Chapter 3 Cellular Level Of Organization

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cytoplasm

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region between the cell surface and nuclear envelope , contains the cytosol , intracellular fluid and organelles.

provides nutrients and raw materials for cell and is organelles.

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cell surface

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defines shape of cell and separates the cytoplasm from the extracellular region

transport materials in and out of cell, protection

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organelles

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specialized intracellular structures, work together to help maintain cellular homeostasis. can be membranous and nonmembraneous.

Non membranous are in direct contact with cytosol

Membranous- are bound by a single or double layered membrane .

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Membranous

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endoplasmic reticulum

mitochondria

golgi apparatus

peroxisomes

lysosomes

nucleus

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Non membranous

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Cytoskeleton including microfilaments and microtubules

ribosomes

centrosome

proteasome

cilia and flagella

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Vacuoles

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temporary, membranous sacs or vesicles that contain substances

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inclusions

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temporary , non membranous bound sacs that can take different forms. ex: glycogen , granules, pigments, protein/lipid droplets.

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Cell or plasma membrane

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flexible yet sturdy barrier to ions and water soluble compounds that surrounds and contains the cytoplasm of the cell . Also known as a Phospholipid bilayer.

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Phospholipids

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are amphipathic , they are very fluid due to the kinks in the fatty acid tail.

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Integral proteins

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extend a portion of the way into the plasma membrane or actually through it .

are amphipathic with hydrophobic and hydrophilic regions

make up bulk of membrane proteins, tightly membrane. cannot be removed without disturbing membrane integrity.

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Peripheral proteins

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associated with the inner and outer of the surface of the membrane . also contact signaling

not common, more loosely with membrane, can be removed without disturbing membrane integrity.

ex: cytoskeletal proteins, enzymes

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enzymes

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catalyze reactions , dipeptides are broken down by extracellular enzymes on cells in the lumen of the intestines.

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Ligand

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large or small hormone that trigger changes in the activity of the cell.

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contact signaling

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cells that touch recognize each other by each cell's unique surface membrane receptors.

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Activated G-protein

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linked receptors indirectly cause cellular changes by activating G proteins, which in turn can affect ion channels,activate other enzymes, or cause release of internal second messenger chemicals such as cyclic AMP or calcium.

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Glycocalyx

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CHO-rich , sugar coated exterior surface of the cell membrane rich in glycolipids and glycoproteins . function in lubrication and protection, anchoring and locomotion, and binding receptors.

Recognition, help determine self from non self .

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impermeable

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lets nothing in and out . Impermeable to ions and charged polar molecules .

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freely permeable

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lets anything pass

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selectively permeable

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restricts movements.

most often freely permeable to non polar , uncharged molecules including oxygen, carbon dioxide and steroids .

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periodic gaps

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water channel . random movement of the phospholipid bilayer. Minor form of water movement.

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Aquaporins

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a transmembranous water channel, that allow water to pass single file through the membrane. Major form of water movement.

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Diffusion

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always passive

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carrier -mediated transport

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passive or active

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vesicular transport

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always active

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concentration

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amount of solute in solvent

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concentration Gradient

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more solute in 1 part of a solvent than another .net movement of solute proceeding down a concentration gradient from a region of higher concentration into a region of lower concentration .

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gradient

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a gradual change from low to high , or high to low

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diffusion

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molecules mix randomly

solute spreads through solvent

eliminate concentration gradient

solutes move down a concentration gradient to reach a state of equilibrium.

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factors affection diffusion rates :

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distance, temperature, molecule size, gradient size, electrical forces, viscosity.

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direct diffusion -

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movement of lipid soluble substances across a cell membrane

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channel mediated diffusion

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most often used for ions but are also used for water (aquaporins

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facilitated diffusion

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a form of diffusion employing a carrier or transporter.

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simple diffusion

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materials that diffuse directly through cell membrane . Ex: lipid soluble compounds ( alcohols, fatty acids, and steroids.)

dissolved gas ( oxygen and carbon dioxide)

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osmosis

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the diffusion of water across the cell membrane

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osmotic pressure

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the force of concentration gradient of water . equals the force needed to block osmosis.

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Tonicity

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The osmotic effect of a solute on a cell

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Isotonic solutions

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a solution that does not cause osmotic flow of water in or out of a cell.

