Chapter 3 (textbook)

Shape

Activity of cells is determined by ___

250, varying in length and shape

How many types of cells are there?

Plasma membrane

Outer boundary of cell, selectively permeable barrier. Seperates major fluid compartments

cytoplasm

intracellular fluid packed with organelles

Nucleus

organelle controls cellular activities

Extracellular fluid

dissolves and transports substances in the body (ex: blood plasma, interstitial fluid, cerebrospinal fluid)

Cellular secretions

extracellular secretions aid in digestions and lubrication

Extracellular matrix

nonliving material in connective tissue consists of ground substance and fibers; seperates the living cells. “cell glue” binds cells together

Fluid mosaic model

Depiction of structure of the membranes of a cell as phospholipid bilayers in which proteins are dispersed.

Membrane lipids (phospholipids and cholesterol)

lipid bilayer forms membrane “fabric”

Phospholipids

Polar hydrophilic heads bathed in water. Nonpolar hydrophobic tail

Cholesterol

Has polar and nonpolar region. Wedges hydrocarbon rings between phospholipid tails and stiffens the membrane (20% of the membrane is this)

Membrane proteins

half of membrane, responsible for function

1. Transport

2. Receptors for signal transduction

3. Enzymatic activity

4. Cell-cell recognition

5. Attachment to the cytoskeleton and extracellular matrix

6. Cell-to-cell joining

Membrane tasks [6]

Integral proteins

Proteins firmly inserted inside the lipid bilayer. Have hydrophilic and hydrophobic regions

Transmembrane proteins

Integral proteins that span entire membrane and protrude on both sides. Involved in transport, forming channels, or pores. small water-soluable molecules can get through.

Carrier proteins

Integral proteins that bind to a substance and move it through the membrane. Some are enzymes, some are hormones, other are chemical messages.

signal transduction

relaying messages to cell interior

Peripheral proteins

Membrane proteins not embedded in bilayer. They attach loosely to integral proteins or have hydrophobic region that anchors them to the membrane. Filaments that help support membrane from the cytoplasmic side. Some are enzymes, others are motor proteins involved in mechanical functions (changing shape during division), some link cells together

Glycolipids

Lipid with one or more attached sugars. Two fatty acid tails, carb replaces phosphate head.

Glycocalyx

Externally facing gylcoproteins and glycolipids on/near cell plasma membrane. Determines blood type and is involved in cellular interactions. Extracellular surface essential for cell recognition. “sugar coating”

identity molecules

Specific biomarkers by which approaching cells recognize each other (provided by glycocalyx)

Cell junctions

Adjacent cells joined together by specialized cell junctions allowing neighbor cells to adhere and communicate

Tight junctions

Area where plasma membrane of adjacent cells are tightly bound together, forming an impermeable barrier. Seperates fluid filled compartments, restricts movement of membrane proteins. (ex: epithelial cell lining digestive track)

Desmosomes

Junction make of thickened plasma membranes joined by filaments. Serves as anchoring junctions. Binds neighboring cells into sheets and contributes to internal network of strong fibers. Distributes tension and reduce chance for sheet tearing (ex: skin/heart tissue)

Plaque

Buttonlike thickening on cytoplasmic face of each plasma membrane. Adjacent cells are held together by thin linker protein filaments that extend from ______ and fit together like velcro in intercellular space

Gap junctions

Communicating junction between adjacent cells. Adjacent cell membranes are very close.

Connexons

Gap junction in which cells are connected by hollow cylinders. Ions and small molecules pass through water filled channels. Present in electrically excitable tissue (Ex: heart and smooth muscle)

Passive transport

membrane transport moves substances down concentration gradient. Doesn’t require ATP

Active transport

ATP required to move cells against the concentration gradient (low to high)

1. Simple diffusion

2. Fascilitated dffusion

3. osmosis

Types of diffusion [3]

Diffusion

Spreading of particles in gas/solution moving towards uniform distribution of particles. Driven by kinetic energy

1. Concentration: greater difference in concentration in two areas, the more collisions, the faster particles diffuse

2. Molecular size: Smaller molecules diffuse faster

3. Temperature: Higher emp, faster movement, faster diffusion

Factors influencing diffusion speed [3]

1. lipid solubility: more it is soluble, more readily it diffuses

2. Size: smaller the molecule, more readily it diffuses

Factors influencing diffusion across selectively permeable membrane [2]

Simple diffusion

unassisted transport across plasma membrane. Particles are nonpolar, lipid soluble.

