesicles of lipids and transmembrane proteins for plasma membrane or organelles
– _________________________ containing digestive enzymes; remain in cell
Lysosomes
* Spherical membranous bags containing digestive enzymes (acid hydrolases)
* "Safe" sites for intracellular __________________
* Digest ingested bacteria, viruses, and toxins
* Degrade nonfunctional _____________________
* Metabolic functions, e.g., break down and release glycogen
* Destroy cells in injured or nonuseful tissue (autolysis)
* Break down bone to release _________________
Peroxisomes
* Membranous sacs containing powerful oxidases and catalases
* Detoxify harmful or toxic substances
* Catalysis and synthesis of ____________________
* Neutralize dangerous free radicals (highly reactive chemicals with unpaired electrons)
Endomembrane System
* Overall function
– Produce, degrade, store, and export biological molecules
– Degrade potentially harmful substances
* Includes ER, Golgi apparatus, secretory vesicles, lysosomes, nuclear and plasma
membranes
Centrosome and Centrioles
* "Cell center" near nucleus
* Generates microtubules; organizes ____________________ spindle
* Contains paired centrioles
– Barrel-shaped organelles formed by microtubules
* Centrioles form basis of cilia and ________________________
Cytoskeleton
* Elaborate series of rods throughout cytosol; proteins link rods to other cell structures
– Three types
* ____________________
* Intermediate filaments
* ____________________
Microfilaments
* __________________ of cytoskeletal elements
* Involved in cell motility, change in shape, endocytosis and exocytosis
Intermediate Filaments
* Tough, insoluble, ropelike protein fibers
* Resist pulling forces on cell; attach to __________________
E.g., neurofilaments in nerve cells; keratin filaments in epithelial cells
Microtubules
* _________________ of cytoskeletal elements; dynamic hollow tubes; most radiate from
centrosome
* Determine overall shape of cell and distribution of organelles
* Mitochondria, lysosomes, secretory vesicles attach to microtubules; moved throughout
cell by motor ____________________
Cellular Extensions
* Cilia and flagella
– Whiplike, motile extensions on _______________ of certain cells
– Contain microtubules and motor molecules
– Cilia move substances across cell surfaces
– Longer flagella propel whole cells (tail of sperm)
* Microvilli
– Minute, fingerlike extensions of ______________ membrane
– Increase surface area for ___________________
– Core of actin filaments for stiffening
Nucleus
* Largest organelle; genetic library with blueprints for nearly all cellular proteins
* Responds to signals; dictates kinds and amounts of proteins synthesized
* Most cells __________________________; skeletal muscle cells, bone destruction cells,
and some liver cells are multinucleate; red blood cells are ________________________
* Three regions/structures
The Nuclear Envelope
* Double-membrane barrier; encloses nucleoplasm
* Outer layer continuous with rough ER and bears ribosomes
* Inner lining (nuclear lamina) maintains shape of nucleus; scaffold to organize DNA
* Pores allow substances to pass; nuclear pore complex line pores; regulates transport of
large molecules into and out of nucleus
Nucleoli
* Dark-staining spherical bodies within nucleus
* Involved in __________________ synthesis and ribosome subunit assembly
______________________
* Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%)
* Arranged in fundamental units called nucleosomes
*
*
Histones pack long DNA molecules; involved in gene regulation
Condense into barlike bodies called chromosomes when cell starts to divide
Cell _________________
* Defines changes from formation of cell until it ________________
* Includes:
* Interphase
-Cell grows and carries out functions
* Cell division (mitotic phase)
-Divides into two cells
Interphase
* Period from cell formation to cell ______________
* Nuclear material called _______________
* Three subphases:
* G1 (gap 1)—vigorous growth and metabolism
* Cells that permanently cease dividing said to be in G0 phase
* S (synthetic)—DNA replication occurs
* G2 (gap 2)—preparation for ______________
* Prior to division, the cell makes a copy of the DNA
* DNA helices separated into replication bubbles with replication forks at each end
* Each strand acts as template for complementary strand
* In DNA, Nucleotides: Adenine with Thymine and Guanine with Cytosine
* DNA polymerase begins adding nucleotides at RNA primer
* DNA polymerase continues from primer
* Synthesizes one leading, one lagging strand
DNA Replication
* DNA polymerase only works in one direction
* Leading strand synthesized continuously
* Lagging strand synthesized discontinuously into segments
* DNA ligase splices short segments of discontinuous strand together
* End result: two identical DNA molecules formed from original
* During mitotic cell division one complete copy given to new cell; one retained in original
cell
* Process is called semiconservative replication
* Each DNA composed of one old and one new strand
Control of Cell Division
* "Go" signals:
* Critical volume of cell when area of membrane inadequate for exchange
* Chemicals (e.g., growth factors, hormones)
* Availability of space–contact inhibition
* "Go" signals
* G1 checkpoints (restriction point) most important
* If doesn't pass  G0–no further division
* Late in G2 MPF (M-phase promoting factor) required to enter M phase
Mitotic cell division - produces __________
* Essential for body growth and tissue repair
*
Occurs continuously in some cells
-Skin; intestinal lining
* None in most mature cells of nervous tissue, skeletal muscle, and cardiac muscle
* Repairs with fibrous tissue
Mitosis—division of _________________
* Four stages ensure each cell receives copy of replicated DNA
* _____________________
* Metaphase
* _____________________
* Telophase
* Cytokinesis—division of cytoplasm by cleavage furrow
Prophase
* ___________________________ become visible, each with two chromatids joined at
centromere
* ___________________________ separate and migrate toward opposite poles
* Mitotic spindles and asters form
* Nuclear envelope fragments
* Kinetochore microtubules attach to kinetochore of centromeres and draw them toward
equator of cell
* Polar microtubules assist in forcing poles apart
____________________________
* Centromeres of chromosomes aligned at equator
* Plane midway between poles called metaphase plate
Anaphase
* ___________________ phase
* Centromeres of chromosomes split simultaneously—each chromatid becomes a
chromosome
* Chromosomes (V shaped) pulled toward poles by motor proteins of kinetochores
* Polar microtubules continue forcing poles apart
Telophase
* Begins when chromosome movement ____________
* Two sets of chromosomes uncoil to form chromatin
* New nuclear membrane forms around each chromatin mass
* __________________________ reappear
* Spindle disappears
Cytokinesis
* Begins during late _____________________
* Ring of actin microfilaments contracts to form cleavage furrow
* Two daughter cells pinched apart, each containing nucleus
__________________________ to original