Final Exam Flashcards
(111 cards)
1
Q
What is a covalent bond?
A
It occurs when atoms share electrons.
Nonpolar: electrons are shared equally without a difference in electronegativity
Polar: electrons are shared unequally and there is a significant difference in electronegativity
2
Q
What are the inputs and outputs of glycolysis, pyruvate oxidation, and the citric acid cycle?
A
Glycolysis:
Input - glucose, 2 ATP, 2 NAD, and 4 ADP
Output - 2 pyruvate, 2 NADH, and 4 ATP (net gain of 2+ ATP)
Pyruvate Oxidation:
Input - pyruvate, coenzyme A, NAD (double for total)
Output - NADH, CO2, acetyl CoA (double for total)
Citric Acid Cycle:
Input - acetyl CoA, 3 NADH, FAD, GDP (double for total)
Output - 3 NADH, FADH2, GTP, 2 CO2 (double for total)
3
Q
What is an ionic bond?
A
Electrons are transferred from one atom to another.
4
Q
What is a hydrogen bond?
A
A weak attraction between a partially negative atom and a partially positive hydrogen atom. They are individually weak, but are stronger when there are a lot of them.
5
Q
How does the structure and properties of phospholipids allow them to form bilayers in the water?
A
They have a hydrophilic head and a hydrophobic tail. The heads interact with water, but the tails do not.
6
Q
How will the structure and properties of amino acid side chains affect their localization within transmembrane proteins?
A
HELP
7
Q
Describe diffusion and facilitated diffusion.
A
Diffusion is a form of passive transport that moves down a concentration gradient. Facilitated diffusion is a form of passive transport that uses channel/carrier protein to move down a concentration gradient.
8
Q
What is active transport?
A
It requires the input of energy to move molecules against a concentration gradient.
9
Q
Describe osmosis.
A
It is the movement of water from areas of low solute concentration to areas of high solute concentration.
10
Q
Contrast endergonic and exergonic reactions.
A
Endergonic: a non-spontaneous reaction that requires an input of energy.
Exergonic: a spontaneous reaction that releases energy
11
Q
How does energetic coupling allow endergonic reactions to occur in cells?
A
Exergonic reactions release energy and endergonic reactions use that energy to proceed.
12
Q
How do enzymes catalyze chemical reactions in cells?
A
They bring substrates together in precise orientations to speed up chemical reactions.
13
Q
What is the root system of a plant and its function?
A
It is the part of the plant that is underground. It anchors the plant and collects nutrients from the soil. Adventitious roots grow from the shoot system.
14
Q
What are the main parts of the human digestive system?
A
The mouth, esophagus, stomach, small intestine, large intestine, and rectum.
15
Q
What are the functions of the mouth, esophagus, stomach, small intestine, large intestine, and rectum?
A
HELP
16
Q
What is the shoot system of a plant and its function?
A
It is the part of a plant that is above ground. Auxiliary bids are where branches start. Nodes are where the leaves start. Apical buds are the endpoint of the plant.
17
Q
What is phenotypic plasticity?
A
It is the variation in phenotypes for a species in different environmental conditions.
18
Q
How is the morphology of leaves an example of plant adaptations to their environment?
A
Leaves with greater surface area take in more light to conduct photosynthesis. Leaves in shady areas will want more surface area than leaves in areas with direct sunlight.
19
Q
What is a dermal tissue system and a vascular tissue system?
A
Dermal tissue is the outer covering of the plant. Epidermal cells protect the surface of the plant. Stomate regulate gas exchange and water loss.
Vascular tissue conducts water and solutes throughout the plant. The xylem moves water and nutrients from the roots to the shoots. The phloem moves sugars, amino acids, and hormones from roots to shoot and vice versa.
20
Q
What are the components of the xylem and the phloem?
A
The xylem conducts water and nutrients from the roots to the shoots. Phloem conducts sugars, amino acids, and hormones from the roots to shoots and vice versa.
21
Q
What is transpiration?
A
The process of water movement through a plant and its evaporation through stomata. Water evaporates from the stomata of leaves, causing a difference in water potential that drives water from the roots to the shoots.
22
Q
What is water potential?