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Hypotonic

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has less solutes , loses water , cell gains water . ruptured (hemolysis of red blood cells)

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hypertonic

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have more solutes, gains water by osmosis, cells loses water and begin to shrivel or undergo crenation.

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dialysis

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The movement of a solute molecule across a selectively permeable membrane. it is to sort solutes of different sizes.

Used to treat renal failure by removing waste products.

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channel mediated diffusion

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materials which pass through transmembrane proteins . are water or water soluble compounds. they are selective to ions such as k+ Na+ or cl-. ions move through changes by diffusion .

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Gated channels

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"Open at all times" . chemically, mechanically or electrically opened after being in a closed resting state

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Carrier -Mediated transport

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-transport of ions and organic substrates

-facilitated diffusion

-active transport (needs ATP)

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specificity

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a single transport protein transports a single set of substances

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regulation

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cofactors such as hormones

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cotransport (symport)

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2 substances move in the same direction at the same time.

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Countertransport (Antiport)

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1 substance moves in while another moves out

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Facilitated Diffusion

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-Passive

- Carrier Mediated

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Glucose Transport

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binds a glucose molecule. Glu T releases glucose on the opposite membrane surface where it is rapidly phosphorylated and trapped inside the cell for further reaction by a kinase enzyme .

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Active transport proteins

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move substrates against concentration gradient . will create a concentration gradient where non exists.

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Active Transport

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require energy , such as ATP since molecules are either too large , charged or in too low a concentration to pass by passive means . ion pumps move ions ( Na+ K+ Ca+ Mg2+)

exchange pump counter transports 2 ions at the same time. move back up .

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transport vesicles

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Bulk tranport . vesicles packages contents surrounded by the cellular envelope , think water balloons.

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phagocytosis

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the act of cell eating , where large particulates are taken into the cell.

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Exocytosis

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is the process of expelling something from the cell fusing a vesicle with the membrane

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Endocytosis

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Is the process of taking something into the cell by surrounding it with and membrane compartment called a vesicle.

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Receptor mediated endocytosis

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receptors bind target molecules (ligands, Ldls)

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Clathrin

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pits coated with a protein , form on the cell surface contain surface receptors that are ligand specific.

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lysosomes

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contain digestive enzymes that break down ligands (LDLs )into amino acids , fatty acids and cholesterol.

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pinocytosis

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Endosomes drink extracellular fluid and smaller dissolved substances are taken into the cell.

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Phagocytosis

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cell eating , engulf large objects that bind to surface receptors in phagosomes.

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Macrophages

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big eaters, which begin as monocytes or agranular white blood cells that differentiate into cells of the Reticulo-Endothelial.

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Microphages

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little eaters , which include neutrophils and eosinophils.

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Transcytocis

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Move across the cell , and exit via exocytosis on the other side of the cell. (just passing through)

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Membrane Polarity

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is polarized with an accumulation of cations on its extracellular surface and an accumulation of anions on its intracellular surface .

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factors contributing to RMP

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The Na-K pump which actively pumps out 3 Na+1 for every 2 K+1 ions pumped in.

The fact that the membrane is 75 times more permeable to K+1 than to Na+1 , therefore more K+1 diffuses out than Na+1 in most effective factor effective factor contributing to resting membrane potential (RMP)

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Electrical charge

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Inside cell membrane is slightly negative , outside positive

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The cell membrane

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contains lipids , carbohydrates, and functional proteins

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Phospholipid

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Double layer of phospholipid molecule : hydrophilic heads towards watery environment , both sides.

Hydrophobic fatty acid :inside membrane barrier to ions and water soluble compounds.

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Integral proteins

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Within the membrane

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Peripheral proteins

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Inner or Outer surface of the membrane .

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Membrane Carbohydrate

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proteoglycans, glycoproteins, and glycolipids : extend outside cell membrane . Form sticky " sugar coat" ( glycocalyx)

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cytosol

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dissolve materials nutrients , ions, proteins, and waste products.

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organelles

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Structures with specific functions . Internal structures of the cell work together to help maintain steady state .

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Non membranous Organelles

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no membrane , direct contact with cytosol

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Membranous organelles

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Covered with plasma membrane , isolated from cytosol.

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Non membranous organelles

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Cytoskeleton

microvilli

centrioles

cilia

ribosomes

proteosomes

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Cytoskeleton

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The microtrabecular framework consisting of microtubules , intermediate filaments and microfilaments. maintain structure and shape.

