Knowt
Biology 120 Final
Immediate Causation- physiological mechanism underlying trait of interest
Development- role of developmental timeline (experience
Both are proximate questions (How?)
Evolution- role of phylogeny, evolutionary history
Adaptive Function- role of trait of interest in increasing reproductive success
Both are ultimate questions (Why?)
Physiological systems require integration of multiple levels of organization.
Ex: atomic + molecular level, cellular level, tissue level, organ level, organ system level, organism level
All levels needed to understand the entire organism
Organismal structure require integration of multiple levels of organization
Ex: cellular level- neuron (small and long structure for rapid send of info)
tissue level- way tissues are formed allow for contraction
organismal level- aquatic animals have specific bodies to reduce drag
Feedback mechanisms drive physiology
Ex: multiple parts responding to a stimulus starting with sensor
Integrator- translation of signal in body (detects stimulus)
Effectors- effect change in body
Negative Feedback- response opposes stimulus that triggered the response
“regulation” (stops stimulus) important for maintaining homeostasis
Homeostasis
balance + stabilitty in chemical + physical conditions
regulated by negative feedback
Positive Feedback (rare)
Ex: child birth
occurs when things need to get done/amplifies
Gradients!!! (super important)
concentration gradients- things move from high → low concentration
size matters in gradients
Proteins are critically important mediators of physiology
1858- Linnaean Society of London
Charles Darwin + Alfred Russel Wallace
Hypotheses:
→ species come from other, pre existing species.
→ species change through time
“Descent with modification” = Evolution
Darwin and Wallace proposed one mechanism for evolution: Natural Selection
Four Postulates
There must be variation among individuals in a population
At least some variation must be heritable
Survival and reproductive success are highly variable. Some individuals produce more offspring that survive to reproduce than others do.
Survival and reproductive sucess are not random: individuals with certain heritable traits are more likely to survive and reproduce in a given environment
General Principle #7: Adaptation and Acclimation are both important, but they are not the same
Adaptation→ Evolutionary Process
by evolution by Natural Selection
occurs in populations (individuals do not change)
Acclimation → in response to current conditions
reversible changes in physiology
occurs at individual level
Trade offs are everywhere
Blinded by the dark: How and why did blind cavefish lose their eyes?
Photoreceptors in retina sends signals to the brain
Macula lutea located in the middle of the retina, contains the highest concentration of cones for color vision, area of greatest visual aquity
fovea= center of macula lutea
Ciliary Body- allows lens to change shape to accommodate close and distance vision
Iris- colored part of the eye, pupil (hole in iris) gets large or small depending on how much light is let in
Anterior + Posterior compartments of eye both filled w/ fluid + allows eyes to be nourished
Cornea- protects eye + is clear to allow light in to strike the lens
How do all these parts work together to help vertebrate animals see?
light is focused on the retina
light sensitive photoreceptors in retina are “excited” by light
neurons from retina are “excited”- sends signals to brain
neurons in brain process info received from neurons at retina
Fertilization
Cleavage
Gastrulation
Organogenesis
Fertilization: 1st
egg + sperm (“germ cells” haploid) come together to produce a zygote (diploid)
Egg: maternal DNA, mitochondria, proteins + RNA, nutrition
Sperm: paternal DNA, centrosomes structures (initiate mitosis)
Cleavage: 2nd
rapid cell divison
end product: Blastula (hollow fluid filled ball of cells/multicellular embryo)
size of embryo does not change much
Gastrulation: 3rd
process of cell movements that give rise to the 3 germ layers
Ectoderm- outside (outer) ex: skin + central nervous system
Mesoderm- middle ex: bone, muscle, heart + blood vessels
Endoderm- inside (inner) ex: lining of digestive system, lungs
most important stage
body plan + axes also begin to develop during gastrulation
Organogenesis: 4th
specific tissues + organs arise
this can occur b/c gastrulation has formed + positioned germ layers such that cells can signal to one another
Four Stages of Eye Development
Neurulation- formation of CNS
optic vessicle formation
optic cup and lens
lens vesicle forms from lens pit
formation of retina + lens
Part 1. Neurulation is the process of central nervous system formation and occurs during organogenesis
formation of neural tube: hollow tube formed from ectoderm becomes CNS (brain, spinal cord)
Once formed, regions of the neural tube (CNS) begin to become specialized
Part 2: Optic vessels form from the neural tube
Part 3: Optic Cup + Lens pit forms
Optic vessels contacts with surface ectoderm
optic cup forms from neural tube
when optic cup is forming optic vessels, lens pit forms
Part 4: Lens vesicle forms
edges of lens pit converge and lens vesicle forms
optic cup now fully formed
Neural Tube → optic vesicle → optic cup → retina
surface ectoderm → lens pit → lens vesicle → lens
Every cell in organism contains the same DNA sequences
How do cells “know” what cell types to become during development?
