Animal Forms and Function (Physiology)

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Table of contents

  1. Chemistry

  2. Cells

  3. Cellular Respiration

  4. Photosynthesis

  5. Cell Division

  6. Heredity

  7. Molecular Genetics

  8. Evolution

  9. Biological Diversity

  10. Plants

  11. Animal Forms and Function (Physiology)

  12. Animal Reproduction and Development

  13. Animal Behavior

  14. Ecology

I. Chemistry
Atoms, Molecules, Ions, Bonds –

  • Atom is made up of neutrons, protons, and electrons. Molecules are groups of 2 or more atoms held together by chemical bonds. Chemical bonds are due to electron interactions

  • Electronegativity = ability of an atom to attract electrons

  • Bond Types:

    • Ionic – transfer of electrons from one atom to another (different electronegativities)

    • Covalent – electrons are shared between atoms (similar electronegativities) – can be single, double, triple

      • Nonpolar = equal sharing of electrons (identical electronegativity)

      • Polar = unequal sharing of electrons (different electronegativity and formation of a dipole)

    • Hydrogen – weak bond between molecules with a hydrogen attached to a highly electronegative atom and is attracted to a negative charge on another molecule (F, O, N)

* Properties of Water:

1. Excellent solvent: dipoles of H2O break up charged ionic molecules.

2. High Heat Capacity: heat capacity is the degree in which a substance changes temp in response to gain/loss of heat. The temp of large water body are very stable in response to temp changes of surrounding air; must add large amount of energy to warm up water. High heat of vaporization as well.

3. Ice Floats: water expands as it freezes, becomes less dense than its liquid form (H-bonds become rigid and form a crystal that keeps molecules separated).

4. Cohesion/Surface tension: attraction between like substances due to H-bonds; the strong cohesion between H2O molecules produces a high surface tension.

5. Adhesion: attraction of unlike substances. (wet finger and flip pages); capillary action: ability of liquid to flow without external forces (e.g. against gravity)
Organic Molecules –

  • Have carbon atoms. Macromolecules form monomers (1 unit) which form polymers (series of repeating monomers)

    • 4 of carbon’s 6 electrons are available to form bonds with other atoms

  • Functional group = particular cluster of atoms, give molecules unique properties

    • Hydroxyl (OH): polar and hydrophilic

    • Carboxyl (COOH): polar, hydrophilic, weak acid

    • Amino (NH2): polar, hydrophilic, weak base

    • Phosphate (PO3): polar, hydrophilic, acid (sometimes shows as PO4?) (y acidic?)

    • Carbonyl (C=O): polar and hydrophilic

      • Aldehyde (H-C=O)

      • Ketone (R-C=O)

    • Methyl (CH3): nonpolar and hydrophobic


  • Monosaccharide = single sugar molecule (e.g. glucose and fructose)

    • Alpha or beta based on position of H and OH on first (anomeric) carbon (down=alpha, up=beta)

  • Disaccharide = two sugar molecules joined by a glycosidic linkage (joined by dehydration)

    • E.g. sucrose (glu+fru), lactose (glu+gal), maltose (glu+glu)

  • Polysaccharide = series of connected monosaccharides; polymer

    • Bond via dehydration synthesis, breakdown via hydrolysis

- Starch: a polymer of α-glucose molecules; store energy in plant cells.

- Glycogen: a polymer of α-glucose molecules; store energy in animal cells. (differ in polymer branching).

- Cellulose: a polymer of β-glucose; structural molecules for walls of plant cells and wood.

