MCAT biology terms Flashcards
Mast Cells
Immune cells in lungs covered with antibodies. Release inflammatory chemicals upon antigen binding to promote immune response. Responsible for respiratory allergic reactions due to reactions with things like pollen and molds.
Bicarbonate Buffer System
Mechanism where respiratory system controls blood pH via controlling carbon dioxide concentrations. Less CO2 in blood = More Basic = Body responds with slower breathing to retain CO2. More CO2 in blood = More Acidic = Body increases breathing rate to remove CO2. Hyperventilation decreases CO2 levels in blood, making blood more basic. Body responds with trying to slow breathing rate.
Intercostal Muscles
Layers of muscles between the ribs
External Intercostal Muscles
contract upon inhalation to pull ribcage up and expand intrathoracic volume (chest cavity volume)
internal Intercostal Muscles
contract upon forced exhalation only
Surfactant
Detergeny covering alveoli to reduce surface tension and prevent alveolus from collapsing on itself. Premature babies do not have surfactant.
“LAMB RAT”
- Left Atrium = (Mitral) Bicuspid Valve,
- Right Atrium, Tricuspid Valve
Intercalated Discs
Connect muscle cells in the myocardium of the heart. Contain many gap junctions to connect the cytoplasm of adjacent cells and allowing for quicker signal propogation and coordinated ventricular contraction.
Portal Systems
Transport systems where blood traveling through these systems goes through two capillary beds in series before returning to the heart. The three portal systems are the:
1) Hepatic (gut –> liver)
2) Hypophyseal (hyopthalamus –> anterior pituitary)
3) Renal (glomerulus -> vasa recta)
Hematocrit
a measure of how many Red Blood Cells are in blood, given as a percentage of total cells in blood. Usually ~45%
Hematopoietic Stem Cell
Stem cell which can differentiate to create Red Blood Cells, White Blood Cells, and Platelets.
Rh Factor
Surface Protein expressed in red blood cells in the presence of allele called D. Leads to (+) or (-) blood type classifications. Dominant allele.
Bohr Effect
a shifting of the oxyhemoglobin curve to the right, indicating a lower affinity of hemoglobin for oxygen so that oxygen can be transported from the RBC to tissues that need it. The Bohr Effect can be due to decreased pH and increasing the H+ concentration in the blood. H+ binds to hemoglobin allosterically and reduces affinity for oxygen. This allows more oxygen to be delivered to tissues that need it for aerobic production of ATP. Decreased pH can be caused by increased CO2 and lactic acid in blood. Right shift of curve can also be caused by increased temperature, and 2,3-bisphosphoglycerate (2,3-BPG).
Fetal Hemoglobin
(HbF) has higher affinity for oxygen than adult hemoglobin (HbA), in order to pull oxygen from mother’s hemoglobin and onto fetal hemoglobin. Results in left shifted oxyhemoglobin dissociation curve
Lysozyme
Enzyme able to attack petidoglycan walls of gram positive bacteria. Found in nasal cavity, tears, and saliva
Humoral Immunity
Division of adaptive immunity that includes antibodies and B-cells which act within the blood rather than within cells.
Thymus
Gland that matures T-cells. Located between the lungs, just above the heart. Adults don’t have
Complement
Proteins that nonspecifically will punch holes in the cell membranes of bacteria, making them osmotically unstable. Can use the classical pathway which requires antibody binding, or alternative pathway which doesn’t)
Interferon
Proteins produced by cell upon viral infection to block cellular and viral protein production. Decrease permeability of cell membrane and upregulate MHC class 1 and class 2 molecules on cell surface to signal immune system. Responsible for malaise, tiredness, muscle soreness, and fever during viral infections.