Cell type- a group of cells that exhibit similar function (e.g. neuron, muscle cell)
Cell lineage- developmental history of a cell or group of cells (e.g. from ecto-, endo-, and mesoderm)
Uncommitted State
cell can become esstentially any cell in adult organism
possibilities are endless
Committed State
cell is now specialized
cell may not look like a specific cell type but it’s committed to a very limited set of potential cell types
Differentiated State
cells look like a specific cell type has associated functions
usually irreversible
This is all possible because of differences in gene expression (production of different proteins)
Chromosomes and genes (segements of DNA that are expressed to from a functional product → RNA → Protein)
Regulation of Transcription and Translation (“gene expression”)
Transcribed Region- DNA sequences that are transcribed to produce RNA
Regulated Region- DNA sequences that allow binding by proteins that control initiation of transcription
What proteins can bind at those regulatory regions?
RNA polymerase (enzyme)- produces an RNA strand whose sequence is complementary to the DNA strand
Transcription Factors- proteins that bind to regulatory region + allow transcription to occur (can turn genes on or off)
Binding of transcription factors can be affected by….
Concentration- how much is present?
affinity- how tightly does it bind to DNA?
How do changes in gene expression in cave fish lead to “eye loss”
Pax6 is an important trancription factor that is required for eye development
Transcription factors are themselves proteins → they are also regulated by gene expression
Without Pax6, eyes do not form correctly
Shh (not a transcription factor but a chemical messenger by “local” secretion (nearby cells), binds receptors → produces an effect) is a protein that controls the abundance of Pax6
Different effects on Pax6 depending on Shh concentration
At high concentration, Less Pax6 (and more Vax1, negative transcription factor)
At low Shh concentrations, more Pax6
In regions where eye structures would normally form, Pax6 levels would be lower with higher levels of Vax1
In blind cavefish, Shh expression is much higher than in surface fish
Shh is for lens development and olfactory system development
1. Energy Use in Animals
1.1 Categories of Energy Use
Generation of Physical Work: This refers to the energy expended in movement and physical activity, crucial for sled dogs during races.
Maintenance: Energy is required for the functioning of vital systems such as the nervous system, circulation, respiration, and digestion.
Biosynthesis: Energy is also used for tissue growth and repair, which is essential for recovery after strenuous activities.
1.2 Energy Molecules
Carbohydrates: These are primary energy sources, categorized into monosaccharides (e.g., fructose, glucose) and polysaccharides (e.g., glycogen).
Fats/Lipids: Composed of glycerol and fatty acids, fats provide long-term energy storage and are more energy-dense than carbohydrates.
Proteins: While not a primary energy source, proteins can be utilized for energy when carbohydrates and fats are scarce.
1.3 ATP and Energy Metabolism
ATP (Adenosine Triphosphate): The main energy currency of the cell, ATP is produced through cellular respiration and is essential for various cellular functions.
Hydrolysis of ATP: The process of breaking down ATP releases energy, which is used for cellular work.
Metabolic Rate: This is the rate at which energy is expended in an organism, influenced by factors such as activity level and environmental conditions.
2. Metabolic Processes in Animals
2.1 Aerobic vs. Anaerobic Metabolism
Aerobic Metabolism: Involves the use of oxygen to convert food into energy, producing CO2 and water as byproducts.