- Chitin: polymer similar to cellulose; but each β-glucose has a nitrogen-containing group attached to ring. Structural molecule in fungal cell walls (also exoskeleton of insects, etc)
Lipids –

  • Hydrophobic molecules. Fxns: Insulation, energy storage, structural (cholesterol and phoslipids in membrane), endocrine

  • Triglycerides (triacylglycerols) = three fatty acid chains attached to a glycerol backbone

    • Saturated: no double bonds (bad for health, saturated = straight chain = stack densely and form fat plaques)

    • Unsaturated: double bonds (better for health, unsaturated = double bonds cause branching = stack less dense)

  • Phospholipid: two fatty acids and a phosphate group (+R) attached to a glycerol backbone

    • Amphipathic = both hydrophilic and hydrophobic properties

  • Steroids = three 6 membered rings and one 5 membered ring –hormones and cholesterol (membrane component)

  • Lipid Derivatives:

    • Phospholipids (covered above)

    • Waxes – esters of fatty acids and monohydroxylic alcohols. Used as protective coating or exoskeleton (lanolin)

    • Steroids (sex hormones, cholesterol, corticosteroids) – 4 ringed structure

    • Carotenoids – fatty acid carbon chains w/ conjugated double bounds and six membered C-rings at each end. Pigments which produce colors in plants and animals.

      • Carotenes and xanthophylls (subgroups)

    • Porphyrins (tetrapyrroles) – 4 joined pyrrole rings. Often complex w/ metal (e.g. porphyrin heme complexes with Fe in hemoglobin, chlorophyll w/ Mg)

Adipocytes (img) are specialized fat cells – white fat cells contain a large lipid droplet composed primarily of triglycerides with a small layer of cytoplasm around it, while brown fat cells have considerable cytoplasm, lipid droplets scattered throughout, and lots of mitochondria

Glycolipids are like phospholipids but w/ carb group instead of phos. Note: lipids are insoluble so they are transported in blood via lipoproteins (lipid core surrounded by phospholipids and apolipoproteins).

Note on lipids in membranes: Cell membranes need to maintain a certain degree of fluidity and are capable of changing membrane fatty acid composition to do so. In cold weather, to avoid rigidity, cells incorporate more mono and polyunsaturated fatty acids into the membrane (lower melting points and are kinked to increase fluidity). Warm weather climates show the opposite trend. Unsaturated fatty acids have lower melting point compared to saturated fatty acids – there are increased "kinks" in packing of the molecules as a result of the double bonds, which decrease the melting point due to less efficient packing (you can look at this two ways; freezing point: harder to pack into crystal/solid form with kinks so temp has to be lowered more, or melting point: less efficient packing means less intermolecular interactions, so less heat is needed to melt the solid liquid form). Cholesterol also has a role (see below).

Remember: the above trends are relevant for fatty acids as a group, not necessarily molecules in general. Random chemistry note: double/triple bonds tend to have decreased polarity vs single bonds in the same (already polar) bond.

Proteins –

  • Polymers of amino acids joined by peptide bonds

    • Amino acid structure: H, NH2, COOH bonded to a central carbon and then a variable R group

  • Structural, storage, transport, defensive (antibodies), enzymes

    • Storage protein: casein in milk, ovalbumin in egg whites, and zein in corn seeds.

    • Transport protein: Hemoglobin carries oxygen, cytochromes carry electrons

    • Enzymes: ATP contains ribose instead of deoxy-ribose (ATP isn’t an enzyme, why is this here?).

- amylase catalyzes the rxn that breaks the α-glycosidic bonds in starch.

- catalyzes a reaction in both forward and reverse directions based on [substrate].

- efficiency is determined by temp and pH.

- cannot change spontaneity of a rxn

Random note: enzymes are almost always considered to be proteins, but sometimes RNA can act as an enzyme (e.g. ribozymes)

- Cofactors are nonprotein molecules that assist enzymes. Holoenzyme is the union of the cofactor and the enzyme (the enzyme is called apoenzyme/apoprotein when NOT combined w/ cofactor); can be organic (called coenzymes e.g. vitamin) or inorganic (metal ions like Fe 2+ and Mg 2+). If cofactor strongly covalent bonds to enzyme = prosthetic group

  • Protein structure:

    • Classifications: simple (entirely amino acids), albumins + globulins (functional and act as carriers or enzymes), scleroproteins (fibrous, structural e.g. collagen), conjugated (simple protein + nonprotein), lipoprotein (bound to lipid), mucoprotein (bound to carb), chromoprotein (bound to pigmented molecule), metalloprotein (complexed around metal ion), nucleoprotein (contain histone or protamine, bound to nucleic acid).