A
The potential energy of water in a certain environment. It is the combination of solute and pressure potential.
23
Q
What is solute potential?
A
The tendency of water to move via osmosis due to differences in solute concentration. It is always negative.
24
Q
What is pressure potential?
A
The physical pressure on water, which can be positive or negative. Turgor pressure is when the water presses against the cell wall. Wall pressure is when the cell wall resists the turgor pressure.
25
What is a symplastic pathway?
Water and solutes travel through the symplast until they reach the endodermis, pass the casparian strip, and enter vascular tissue.
26
What is an apoplastic pathway?
Water and solutes travel through the apoplast until they reach the endodermis casparian strip and have to enter the symplast. They then cross the endodermis and enter the vascular tissue to be transferred to the rest of the plant.
27
What is the function of the Casparian strip?
It is a layer that blocks the apoplectic pathway at the endodermis. It is a protection mechanism.
28
What is the cohesion tension theory and how does it aid in water movement?
Water is pulled up through the plant xylem by the combined forces of cohesion and tension. As water evaporates from the stomata into the he leaves it creates negative pressure at the leaf surface, pulling water upwards from the xylem. Water molecules are highly cohesive so when one is pulled up, others will follow.
29
What is source and sink in a plant cell?
A source is a tissue where sugars enter the phloem. A sink is a tissue where sugars exit the phloem.
30
Describe the anatomy of the phloem.
There are sieve tube elements that lack nuclei and organelles. They are connected by sieve plates and maximized for transport. Companion cells are next to the sieve tubes and have many organelles to support the metabolism of the sieve tubes. They are connected by plasmodesmata.
31
What is the pressure-flow hypothesis?
Differences in pressure potential in phloem near sources and sinks generate force to transport sugars. The water in the phloem moves down the pressure gradient and brings solutes along with it.
32
What are the main parts of the human digestive system and their functions?
Mouth: chews food (salivary amylase - starch; lipase - lipids)
Esophagus: moves food to the stomach uses peristalsis (muscles contract)
Stomach: acidic environment for digestion and food accumulation (pepsin - proteins)
Small Intestine: final food digestion where absorption begins (bile/pancreatic enzymes)
Large Intestine: reabsorbed water and mineral; forms and stores feces
Rectum: stores and expels feces
32
Explain phloem loading and unloading.
Loading occurs when sugars move out of the sources and reduce the water potential of the phloem sieve tube. Unloading occurs when sugars move into the sinks and increase the water potential of the phloem sieve tube.
33
Where are these enzymes produced and what is their function? Pepsin, salivary amylase, pancreatic amylase, pancreatic lipase, and trypsin.
Salivary amylase: mouth, breaks down starch/carbs
Salivary lipase: mouth, breaks down lipids
Pepsin: stomach, breaks down proteins
Pancreatic amylase: small intestine made in pancreas, breaks down starch/carbs
Pancreatic lipase: small intestine made in pancreas, breaks down lipids
Trypsin: small intestine made in pancreas, breaks down proteins
34
How is the structure of the small intestine related to its function.
Villa and microvilli increase the surface area of the small intestine allowing for more absorption.
35
Why can ruminants digest cellulose?
There stomach have symbiotic bacteria that produce cellulose, which breaks down cellulose.
36
What is the cotransport mechanism of glucose and Na+ in the small intestine?
In the lumen of the small intestine, there is a high [Na+] and a low [glucose]. A cotransporter brings Na+ and glucose into the cytoplasm of an intestinal cell. The [Na+] is low because it is being actively pumped out and the [glucose] is high. Na+ actively leaves the cell into the bloodstream and glucose leaves by a transport protein through facilitated diffusion.
37
What is the difference between macro and micro nutrients in plants?
Macro: essential for the plant to live and to determine the plant growth.
Micro: facilitate enzyme-controlled reactions, but are not necessary for plant survival.
38
How are cations and anions absorbed into plant roots?
Roots have a higher [nutrient] than the soil. Proton pumps push H+ outside the root cell to give it a slight (-) charge. Anions then enter the cell using protons as cotransporters.
39
How does symbiotic bacteria make nitrogen available to plants?
