Molecular Cell Final

Most abundant molecule in cells

Water

What bonds form between amino acids in different parts of a protein?

Hydrogen bonds

Why do ions dissociate in aqueous solutions?

Ions interact with polar water molecules

Reaction will proceed in what direction when gibbs free energy (deltaG) is less than 0?

reaction will proceed forward

Reaction will proceed in what direction when gibbs free energy (deltaG) is greater than 0?

reverse direction

Many biological reactions are thermodynamically unfavorable. What direction do these reactions go?

reverse

Bonds between ATP are high energy. Is hydrolysis of them accompanied by a large increase or decrease in free energy?

decrease

Energy-yielding reactions are coupled by ATP synthesis or hydrolysis?

Synthesis

What molecules are the major nutrients of the cell?

Monosaccharides

Principle source of cellular energy

glucose

How are monosaccharides linked? (what type of reaction?)

Dehydration reactions

Sugars are linked by what type of bond?

Glycosidic

Which has more polymers? Oligosaccharides or polysaccharides?

Polysaccharides

Formation of glycosidic bonds is energetically _____ and thus coupled to energetically ______ reactions.

unfavorable, favorable

Two common polysaccharides and what type of cell they’re used in

Glycogen (animal cell) and starch (plant cell)

Glycogen and starch are composed of what molecule and in what configuration?

Glucose molecules in the alpha configuration

What kind of linkages make up cellulose?

Glucose in beta (1-4) linkages

Fatty acids

long hydrocarbon chains with a carboxyl group at one end

Unsaturated fatty acids

one of more double bonds

Saturated fatty acids

No double bonds and hydrocarbon chain is hydrophobic

Are fats or carbohydrates better energy storage?

Fats

Sphingomyelin is the only _____?

nonglycerol phospholipid in cell membrane

What is the polar head of sphingomyelin formed from?

Serine instead of glycerol

2 common lipids found in cell membranes

glycolipids and cholesterol

steroid hormones are derivatives of what?

cholesterol

nucleotide polymers

purine and pyrimidine

how many hydrogen bonds are made between each pair of bases?

G + C = 3

A + T = 2

denaturation disrupts what types of bonds?

non-covalent bonds

Primary protein structure

sequence of amino acids in the polypeptide chain

Secondary protein structure

regular arrangement of amino acids within localized regions held together by hydrogen bonds between peptide bond groups

Tertiary protein structure

folding of the polypeptide chain due to interactions between side chains of amino acids

Quaternary protein structure

interactions between different polypeptide chains in proteins composed of more than one polypeptide

equilibrium is determined by ______

the final energy states of S and P (substrate and product)

basal laminae

thin layers on which epithelial cells rest and also surrounds other kinds of cells

where is extracellular matrix most abundant?

connective tissues

what are connective tissues

bone, tendon, and cartilage

tendons

high proportion of fibrous proteins

cartilage

high levels of polysaccharides that form a compression-resistant gel

bone matrix

calcium phosphate crystals

loose connective tissue

beneath dermis of skin, tracts, and around blood vessels and joints to cushion and support independent movement

adipose tissue

deep to the skin for padding and insulates heat and stores energy

dense connective tissues

between skeletal muscles, bones, and capsules of internal organs to provide firm attachment and movement of muscles by reducing friction and overexpansion of organs

What is the major structural protein

collagen

what is the smallest amino acid that allows polypeptides to pack closely together?

glycine

what two amino acids stabilize the helices in collagen?

proline and hydroxyproline

what groups stabilize the triple helix in collagen and how?