    • Primary structure = sequence of amino acids

    • Secondary structure = 3d shape resulting from hydrogen bonding between amino and carboxyl groups of adjacent amino acids (e.g. alpha helix, beta sheet)

    • Tertiary structure = 3d structure due to noncovalent interactions between amino acid R groups (subunit interaction) (factors: H-bonds, ionic bonds, hydrophobic effect [R groups push away from water center], disulfide bonds, van der waals)

    • Quaternary structure = 3d shape of a protein that is a grouping of two or more separate peptide chains

Note:All proteins have a primary structure, and most have a secondary structure. Larger proteins can have a tertiary and quarternary structure. There are three main protein categories: globular proteins (somewhat water soluble, many fxns: enzymes, hormones, inter and intracellular storage and transport, osmotic regulation, immune response, etc., mostly dominated by 3ary structure), fibrous/structural proteins (not water soluble, made from long polymers, maintain + add strength to cellular and matrix structure, mostly dominated by 2ndary structure), and membrane proteins (membrane pumps/channels/receptors)

Note: Protein denaturation means the (secondary onward) structure of the protein is basically removed, not necessarily that the protein itself is broken down into individual amino acids. Denaturation is usually irreversible, but in some cases it can be reversed with the removal of the denaturing agent (implies all info needed for protein to assume its native state is encoded in the primary structure)

Nucleic Acids –

  • DNA is a polymer of nucleotides

    • Nucleotide: nitrogen base, five carbon sugar deoxyribose, phosphate group

      • Purines (2 rings) – adenine, guanine (double ring)—2 H bonds (AT2, GC3)

      • Pyrimidines (1 ring): thymine, cytosine (singe ring) – 3 H bonds (to remember: CUT the PYE)

      • A nucleoside is just the sugar+base

    • Two antiparallel strands of a double helix

  • RNA is a polymer of nucleotides that contain ribose, not deoxyribose

    • Thymine is replaced by uracil (which pairs with adenine)

    • Usually single stranded

Cell doctrine/theory: 1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of structure, function, and organization in all organisms. 3. All cells come from preexisting, living cells. 4. Cells carry hereditary information

RNA world hypothesis proposes that self-replicating ribonucleic acid (RNA) molecules were precursors to current life (based on deoxyribonucleic acid (DNA), RNA and proteins). RNA stores genetic information like DNA + catalyzes chemical reactions like an enzyme protein may have played a major step in the evolution of cellular life. RNA is unstable compared to DNA, so more likely to participate in chemical rxns (due to its extra hydroxyl group).

Central dogma of genetics: biological information cannot be transferred back from protein to either protein or nucleic acid; DNA  RNA  proteins

Know basic microscopy:

-Stereomicroscope (light): Visible light for surface of sample. Can look at living samples, but low resolution vs compound light micro.

-Compound microscope (light): Visible light for thin section of sample. Can look at some living samples (single cell layer). May require staining for good visibility.

-Phase-contrast: Uses light phases and contrast. Allows for detailed observation of living organisms (including internal structures) if thin. Good resolution/contrast, but not good for thick samples and produces “Halo effect” around perimeter of samples.

-Confocal laser scanning + fluorescence: Can look at thin slices while keeping sample intact; can look at specific parts of cell via fluorescent tagging. Can look at living cells, but only fluorescently tagged parts. Fluorescence can cause artifacts. Used to observe chromosomes during mitosis. Note: confocal laser scanning microscope can be w/out fluorescence as well. Uses laser light to scan dyed specimen, then displays the image digitally.

-Scanning elctron microscope (SEM): Look at surface of (3D) objects with high resolution. Can’t use on living: preparation is extensive (sample needs to be dried and coated). Costly.

-CryoSEM: Like SEM but no dehydration so you can look at samples in more “natural” form. Can’t use on living: samples frozen for prep, which can cause artifacts.

-Transmission electron microscope (TEM): look at very thin cross-sections in high detail. Can look at internal structures, very high resolution, but can’t be used on living things (preparation is extensive). Costly.

-Electron tomography: 3D model buildup using TEM data. Can look at objects in 3D and see objects relative to one another. Can’t be used on living things (see TEM above).