Bacteria and plants have a mutualistic symbiotic relationship where the bacteria infects root cells and fixes nitrogen, providing the plant with nitrogen.
40
Describe the mutualistic relationships between mycorrhizal fungi and plants.
Fungi get sugars from the plants while plants receive soil nutrients from the fungi.
41
Describe the difference between arbuscular mycorrhizal fungi and ectomycorrhizal fungi.
AMF grow into the cells of the root tissue but do not form a sheet around the root. They connect to the plasma membrane of the root cell.
EMF do not penetrate the cell wall, but they form a sheath around the root. They extend outward into the soil.
42
What are parasitic, epiphytic, and carnivorous adaptations in plants?
Parasites live in or on host and steal the hosts's water and nutrients from the xylem of the host, often using haustoria structures.
Epiphytes grow on the leaves or branches of trees. They absorb water and nutrients from their new vantage point better.
Carnivorous plants use leaves to trap insects and other animals. Consuming others organisms supplements the nitrogen that is not available in their environment.
43
How are gases exchanged between organisms and their environments?
It is based on diffusion. Oxygen is a small, nonpolar molecule that easily diffuses across cell membranes. O2 is high in the environment and low in tissues. CO2 is low int he environment and high in tissues. Gases flow down their partial pressure gradient. Large surface areas allow for maximum diffusion.
44
Describe mammalian lung anatomy.
The trachea leads into the lungs. Bronchi are throughout, with bronchioles branching off. Alveoli are at the end of the bronchioles and have capillaries where gas exchange occurs.
45
Why does O2 move from lungs to plasma to red blood cells?
The differences in partial pressure move O2. P O2 is highest in the alveoli of lungs. O2 diffuses into the blood because the pressure and concentration is lower.
46
Explain cooperative binding and the Bohr shift.
When O2 binds to hemoglobin, its affinity increases and there is more O2 for tissues. When someone excersizes, blood pH becomes more acidic. This makes it easier to unbind O2 from hemogloboin. This allows fro more )2 for tissues.
47
How is O2 transported and what is carbonic anhydrase?
As O2 rich blood is circulated throughout the body, O2 moves down its partial pressure gradient into tissues with the least O2. Exercising muscles need a lot of ATP and will use a lot of O2, meaning there will always be a gradient to allow O2 to diffuse into muscle cells. Carbonic anhydrase makes blood pH more acidic - favors more unloading of oxygen from hemoglobin.
48
Trace the path of O2 in the body.
Air - trachea - bronchi - bronchiole - alveolus - capillary - pulmonary vein - left atrium - left ventricle - aorta - arteries/arterioles - muscle capillary - muscle cell
Left is O2 rich blood!
49
Explain the four main types of species interactions, and identify the nomenclature of +/0/-
Commensalism (+/0): One species benefits and the other is unaffected.
Competition (-/-): Both species compete against each other, which takes energy from other resources.
Consumption (+/-): One organism eats another; herbivory, predation, and parasitism.
Mutualism (+/+): Both species benefit.
50
Explain niche.
An ecological niche is the range of resources that a species can use and the range of conditions it can tolerate.
51
Contrast species richness and species evenness.
Richness: The distinct number of species in a region.
Evenness: The relative abundance of different species in a region.
52
Interpret and draw a food web (what is at the bottom—what is at the top?).
Predators are at the top and prey are at the bottom. Arrows point to the predator, who consumes the organism.
53
Contrast bottom-up and top-down effects in a food web.
Bottom-Up: The nutrients, sunlight, or water determines the abundance of primary producers who are at the bottom of the food web.
Top-Down: The presence or absence of consumers from the top of the food web that may change the species composition in the community.
54
Define and explain the role of a keystone species.
They may have a greater impact on the community structure that their abundance would suggest.
55
Explain primary vs. secondary succession—articulate the differences between the two.
Succession is the recovery of the community following a severe disturbance.
Primary succession is when a disturbance removes the soil and organisms in a community (glaciers, volcanoes, floods).
Secondary succession is when a disturbance removes all or some of the organisms but the soil is intact (hurricanes, fires).
56
Distinguish between r- and K-selected species, and relate them to succession.
