wk 14 - proteins

Disulfide bonds

Strong chemical side bonds formed when the sulfur atoms in two adjacent protein chains are joined together

Primary structure of protein

The first level of protein structure; the specific linear sequence of amino acids joined by peptide bonds making up a polypeptide chain. coded for in the gene of DNA

Dipeptide

Two amino acids bonded together

Peptide bond

a bond that holds amino acids together; chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid

Sickle cell anemia

a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle (half moon) shape. happens when one amino acid is out of place. the GLU is replaced with a valene

The 'R' in a amino acid represents

a hydrogen or carbon-hydrogen group

What is formed by the linking of two amino acids

a peptide bond

Following a dehydration reaction of an amino acids

a peptide bond joins two amino acids and a water molecule is realeased

Actin and myosin

account for the movement of cells and the ability of our muscles to contract

Functional proteins are usually

alpha helix

Functional proteins shape

alpha helix

Coiling of the chain results in a

alpha helix - right handed spiral or slinky like shape

Two types of secondary structure

alpha helix and beta pleated sheet

Two types of secondary structure are possible. They are called the __________ and the ________

alpha helix and the beta pleated

The secondary structure is often an ______ or ________

alpha helix; beta pleated sheet

Building blocks of proteins

amino acids

Genes determine the sequence of

amino acids (eye color, hair, skin, nails, etc)

Proteins usually have >50

amino acids and are usually used more than once

Amino acids contain what functional groups

amino and carboxyl

-NH2 represents

amino group

Amino acid contains

amino group (-NH2), carboxyl group (-COOH) and R group varies, determining uniqueness of each amino acid

All amino acids have a _____ group and a _____ group

amino; carboxyl

The activity of many proteins (and enzymes) depends on the presence of

an active site that "fits" into a specific substrate

In enzymes the polypeptide..

bend and twists in different ways

Structural proteins are usually

beta pleated

Structural proteins shape

beta pleated proteins

Folding of the chain results in a

beta pleated sheet - similar to a hand held fan

The tertiary structure gives proteins their

biological activity

If a protein is denatured then the parts of the active site are no longer in close proximity, can no longer "fit" into the substrate, and therefore

cannot react

4 types of organic molecules

carbohydrates, lipids, proteins, nucleic acids

All proteins contain the same 4 elements

carbon, hydrogen, oxygen and nitrogen

-COOH represents

carboxyl (acid) group

in a peptide bond, the bond occurs between a

carboxyl group of one amino acid and amino group of another amino acid

Functional proteins

category of proteins that affect the functional operations of a cell; proteins that cause chemical changes in the molecules

Dentaure

change in the shape of an enzyme so that it can no longer speed up a reaction

The 'R' group gives each amino acid its

chemical properties

Hemoglobin

complex protein (iron-containing protein) in red blood cells that carries oxygen to your body's organs and tissues and transports carbon dioxide from you organs and tissues back to your lungs

Amino acid

compound with an amino group on one end and a carboxyl group on the other end

When proteins are exposed to extreme heat or pH they undergo an irreversible change in shape

denature. a protein denatures when it loses structure and function.

Hydrogen bonds in a protein are broken, then the shape of the protein can change, making it incapable of performing its physiologic function. The protein is said to be

denatured

What type of bond holds the secondary structure together

hydrogen bonds holds the secondary structure together

Amino acids are put together by dehydration synthesis and broken up by

hydrolysis reaction

The hydrogen bonding in amino acid

influences the structure and shape of a protein

If the hydrogen bonds in a protein can easily re-form, then the denaturation reaction is said to be

reversible

the regular reoccurring arrangement of the amino acid chains is called the ______________ of a protein

secondary structure

Hydrogen bonds hold

secondary structure together

Tertiary structure occurs when a polypeptide bends and twists into a

three-dimensional shape

Most enzymes have a quaternary structure

thus, proteins can differ in many ways, such as in length, sequence and structure

A ______ consists of three amino acids held together by ________ bonds

tripeptide; peptide

Each individual protein is

unique

Tertiary structure is maintained by

various types of bonding between R-groups; covalent bonding, ionic bonding, hydrogen bonding and disulfide bonding

Final shape of protein

very important; determines its function

The hydrophobic portions are packed mostly on the inside and the hydrophilic portions are on the outside where they can make contact with..

water

Everything is determine by the primary structure. If the primary structure is out of sequence then the rest of the sequence

will be out of whack

_______ bonds between the peptide bonds holds the shape in place

hydrogen

Proteins perform many functions

-catalyzing biochemical reactions -serving as receptors and transporters -aiding movement

Examples of structural proteins

-keratin (makes up hair and nails) -collagen (leads support to ligaments, tendons, and skin) -spiderwebs -silk

Proteins in plasma membranes of cells have various functions

-some form channels that allow substances to enter and exit (channels allow substances to cross membranes) -some are carriers that transport molecules into and out of the cell -some are enzymes

Examples of functional proteins

1. enzymes 2. hormones 3. actin and myosin 4. hemoglobin 5. immunoglobulins

Proteins 4 levels of structure

1. the sequence of its amino acids 2. the folding or coiling of the polypeptide chain 3. the complete, three-dimensional arrangement of a polypeptide chain 4. (only if the protein has more than one chain) the way in which the different polypeptides are arranged

There are _____ common amino acids found in living organism's

20

Primary structure of a polypeptide is its own particular sequence of the possible

20 types of amino acids

As these chains form the polypeptide develops multiple levels of structure, which contributes to its overall shape

4 levels of protein organization

Polypeptide

A polymer (chain) of many (~4-50) amino acids linked together by peptide bonds.