Major Histocompatibility Complex
(MHC) binds to pathogenic peptides (antigens) and carries it to cell surface where it can be recognized by other immune cells. Produced by virally infected cells via interferons. Also produced by macrophages. MHC-1 is produced by all cells except RBC’s and carries many proteins to cell surface; platelets also have MHC–1. When foreign proteins are presented, immune cells know that the presenting cell is infected and needs to be destroyed. Called endogenous pathway. MHC-2 are mainly displayed by professional antigen presenting cells like macrophages, dendritic cells, and some B-cells. Takes antigens from environment, processes them inside the cell, then displays them to activate the rest of the immune system. Called exogenous pathway.
MHC I
- can present self OR non-self antigens
- they are found in every cell of the body EXCEPT for red blood cells.
- bind to CD8 Cells, aka cytotoxic T cells
MHC II
only present non-self antigens
* they are found on only Antigen-Presenting Cells (APC’s)
* bind to CD4 Cells, aka helper T cells
Pattern recognition receptors
(PRR) able to recognize category of invaders (bateria, virus, fungus, parasite) in order to initiate appropriate cytokine response. These receptors are presented on macrophages and dendritic cells.
Natural Killer Cells
Detect and destroy cells with downregulated MHC; they basically poke holes in the cell’s membrane, which prevents that cell from keeping a stable membrane potential and therefore it dies. Includes cancer cells and some virally infected cells
Neutrophils
Most abundant type of white blood cells in the body. They are quicker to respond than macrophages because they “come in hot with guns-a-blazing and ask questions later”. Short lived (5 days). Dead neutrophils are responsible for formation of pus. Follow bacteria via chemotaxis and phagocytize them. Can also destroy opsonized cells.
Eosinophils
Release large amounts of histamine upon activation for inflammation. Contain bright, red-orange ganules in a typical histological stain.
Histamine
Released by Eosinophils and Basophils. Cause inflammation by inducing vasodilation and increased leakiness of blood vessels so additional immune cells can enter tissue.
Basophils
Have large, purple granules in a typical histological stain. Least populus leukocyte. Produce large amount of histamine in response to allergens. Closely related to mast cells.
Plasma Cells
(Effector B-Cells)
“antibody creating factories”
Memory B Cells
stick around longer than Plasma Cells; their main function is to make proliferation easier (more rapid and more prolonged proliferation) for the NEXT time you encounter a certain antigen
Salivary Amylase (ptyalin)
Enzyme in saliva capable of hydrolyzing starch into smaller sugars.
Lipase
Enzyme in saliva that catalyzes the hydrolysis of lipids.
Epiglottis
Cartilaginous structure that folds down to cover larynx during swallowing, so food doesn’t enter and lead to choking.
Peristalsis
Involuntary, rhythmic contraction of smooth muscle that propels food down digestive tract. Can be reversed during emesis (vomiting) to move contents from the stomach, out the mouth.
Stomach Anatomy
Consists of the Fundus (top), Body (middle), Pylorus (bottom), and Antrum (exit). Lesser curvature is the inside curve, Greater Curvature is the outside curve. Rugae is the internal, folded lining of the stomach.
Gastric Glands
Dominant glands in the Fundus and Body. Stimulated by the Vagus Nerve of the Parasympathetic Nervous System. Contain three main cell types: Mucous Cells, Chief Cells, and Parietal Cells.
Mucous Cells
secretes bicarbonate-rich mucous that protects the inner lining of the stomach from the harshly acidic pH environment.
Chief Cells
secretes pepsinogen in the stomach, the inactivated form of pepsin; digests proteins once the persinogen is activated by H+
Pepsin
Enzyme produced from pepsinogen being cleaved by hydrogen ions in the stomach. Cleaves peptide bonds near aromatic amino acids, resulting in short, peptide fragments. Uniquely most active at low pH.
