molecules and membranes

Water

Most abundant molecule in cells

Monosaccharides

Simple sugars

Dehydration reactions

Join together glucose forming glycosidic bonds

Polysaccharides

Polymers of many sugars

Oligosacchrides

Polymers of few sugars

Glycogen, starch, cellulose, chitin

Examples of polysaccharides

Stores glucose in animal cells, alpha config

Glycogen

Stores glucose in plant cells, alpha config

Cellulose

Main structural component of plant cell walls, beta config

Cellulose

Forms exoskeletons of crabs and insects

Chitin

Energy storage, cell signaling, messenger molecules

Main functions of lipids

Long hydrocarbon chains with carboxyl group at one end

Fatty acid

Fatty acid with no double bond

Saturated fatty acid

Fatty acid with at least 1 double bond

Unsaturated fatty acid

3 fatty acids linked to glycerol molecule

Triglycerides/fats

Principal components of cell membranes

Phospholipids

Polymers of 20 different amino acids

Proteins

Transport+storage of small molecules, transmit information between cells, defense against infection, enzymes

Functions of proteins

Secondary structure of protein

Tertiary structure of proteins

Quaternary structure of proteins

Principal information molecules of the cell

Nucleic acids

MRNA

Carries information from DNA to ribosomes

RRNA and tRNA

Nucleic acids involved in protein synthesis

Purines

Adenine and guanine

Pyrimidines

Cytosine, thymine/uracil

Oligonucleotides

Polymers of few nucleotides

Polynucleotides

Polymers of many nucleotides

Enzymes

Catalysts that increase the rate of all chemical reactions in cells

Enzymes work by lowering what

Activation energy

Activation energy

Energy required to reach transition state

Lock-and-key model

Substrate fits precisely into the active site

Induced fit model

Conformation of both enzyme and substrate is modified

Serine proteases

Enzymes that cleave peptide bonds adjacent to specific types of amino acids

Active sites

Serine, histidine, aspartame

Chymotrypsin

Serine protease produced by pancreas that hydrolysis peptide bonds of tryptophan, leucine, and phenylalanine

Nicotineamide adenine dinucleotide (NAD+)

Coenzyme that carries electrons in oxidation-reduction reactions

Prosthetic groups

Small molecules bound to proteins that have critical functional roles

Critical group in myoglobin and hemoglobin, carries oxygen

Heme

Allosteric regulation

Enzyme activity is controlled by the binding of small molecules to regulatory sites on the enzyme

Feedback inhibition

Changes the conformation of the enzyme and alters the active site

Phosphorylation

Phosphate groups are added to the side chain OH groups of serine,threonine or tyrosine ; common mechanism of enzyme regulation (stimulate/inhibit)

Phospholipid structure in cell membrane exposed to water

Polar head groups

Phospholipid structure in cell membrane buried in interior of the membrane

Hydrophobic tails

What chemical helps determine membrane fluidity because of its ring structure

Cholesterol

How does cholesterol maintain membrane fluidity at lower temperatures

By reducing interaction between fatty acids

Can diffuse freely through a phospholipid bilayer

Gases, hydrophobic and small uncharged molecules

Molecules the phospholipid bilayer is impermeable to

Large polar molecules including glucose, amino acids, and ions

Channel proteins

Form open pores through which molecules of the appropriate size such as ions can cross the membrane

Carrier proteins

Selectively bind the small molecules to be transported and the undergo a conformational change to release the molecule on the other side of the membrane