Anaerobic Metabolism: Occurs when oxygen is not available, leading to processes like lactic acid fermentation, which produces less energy and results in lactate accumulation.
2.2 Cellular Respiration Overview
Stages of Cellular Respiration:
Glycolysis: Breakdown of glucose into pyruvate, producing ATP and NADH.
Pyruvate Processing: Conversion of pyruvate into Acetyl CoA, releasing CO2 and generating NADH.
Citric Acid Cycle: Further breakdown of Acetyl CoA, producing CO2, ATP, NADH, and FADH2.
Electron Transport Chain: Uses electrons from NADH and FADH2 to produce ATP, with oxygen as the final electron acceptor.
2.3 Importance of Oxygen and CO2
Role of Oxygen: Essential for aerobic respiration, oxygen acts as the final electron acceptor in the electron transport chain.
CO2 as a Byproduct: Produced during the breakdown of glucose, CO2 is expelled from the body and is a key indicator of metabolic activity.
3. Metabolic Rates and Thermoregulation
3.1 Endothermy vs. Ectothermy
Endotherms: Birds and mammals maintain a high metabolic rate and body temperature through metabolic heat production.
Ectotherms: Other animals rely on environmental conditions to regulate body temperature, resulting in a lower metabolic rate.
3.2 Measuring Metabolic Rate
Basal Metabolic Rate (BMR): The energy expenditure of endotherms at rest, not thermoregulating or recently fed.
Standard Metabolic Rate (SMR): Similar to BMR but for ectotherms, measured under standard conditions.
3.3 Factors Affecting Metabolic Rate
Temperature: Affects metabolic rate; within the thermoneutral zone, metabolic rate remains stable.
Activity Level: Increased activity raises metabolic rate significantly.
Food Intake: Energy availability influences metabolic processes and performance.
4. Sled Dogs: Adaptations for Endurance
4.1 Physiological Traits
Muscle Mass: Sled dogs possess greater muscle mass compared to humans, enhancing their physical capabilities.
Mitochondrial Density: Training and a high-fat diet increase the number of mitochondria, improving energy production efficiency.
4.2 Dietary Considerations
Diet Composition: Sled dogs thrive on a diet high in fats (50%), moderate in proteins (35%), and low in carbohydrates (15%).
Carbohydrate Limitations: High carbohydrate intake can lead to muscle cramping and depletion of glycogen stores.
4.3 Energy Utilization During Races
Glycogen Utilization: Sled dogs can increase muscle glycogen levels during races, allowing for sustained energy production.
Gluconeogenesis: The liver can produce glucose from non-carbohydrate sources, supporting energy needs during prolonged activity.
Physiological Adaptations to Environmental Challenges
Glycogen Metabolism and Blood Glucose Regulation
Glycogen breakdown in the liver elevates blood glucose levels, providing energy during fasting or stress.
Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources such as fats and proteins, crucial during prolonged fasting.
The liver plays a central role in maintaining blood glucose homeostasis, especially during exercise or stress.
Hormonal regulation (e.g., glucagon and insulin) influences glycogenolysis and gluconeogenesis, ensuring energy availability.
Case Study: In diabetic patients, impaired gluconeogenesis can lead to hypoglycemia or hyperglycemia, highlighting the importance of this process.
Thermoregulation in Cold Environments
Animals in the thermoneutral zone (TNZ) must maintain body temperature despite external conditions.
Insulative fur coats provide a barrier against cold, reducing heat loss.
Special vascular arrangements in extremities minimize heat loss, allowing core temperature to remain stable.
Heat gradients in blood vessels help maintain temperature by keeping feet cold while preserving core warmth.
Example: Arctic mammals exhibit adaptations like thick fur and fat layers to survive extreme cold.
Nervous System Organization and Function
Overview of the Nervous System
The nervous system is divided into the Central Nervous System (CNS) and Peripheral Nervous System (PNS).
CNS includes the brain and spinal cord, responsible for processing information and coordinating responses.
PNS encompasses all neural elements outside the CNS, facilitating communication between the CNS and the body.