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Microfilaments

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Thin, thread like filaments composed of the protein actin , Interact with proteins to maintain the consistency of the cytoplasm . Pairs with thick filaments of myosin for muscle movement . support microvilli

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Intermediate Filaments

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Mid-sized between microfilaments and thick filaments. . Durable (collagen) strengthen cell and maintain shape , Stabilize organelles, stabilize cell position.

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Microtubules

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Large , hollow tubes composed of monomers of tubular protein : Attach to centrosome , form cilia , flagella , centrioles, basal bodies. change cell shape, form spindle of mitotic apparatus

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Microvili

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Increase surface area for absorption, attach to cytoskeleton

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Centrioles

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cylindrical structures composed of nine clusters of 3 microtubules each . give rise to the spindle or mitotic apparatus essential to proper chromosomes migration during mitosis. Give rise to basal bodies that forms cilia used for surface transport and flagella used for cell movement.

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Cilia

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Small, numerous hair-like processes that are responsible for the movement of fluid across the cell surface. Abundant in the upper respiratory tract and in the male and female reproductive system. cilia moves fluid across the cell surface , clears fluid from the lungs.

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centrosome

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a singular non membranous somewhat central region of dense cytoplasm in which are embedded two centrioles.

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Flagella

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larger , usually singular structures responsible for movement of the cell. Found only on sperm cells in mammals.

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Ribosomes

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build polypstides in protein synthesis , small non membranous structures composed of two subunits of r-RNA and protein. Synthesized in the nucleolus. Function in translation or protein synthesis.

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Free ribosomes in cytoplasm

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proteins for cell

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find ribosomes attached to rough ER

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Protein secretion

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Proteasomes

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Contain enzymes (proteases) disassemble damaged and unneeded proteins for recycling. Proteasomes may be implicated in certain diseases like cystic Fibrosis .

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Membranous organelles

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endoplasmic reticulum, golgi apparatus, lysosomes, peroxisomes, mitochondria .

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Endoplasmic reticulum

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a collection of membrane bound channels interconnecting the nucleoplasm, cytoplasm and the cell surface .

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Smooth ER

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Devoid of ribosomes

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Rough ER

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studded with ribosomes

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Functions of ER

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synthesis of proteins , carbohydrate , and lipids

storage of synthesized molecules and materials

transport of materials within the ER and to the golgi apparatus

Detoxification of drugs or toxins.

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smooth ER

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No ribosomes attached , contains enzymes for various anabolic processes. synthesized lipids and carbohydrates, phospholipids and cholesterol. steroid hormones , glycerides and glycogen. detox drugs in liver and kidneys, store of Calcium in muscle and nerve cells.

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Rough ER

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surface covered with ribosomes, active in protein and glycoprotein synthesis. Abundant in most secretory cells including hepatocytes and pancreatic cells.

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Golgi apparatus

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a collection of 4 to 7 flattened membrane bound sacs or cisternae. Modification of hormones and enzymes, form special enzyme packages ( lysosomes)

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secretory vesicles

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modify and package products for exocytosis

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Lysosomes

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carry enzyme to cytosol, powerful enzyme containing vesicles. membrane bound sacs of digestive enzymes that digest proteins that are brought to them in vesicles

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transport vesicles

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carry materials to and from Golgi apparatus

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exocytosis

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ejects secretory products and waters.

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primary lysosomes

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formed by Golgi and inactive enzymes

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secondary lysosome

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lysosome that fused with damages organelle , digestive enzymes activated, toxic chemicals isolated .

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lysosome functions

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clean up inside cells, break down large molecule, attack bacteria, recycle damaged organelles, ejects wastes by exocytosis. assisting in phagocytosis

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autolysis

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self destruction of damages cells,

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apoptosis

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programmed cell death

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peroxisomes

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small enzyme containing vesicles that are rich in oxidase, break down fattu acids and organic compounds, neutralize free radicals, produce hydrogen peroxide, produced by rough ER , abundant in liver.

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Mitochondrion structure

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have smooth outer membrane and folded inner or intramitochondrial membrane both composed of a phospholipid bilayer. provides cells with energy for life, required oxygen and organic substrates, generate carbon dioxide and ATP

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apoptosis

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programmed cell death

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cytosol composition and functions

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cytosol or intracellular fluid contains dissolved nutrients , ions, soluble and insoluble proteins and waste products.

