WORKSHEET 1 feedback loops

similarities between negative feedback and positive feedback

-they both work through a stimulus, signal, and response; -they both are cyclical; -they both are feedback mechanisms, etc.

Most IVs contain a 0.9% saline solution, because this salinity is isotonic to blood cells. Assume that your nurse makes a mistake and infuses you instead with a 2.0 % saline solution. Describe what will happen to your blood cells.

A 2.0% saline solution is hypertonic to the blood. If you were infused with this, water would be pulled from your blood cells and into the extracellular solution surrounding them. This would cause your blood cells to shrivel and become nonfunctional.

A hypertonic extracellular solution has a _____________ (higher/lower) concentration of solutes than the cell that is suspended in it.

A hypertonic extracellular solution has a higher concentration of solutes than the cell that is suspended in i

A hypotonic extracellular solution has a ______________ (higher/lower) concentration of solutes than the cell that is suspended in it

A hypotonic extracellular solution has a lower concentration of solutes than the cell that is suspended in it.

which feedback mechanism, negative or positive feedback would be most useful for stopping a condition that is either detrimental or needs to be limited to certain levels?

A negative feedback mechanism would be best for either stopping or limiting a situation, as the response decreases the stimulus.

A function of the plasma membrane and the cell membrane

A plasma membrane compartmentalizes structures inside the cell, while the cell membrane acts as a boundary between the cell and its outer environment.

which feedback mechanism, negative or positive feedback be most useful for amplifying a condition that is advantageous?

A positive feedback mechanism would be best for amplifying a condition that is advantageous because in positive feedback the response increases the stimulus.

Diffusion, facilitated diffusion, and osmosis are all passive transport processes that don't require energy from the cell. Explain why active transport requires energy input by the cell.

Active transport is going against what would happen naturally—that molecules would spread out from areas where they are more highly concentrated into areas where they are less highly concentrated. The cell doesn't have to force substances to move with passive transport because the substance will naturally do it on its own in this type of situation. With active transport, the cell needs the molecules to move in a direction opposite that which they would naturally move, so the cell will physically have to force them to that area. And that requires energy on the part of the cell. Whether a cell uses active or passive transport to move an atom or molecule depends on the needs of the cell at the time, and where it needs the substance to go. If at all possible, cells will try to get substances to move through passive transport so that they have to exert as little energy as possible. I would say they're lazy, but the reality is they're smart! Rarely in human history has food (and therefore energy) been abundant. For most of our time on this earth, we've been a few missed meals from starving. So it makes sense that cells would be adapted to be as efficient as possible with their energy resources J.

How does the ATP changing from ATP to ADP provide energy to move the transported substance?

After the ATP binds the protein it becomes ADP. ATP stands for adenosine triphosphate. Essentially, it is a molecule with three phosphorous containing groups attached to it. When it binds the ATP binding site, one of those phosphorous containing groups breaks off and it becomes ADP or adenosine diphosphate.

Proteins that span the membrane form channels that protect hydrophilic atoms and molecules from the hydrophobic environment inside the phospholipid bilayer. Which of the atoms and/or molecules from the list above would have to cross the cell membrane through a channel?

All of the atoms/molecules on the list with the exception of CO2 and O2 are charged and thus polar. This means they would have to pass through a channel even though they technically would be small enough to squeeze between adjacent phospholipids. Even though they are small enough to fit, they won't enter or exit the cell in this way because they won't enter the hydrophobic tail region of the bilayer.

Any substance that is going to squeeze between adjacent phospholipids to enter or exit the cell will have to go across the hydrophobic portion of the membrane. Would polar atoms (ions) or other polar molecules be able to do this?

Anything that is charged or polar is also hydrophilic. A hydrophilic substance will not penetrate through the hydrophobic area formed by the phospholipid tails. Thus ions like Na+, K+ and Cl- and charged molecules such as water will not move across the membrane by squeezing between adjacent phospholipid molecules.

When the intensity of contractions increases, will the stimulus increase or decrease?

As the intensity of contractions increases, the push of the baby's head against the cervix (stimulus) increases.

Cholesterol is a rather rigid molecule. Would its placement in the phospholipid bilayer increase or decrease the flexibility of a membrane?