Cephalization indicates the concentration of sensory organs and nervous tissue in the head region, enhancing sensory processing.
Segmental organization allows for localized control and coordination of body segments.
Neuron Structure and Function
Neurons are the fundamental units of the nervous system, transmitting electrochemical signals.
Dendritic spines increase surface area for synaptic connections, enhancing information transfer.
Neurons communicate across synapses through chemical and electrical signals, facilitating rapid information exchange.
Classification of neurons can be based on structure (multipolar, bipolar, unipolar) and function (sensory, motor, interneurons).
Example: Sensory neurons relay information from sensory receptors to the CNS, while motor neurons transmit commands to effectors.
Membrane Dynamics and Action Potentials
Cell Membrane Structure and Function
The phospholipid bilayer serves as a barrier and gatekeeper, regulating ion movement in and out of the cell.
Membrane proteins, including channels and pumps, facilitate selective ion transport across the membrane.
Ions such as Na+, K+, and organic anions play critical roles in establishing membrane potential.
The resting potential of a neuron is typically around -65 mV, maintained by ion gradients and membrane permeability.
Sodium-potassium ATPase pumps are essential for maintaining K+ and Na+ gradients, crucial for neuronal excitability.
Mechanisms of Action Potentials
Action potentials are rapid changes in membrane potential, triggered by the opening of voltage-gated ion channels.
Depolarization occurs when Na+ channels open, allowing Na+ to flow into the cell, making the inside more positive.
Hyperpolarization happens when K+ channels open, allowing K+ to exit the cell, increasing the negative charge inside.
The all-or-nothing principle dictates that once the threshold potential (~-55 mV) is reached, an action potential will occur.
Nerve impulses propagate as waves of action potentials along the axon, enabling rapid communication within the nervous system.
Chemical Communication in the Body
Endocrine and Nervous Systems
The endocrine system uses hormones for widespread chemical communication throughout the body via the bloodstream.
Hormones can affect multiple target cells, leading to coordinated physiological responses.
The nervous system employs point-to-point communication through electrical and chemical signals between neurons.
Neurotransmitters are chemicals released into synapses, facilitating communication between neurons.
Example: Grayanotoxins can disrupt neurotransmitter function, leading to impaired neuronal communication.
Autonomic Nervous System Functions
The autonomic nervous system regulates involuntary bodily functions, divided into sympathetic and parasympathetic systems.
The sympathetic system prepares the body for 'fight or flight' responses, increasing heart rate and dilating pupils.
The parasympathetic system promotes 'rest and digest' activities, slowing heart rate and stimulating digestion.
Balance between these systems is crucial for maintaining homeostasis during stress and relaxation.
Example: During a stressful situation, the sympathetic system activates to prepare the body for immediate action.
Neurons: the resting membrane
Phospholipid bilayer allows intracellular fluid to maintain different concentration of ions than extracellular fluid
The cell membrane: barrier and gatekeeper
proteins embedded in membrane, some allow substances to cross
e.g. channels; always open or gated
transport proteins
pumps ( e.g. more ions against concentration gradient)
ions will move according to….
1) concentration gradient
Diffusion: movement from area of higher → lower concentration
2) electrical gradient (charge matters)
“electrical potential”
membrane is polarized ( unequal distribution of charge)
What factors contribute to resting potential?
The Primary Players
charge- carrying ions/molecules
sodium (Na+)
Potassium (K+)
organic anions (A-)
proteins also have a negative charge
membrane proteins
Na+/K+ ATPase pumps
open K+ channels (“leak” channels)
Distribution of ions across the membrane differs:
K+ and A- more concentrated on inside
Na+ and Cl- more concentrated on outside
Distribution established and maintained by ion pumps
What contributes to resting potential of neuronal membrane?
Sodium-Potassium ATPase pump produce and maintain K+ and Na+ gradients across the membrane (high K+ in, high Na+ out) 3Na+ out, 2K+ in
At rest, neuronal membrane is highly permeable to K+ due to presence of potassium “leak” channels (permeability to K+ is 40x higher than it is to Na+)
Movement of K+ ions through these channels (out, along concentration gradients) leaves inside membrane negatively charged relative to outside
How ion movement leads to action potentials…?