R-selected species maximize their reproductive rate. They have high fecundity and low survivorship. These species appear early in succession.
K-selected species live at the carrying capacity and invest more energy in fewer offspring. They have low fecundity and high survivorship. These species appear later in succession when the habitat has stabilized.
57
Distinguish between NPP and GPP.
Net Primary Productivity: the energy that primary producers invest in building biomass (the weight of organic material)
Gross Primary Productivity: the total chemical energy produced in the given area and time (not useful bc some is lost as heat/cellular respiration)
58
Explain energy transfer between trophic levels—how does productivity decline at higher trophic levels? Explain the pyramid of productivity.
Energy dissipates at each level. 90% of energy is lost at each trophic level. Only 10% of energy is transferred to the next level.
59
Explain biomagnification, and provide an example.
It is the increasing concentration of toxic substances in organisms at higher trophic levels. This occurs because the biomass decreases up a level, but the toxin does not, so its concentration increases.
60
Define homeostasis and its importance.
The maintenance of a dynamic equilibrium in the body; keeps the internal environment of an organism in a tolerable range. Stable internal environments maximize enzyme efficiency and membrane permeability.
61
What are the factors that can be control by homeostasis? Explain.
Factors can be maintained in a physiological range. Some include blood pressure, blood glucose levels, blood pH, blood osmolarity, core body temperature, and levels of memorabilia waste like, CO2.
62
Compare and contrast regulators and conformers.
Conformers allow their internal conditions to become similar to the external conditions. They have lower energy expenditure, but they are less functional in certain environments. Regulators maintain a stable internal environment. They have higher energy expenditure but can function in more environments.
63
What are the functions of the 3 components of a homeostatic system?
1. Sensor: detects the value of what is being measured
2. Integrator: evaluates sensory information to determine if the measurement is too high, low, or just right
3. Effector: mechanism that returns the condition to a normal range
64
What are the four mechanisms of heat exchange?
Conduction: heat transfer between two touching solids
Convention: heat transfers between a touching solid and liquid/gas
Radiation: heat transfer between two objects that are not in direct contact (the sun)
Evaporation: heat transfer when a liquid become a gas; no heat gain
65
What is endothermic, ectothermic, homeothermic, and poikilothermic strategies?
Endotherms receive heat as a byproduct of internal chemical reactions. Ectotherms receive heat from their environment.
Homeotherms keeps their body heat constant in a narrow range. Poikilotherms allow their body temperature to rise/fall based on environmental conditions.
66
Compare and contrast adaptive advantages/disadvantages of endothermic and ectothermy.
Endotherms are able to maintain enzymes at a constant temperature, remain active in winter and during the night, and have high levels of aerobic activity thanks to their high metabolic rate. However, they must consume large quantities of energy-rich food and the energy used to produce heat is unavailable for other things.
Ectotherms can survive on much less food and devote more of their energy to reproduction. However, temperature-dependent chemical reactions slow as body temperature drops, molecule activity slows which makes them more vulnerable to predators, and they are less successful at inhabiting cold environments.
67
Define osmolarity and osmoregulation.
Osmolarity is the concentration of all the solutes in a solution. Higher solute concentration have higher osmolarity. Osmoregulation maintains homeostasis by regulating water and solute levels.
68
What is the difference between osmolarity and tonicity?
Osmolarity refers to solutions while tonicity always refers to cells.
69
Define hyper-, hypo-, and isosmotic; define hyper-, hypo-, and isotonic
Hyper: higher osmolarity/concentration
Hypo: lower osmolarity/concentration
Isosmotic: same osmolarity
Isotonic: same concentration
70
Explain the difference between osmoconformers and osmoregulators.
Osmoconformers are in osmotic equilibrium with their environment. The extracellular fluids outside the cells but inside the body are isosmotic to seawater. Osmoregulators actively maintain a constant blood osmolarity that is different from the surrounding environment.
71
Explain the adaptations that freshwater and marine (saltwater) fishes use to osmoregulate.
Freshwater fish live in a hypoosmotic environment where the water has a lower solute concentration. They gain water by osmosis and lose electrolytes through diffusion. They drink little water, excrete large amounts of dilute urine, and activity take up ions though gills.