Centrifugation (spins + seperates liquified cell homogenates separate into layers based on density: (most dense/fastest to pellet out/the bottom is nuclei layer, spin faster then mitochondria/chloroplasts/lysosome/peroxisomes, spin faster  then microsomes [internal membranes from ER]/small vesicles, spin faster  then ribosomes/viruses/larger macromolecules). Centrifugation can be differential centrifugation or density centrifugation, the former is density + shape factor based on speed the macromolecule travels at whereas density is just density based. The above described spin pattern is differential centrifugation, we spin and take the dense pellet and then spin again repeat. Density centrifugation is continuous layers of sediment.

Chemical Reactions in Metabolic Processes –

  • Catalysts lower activation energy, accelerating the rate of the rxn

  • Metabolism = catabolism + anabolism + energy transfer

  • Characteristics of chemical reactions

    • Concentration of reactants and products determines which way a rxn will go

      • Equilibrium: rate of forward and reverse rxns is the same = 0 net production

    • Enzymes are globular proteins that act as catalysts

      • Substrate specific, unchanged during rxn, catalyzes in both forward and reverse directions, temperature and pH affect enzyme function, active site and induced fit is how enzymes bind

    • Cofactors are nonprotein molecules that assist enzymes usually by donating or accepting some component of a rxn like electrons

      • Coenzyme are organic cofactors , usually donate or accept electrons

        • Vitamins

      • Inorganic cofactors are usually metal ions (Fe 2+ and Mg 2+)

      • If binds tightly/covalently, prosthetic group

    • ATP – common source of activation energy. New ATP formed via phosphorylation (ADP + phosphate using energy from energy rich molecule like glucose). Note that ATP contains, but is not itself, potential energy.

  • Regulation (more here):

    • Allosteric enzymes – have both an active site for substrate binding and an allosteric site for binding of an allosteric effector (activator, inhibitor)

    • Competitive inhibition – substance that mimics the substrate inhibits the enzyme by binding at the active site. Can be overcome by increasing substrate cxn. Km changed (raised) but Vmax is not

    • Noncompetetive inhibition – substance inhibits enzyme by binding elsewhere than active site, substrate still binds but reaction is prevented from completing. Km unchanged but Vmax is not.

    • Uncompetitive/anti-competitive inhibition: enzyme inhibitor binds only to the formed E-S complex, preventing formation of product (Vmax lowered). Km is also lowered (Le Chetalier’s principle: the equilibrium between E-S complexes and ESI (inhibitor attached) complexes is disrupted by this type of inhibition, as it favors the ESI: so ES complexes are depleted. E+S  ES complex is subsequently shifted forward, so the enzyme’s apparent affinity for the substrate is raised = lower Km).

    • Cooperativity – enzyme becomes more receptive to additional substrate molecules after one substrate molecule attaches to an active site (e.g enzymes w/ multiple subunits that each have active site [quaternary structure])

      • Example of process: hemoglobin binding additional oxygen (although hemoglobin enzyme!)

    • Km is the Michaelis constant. It represents the substrate cxn at which the rate is half of Vmax. In a way it indirectly represents binding affinity, inversely: small Km indicates that the enzyme requires only a small amount of substrate to become saturated. Hence, the maximum velocity is reached at relatively low substrate concentrations. A large Km indicates the need for high substrate concentrations to achieve maximum reaction velocity. So raised Km = substrate is binding worse, lowered Km = substrate is binding better.


II. Cells

  • Membrane proteins: peripheral (loosely attached to one side surface), integral (embeds inside membrane), transmembrane (all the way through, both sides – this is a TYPE of integral)

  • Phospholipid membrane permeability – small, uncharged, nonpolar molecules (polar can only if small and uncharged) and hydrophobic molecules can freely pass across the membrane. Everything else requires transporter (large, polar, charged molecules). Another way of saying impermeable is “resistant to”.

  • Note: peripheral membrane proteins are generally hydrophilic; held in place by H-bonding and electrostatic interaction. Disrupt/detach by changing salt cxn or pH to disrupt these interactions. Integral proteins are hydrophobic; use detergent to destroy membrane and expose these proteins.