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cytosol Vs extracellular fluid

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sodium /potassium ion concentration high K+ and low Na+ intracellular compare to extracellular, small quantities of carbohydrates for energy production, small reserved of amino acids for protein synthesis, small reserved of lipids for energy production in the absence of carbohydrates , contains a much higher concentration of proteins in a colloidal suspension.

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colloidal solution or suspension

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a complex mixture of organic and inorganic molecules , granules, vesicles, organelles in a watery matrix

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colloid

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a substance in which the particle size is midway between those of a solution and those of a suspension ( can scatter light like milk, gelatin)

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solution sized particles

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cannot be removed by filtration and will not settle out , include inorganic salts, monosaccharides and amino acids.

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suspension sized particles

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can be removed by filtration and will settle out if constant agitation is not provided. include granules, vesicles and proteins , enzymes and cytoskeletal.

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gel state

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semi solid , more orderly arrangement of colloidal particles with water trapped between . substance has a gel-like character

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sol state

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marked by more randomized arrangement of colloid particles with water , less ordered and therefore runny or liquidy

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Nucleus

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the cell's control center and largest organelles ,

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nuclear envelope

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double phospholipid bilayer membrane around the nucleus

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nuclear pores

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communication passages that allow transport of specific proteins and RNA

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DNA

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all information to build and run organisms

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Nucleoplasm

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fluid containing ions, enzymes, nucleotides, and some RNA

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Nuclear Matrix

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support filaments

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Nucleoli in Nucleus

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are related to protein production. made of RNA , enzymes, and histones, synthesize rRNA and ribosomal subunits

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Nucleosomes

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DNA coiled around histones

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Chromatin

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loosely coiled DNA (cell not dividing )

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Chromosomes

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tightly coiled DNA ( cell dividing )

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Cell Cycle

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A sequence of events by which the cell prepares for division by duplicating its chromosomes, organelles and necessary cellular components.

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G0

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an indefinite period where the cells leave the cell cycle to perform their specialized functions.

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G1

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first growth stage is marked by the duplication of organelles and other cytoplasmic constituents.

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G2

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marked by centrosomal duplication and production of components necessary for mitosis.

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S phase

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DNA synthesis and is the period during which chromosomal duplication occurs.

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2 major checkpoints

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1) one before the cell enters the S phase

2)one before entering mitosis

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Cyclin

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GO proteins include cyclin which attaches to cyclin dependent kinase which helps begin and continue the cell cycle.

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Oncogenes

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Mutated GO proteins can give a continuous signal and cause uncontrolled cell growth.

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3 stages of cell division

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1) DNA replication duplicates genetic material exactly

2) Mitosis divides genetic material equally

3) cytokinesis divides cytoplasm and organelles into 2 daughter cells.

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Mitosis

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DNA coils tightly into chromatids, chromatids connect at a centromere , protein complex around centromere is the kinetochore.

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Prophase

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chromatin begins to shorten and condense into recognizable duplicated chromosomes . The Nucleoli disintegrates and the chromatids are afloat in the cytoplasm. Centrosome duplication occurs with each new centrosome .

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Metaphase

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sister chromatids align at a region known as the metaphase plate, midway between the two mitotic spindle centers.

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Anaphase

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Microtubules pull chromosomes apart . daughter chromosomes groups near centrioles . Cytokinesis or cytoplasm division.

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Telophase

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chromosomes complete their migration to opposite poles of the cell

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Cytokinesis

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Division of the cytoplasm , when cytokinesis is complete it yields two new daughter cells.

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cell differentiation

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after cell division most cells leave the cell cycle and differentiate where they take on specific functions . Does not happen with stem cells . all cells have the same genetic make up.

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Meiosis

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reproductive cell division that occurs in the gonads (ovaries or testes ) that produces gametes with half the number of chromosome

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Haploid cells

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Gametes contain a single set of 23 chromosomes

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Synapsis

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the two sister chromosomes of each homologous pair pair off. not seen in mitosis.

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homologous

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have same genes in the place

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Meiosis 1

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begins with a diploid cell (2n) and ends with two cells having the haploid number of chromosomes.

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Meiosis 2

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each of the two haploid cells divides , the net result is four haploid gametes that are genetically different from the original diploid starting cell.