Saltwater fish live in a hyper osmotic environment where the water has a higher solute concentration. They lose water by osmosis and Gian electrolytes by diffusion. they drink a lot of seawater, excrete concentrated urine, and actively excrete ions through gills.
72
List the major parts of the kidney.
The renal corpuscle, proximal tubule, loop of henle, distal tubule, and the collecting duct.
73
What is the function of the renal corpuscle?
Filtration occurs and urine formation begins. Blood enters the glomerulus, which is a cluster of capillaries that bring blood to the nephron from the renal artery.
Blood pressure from the heart pushes water and solutes through capillary pores and into the lumen of Bowman's capsule, which surrounds the glomerulus. the filtered pre-urine will enter the renal tubule.
74
What is the function of the proximal/renal tubule?
The renal tube reabsorbs the filtrate from the renal corpuscle (75%). Microvilli in the lumen of the tubule increase absorption. Active transport moves solutes from the proximal tubule and into epithelial cells (water follows osmotic gradient) and the solutes/water are reabsorbed.
75
What is the function of the Loop of Henle?
The Loop of Henle continues reabsorption. As fluid goes down the descending limb, water passively diffuses out and down its osmotic gradient. In the thin acceding limb, solutes passively diffuses out according to the solute gradient.
In the thick ascending limb, the osmolarity of the surrounding interstitial fluid is low and the solutes are actively transported out of the nephron.
76
What is the function of the distal tubule?
The distal tubule connects the ascending limb to the collecting duct and deals with secretion. When aldosterone is present, Na+ is reabsorbed. When it is not present, Na+ is not reabsorbed.
77
What is the function of the collecting duct?
It regulates water retention. When ADH is present, the duct is permeable to water. Water leaves the filtrate, causing a smaller amount of urine to be produced that is hyperosmotic to blood.
When ADH is not present, the duct is not permeable to water. Water stays int eh filtrate, causing a larger volume of urine that is hypoosmotic to blood.
Urea leaks out by passive transport, establishing high osmolarity of inner medulla.
78
Articulate the mechanisms of secondary active transport observed in the proximal tube—
how does it promote reabsorption of water and other solutes?
Na+/K+ ATPase ejects Na+ into interstitial fluid, creating a gradient that encourages Na+ to diffuse from the lumen of the proximal tubule.
Na+ cotransporters use the Na+ gradient to selectively remove ions & nutrients from the filtrate (secondary active transport).
Solutes moved into the cell with Na+ diffuse across membranes and into nearby blood vessels through facilitated diffusion.
Water follows the ions from the proximal tubule, through the cell, and into the blood vessels through facilitated diffusion.
Filtrate reduced to 1/4 volume.
79
Explain what molecules (water or Na/Cl) diffuse in which direction in the loop of Henle
and the interstitial fluid/blood vessels surrounding it. Explain how these osmolarity
differences are self-sustaining.
As fluid goes down the descending limb, water passively diffuses out and down its osmotic gradient. In the thin acceding limb, solutes passively diffuses out according to the solute gradient.
In the thick ascending limb, the osmolarity of the surrounding interstitial fluid is low and the solutes are actively transported out of the nephron. The descending limb provides an electrochemical gradient for the ascending limb while the ascending limb provides an osmolarity gradient for the descending limb.
80
Explain the purpose and function of ADH.
ADH regulates water retention by determining if the collecting duct is permeable to water.
81
What are hormones?
They are chemical signals that regulate and coordinate metabolism, growth, development, and homeostasis.
82
Define transduction.
The conversion of a signal from outside the cell to inside the cell.
83
What is a ligand?
A signaling molecule (hormone). it binds to the ligand binding site on the receptor.
84
What is a kinase?
An enzyme that helps phosphorylate (attach a phosphate) to a molecule.
85
Distinguish between lipid-soluble (hydrophobic) and lipid-insoluble (hydrophilic)
mechanisms of signal processing.
Hydrophobic ligands use extracellular receptors for signal processing. Since the hydrophobic molecule cannot cross the plasma membrane, it must rely on cell-surface receptors.
Hydrophilic ligands use intracellular receptors because the small, non polar molecules can pass through the membrane.
