6.2 KiB
6.2 KiB
Proteins are large, complex, organic molecules made up of amino acids. - Contain carbon, hydrogen, oxygen, and nitrogen - Found in plants, animals, bacteria, and viruses
- Major functions of protein in the body:
- To build new cells and many parts of cells
- As a component in hardened structures like hair and nails
- As enzymes to speed chemical reactions
- As lubricants to ease movement
- In clotting compounds in blood
- To build antibodies that fight disease organisms
- As compounds that help maintain fluid and pH balance
- As transporters
- To make certain hormones
- As an energy source (as a last resort)
Introduction
- By helping to maintain fluid balance, proteins prevent edema (accumulation of fluid in tissues
- Proteins also help maintain acid-base balance.
- Maintaining the proper pH of body fluids
- Acts as a buffer
Amino acids
- Amino acids are nitrogen containing chemical units that comprise proteins
- There are 20 different amino acids found in the proteins of the human body
- Each amino acid has a carbon atom that anchors
- Hydrogen atom
- Amino or nitrogen containing group
- R group (side chain)
- carboxylic acid group
- nonessential amino acids are a group of amino acids that the body can make
- Essential amino acids are amino acids the body cannot make or cannot make enough of to meet its needs
- Conditionally essential amino acids are the amino acids the body cannot make or cannot make enough of to meet its needs
- There are 9 essential acids and 11 non-essential acids
| Essential | Nonessential |
|---|---|
| Histidine | Alanine |
| Isoleucine | Aspartic acid |
| Leucine | Asparagine |
| Lysine | Glutanic acid |
| Methionine | Serine |
| Phenylanaline | Argine |
| Threonine | Cysteine |
| Tryptophan (extra important) | GLutamine |
| Valine | Glycine |
| Proline | |
| Tyrosine | |
| TT HILL MVP |
Synthesis
A specific order of amino acids is needed to formulate a protein.
DNA
- DNA (deoxyribonucleic acid) provides instructions for making proteins.
- Genes are a portion of DNA
- To make proteins, cells assemble amino acids into specific sequences according to information from DNA
- A peptide bond is a chemical attraction that connects two amino acids together
DNA Process
- Protein synthesis begins when a section of DNA unwinds, exposing a single portion (a gene). The gene contains coded info about the order of amino acids that comprise a specific protein
- The gene undergoes transcription, that is, the sequence of amino acids copied is copied in a special manner, forming messenger RNA (mRNA) in the process.
- mRNA transforms the information concerning the amino acid sequence form the nucleus to ribosomes, protein manufacturing sites in cytoplasm.
- During the translation process, ribosomes "read" mRNA. The coded instructions indicate which amino acid to add to the polypeptide chain and its sequence.
- Each specific transfer RNA (tRNA) molecule conveys a particular amino acid to the ribosome.
- At the ribosome, the amino acid that has been delivered by the tRNA attaches to the peptide chain, lengthening it.
- When the translation process is complete, the ribosome release the polypeptide, and the new protein generally undergoes further processing at other sites within the cytoplasm.
Summary:
- Transcription: DNA unwinds, gene gets copied forming mRNA, happens in the nucleus
- DNA -> mRNA
- Translation: mRNA give info to ribosomes and they "read" mRNA. trNA gets each amino acid and brings it to the ribosome to be attached to the peptide chain. Happens in cytoplasm.
- mRNA -> ribosomes, ribosomes read mRNA -> tRNA grabs the amino acid needed -> ribosomes create peptide chain
Protein Structure
- The shape of protein is important because it influences the compound's function
- Sickle cell anemia is an inherited form of anemia.
- Denaturation alters a protein's natural shape and function by exposing it to conditions such as heat, acids, and physical agitation. This change is permanent.
In Foods
-
Animal foods generally provide higher amounts of protein than similar quantities of plant foods.
-
Certain parts of plants provide more protein than other parts
- Seeds, tree nuts, legumes supply more
- Fruits or edible leaves, roots, flowers, and stems of vegetables provide less
-
Legumes are parts of plants that produce pods with a single row of seeds.
- Peas
- Peanuts
- Lentils
- Soybeans
-
High quality (complete) protein is a protein that contains all essential amino acids in amounts that support the deposition of protein in tissues and the growth of a young person.
- Meat, fish, poultry, eggs, milk
-
Low quality (incomplete) protein is a protein that lacks or has inadequate amounts of one or more of the essential amino acids
-
A limiting amino acid is the essential amino acid found in the lowest concentration of a particular protein source\
-
A healthy adult's RDA for protein is 0.8 g/kg (apparently low)
-
Protein needs increase during
- Pregnancy
- Breastfeeding
- Periods of rapid growth
- Recovery
- Serious illness
- Blood losses
- Burns
Digestion
- Protein digestion begins in the stomach
- Hydrochloric acid denatures food proteins and activates pepsin
- Gastric enzymes that break proteins down into smaller polypeptides
- After polypeptides enter the small intestine, the pancreas secretes protein splitting enzymes.
- Trypsin and chymotrypsin
- Enzymes released by absorptive cells break down shortened peptides into dipeptides and tripeptides
- Two and three amino acids respectively
- Amino acids are carried to absorptive cells by carrier systems
- After absorption, amino acids enter the capillary of villus
- Travel to liver via hepatic portal vein
- Liver keeps some amino acids
- Release the rest into circulation
- Protein turnover is the cellular process of breaking down proteins and recycling their amino acids.
- Endogenous is a source of nitrogen