117 lines
6.2 KiB
Markdown
117 lines
6.2 KiB
Markdown
Proteins are large, complex, organic molecules made up of **amino acids**.
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- Contain carbon, hydrogen, oxygen, and nitrogen
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- Found in plants, animals, bacteria, and viruses
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- Major functions of protein in the body:
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- To build new cells and many parts of cells
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- As a component in hardened structures like hair and nails
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- As enzymes to speed chemical reactions
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- As lubricants to ease movement
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- In clotting compounds in blood
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- To build antibodies that fight disease organisms
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- As compounds that help maintain fluid and pH balance
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- As transporters
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- To make certain hormones
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- As an energy source (as a last resort)
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# Introduction
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- By helping to maintain fluid balance, proteins prevent **edema** (accumulation of fluid in tissues
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- Proteins also help maintain **acid-base balance**.
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- Maintaining the proper pH of body fluids
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- Acts as a buffer
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# Amino acids
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- Amino acids are nitrogen containing chemical units that comprise proteins
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- There are 20 different amino acids found in the proteins of the human body
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- Each amino acid has a carbon atom that anchors
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- Hydrogen atom
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- Amino or nitrogen containing group
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- R group (side chain)
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- carboxylic acid group
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- nonessential amino acids are a group of amino acids that the body can make
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- Essential amino acids are amino acids the body cannot make or cannot make enough of to meet its needs
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- Conditionally essential amino acids are the amino acids the body cannot make or cannot make enough of to meet its needs
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- There are 9 essential acids and 11 non-essential acids
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| Essential | Nonessential |
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| ---------------------------- | ------------- |
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| Histidine | Alanine |
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| Isoleucine | Aspartic acid |
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| Leucine | Asparagine |
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| Lysine | Glutanic acid |
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| Methionine | Serine |
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| Phenylanaline | Argine |
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| Threonine | Cysteine |
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| Tryptophan (extra important) | GLutamine |
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| Valine | Glycine |
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| | Proline |
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| | Tyrosine |
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TT HILL MVP
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# Synthesis
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A specific order of amino acids is needed to formulate a protein.
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# DNA
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- DNA (deoxyribonucleic acid) provides instructions for making proteins.
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- **Genes** are a portion of DNA
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- To make proteins, cells assemble amino acids into specific sequences according to information from DNA
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- A **peptide bond** is a chemical attraction that connects two amino acids together
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# DNA Process
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1. 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
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2. 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.
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3. mRNA transforms the information concerning the amino acid sequence form the nucleus to **ribosomes**, protein manufacturing sites in cytoplasm.
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4. During the **translation** process, ribosomes "read" mRNA. The coded instructions indicate which amino acid to add to the polypeptide chain and its sequence.
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5. Each specific **transfer RNA** (tRNA) molecule conveys a particular amino acid to the ribosome.
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6. At the ribosome, the amino acid that has been delivered by the tRNA attaches to the peptide chain, lengthening it.
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7. 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.
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Summary:
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- Transcription: DNA unwinds, gene gets copied forming mRNA, happens in the nucleus
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- DNA -> mRNA
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- 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**.
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- mRNA -> ribosomes, ribosomes read mRNA -> tRNA grabs the amino acid needed -> ribosomes create peptide chain
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# Protein Structure
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- The shape of protein is important because it influences the compound's function
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- Sickle cell anemia is an inherited form of anemia.
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- **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.
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# In Foods
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- Animal foods generally provide higher amounts of protein than similar quantities of plant foods.
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- Certain parts of plants provide more protein than other parts
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- Seeds, tree nuts, legumes supply more
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- Fruits or edible leaves, roots, flowers, and stems of vegetables provide less
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- Legumes are parts of plants that produce pods with a single row of seeds.
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- Peas
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- Peanuts
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- Lentils
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- Soybeans
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- 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.
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- Meat, fish, poultry, eggs, **milk**
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- Low quality (incomplete) protein is a protein that lacks or has inadequate amounts of one or more of the essential amino acids
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- A limiting amino acid is the essential amino acid found in the lowest concentration of a particular protein source\
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- A healthy adult's RDA for protein is **0.8 g/kg** (apparently low)
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- Protein needs increase during
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- Pregnancy
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- Breastfeeding
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- Periods of rapid growth
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- Recovery
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- Serious illness
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- Blood losses
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- Burns
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# Digestion
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- Protein digestion begins in the stomach
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- Hydrochloric acid denatures food proteins and activates pepsin
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- Gastric enzymes that break proteins down into smaller polypeptides
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- After polypeptides enter the small intestine, the pancreas secretes protein splitting enzymes.
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- Trypsin and chymotrypsin
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- Enzymes released by absorptive cells break down shortened peptides into dipeptides and tripeptides
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- Two and three amino acids respectively
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- Amino acids are carried to absorptive cells by carrier systems
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- After absorption, amino acids enter the capillary of villus
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- Travel to liver via hepatic portal vein
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- Liver keeps some amino acids
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- Release the rest into circulation
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- Protein turnover is the cellular process of breaking down proteins and recycling their amino acids.
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- Endogenous is a source of nitrogen |