Parietal Cells
secretes HCl and intrinsic factor. The HCl decreases pH so that the H+ ions can cleave pepsinogen into pepsin. The low pH also helps kill most harmful bacteria and denature proteins and break down some intramolecular bonds that hold food together. Intrinsic factor aids in the absorption of vitamin B12
Intrinsic Factor
Glycoprotein secreted by the parietal cells in the gastric glands in the stomach. It is involved in the absorption of vitamin B12
G-Cells
Cells in the pyloric glands of the stomach that secrete Gastrin
Gastrin
Peptide Hormone that induces the parietal cells in the stomach to secrete more HCl and also signals the stomach to contract. Secreted by G-cells
Pyloric Glands
Dominant glands in the Antrum and Pylorus sections of the stomach. Contain G-cells that secrete gastrin.
Chyme
Acidic, semifuild mixture in the stomach resulting from the digestion of solid food.
Cardiac Sphincter
Sphincter that controls the movement of the bolus from the esophagus into the stomach
Pyloric Sphincter
Sphincter that controls movement of chyme from the stomach to duodenum
Small Intestine
Responsible for continued digestion and absorption of nutrients. Approximately 7 meters long. Consists of three segments: Duodenum, Jejunum, and Ileum. The majority of chemical digestion takes place in the duodenum while the majority of absorption takes place in the jejunum and ileum.
Duodenum
Site of chemical digestion in the small intestine. Releases tons of enzymes such as brush border enzymes, secretin, and cholecystokinin.
Brush Border Enzymes
Enzymes present on the inside surface of cells lining the duodenum that are released in the presence of chyme. These enymes break down dimers and trimers of biomolecules into absorbable monomers. Include disaccharidases and peptidases
Lack of Digestive Enzyme
Intestines can’t cleave disaccharaide for digestion. This increases osmolarity and pulls water into the intestines to form diarrhea. Bacteria in the small intestine are able to break down disaccharides, but result in methane gas as a biproduct, resulting in farts.
Bile
Complex fluid of bile salts, pigments, and cholesterol. Produced by the liver and stored in the gallbladder before secretion into the small intestine.
Bile Salts
Have hydrophobic and hydrophilic regions to act as an emulsifier in the duodenum to allow fats and cholesterol to form micelles and giving access to pancreatic lipase digestion (a water soluble enzyme). The creation of micells increases surface area of fats for aided digestion by lipases. Formation of micelles is a form of mechanical digestion.
Pancreatic Juices
Secreted by pancreas into duodenum due to stimulation by cholecystokinin (CCK). Complex mixture of ezymes in bicarbonate-rich solution. This basic solution neutralizes chyme to allow for ideal pH for enzymatic digestion (most active around pH 8.5). Contains enzymes to digest carbohydrates, fats, and proteins.
Acinar Cells
Cells that make up the bulk of the pancreas and participate in its exocrine functions. Produce pancreatic juices.
Pancreatic Enzymes
Secreated by Acinar Cells.
Pancreatic Amylase: Digests carbohydrates.
Trypsinogen: Activated by Enteropeptidase (produced in Duodenum) to form trypsin, which then activates chymotrypsinogen. Procarboxypeptidases A and B to protein digestion.
Pacreatic Lipase: Breaks down fats into free fatty acids and glycerol
Duodenal Papillae
Secretion point of pancreatic juices into duodenum from pancreatic ducts.There is a major and a minor duodenal papilla.
Liver
- Regulates blood sugar via glyogenesis, glycogenolysis, gluconeogenesis, and the storage and release of fats.
- Converts Ammonia (waste product of amino acid metabolism) into Urea
- Detoxifies chemicals such as drugs and alcohol
- Produces Bile
- Synthesizes albumin and clotting factors
bilirubin
Major pigment in Bile, which is the byproduct of the breakdown of hemoglobin. Inability to process or excrete bilirubin results in Jaundice.
Gallbladder
Stores and concentrates bile. CCK stimulates the gallbladder to contract and push bile into the billiary tree, which merges with the pancreatic duct before entering the duodenum via the duodenal papillae. Gallbladder stones made of cholesterol or bilirubin can cause inflammation of the gallbladder and blockage of both the biliary tree and pancreatic ducts.