Because cholesterol is rigid, when it's placed in the phospholipid bilayer it makes the phospholipid bilayer more rigid. For that reason the cells of our body (which contain cholesterol embedded in the phospholipid bilayer) are sturdier than soap bubbles.

Why is the molecule in model 1 known as a "phospholipid".

Because of its structure. One part of the molecule contains a phosphorus atom which is where the " phosphor" part of the name comes from. Chemically, the fatty acid tail is a lipid, so that is where the "lipid" part of the name comes from

Consider the state of homeostasis—maintaining conditions in the body within certain limits. Would a positive feedback loop ever be helpful in maintaining homeostasis?

Because positive feedback loops do not negate the stimulus (they amplify it) they would not be able to keep internal conditions in the body the same over time. As an example, if positive feedback regulated body temperature, an increase in body temperature would lead to further increase in body temperature (until you started on fire or something). It wouldn't lead to a decrease in body temperature. Conversely, a decrease in body temperature would lead to further decreases in body temperature until you died of hypothermia. Positive feedback (because it amplifies the stimulus rather than negating it) does not help you maintain a stable environment in your body

Explain why the cell and plasma membranes are also referred to as the "phospholipid bilayer"

Cells are filled with fluid on the inside, and they are also bathed in interstitial fluid on the outside. Thus the plasma and other cell membranes have to be phospholipid bilayers so that we don't have the hydrophobic tails of the phospholipids in contact with water.

Is childbirth an example of a positive or negative feedback system?

Childbirth is a positive feedback loop because the response amplifies or encourages the stimulus.

does cholesterol appear to be mostly polar or mostly nonpolar?

Cholesterol is nonpolar because there isn't a charge on it

What is providing the energy to move stuff in active transport?

Energy coming from breaking bonds in ATP molecules provides the energy necessary to move stuff in active transport. The cell must provide the ATP.

Functions of feedback mechanisms

Feedback mechanisms are used to keep the body in homeostasis. Basically, they ensure that the body's internal environment doesn't change too much, so that all the functions that need to occur can continue. To stay alive, these feedback mechanisms ensure that oxygen levels in the body do not get too low, temperature and pH are kept within their normal ranges, and they also regulate a variety of other activities as well to ensure that everything stays within the normal levels. If they fail to maintain homeostasis, or keep the body's internal environment the same, you may become very sick and possibly even die.

When molecules are stacked tightly together, they form more rigid structures. When they are stacked less tightly, they form more fluid and flexible structures. Explain why the fluidity of a membrane increases when more of the phospholipids in the layers contain carbon double bonds.

Fluidity increases when there are more carbon=carbon double bonds, because it prevents the molecules from stacking tightly together due to the kinks in chains that contain double bonds

Why did the glucose molecules need a channel to move across the plasma membrane? Why couldn't they squeeze between adjacent phospholipid molecules?

Glucose is quite a large molecule. As such, it is too big to squeeze between adjacent phospholipids.

When a carbohydrate is attached to a phospholipid, what is the structure called?

Glycolipid

When a carbohydrate chain is attached to a protein, what is the structure called?

Glycoprotein

What type of molecules attach to the protein?

Hormones attach to the protein.

What do the terms "hydrophilic" and "hydrophobic" mean?

Hydro means water. Philia means loving. Phobia means hating. So hydrophilic means it loves water and hydrophobic means it hates water

In a concentrated solution is there more or less water.

In a concentrated solution there is less water.

In a dilute solution is there more or less water

In a dilute solution there is more water

What is providing the energy to move stuff in passive transport?

In passive transport the energy to move stuff is coming from Brownian movement leading to collision of molecules. The cell does not need to provide the energy.

In passive transport substances diffuse from an area of their ____________ (higher/lower) concentration to an area of their _________ (higher/lower) concentration. In active transport substances are pumped from an area of their ___________ (higher/lower) concentration to an area of their ____________ (higher/lower) concentration.

In passive transport, substances diffuse from an area of their higher concentration to an area of their lower concentration. In active transport, substances are pumped from an area of their lower concentration to an area of their higher concentration.

Why in simple diffusion do molecules naturally move from areas where there is a higher concentration to areas where there is a lower concentration?