* Proteins:

- Channel proteins: provide passageway through membrane for hydrophilic (water-soluble) substances (polar, and charged).

**- Recognition proteins: such as major-histocompatibility complex on macrophage to distinguish between self and foreign; they are glycoproteins due to oligosaccharides attached.

- Ion channels: passage of ions across membrane. Called gated channels in nerve and muscle cells, respond to stimuli. Note that these can be voltage-gated (respond to difference in membrane potential), ligand-gated (chemical binds and opens channel), or mechanically-gated (respond to pressure, vibration, temperature, etc).

**- Porins: allow passage of certain ions + small polar molecules. Aquaporins increase rate of H2O passing (kidney and plant root cells). These tend not to be specific, they’re just large passages, if you can fit you’d go through.

- Carrier proteins: bind to specific molecules, protein changes shape, molecule passed across. E.g. glucose into cell.(this is a type of transport protein). Carrier seems to be specific to movement across membrane via integral membrane protein.

- Transport proteins: can use ATP to transport materials across (not all transport use ATP). Active transport. E.g. Na+-K+ pump to maintain gradients. Facilitated diffusion as well. Transport protein is a broad category that encompasses many of the above. Chad’s quiz says transport use ATP but other sources contradict: transport can by facilitated diffusion.

**- Adhesion proteins: attach cells to neighboring cells, provide anchors for internal filaments and tubules (stability)

- Receptor proteins: binding site for hormones + other trigger molecules
- Cholesterol: adds rigidity to membrane of animal cells under normal conditions (but at low temperatures it maintains its fluidity); sterols provide similar function in plant cells. Prokaryotes do not have cholesterol in their membranes (use hopanoids instead)

**- Glycocalyx: a carbohydrate coat that covers outer face of cell wall of some bacteria and outer face of plasma membrane (some animal cells). It consists of glycolipids (attached to plasma membrane) and glycoproteins (such as recognition proteins). It may provide adhesive capabilities, a barrier to infection, or markers for cell-cell recognition.
* Organelles

- Nucleus: chromatin is the general packaging structure of DNA around proteins in eukaryotes, the tightness of the packaging varies depending on cell stage; chromosomes is tightly condensed chromatin when the cell is ready to divide; histones serve to organize DNA which coil around it into bundle nucleosomes (8 histones); nucleolus inside the nucleus are the maker of ribosomes (rRNA). rRNA is synth’d in nucleolus + ribosomal proteins imported from cytoplasm = ribosomal subunits form; these subunits are exported to the cytoplasm for final assembly into complete ribosome. Nucleus bound by double layer nuclear envelope w/ nuclear pores for transport (mRNA, ribosome subunits, dNTPs, proteins like RNA polymerase + histones, etc) in/out. Note there is no “cytoplasm” in nucleus, there’s a nucleoplasm instead.

**- Nuclear Lamina: dense fibrillar network inside nucleus of eukaryotic cells (Intermediate filaments + membrane assoc. proteins). Provides mechanical support; also helps regulate DNA replication, cell division, chromatin organization.

- Nucleoid: irregular shaped region within the cell of prokaryote that contains all/most generic material

- Cytoplasm: this is an area, not a structure! metabolic activity and transport occur here. Cyclosis is streaming movement within cell. Doesn’t include nucleus, but does included cytosol, organelles, everything suspended w/in cytosol but nucleus

- Cytosol: difference vs cytoplasm here (cytosol doesn’t include the stuff suspended within the gel-like substance, it is JUST the gel-like stuff. Think jello vs veggie stew.) (the cytosol is also known as cytoplasmic matrix)

- Ribosomes: 60S + 40S = 80S, prokaryote (50S + 30S = 70S); the two subunits produced inside the nucloleus moved into the cytoplasm where they assembled into a single 80S ribosomes (larger S value indicates heavier molecule). Made of rRNA+protein, function to make proteins.