Membrane potential is the difference in electrical charge b/n inside + outside of membrane
@Rest → -65mV
What happens if we open a bunch of Na+ channels?
Na+ moves inside of cell
The membrane potential becomes less negative, more positive (depolarizes- less separation of charge)
What happens if we open a bunch of K+ channels?
K+ moves outside the cell
Membrane potential becomes more negative (hyperpolarizes)
Membrane potentials can change: Graded potentials (changes in membrane potential that vary in amplitude + duration)
Voltage-gated ion channels- allows for membrane potential to change, communication b/n neurons
Neurons
Excitable membranes- all or none response
Action potentials- a brief, all or none change in membrane potential
Threshold potential (-55mV) to cause action potential
local change of membrane potential in a neuron “domino effect”
Depolarization ← Na+ channels open, reduces charge separation
Hyperpolarization ← K+ channels open, increases charge separation
What makes a neuronal membrane “excitable”?
Voltage gated Na+ channels
Voltage gated K+ channels
both open in response to a change in membrane potental (voltage) -55mV → threshold, when they open varies (timed) depolarizing signal is required
Voltage Gated Sodium Channels
At rest
channel opens, Na+ moves into the cell (threshold) opens mSec
inactivates- Na+ can not move through- remains inactive for a few mSec, “refractory period” ← no longer in effect
channel closes- no longer activated “deactivation” happens when membrane returns to resting potential
Voltage Gated Potassium Channels
open in response to depolarization of membrane
with a milisecond delay
Blood Sugar on the Rise: What is diabetes mellitus and why is it a major public health concern?
Chemical messengers and the endocrine system
General Categories of Chemical Messengers (short distances)
Autocrine secretion- chemical messenger affects cell that secreted it (extra local)
Paracrine Secretion- chemical messenger secreted by one cell and affects nearby cell
Neurotransmitters- chemical messenger secreted by neurons @ synapses
“Endocrine” secretions travel through the blood to affect distant cells
Endocrine Secretion- “hormone,” secreted into blood, affects distant cells (long distant messengers). These hormones play crucial roles in regulating various physiological processes, including metabolism, growth, and mood.
Neuroendocrine Secretion- “neurohormone”, neuron secretes chemical messenger into blood, affects distant cells
Hormones and Receptors
A focus on endocrine secretions: general features
Gland- ductless, rich blood supply
Hormone- secreted into the blood
Transport- reaches every cell in the body (does not mean all cells are affected)
Target Cell- only cells affected by hormones
Three Main Chemical Types of Hormones
Peptide/Polypeptide/ “Protein Hormones”: Composed of amino acids, these hormones are water-soluble and cannot easily cross cell membranes, thus they bind to receptors on the surface of target cells. Most abundant type, tends to be species specific. Made via gene expression transcription-translation
Steroid Hormones: Derived from cholesterol, these fat-soluble hormones can pass through cell membranes and bind to intracellular receptors, influencing gene expression directly. There are 5 classes with it being not being species specific
Amine Hormones: These are derived from amino acids and can be either water-soluble or fat-soluble, depending on their specific structure.
Hormones must interact with a receptor to exert an effect.
Receptors are specific
2 General classes of receptors
Membrane Bound Receptors (signal transduction or signal amplification and hormone never enters the cell) and Intracellular Receptor (changes in cell are slower than in membrane receptor activation)
Membrane receptor activations leads to rapid changes in cells with most of the time ATP being required for signal amplification
Hormone receptor complex acts as a gene transcription factor
More mRNA transcripts are produced and each transcript is translated many times…both examples of signal amplification
“Mechanism of Action”- how a receptor works to effect change in cell
Peptides+ Polypeptides- cannot cross membrane (polar + charged)
Amino Acid Derivatives- most cannot cross (polar)
Steroids- can cross/are lipid soluble
Membrane Receptors (polypeptides + peptides/amino acid) and Intracellular Receptor (Steroids)
Glucose Homeostasis
Glucose: if too low= hypoglycemic→ not enough fuel to produce ATP, if too high= hyperglycemic→ high glucose levels, toxic to neurons and blood vessels
Insulin + Glucagon: 2 pancreatic hormones that are important in maintaining glucose homeostasis
Pancreas is an endocrine organ: secretes hormones (not thru ducts), exocrine organ- secretes digestive enzymes (thru ducts)
Islets of Langerhans= Pancreatic Islets
Alpha Cell → glucagon Beta Cell→ insulin
Glycogenesis: The process by which glucose molecules are linked together to form glycogen, which is stored primarily in the liver and muscle cells. This process occurs when glucose levels in the blood are high, allowing the body to store excess glucose for future energy needs.