In simple diffusion molecules move from areas where they are having more collisions to areas where they are having less collisions, simply because when they collide they move away from the collision site. Because more collisions happen when more molecules are present, this naturally spreads molecules from areas of higher concentration to areas of lower concentration.

why facilitated diffusion is necessary for the transport of ions such as Na+ and K+ across the plasma membrane? In other words, why can't Na+ and K+ cross by simple diffusion?

In the example we saw here, glucose couldn't squeeze between adjacent phospholipids because it was too large. For that reason, the glucose molecules had to go through channels in the membrane. By the same token, anything that is polar (such as Na+ and K+) cannot squeeze between adjacent phospholipids to cross the membrane because it cannot be in the hydrophobic environment created by the phospholipid tails. Instead, charged or polar atoms have to pass through a channel which "protects" them from the hydrophobic environment on the interior of the phospholipid bilayer.

Consider the feedback loop that heats the body when it is too cold. Identify the "stimulus" and "response" in that feedback loop.

In the feedback loop that heats the body when it is too cool, the stimulus is decreasing temperature and the response is shivering and blood diversion away from the skin.

In the scenario given in the previous question, the puppy chasing the ball is the ____________ (stimulus/response), and you rubbing his head and saying "good job" is the ____________ (stimulus/response).

In the scenario given in the previous question, the puppy chasing the ball is the stimulus, and you rubbing his head and saying "good job" is the response.

In the scenario given in the previous question, the puppy urinating on the couch is the ___________ (stimulus/response), and you saying "No, bad dog!" is the ____________ (stimulus/response).

In the scenario given in the previous question, the puppy urinating on the couch is the stimulus, and you saying "No, bad dog!" is the response.

List two binding sites found on the protein.

Ion binding site and ATP binding site

What is the relative concentration of solutes between a cell and an isotonic solution?

Iso = same. So an isotonic solution has the same concentration of solutes as a cell that is suspended within it.

What does it mean that the plasma membrane is "selectively permeable"?

It means that the plasma membrane allows some molecules and atoms to cross it, while preventing other atoms and molecules from crossing.

Would the nonpolar part of a molecule mix well with water? Why or why not

No it wouldn't because water is charged (polar) , it forms attractions with other charged molecules. Nonpolar molecules are not charged , thus no part of them is attracted to water

Part of a phospholipid is nonpolar. What does nonpolar mean

Nonpolar In in terms of chemistry means not charged. A nonpolar molecule is a molecule that doesn't have a charge to it.

Would nonpolar molecules be able to cross the membrane by squeezing between adjacent phospholipids and crossing the hydrophobic portion of the phospholipid bilayer?

Nonpolar molecules and atoms are able to cross by squeezing between adjacent phospholipids as long as they are small enough to do so because they do not have a problem being in the hydrophobic tail region of the bilayer

What hormone, released from the hypothalamus in the brain, increases the intensity of contractions?

Oxytocin

Particles move along the concentration gradient from BLANK to BLANK concentration until a state of equilibrium is reached.

Particles move along the concentration gradient from high to low concentration until a state of equilibrium is reached.

Part of a phospholipid is polar. What does polar mean

Polar in terms of chemistry means charged. A polar molecule that has a change

What are the two major types of biological (organic) molecules that compose the majority of the cell membrane

Proteins and lipids are the two types of biological molecules that make up the majority of the plasma membrane.

Simple diffusion, facilitated diffusion, and osmosis are all what type of transports

Simple diffusion, facilitated diffusion, and osmosis are all passive transport processes.—they are ways to move substances across the plasma membrane either into the cell or out of the cell without the cell needing to exert any energy to do so.

What types of molecules are shown moving directly across the membrane by squeezing through adjacent phospholipids?

Small nonpolar molecules

Think about soap bubbles which are very similar to the cell and plasma membranes. Do they seem to be rigid in their structure or more fluid and flexible?