Plasma membrane

A selectively-permeable phospholipid bilayer forming the boundary of the cells

What types of bond holds these secondary structures together

hydrogen bonds

Enzymes

Catalysts for chemical reactions in living things; some proteins act as enzymes

Hormones

Chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another, influence cellular metabolism

Polarity of peptide bond

H bonding is possible between C-O of one amino acid and N-H of another amino acid in polypeptide

The chemical differences between one amino acid and another is due to

R group

Amino acids differ from one another by their

R group. R group varies from having a single carbon to being a complicated ring structure

In enzymes, the polypeptide bends and twists in

different ways

A ______ consists of two amino acids held together by a ________ bond

dipeptide; peptide

Proteins are broken down by

enzymes; hydrolyze them into amino acids

Amino acids are usually abbreviated by the

first 3 letters of their name

10 essential amino acids

for building proteins in body, need to get them from diet

Two or more polypeptides bond to make

functional protein

Genes tell your body how to sequence amino acids

genes are instructions for proteins that regulate the activity of other genes

In muscles, myosin molecules have a rod shape ending in a

globular (globe-shaped) heads

Examples of proteins with quaternary structures are

hemoglobin and the sodium channels in the cell membranes

In the denaturation of a protein, ________ bonds are broken

hydrogen

If the hydrogen bonds cannot re-form then the process is termed

irreversible denaturation

Each polypeptide has its own sequence of amino acids and

its own sequence of R groups

The shape of proteins determines

its structure

Proteins

long chain molecules composed of amino acids bonded together

Protein buffers

nearly all proteins can function as buffers. Proteins are made up of amino acids, which contain positively charged amino groups (-NH2) which acts as an H+ acceptor, and negatively charged carboxyl groups (-COOH) which act as an H- donor. The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers.

If the hydrogen bonds in a protein are broken, can the protein easily maintain its structural shape?

no

Enzymes cannot function unless they have their

normal shape

Tripeptide

three amino acids bonded together

Beta pleated sheet consists of parallel strands of polypeptides

parallel strands of polypeptides

What type of bond holds the amino acids together in the primary structure

peptide

What type of bond holds the primary structure together

peptide bonds hold the primary structure together

A ______ consists of many amino acids held together by a ________ bonds

polypeptide; peptide

The linear sequence of amino acids in a protein is called _____________ of that protein

primary structure

Some proteins have only one polypeptide and others have more than one polypeptide, each with its own....

primary, secondary and tertiary structures

4 levels of protein organization

primary, secondary, tertiary, quaternary

Immunoglobulins

protect cells. proteins that bind with specific antigens (foreign substances; toxins) in the antigen-antibody response. preventing them from destroying cells and upsetting homeostasis.

Every cell in the body carries out

protein synthesis (dehydration synthesis)

Amino acids bond together to form

proteins

Polymers composed of amino acids monomers

proteins

Denaturation occurs when

proteins encounter hostile environments such as temperature and pH, and therefore lose their shapes and functions; the normal bonding between R-groups are disturbed

Structural proteins

provide physical stability and movement; form an organism's physical attributes, give support.

Hemoglobin is a complex protein that has a _________ structure

quaternary

What level protein structure is determined by interactions of more than one polypeptide chain

quaternary

A protein can contain several, polypeptides and this accounts for a possible _________

quaternary structure

In proteins with multiple polypeptide chains these separate polypeptides are arranged to give such proteins a fourth level of structure termed..

quaternary structure

Separate polypeptide chains are arranged to give this the highest structure

quaternary structure

Factors that can denature proteins include

strong acids, heat, alcohol, and salts of heavy metals

Bond between R groups are

strong bonds

Proteins are molecules of

structure and function

Some proteins contain

sulfur, iron and phosphorus in addition to carbon, hydrogen oxygen and nitrogen

Interactions between r-groups hold

tertiary and quaternary structure together

Polypeptide chains can be made up of any combination of

the 20 different amino acids

Quaternary structure of protein

the 4th level of protein structure; the shape resulting from the association of two or more polypeptide subunits, only if proteins have more than one chain. occurs when two or more polypeptides interact to perform a biological function

Following a hydrolysis reaction of a polypeptide

the bond is broken with the addition of water

Secondary structure of protein

the second level of protein structure; the folding or coiling of the polypeptide chain. Protein takes on a certain orientation in space due to hydrogen bonding between amino acids causing the polypeptides to form and beta pleated sheet or and alpha helix.

Tertiary structure of protein

the third level of protein structure; the overall 3D shape of a polypeptide due to the interactions of the amino acid side chains with water, covalent bonding between R-groups, and other chemical interactions determine the folded 3D shape of a protein. complete 3D arrangement of a polypeptide

Atoms associated with peptide bond unevenly because oxygen is more electronegative than nitrogen

therefore, a hydrogen attached to nitrogen has a slightly positive charge, while oxygen has a slightly negative charge

In some cases proteins can form quaternary structures, which consists of interactions between multiple proteins

these interactions often result in the formation of large protein complexes

The coil of alpha-helix consists of loops of the linear arrangement of the amino acids

these loops are held together by bonds between the O of the C=O of one amino acid and the H of the NH of another amino acid

When your body breaks down proteins

they break down into amino acids and then your body reassembles them for different use