86
Explain the differences between two common signal transduction systems: G-protein
coupled receptors and enzyme-linked receptors. Focus on the outcomes (what does each
trigger?)
G-Protein: production of second messengers; amplification
Enzyeme: directly triggers phosphorylation cascade; each kinase phosphorylates a different one untila response is triggered.
87
List and contrast the five categories of chemical signals.
Autocrine signals act on the same cell that secretes them.
Paracrine signals diffuse locally and act on nearby cells.
Endocrine signals are hormones carried between cells by blood/bodily fluids.
Neural signals (neurotransmitters) diffuse a short distance between neurons.
Neuroendocrine signals (neurohormones) are hormones released from neurons that travel in the bloodstream.
88
Explain the mechanisms of the three main signaling pathways.
Endocrine pathway: A stimulus acts on an endocrine cells, causing it to secret a hormone into the bloodstream. The hormone reaches the effector cell and a response is initiated.
Neuroendocrine pathway: A stimulus acts on a sensory cell, which sends the information to a neurotransmitter. A neurohormone is released into the bloodstream, which will reach an effector cell and initiate a response.
Neuroendocrine-to-endocrine pathway: A stimulus acts on a sensory cell, which sends the information to a neurotransmitter. A neurohormone is released into the bloodstream and reaches an endocrine cell. The cell releases a hormone into the bloodstream. The hormone reaches the effector cell and a response is initiated.
89
Explain the epinephrine response as an example of a G protein-coupled receptor.
Epinephrine binds to an extracellular receptor. The receptor activates a G protein, which then activates Adenyly Cyclase. This activates cAMP, which triggers the activation of kinases and phosphorylase. Phosporylase is an enzyme that triggers glycogen to break down into glucose. Glucose is eventually released. This is an example of a GPCR because it involves a G protein and a second messenger, cAMP.
90
Explain how blood glucose levels are maintained (the role of insulin and glucagon).
When blood glucose levels rise, the pancreas secretes insulin. It stimulates liver and muscle cells to convert glucose to glycogen to be stored in cells. The blood glucose level will then fall.
When blood glucose levels drop, the pancreas secretes glucagon. It stimulates liver cells to convert glycogen to glucose, releasing it into the bloodstream and raising blood glucose levels.
91
Explain how blood osmolarity is maintained (the role of ADH as a G protein-coupled
receptor).
ADH is a neurohormone that is produce in the brain and transported to the kidneys. When our brain perceives changes in the blood osmolarity that we are dehydrated and do not have enough water, ADH is produced. It binds to a receptor, which activates a G protein. The G protein will then release GDP and bind GTP, which stimulates aquaporin production to reabsorb water in the collecting duct.
92
Contrast negative and positive feedback.
Negative feedback reduces or counteracts in initial change to bring the system back to homeostasis. Positive feedback amplifies the initial change (childbirth, blood clotting).
93
Explain the difference between phosphorylase (fight-or-flight) and glucagon (daily
homeostasis).
Phosporylase quickly releases large amount of glucose while glucagon release smaller amounts slower.
94
What are the symptoms of diabetes insipidis? Discuss water reabsorption.
The symptoms are extreme thirst, excessive increase of urination, and nighttime urination. The extreme thirst and frequent urination is due to a lack of proper water reabsorption.
95
Explain the action of desmopressin; articulate how desmopressin is distinct from ADH (vasopressin).
Desmopressin is similar to ADH and used to treat diabetes insipidus. It is more resistant to enzymatic breakdown, so its effects last longer.
96
Explain how ABA functions in water homeostasis.
ABA inhibits the growth of plants. It closes the stomata to prevent water loss and gas exchange. it maintains dormancy insides and closes stomate in response to water stress. It promotes the elongation of primary roots and suppress lateral root growth.
97
Explain how gibberellins promote seed germination.
When an embryo swells with water, gibberellins is secreted and triggers the synthesis of hydrolytic enzymes. The enzymes move into the endosperm and hydrolyze protein and starch for the developing embryo to use for energy.
98
Distinguish between dendrites and axons.
Dendrites are the branches off of the cell body that receive signals and convert them from chemical signals to electrical signals. more dendrites increase the ability to detect sensory inputs. Axons are where the signal travels and is conducted.
