midterm 2/exam Flashcards
What are the 9 indispensable (essential) amino acids?
Phenylalanine, Valine, Threonine, Tryptophan, Methionine, Histidine, Isoleucine, Lysine, Leucine
Where does digestion of proteins start?
Mechanical digestion beings in the mouth
- no chemical digestion occurs in mouth
What breaks peptide bonds? And what amino acids do they target?
Pepsin
- tryptophan and leucine
- breaks very large proteins into smaller but still large polypeptides
What does hydrochloric acid (HCl) do in the stomach?
Denatures polypeptides
- breaks secondary, tertiary and quaternary structures
- exposes primary structure of polypeptides to pepsin
- HCl activates pepsin
What does pancreatic juice contain? (4)
Chymotrypsin, Carboxypeptidase, Elastase, Trypsin
What does trypsin do?
Breaks peptide bonds targeting lysine and arginine
- activates other pro-enzymes in pancreatic juice
What does the brush border release? (2)
Dipeptidases, Aminopeptidases
What do dipeptidases do?
break peptide bonds of dipeptides creating individual amino acids
What do aminopeptidases do?
Breaks terminal (end) amino acid off of amino end of peptide releasing an amino acid
Where are proteins primarily absorbed?
jejunum and ileum
What are 2/3 of proteins absorbed as?
di- or tripeptides (broken-down into amino acids inside endothelial cells
What are 1/3 of proteins absorbed as?
individual amino acids
What are carrier molecules for peptides and amino acids?
Active transport - Na+ and H+ (requires ATP)
Facilitated diffusion - Na+
What is absorbed quicker: indispensable or dispensable amino acids?
indispensable
What is the difference between exogenous and endogenous proteins?
Exogenous - come from our food
Endogenous - come from our body
Where are amino acids taken after absorption? And why?
Liver - clearinghouse for most amino acids
Blood - some circulate in the blood for several hours after a meal, branched chain amino acids (BCAA) circulate immediately in plasma
Amino Acid pool - free amino acids circulating in blood or fluid near cells, always in flux because of protein turnover
What are proteins biological functions? (5)
Structure and movement, enzymes, hormones and regulators, transportation, bodily defence (immune function)
What proteins are used for structure and movement? (3)
- Actin and myosin interact for muscular contractions
- Collagen is most abundant structural protein (6% of body weight), found in connective tissue, bone tissue, ligaments and tendons
What do enzymes do?
Allow reactions to happen
How do enzymes speed up chemical reactions?
Lowering activation energy
What do hormones do?
Control bodily processes
- endocrine glands secrete hormones that act on cells in the body
- activation and deactivation of enzymes in critical function
What are transporters and carrier molecules? (proteins)
-Membrane transporters bring substances into and out of the cell
- Many molecules must be bound to proteins to enable transportation through the blood plasma or lymph
-Liver makes all proteins found in the blood
- Cell membranes are not permeable to large molecules and rely on embedded protein carriers (transporters)
What do albumins, lipoproteins (HDL and LDL) and Hemoglobin bind to and transport?
Albumins - fatty acids, some vitamins, essential minerals, drugs
Lipoproteins - cholesterol, other fats
Hemoglobin - oxygen
What is the immune system made of?
Lymphocytes (white blood cells that make antibodies)
What do lymphocytes do?
antibodies are polypeptide chains that work like a lock and key with their target pathogen
What is protein synthesis?
Assembly of functional polypeptides in cytoplasm
What is gene activation?
uncoiling of DNA for transcription
What is transcription?
synthesis of mRNA from DNA
- makes temporary ‘copy’ of DNA used during protein synthesis
What adds new RNA bases to mRNA? (copies gene from DNA)
RNA polymerase
- before leaving nucleus unused portions of mRNA are removed (introns), and used portions are spliced together (exons)
What are codons?
three-base sequences of mRNA
Correspond with specific amino acids
What is the difference between saturated and unsaturated fatty acids?
Saturated - fully loaded with hydrogen, no double bonds
Unsaturated - missing hydrogens, has double bonds
What is the difference between mono- and polyunsaturated fatty acids?
Mono - 1 double bonds
Poly - more than 1 double bonds
What are the orientations and positions of double bonds? and what do they mean?
Cis - naturally occurring, hydrogens on same side of double bond, adds bend to molecule
Trans - created in commercial food process called hydrogenation, hydrogens are on opposite sides of double bond, bend is removed
What are triglycerides?
3 fatty acids attached to 1 glycerol molecule
- The 3 fatty acids can be the same but are usually different
How can you tell between saturated, poly- and monounsaturated fats?
Saturated - usually solid at room temperature, ex. coconut oils, animal fats
Monounsaturated - usually liquid at room temperature, ex. olive and canola oils
Polyunsaturated - tend to be liquid at room temperature, ex. safflower and corn oils