Hydroxyl groups stabilize by forming hydrogen bonds

fibril-forming collagen

fibers formed in connective tissues (skin, bone, and cartilage)

network forming collagen

formation of basal laminae

fibril-associated collagen

association of collagen fibrils with other extracellular matrix components

anchoring collagen

attachment of basal laminae to underlying connective tissue

transmembrane collagen

cell surface molecules with transmembrane domains

most abundant and fibril-forming collagen

Type 1 forming staggered arrays

lysine and hydroxylysine function in fibrils

strengthen through covalent cross-links between side chains

what type of collagen are basal laminae

mostly type IV, VI, and XVIII (all network forming collagens)

what are extracellular matrix gels formed from?

polysaccharides called glycosaminoglycans (GAGs)

the sugars in extracellular matrix gels are modified with sulfate groups except for what sugar?

hyaluronan

what makes GAGs highly negatively charged?

addition of sulfate groups

what is the only GAG that is a single long polysaccharide chain?

Hyaluronan

All other GAGs are linked to proteins to form what?

Proteoglycans

Fibronectin has binding sites for what two molecules and is recognized by what?

binding sites for collagen and GAGs and recognized by integrin

integrins

surface receptors in extracellular matrix

Heterodimer composition

18 alpha subunits and 8 beta subunits creating 24 different integrins

what does integrin bind to (3)

collagen, fibronectin, and laminin

the two types of cell-matrix junctions

focal adhesions and hemidesmosintegrinssssssomes

focal adhesions

bundles of actin filaments anchored to beta subunits of integrins

Hemidesmosomes

anchor epithelial cells to basal laminae

integrins link basal lamina layer of extracellular matrix to what?

intermediate filaments

The four groups of cell adhesion molecules

-selectins

-integrins

-immunoglobulin superfamily (Ig)

-cadherins

Many adhesions depend on what type of cations?

divalent (+2 charge)

selectins ligans recognized

carbs

integrins ligands recognized

extracellular matrix and members of ig superfamily

Ig superfamily ligands recognized

integrins and other Ig superfamily proteins

Cadherins ligans recognized

other cadherins

Selectins do what between leukocytes and endothelial cells?

mediate transient interactions

When selectins bind to endothelial cells, what happens after?

more stable interactions between leukocyte integrins and the intercellular adhesion molecules on the endothelial cells

heterophilic interaction

an adhesion molecule on one cell recognizes a different molecues on another cell

homophilic interactions

adhesion molecules on one cell binds to the same molecule on another cell

cadherins mediate what type of interactions?

homophilic

tight junctions

form a seal that prevents free passage of molecules and ions between cells in epithelial cells

tight functions are associated with what?

adherens functions and desmosomes in a functional complex

gap junctions

open channels through the plasma membrane for small molecules and ions

excitable cells such as heart muscle how are contractions of neighboring cells synchronized

passage of ions through gap junctions

Gap junctions allow the passage of signaling molecules such as what?

cAMP and Ca+2

electrical synapse

specialized gap junctions on specific nerve cells

middle lamella

pectin-rich region that acts a glue to hold adjacent cells together

plasmodesmata

cytoplasmic connections between plants, analogous to gap junctions

how do plasmodesmata form?

incomplete separation of daughter cells following mitosis

direct cell-cell signaling

direct interaction of a cell with its neighbor via integrins and cadherins

Endocrine signaling

secreted by endocrine cells and carried through the circulation to target cells at distant body sites

Paracrine signaling

released by one cell that acts on neighboring target cells (neurotransmitters)

Autocrine signaling

cells respond t signaling molecules that they produced themselves (T lymphocytes driving their own proliferation)

intracellular receptors respond to what?

small hydrophobic molecules that can diffuse across the membrane

Examples of small hydrophobic molecules that can diffuse across the plasma membrane

steroid hormones, thyroid hormones, vitamin D, and retinoic acid

adrenal gland steroids

corticosteroids

glucocorticoids function

stimulate production of glucose

mineralocorticoids function

act on the kidney to regulate salt and water balance

thyroid hormone

synthesized from tyrosine and important in development and metabolism

vitamin D

regulates Ca+2 metabolism and bone regrowth

Retinoic acid

synthesized from vitamin A and important in development

receptors for small hydrophobic molecules

nuclear receptor superfamily