99
Explain how resting membrane potential is achieved, including the locations of sodium
and potassium ions. Explain the role of the NA+/K+ pump and the K+ leak channels.
Identify the resting potential (in millivolts) in humans.
Membrane potential is the charge difference between the inside and outside of a cell due to differences in charge voltage. When a neuron is not active, the resting membrane potential is negative. There is more K+ inside the cell and more Na+ outside the cell. A sodium/potassium pump pumps 3 Na+ out the cell and 2 K+ in. K+ leak channels let K+ leak down the [K+] until equilibrium (-65 mV). This results in negative membrane potential.
100
List the three steps of an action potential, and explain what happens at each stage (which ions are moving where, in what direction is the signal moving). Be sure to incorporate refractory states into your explanation.
1. Depolarization
During depolarization, Na+ flows in while K+ flows out. At threshold potential (-55 mV), voltage-gated Na+ channels open as a result of a shape change when the membrane is depolarized and allow Na+ inside the cell. They remain open until the potential is 40 mV. The gate then closes and stays closed for a refractory period. This ensures it only goes in one direction. When Na+ enter the axon, it repels positive charges and depolarizes nearby areas, causing more gates to open.
2. Repolarization
The Na+ gates are closed and K+ channels open. K+ leaves the cell and causes the membrane to repolarize.
3. Hyperpolarization
As K+ exits, the membrane become hyper polarized, but eventually goes back to normal after the K+ channels close.
101
How do myelin sheaths propagate a signal?
Myelin sheaths speed up signal transmission by acting as an insulator, allowing electrical signals (action potentials) to "jump" between gaps in the myelin.
102
Describe the pools of water, nitrogen, and phosphorus. How are they used and how can they be replenished?
Water: It pools in the ocean, leaves through evaporation, and is replenished by precipitation and runoff
Nitrogen: It pools in the atmosphere/organisms and soil as nitrate or ammonia, leaves when fixed by bacteria, and is replenished when N2 is released as a byproduct of cellular respiration by bacteria or industrial pollution
Phosphorus: It pools in rocks, leaves by weathering and the human mining of rocks to make fertilizer, and is replenished when it settles at the edge of the ocean and slowly returns to rock
103
Explain how the term cycle is appropriate when discussing biogeochemical cycles
Nutrients cycle through ecosystems and are reused. It gathers in pools, is used, and then returned back to the pool
104
Explain the process of eutrophication, and provide an example of a current dead zone.
Eutrophication is when there is an overabundance of nutrients, causing an increased growth in organisms that deplete O2, which can kill other organisms. Dead zones occur on the coasts, like the Gulf of Mexico.
105
List the pools and processes that help carbon cycle through an ecosystem
Pools: atmosphere, ocean, rocks/sediments, trees, organic biomass, and fossil fuels
Processes: photosynthesis, cellular respiration, burning fossil fuels, fermentation, combustion, and weathering
106
Explain how carbon cycling occurs in a food web.
Primary producers use photosynthesis to obtain carbon, which consumers then eat. When the consumer dies, decomposers consume it and make carbon available to primary producers.
107
List ways in which humans can impact the concentration of carbon in the atmosphere.
Burning fossil fuels, deforestation, and agriculture/industrial practices.
108
Explain how the increase in carbon in the atmosphere contributes to global climate
change.
Carbon dioxide is a greenhouse gas that traps heat in the atmosphere and increases temperature.
109
Explain the function of a greenhouse gas (how does it affect temperature on Earth)
It traps heat that has radiated from the Earth and keeps it from being lost to space. This causes the temperature to increase.
110
Explain the consequences of climate change on species as well as ecosystems.
1. Geographic range shifts
The area that a species inhabits will shift as climates shift.
2. Phenology shifts
Changing seasons will impact animal adaptation.
3. Evolutionary adaptation
Organisms more suited to the new environment will have a higher allele frequency in the population.
4. Extinction
Some animals will die because they cannot adapt to the new environment.
5. Ocean Acidification & Deoxygenation
The ocean will get more acidic as it absorbs more CO2 and there will be less oxygen available.