Soap bubbles are really fluid and flexible. They are easy to pop. If you watch them after they are blow, they will twist and turn on themselves as they float in the air.

identify the stimulus and the response and state whether the process is positive or negative feedback. -When a person has not taken in sufficient water, they become dehydrated. This may cause a loss of blood pressure, which will trigger the release of antidiuretic hormone (ADH) from the hypothalamus and pituitary glands in the brain. This hormone signals the kidney to decrease the amount of urine produced, so that more water stays in the blood, helping to bring the blood pressure back up to normal levels.

Stimulus: blood pressure decreases; Response: releases of ADH and decrease in urine production; Negative feedback

identify the stimulus and the response and state whether the process is positive or negative feedback. -When human tissue, such as the skin or a blood vessel, is torn or cut, the cells near the damage send out a chemical signal that activates platelets in the vicinity. As the platelets begin to form a plug, they release more chemical signals to attract more platelets and other clotting chemicals to the area, until the bleeding is stopped.

Stimulus: chemical signal; Response: platelets adhere to form a plug; Positive feedback

identify the stimulus and the response and state whether the process is positive or negative feedback. -When a human increases physical activity, the amount of fuel burned in its cells also increases, which in turn increases the concentration of carbon dioxide dissolved in the blood. The carbon dioxide reacts with water in the blood to make a weak acid, which lowers the pH of the blood. Sensory cells in an area of the brain known as the medulla detect this drop in pH and send signals to the muscles used for breathing to increase respiration, and to the heart to increase the rate at which it is beating. This will clear the carbon dioxide from the bloodstream.

Stimulus: decrease in pH; Response: increased respiration/heart rate; Negative feedback

Which molecules will not be able to move through the membrane

Sugar will not be able to move because it is too large to fit through the pores.

What is the difference between the position of the surface proteins and the membrane-spanning proteins?

Surface proteins sit on the surface of the phospholipid bilayer (either on the inner surface or the outer surface). Membrane-spanning proteins span the width of the phospholipid bilayer from the inside to the outside.

Describe what happened to the cell in the hypertonic solution. What word is used to summarize these changes to the cell?

The cell in the hypertonic solution lost some of its internal water volume to the extracellular solution. This caused the cell to shrivel. The word used to summarize these changes is crenated.

Describe what happened to the cell in the hypotonic solution. What word is used to summarize these changes to the cell?

The cell in the hypotonic solution gained water from the extracellular solution, which caused the cell to expand until it burst. The word used to summarize these changes is lysed.

Describe what happened to the cell in the isotonic solution.

The cell in the isotonic solution had neither a net water increase nor decrease. Nothing happened to its shape or size because of this.

What becomes of the ATP after it binds to the protein?

The energy from ATP is being used to pump the ions across the plasma membrane

Describe the concentration of the extracellular solution surrounding hypertonic cells, relative to the intracellular concentration of that solution inside hypertonic cells.

The extracellular concentration of saline surrounding hypertonic cells must be higher than the concentration inside the cell, because the cell is losing water to its external environment, causing it to decrease in size.

Describe the concentration of the extracellular solution surrounding hypotonic cells, relative to the intracellular concentration of that solution inside hypotonic cells

The extracellular concentration of saline surrounding hypotonic cells must be lower than the concentration inside the cell, because the cell is gaining water from its external environment, causing it to increase in size.

Describe the concentration of the extracellular solution surrounding isotonic cells, relative to the intracellular concentration of that solution inside of isotonic cells

The extracellular concentration of saline surrounding isotonic cells must be the same as the concentration inside the cell, because there is no net movement of water into or out of the cell. This is clear because the cell is not changing shape from a net gain or net loss of water.

Is the feedback loop that cools the body when it is too warm an example of positive or negative feedback? Justify your reasoning.

The feedback loop that cools the body when it is too warm is an example of negative feedback. The reason is, the stimulus (rising temperature) is negated by the response (sweating, blood diversion to the skin).

Is the feedback loop that heats the body an example of positive or negative feedback? Justify your reasoning.

The feedback loop that heats the body is an example of negative feedback, because the stimulus (decreasing temperature) is negated by the response (shivering and diverting blood away from the skin). Please note: Negative feedback isn't about decreasing the stimulus and positive about increasing the stimulus. In both scenarios given in this section (whether temperature is increased or decreased) we are dealing with negative feedback because the stimulus was negated. When temperature was too low, it was brought back up. When temperature was too high, it was brought back down.