Gases, steroid hormones, fatty acids. (small, nonpolar, lipid soluble)

What can pass through membrane unassisted (simple diffusion)

Facilitated diffusion

Passive transport used by large/charged molecules that cannot pass through unaided. Movement is through channels or facilitated by membrane carrier

Carrier-mediated facilitated diffusion

Carrier changes shape to move binding site from one face to other. Moves down concentration gradient

Carrier

Transmemrane protein that forms an aqueous pore, allows substances to move from one side to the other. Transports polar molecules (sugars, amino acids)

Chanel-mediated facilitated diffusion

Channel allows substances to move from one side of membrane to the other. Transports ions, water. Selectively permeable due to pore size and charge of amino acids.

Channel

transmembrane protein that forms an aqueous pore

Leakage channels

Channel that is always open and allows ions/water to move according to the gradient

Gated channel

Channel controlled by chemicals, electrical signals. Channels can be inhibited by certain molecules. Substances always follow concentration gradient. Oxygen, water, glucose, and various ions.

Osmosis

Diffusion of solvent through selectively permeable membrane from dilute into more concentrated solution. Important in determining distribution of water. Occurs when water concentration differs on both sides of the membrane.

Aquaporin

Transmembrane proteins form water channels. Abundant in red blood cells and kidney cells

Number of solute particles. every one molecule/ion typically displaces one water molecule.

Decrease in water concentration depends on …

Osmolarity

Number of solute particles present in one liter of solution

Hydrostatic pressure

Pressure of fluid in system

Osmotic pressure

measure of tendency of a solvent to move into a more concentrated solution

Tonicity

measure of ability of solution to cause a change in cell shape or tone by altering cell’s internal water volume. How solution affects cell volume.

Isotonic solution

Same concentration of nonpenetrating solute as those found in cells. Cell retains shape, no net gain/loss of water. Ex: extracellular fluids and IV solutions

Hypertonic solution

Higher concentration of nonpenetrating solutes outside cell than inside cell. Cell loses water and shrivels.

Hypotonic solution

Higher concentration of nonpenetrated solutes inside the cell than outside. Cells plump up rapidly as water rushes into them.

Extreme hypotonicity

Water continues to enter cell rapidly until it bursts.

Specificity

Carriers/channels are specific to certain solutes

Saturability

If all protein channels are being used, then more cannot get through. Limited number of carriers/channels.

Active transport

Transport proteins combine specifically and reversibly with the transported substances. Moves against concentration gradient

Primary active transport

Energy to do work comes from hydrolysis of ATP by transport proteins called pumps

Phosphorylation

Transport proteins are energized by the transfer of phosphate group from ATP. Causes protein to change shape so it pumps the solute across the membrane.

Sodium potassium pumps

Primary active transport system, drives out Na+ against a gradient and pumps K+ back in.

3 Na+ / 2 K+

For each molecule of ATP used, pump drives out ______ and pumps _______ back in

10x higher

K+ concentration is ______ than outside

Electrochemical gradients

Ions diffuse according to this. Recognizes the effect of both electrical and concentration forces.

Secondary active transport

Driven by energy stored in concentration gradients of ions created by primary active transport pumps

Cotransport protein

Moves more than one substance at a time

Symport system

Two transported substances move in the same direction

Antiport system:

Transported substances “wave to each other” as they cross the membrane in opposite directions

Vesicular transport

Large particles and macromolecules into and out of cell or between compartments in membrane-bound sacs.