**- ER: rough ER (with ribosomes) creates glycoproteins by attaching polysaccharides to polypeptides as they are assembled by ribosomes. In eukaryotes the rough ER is continuous with the outer nuclear membrane. Smooth ER (no ribosomes) synthesizes lipids and steroid hormones for export. In liver cells, smooth ER has functions in breakdown toxins, drugs, and toxic by-products from cellular rxn. Smooth and striated muscle have smooth ER’s called sarcoplasmic reticulums that store and release ions, e.g. Ca 2+

**- Lysosomes: vesicles produced from Golgi that contain digestive enzymes (low pH for function); break down nutrients/bacteria/cell debris. Any enzyme that escape from lysosomes remains inactive in the neutral pH of cytosol (other source says autolysis) (lysosomes in plant cell – maybe, but generally taught as none). Functions in apoptosis (releases contents into cell).

- Golgi: transport of various substances in vesicles (cis face is for incoming vesicles, trans face for secretory vesicles). Has flattened sacs known as cisternae.

**- Peroxisomes: break down substances (H2O2 +RH2 => R + 2H2O), fatty acid, and amino acid; common in liver and kidney where they break toxic substances. In plant cell, peroxisomes modify by-products of photorespiration. In germinating seeds, it is called glyoxysomes break down stored fatty acids to help generate energy for growth. Peroxisome produce H2O2 which they then use to oxidize substrates, they can also break down H2O2 if necessary (H2O2 => H2O + O2)

**- Microtubules: made up of protein tubulin, provide support and motility for cellular activities; spindle apparatus which guide chromosomes during division; in flagella and cilia (9+2 array; 9 pairs + 2 singlets in center) in all animal cells and lower plants (mosses, ferns).

**- Intermediate filaments: provide support for maintaining cell shape. E.g. keratin.

- Microfilament: made up of actin and involved in cell motility. (skeletal muscle, amoeba pseudopod, cleavage furrow)

**- Microtubules organizing centers (MTOCs): include centrioles and basal bodies (are at the base of each flagellum and cilium and organize their development). 9x3 array. Plant cells lack centrioles and its division is by cell plate instead of cleavage furrow – note that plants DO have MTOC’s.

- Transport vacuoles: move materials between organelles or organelles and the plasma membrane

- Food vacuoles: temporary receptacles of nutrients; merge with lysosomes which break down food.

- Central vacuoles: large, occupy most of plant cell interior, exert turgor when fully filled to maintain rigidity. Also store nutrients, carry out functions performed by lysosomes in animal cells. Have a specialized membrane (tonoplast)

**- Storage vacuoles: plants store starch, pigments, and toxic substances (nicotine).

**- Contractile vacuoles: in single-celled organisms that collect and pump excess water out of the cells (prevent bursting). Active transport. Found in Protista like amoeba and paramecia, organisms live in hypotonic environment.

- Cell walls: found in plants, fungi, protists, and bacteria (cellulose in plants; chitin in fungi; peptidoglycans in bacteria, polysaccharides in archea). Provides support. Sometimes a secondary cell wall develops beneath the primary one.

**- Extracellular matrix: found in animals, in area between adjacent cells (beyond plasma membrane and glycocalyx); occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by cells; provide mechanical support and helps bind adjacent cells (collagen is most common here, we also see integrin+fibronectin; network of collagen and proteoglycans connected to integrins in the cell membrane via fibronectin). Laminin can be seen as well (acts similar to fibronectin). Images here. Note that cells adhere to the ECM in two ways: focal adhesions (connection of ECM to actin filaments in the cell) and hemidesmosomes (connection of ECM to intermediate filaments e.g. keratin).

- Plastids: found in plant cells. Chloroplasts (site of photosynthesis), leucoplasts (can specialize to store starch/lipid/protein as amyloplasts/elaioplasts/proteinoplasts respectively, or serve general biosynthetic fxns), chromoplasts (store carotenoids)

Mitochondria: make ATP, also fatty acid catabolism (B-oxidation)! (fatty acids are made in cytosol). Also have their own circular DNA and ribosomes (gives rise to endosymbiotic theory!). Have a double layered membrane.

**Cytoskeleton: microtubules (ex. flagella & cilia), microfilaments, intermediate filaments. In eukaryotic cells, aids in cell division, cell crawling, and the movement of cytoplasm and organelles.