Glycogenolysis: The process by which glycogen is broken down into glucose, allowing for the release of glucose into the bloodstream when blood sugar levels are low. This is crucial for maintaining glucose homeostasis in the body.
Recall: lipid bilayers are selectively permeable
Glucose Transporters (GLUT transporters)- membrane proteins that allow glucose to cross membrane
Facilitated Diffusion- diffusion of substances across membrane with assistance of protein transporter/channel
Some are not regulated: always present in membrane (no special signal required to insert in membrane) GLUT 1, GLUT 2, and GLUT 3
GLUT 1- most cells in body, GLUT 2- abundant in liver cells, GLUT 3- abundant in CNS
Others are regulated: they require a signal to be inserted in the membrane.
GLUT 4
pool of vesicles inside of the cell containing GLUT 4 transporters
insulin binds receptor receptor, stimulates insertion of GLUT 4 transporter into membrane
GLUT 4 is insulin regulated
found in skeletal muscle cells and adipose (fat) cells
Insulin stimulates uptake glucose by cells
Insulin has important actions in liver, adipose, and skeletal muscle tissue
Insulin Action on Liver Cells
glucose uptake occurs through GLUT 2 transporters (non insulin regulated)
insulin binds receptors on liver cells, signal transduction stimulates glycogenesis (formation of glycogen)
glucose is also metabolized here to produce ATP
Insulin Action on Skeletal Muscle Cells
most abundant glucose transporter= GLUT 4 (insulin dependent)
insulin stimulates insertion of GLUT 4 into membrane
glucose → ATP
other actions of insulin @ muscle cells
glycogenesis (formation of glycogen)
stimulates protein synthesis w/ amino acid uptake into muscle cells
Insulin Action on Adipose Tissue Cells
insulin binding to receptor stimulates insertion of GLUT 4 transporters into membrane
insulin also stimulates formation of glycerol and uptake of fatty acids.. overall triglyceride production
Diabetes mellitus is a disorder of glucose regulation
Type 1 Diabetes: individual doesnt secret sufficient insulin to stay in glucose homeostasis, * Beta cells of pancreas are attacked by immune system → no insulin
Type 2 Diabetes: target cells don’t respond properly to insulin → receptor issue, “insulin resistance” *origins: lifestyle factors (diet, exercise, etc) + genetic predisposition (Major Public Health Concern)
Type 2 Diabetes Risk Factors
obesity
high sugar diet
lack of exercise
metabolic syndrome
What are the consequences of chronic hyperglycemia?
Marcovascular complications (effects on arteries)
Glycoslyation- glucose binds to proteins in the blood
Atherosclerosis- thickening, hardening of arteries due to build up of plaques, *reduced blood flow, can lead to heart attack, stroke, coronary heart disease, peripheral artery disease (extremities don’t get blood supply)
Mircovascular complications (problems w/ capillaries)
Diabetic nephropathy- kidney disease, problems w/ capillaries and filtration, damage to capillaries in kidneys
Diabetic retinopathy- problems w/ capillaries can lead to blindness, disease of the retina, vision problems due to damage of capillaries at the retina
Neuropathy (problems with neurons)
Diabetic neuropathy- problems w/ neuronal communication, nerves shrivel when blood vessels disappear due to the reduced blood flow. * loss of sensation and greater likelihood of injuries that may be unnoticed
What are the most common treatment approaches?
pharmaceuticals- drugs that attempt to mitigate certain aspects of disease, increases cellular responsiveness to insulin and insulin production. e.g. metformin, GLP-1 agonists, sulfonoureas
lifestyle changes- diet, exercise
Why is diet important? foods you eat determine how much glucose is in your blood which impacts insulin production
Why is exercise important? GLUT 4 receptors: exercise stimulates insertion in the membrane too.
