Digestion
How do arbuscular mycorrhizae fungus benefit plants with nutrient absorbance?
they greatly increase the surface area for absorption (fractal structures maximize surface area/volume ratio)
What is mutualism?
an interaction between two organisms in which both organisms benefit
How does movement of water occur in the xylem?
water is pulled upwards unidirectionally by negative pressure caused by transpiration and water cohesion
What is the resting potential of the cell?
inside is negative (-70mV), outside is negative
What are the three forms of nitrogenous waste?
Ammonia, urea, uric acid
What is the role of bile in digestion?
it helps to break down big lipid bubbles that are clustered together by hydrophobic interactions. It emulsifies the lipid clusters and breaks them into smaller ones so that there is a larger surface area that digestive enzymes can access.
How did eukaryotic cells come to contain chloroplasts and mitochondria?
endosymbiosis, at one point a cell engulfed an O2 respiring bacterium and this became the mitochondria, and similarly with an oxygenic phototrophic bacterium for chloroplasts
What is the role of valves in the veins and heart?
Prevent backflow of blood
What kind of habitat would you expect a conformer to live in and why?
Conformers typically live in stable, marine habitats. This is because their cells are always iso-osmotic with the environment, so they need to live in an environment that does not change very much!
What hormones regulate reabsorption of water and salts? (there are two!)
ADH/vasopressin and aldosterone
How is pepsin, a protein-digesting enzyme, stored in cells safely before secretion? Describe the process of pepsin secretion and activation.
Pepsin is stored in cells as an inactive zymogen, pepsinogen in chief cells. When there is food in the stomach, the chief cells secrete pepsinogen and the parietal cells secrete H+ protons and Cl- anions, which form acid in the stomach. The HCl acid converts pepsinogen into pepsin, the active form which can digest proteins. Then there is a positive feedback loop as pepsin can activate more pepsinogen.
Where do gut microbiota come from and what influences them?
Gut microbiota first come from the birth canal. After this they are influenced mostly by the environment (diet, lifestyle, drugs, etc).
compare the pressure, cross sectional area, and velocity of blood in blood vessels as you move through the circulatory system
Describe the adaptations of a saltwater bass who lives in the ocean to maintain osmolarity of its body.
problems are desiccation and inward salt diffusion. The urine will be highly concentrated, releasing high amounts of salt ions and low levels of water. The gills will also actively secrete out Cl- ions (Na+ ions follow actively/passively)
What is the osmolarity of filtrate relative to blood after leaving the thick ascending limb of the loop of Henle?
hypoosmotic
how is gut length affected by the diet of a species?
In carnivores, the large intestine is rather short and the small intestine is long, with a very small cecum. In herbivores the small intestine is shorter and the large intestine is much longer as this is needed to digest vegetation. In non-ruminant herbivores, the cecum is very long to help fermentation of plant material.
What are the three key functions of gut microbiota?
- immunity (prevents colonization by pathogens, educates immune system, stabilizes gut barrier function)
- metabolic role (caloric salvage, produces short chain fatty acids, produces vitamin K and folate)
- chemical modulator (participates in drug metabolism, deconjugates bile acids)
What process does the QRS complex on an EKG correspond to in the heart?
ventricular depolarization and thus ventricular systole
Where/how does the body sense hypovolemia?
Baroreceptors in arteries sense decreased stretch of blood vessels. Also, kidney cells sense a decrease in renal perfusion in the kidneys.
What are the forces that control net filtration of blood into the Bowman's capsule?
glomerular hydrostatic pressure (dominant), glomerular oncotic pressure, Bowman's capsule hydrostatic pressure
What enzymes are needed to break down carbohydrates into monosaccharides? Where does each enzyme act in the digestive tract?
salivary amylase in the mouth breaks polysaccharides into smaller polysaccharides. These are broken down by pancreatic amylases in the duodenum into disaccharides. These are then broken down by disaccharidases in the small intestine into monosaccharides.
Describe the symbiotic relationship between legumes and Rhizobia bacteria. (how do they communicate, who gets what benefits/harms)
Root cells signal to the bacteria by releasing flavonoids into the soil, and the rhizobia respond by releasing Nod factors which induce cause the plant to form root nodules for the bacteria to live in. This benefits both. The bacteria obtain photosynthesis products like sugar from the plant and a protected environment, and the rhizobium supplies the plant with fixed, usable nitrogen.
Describe all the steps of an action potential, from initiation to returning to resting membrane potential, in an SA node cell.
Na+ leaks in through a channel down its gradient, depolarizes the cell until a threshold is reached. Then voltage gated Ca++ channels open and the cell depolarizes significantly as calcium rushes in. Then the calcium channels will close and potassium channels will open. K+ flows into the cell and repolarizes it. K+ flow causes the cell to hyperpolarize, then the K+ channels close and the Na+/K+ ATPase returns the cell to resting membrane potential.
Describe hypertonic dehydration. (how is it caused, what is the osmolarity of blood compared to cells, what are the sensors and the rest of the pathway, how do you treat it?)
Hypertonic dehydration is caused by a loss of fluid without a loss of salt (ex. sweating, not drinking water). The blood is hypo-osmotic to the cells (causes cells to shrivel, intracellular thirst). It is sensed by osmoreceptors in the hypothalamus and saliva production decrease in the mouth. Treatment is to drink water.
Name all places where water can be reabsorbed or secreted in the kidney.
proximal tubule, loop of Henle (descending loop), distal tubule, collecting duct