Note on plant cells: in a hypotonic solution (their normal state), vacuole swells  turgid. In isotonic, the plant cell is flaccid. In hypertonic, the cell is plasmolyzed – cytoplasm is pulled away from the cell wall. Fungal cells also remain turgid due to cell wall, but animal cells will burst (cytolysis).

The endomembrane system is the network of organelles and structures, either directly or indirectly connected, that function in the transport of proteins and other macromolecules into or out of the cell.Includes plasma membrane, endoplasmic reticulum, golgi apparatus, nuclear envelope, lysosomes, vacuoles, vesicles, endosomes but not the mitochondria or chloroplasts.

* Circulation:

  • Intracellular Circulation

    • Brownian movement (particles move due to kinetic energy, spreads small suspended particles throughout cytoplasm)

    • Cyclosis/streaming: circular motion of cytoplasm around cell transport molecules

    • Endoplasmic Reticulum: Provides channel through cytoplasm, provides direct continuous passageway from plasma membrane to nuclear membrane

  • Extracellular Circulation

    • Diffusion: If cells in close contact with external environment, can suffice for food and respiration needs. Also used for transport of materials between cells and interstitial fluid around cells in more complex animals

    • Circulatory system: complex animals w/ cell too far from external environment require one. Use vessels.

* Junctions:

**- Anchoring junctions: desmosome (keratin filaments inside attach to adhesion plaques which bind adjacent cells together via connecting adhesion proteins, providing mechanical stability, hold cellular structures together). In animal cells. Present in tissues with mechanical stress – skin epithelium, cervix/uterus. img

- Tight junctions: completely encircles each cell, producing a seal that prevents the passage of materials between cells; characteristic of cells lining the digestive tract where materials are required to pass through cells into blood (They prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue). In animal cells. img

- Gap junction: narrow tunnels between animal cells (connexins); prevent cytoplasms of each cell from mixing, but allow passage of ions and small molecules; essentially channel proteins of two adjacent cells that are closely aligned (smooth muscle single of spreading action potential). In animal cells. Tissue like heart have these to pass electrical impulses. img

- Plasmodesmata: narrow tunnels between plant cells (narrow tube of endoplasmic reticulum-desmotubule; but exchange material through cytoplasms surrounding the desmotubule). img
* Prokaryotes and Eukaryotes:

**Eukaryotes include all organisms except for bacteria, cyanobacteria, and archaebacteria. Prokaryotes have a plasma membrane, DNA molecule, ribosomes, cytoplasm, and cell wall. In prokaryotes:

1. No nucleus. 4. Cell walls (peptidoglycan); archea (polysaccharides) – many have sticky capsules on wall

2. Single (circular) naked ds DNA (no chromatin).

3. Prokaryote (50S + 30S = 70S); 5. Flagella are constructed from flagellin not microtubules in prokaryotes.

  • Substance Movement:

    • Hypertonic (higher solute concentration), hypotonic (lower solute concentration), isotonic (equal solute concentration)

    • Bulk Flow = collective movement of substances in the same direction in response to a force or pressure (e.g. blood)

    • Passive Transport –

      • Simple diffusion, osmosis, dialysis (diffusion of different solutes across a selectively permeable membrane), plasmolysis (movement of water out of a cell that results in its collapse), facilitated diffusion, countercurrent exchange (diffusion by bulk flow in opposite directions – blood and water in fish gills). Note: diffusion is net, some few particles still move against the gradient because molecule movement is random, but net diffusion is generally what we talk about.

    • Active Transport – movement of transports against their concentration gradients requiring energy. Usually solutes like small ions, amino acids, monosaccharides

* Endocytosis: uses ATP (active process) (exocytosis is also active process) (Cliff’s FC says bulk flow is active too…?)

- Phagocytosis: undissolved material (solid) enters cell; white blood cell engulfs. Plasma membrane wraps outward around.

- Pinocytosis: dissolved material (liquid). Plasma membrane invaginates.

- Receptor-mediated: a form of pinocytosis; specific molecules (ligand) bind to receptors; proteins that transport cholesterol in blood (LDL) and hormones target specific cells by this.

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