GLUT 4- skeletal muscle tissue, GLUT 4 is abundant, regulated insulin and muscle contraction
Living Life in the Clear: How can Antarctic icefish survive without red blood cells?
What is blood useful for?
gas transport (O2 , CO2)
fighting infections, coagulation/clotting
transport of heat
transport of waste
transport of hormones
nutrient transport
Which blood gases are most important? O2 , CO2
Cellular Respiration: C6H12O6 + 6O2 ——→ 6CO2 + 6H2O + ATPs + Heat
Red Blood Cells, Respiratory Pigments, and Physiological Functions
Whether fish or human, gas exchange occurs at the respiratory surface which is characterized by thin membrane and lots of capillaries (allows for efficient gas exchange)
Recall: lipid bilayers are selectively permeable
Gases are diffusing across membranes (based on concentration gradients)
Red Blood Cells and Respiratory Pigments
Erythrocytes (45% of total blood) → Hematocrit= 45
Blood can carry way more O2 than what is simply dissolved
Each red blood cell contains several hundred million hemoglobin (respiratory pigment) molecules which transport oxygen
Respiratory pigments bind O2 reversibly
Hemoglobin (Hb)
4 subunits
protein portion- “-globin”
heme portion- iron containing
each subunit can bind 1 O2
cooperative binding: when 1 O2 binds, Hb has a conformational change that increases likelihood of more O2 binding
O2 dissolves into blood plasma→ enters red blood cells, binds to Hb (now it is taken out of solution → not containing to concentration)
majority of O2 binded to Hb
Hb binds to oxygen reversibly: Hb + O2 —> HbO2
what happens when O2 concentration is high? When O2 concentration is high, hemoglobin (Hb) has a higher likelihood of binding to oxygen due to cooperative binding. This means that as one O2 molecule binds to hemoglobin, it induces a conformational change in the hemoglobin structure that increases the affinity for additional O2 molecules to bind. This process helps in efficiently transporting oxygen from the lungs to the tissues that require it.
what happens when O2 concentration is low? When O2 concentration is low, hemoglobin (Hb) exhibits decreased binding affinity for oxygen. This means that hemoglobin will release oxygen more readily into the tissues that require it. The reduced availability of oxygen stimulates mechanisms in the body to increase oxygen delivery, such as increased heart rate and respiratory rate, and can also trigger the production of red blood cells by stimulating erythropoietin from the kidneys.
The amount of O2 blood to the Hb depends on how much O2 is dissolved in the blood plasma→ concentration of dissolved O2 in plasma → partial pressure of O2 = PO2
O2 saturation (%) of Hb ← % of Hb binding sites bound
PO2 ← amount of O2 dissolved in blood plasma
Cooperative binding- when 1 O2 binds to Hb, the other binding sites bind O2 more readily (conformational change)
Where in body is PO2 low?- anywhere in the body that isn’t the respiratory surface or the lungs
Where in the body PO2 high? - respiratory surface + the lungs
General Principle Alert: Tradeoffs: b/n loading of O2 onto Hb @ respiratory surface and unloading (‘delivery’) of O2 from Hb @ systemic tissues
Hb’s affinity ( the ease w/ which Hb will bind O2 when it encounters O2) for O2 tells us which one is favored
High Affinity (saturated @ low PO2)- readily binds O2, even when there’s not much available
Low Affinity (saturated @ high PO2)- binds O2 less readily; becomes saturated only when there’s alot of O2 available
P50 is a measure of O2 affinity
higher affinity respiratory pigment has lower P50 value
One more respiratory pigment: Myoglobin (Mb)
single subunit
globin portion (protein)
heme unit (Fe-containing)
very high affinity for O2
only found in muscle cells
skeletal + cardiac muscle
What is function of myoglobin?- O2 reserve “storage” for muscles, holds onto O2, gives it up only when concentration drops very low
Some icefish also lack myoglobin