Transcytosis

Moves substances into THEN out of cell

Vesicular traffickin

Moves substances from one area in the cell to another. Uses ATP or sometimes GTP

Endocytosis

Vesicles provide main route for bringing fluids into the cell. Relies on receptors to be transported

Coated pit

infolding in membrane. has protein coating o cytoplasmic face that deforms membrane to produce the vesicle

Phagocytosis

Engulfing of solids by phagocytic cells. When particle binds to receptors on the cell’s surface, pseudopods form and flow around the particle. Forms phagosome (vesicle). Vesicle fuses with lysosome and is digested.

Macrophages or phagocytes

undergoes phagocytosis. protect body by ingesting and disposing bacteria and dead tissue cells. Moves by amoebid motion.

Pinocytosis/fluid-phase endocytosis

englding of extracellular fluid by cells. Membrane surrounds small volume of fluid containing dissolved molecules. droplets enter and fuse to endosome. Bits of membrane removed are recycled.

Receptor-mediated endocytosis

engulfed particles attach to receptors before endocytosis occurs. Concentrates material present in small amounts in extracellular fluid. Plasma membrane proteins only bind to certain substances.

Exocytosis (hormonee, neurotransmitters, eject waste)

Substances moved from the cell interior to extracellular space as secretory vesicle fuses with the plasma membrane. Enclosed in secretory vesicle, which migrates to membrane, fuses with it, ruptures, spills sac contents.

Nucleus. Nuclear envelope, nucleoli, and chromatin

Largest organelle, with three regions

Nuclear envelope

Double membrane barrier of nucleus separated by fluid filled space. Selectively permeable. Small particles pass through large pore complex unhindered. Proteins move through central channel

Outer membrane of nuclear envelope

Continuous with rough ER, is studded with ribosomes

Inner membrane of nuclear envelope

Lined by nuclear lamina that maintains shape of nucleus and scaffolding to organize DNA in nucleus

Nuclear pores

Complex lines each pore, forms aqueous transport channel that regulates entry and exit of material on nuclear envelope

Nucleoplasm

Jelly-like, where material is suspended in nucleus. Dissolves salts, nutrients, and essential solutes

nucleoli

Dense spherical bodies involved in rRna synthesis and ribosomal subunit assembly. Not membrane bound. 1-2 per nucleus. Center around DNA that codes for rRNA.

Chromatin (30% DNA, 60% globular histone proteins, 10% RNA chains)

Strands of DNA and associated protein; forms chromosomes.

Nucleosomes

fundamental unit of chromatin. consists of DNA strand wound around cluster of 8 histone proteins

Chromosomes

Bar-like bodies of tightly coiled chromatin, visible during cell division. Prevents chromatin from tangling/breaking during movements

1. Replication bubble: enzymes unwind DNA

2. H bonds break, “unzips” at replication fork

3. DNA polymerase puts free nucleotides, strands synthesizing in opposite directions, 2 new molecules

4. Restoration: ligase splices segments together

DNA replication process [4]

Interphase (90% of time)

1. G1

2. S

3. G2

Cell division

1. Mitotic

2. cytokinesis

Phases of Cell cycle in order

Gene

Unit of heredity located in DNA; transmits hereditary information

Triplet

3 bases that code for an amino acid

Exons

Amino acid-specifying sequence in genes

Intron

Non-coding segment of DNA (60,000 to 100,000 nucleotides long)

1. Critical cell volume: “outgrowing itself”

2. Chemicals: growth factor, hormones

3. Contact inhibition: availability of space. Too many cells, too packed

Controls of cell division [4]

Cancer

When controls of cell division stop working. Random/rapid cell division.

1. transcription

2. translation

Parts of protein syntheses [2]

transcription

Transferring genetic material from DNA to mRna. mRna can exit the nucleus, DNA cannot

Translation

mRNA codes for polypeptide chain. tRNA decodes mRNA

rRNA

RNA forms ribosomes in nucleoli. Ribosomal RNA

tRNA

RNA carries amino acid sequence from cytoplasm