3 vertebrate circulatory systems: anatomy and function
Atria (plural) ventricles
Fish Heart: 1 circuit, “2 chambered” heart
Closed systems: blood vessels; a) capillaries (gas exchange)are small and extremely thin walled
Dynamics of Blood Flow through the capillaries: slow for gas exchange
Fish Heart: 2 chambers, only pumps deoxygenated blood, 1 ventricle, 1 atrium , relatively low blood pressure
Heart Action: cardiac output= volume pumped per unit time, CO= HR x SV
Loss of Hb in icefish is disadvantageous (Hb loss is considered a disadaptation)
disadaptation- trait that is inferior to ancestral trait
Question 1: How did icefish lose the ability to produce hemoglobin?- loss of genes themselves
globin genes in fish- partial alpha globin gene, no beta globin gene “gene delection”
Question 2: When did loss of Hb genes occur in icefish evolution? 5.5-2 million years ago
loss of functional globin genes: happened 1x in ancestor common in icefish
synapomorphy= shared derived trait
Question 3: If not advantgeous, why did this condition persist?
cold H2O- higher O2 content
well aerated (always moving, distributed)- higher O2 content
cold H2O lowers MR of icefish (lower O2 demand)
lack of competition → many species that lacked sufficient antifreeze protein production disappeared when ocean cooled
Hb loss = sublethal trait (only disadvantageous in the context of competition)
Icefish have a low thermal tolerance compared to red blooded fish
Things to Know if you’re stranded on a deserted island: Can coconut water replace IV fluids?
Body water in 3 major “compartments”
Intracellular fluid
interstitial fluid
blood plasma
ICF= intracellular fluid (fluid inside of cells)
most of body H2O is ICF
ECF= extracellular fluid
interstitial fluid (between cells)
blood plasma
Recall: lipid bilayers are selectively permeable
Cell membranes function as barriers and gatekeepers
Active Transport(uses ATP)- secretion in vesicles
Passive Transport (no ATP required)- simple diffusion across membrane
Protein mediated
Primary Active Transport
Na+/K+ ATPase Pump (secondary active transport)
cotransporters
Facilitated Diffusion
transporters (e.g. GLUT)
channels (e.g. ion channels)
aquaporins = H20 channels
Aquaporins are membrane channels that allow water to move through (facilitated diffusion)
New Vocabulary: solutes are dissolved particles in solution (the type of particle doesn’t matter)
Osmosis is the diffusion of water across a semipermeable membrane
depends on solute concentrations
H2O moves from area of lower solute concentration to higher solute concentration
Fluid outside has a higher solute concentrations of solutes can’t cross:
water moves out (cell shrinks)
Fluid outside has a lower solute concentrations of solutes can’t cross:
water moves in (cell swells)
Fluid outside has a equal solute concentrations of solutes can’t cross:
no net movement, equal (no net charge)
osmolarity: concentration of solutes in solution- Osm, mOsm
Hyperosmositc: solution has a greater concentration of solutes
Hypoosmostic: solution has a lower concentration of solutes
Isomotic: solution has an equal concentration of solutes
Osmoregulators- regulate internal osmolarity within a narrow range, despire differences in environmental osmolarity
Osmoconformer- internal osmolarity matches environmental osmolarity
Fresh H20 fish- hyperosmotic regulator
challenges: H2O gain, salt loss
solutions: produces lots of dilute urine, active uptake of salts
Salt H20 fish- hyposmotic regulator
challenges: H20 loss, salt gain
solutions: produce little urine that is concentrated than fresh H2O fish active transport of salts out of the body
desication/dehydration- drying out, mass water loss
change activity levels (reduce H2O loss via evaporation)
Drink H20! (eat food w/ high H2O content)
metabolic H2O production
produce concentrated urine (mammals, birds, insects)
One solution: reduce water loss from body surface
ex: waxy covering for insects
Another solution: reduce water loss in urine