Why did the glucose molecules move in the direction they did through the channel? Why didn't they move in the opposite direction?

The glucose molecules moved from areas of their higher concentration to areas of their lower concentration. They don't move in the opposite direction because they are still being driven by collisions and those collisions are happening more where the glucose is more highly concentrated.

how phospholipids would orient themselves if spread on the surface of the water in the beaker below.

The hydrophilic portion of the phospholipid would want to be in contact with the water, and the hydrophobic portion would not.

Oil is nonpolar (and thus hydrophobic). When a small amount of oil is added to a beaker of water containing phospholipids, the phospholipids will surround the oil droplets forming micelles. Use several cartoon representations of phospholipid molecules to show the arrangement or orientation of phospholipids in a micelle.

The hydrophobic portion of the phospholipid would want to be in contact with another nonpolar molecule, and the hydrophilic portion of the phospholipid would want to be in contact with the water.

define diffusion

The net movement of particles along the concentration gradient is called diffusion.

All of the atoms and molecules listed here are small enough to squeeze between adjacent phospholipids: Na+, CO2, O2, K+, Ca2+, OH- . Which of them would actually enter or exit the cell in that way?

The only molecules in the list that would actually in reality cross the cell membrane by squeezing between adjacent phospholipids are CO2 and O2. They are the only ones that are not charged and thus can enter the hydrophobic tail region of the bilayer.

What sections of the embedded protein chain are most likely to contain hydrophobic amino acids?

The portions of the protein that are within the hydrophobic tail area of the phospholipid bilayer are likely to be composed of nonpolar amino acids because they are positioning themselves away from water.

Would the puppy urinating on the couch scenario be an example of negative or positive feedback? You must justify your reasoning using the words "stimulus" and "response" in your answer.

The puppy urinating on the couch scenario is an example of negative feedback, because the response decreased the stimulus.

Imagine that you have just gotten a puppy. In the course of playing with the puppy you throw a ball and the puppy chases after it. You then say "Good job!" and rub the puppy's head to show him he did what you wanted him to do. Is the puppy likely to chase the ball the next time you throw it? Justify your reasoning.

The puppy would likely chase the ball again because he enjoyed being praised and having his head rubbed.

Later that day your puppy urinates on the couch. You then say, "No, bad dog!" and place the puppy outside. Is the puppy likely to urinate on the couch again? Justify your reasoning.

The puppy would not be likely to urinate on the couch again because he didn't enjoy being reprimanded or placed outside.

What will eventually stop the stimulus and thus stop the childbirth feedback loop?

The response will continue to increase the stimulus (and vice versa) until the baby is pushed so hard against the cervix that it exits the body. At that point, there is no more stimulus (no more baby head pushing on the cervix) and so no more response (release of oxytocin and ensuing contractions).

What sections of the embedded protein chain are most likely to contain hydrophilic amino acids?

The sections of the protein that are oriented facing into watery areas (on both sides of the phospholipid bilayer) are likely to be composed of hydrophilic amino acids.

what is the stimulus and what is the response during childbirth?

The stimulus is the baby's head against the cervix, which stretches the cervix. The response is release of oxytocin (leading to uterine contractions).

Since a beaker of water is three-dimensional, what is the three-dimensional shape of the micelle?

The three dimensional shape of the micelle would be a sphere—like a basketball or a globe.

which molecules will be able to move through the selectively permeable membrane?

The water molecules will be able to move because they are small enough to fit through the pores in the membrane.

How does the concentration of the small nonpolar molecules inside the cell compare to that outside the cell?

There is a higher concentration of small, nonpolar molecules outside the cell than there is inside the cell.

Where exactly in the membrane do the small nonpolar molecules pass through?

These molecules are squeezing between adjacent phospholipids in the bilayer.

Is this scenario an example of negative or positive feedback?

This is an example of positive feedback because the response increases the stimulus.

what are two mechanisms the body uses to cool itself?

To cool itself, the body increases sweat production and it dilates the blood vessels to the skin so that blood moves towards the skin and loses heat to outside of the body.

what are two mechanisms the body uses to heat itself?

To heat itself, the body shivers (which generates heat through muscle contraction) and it also diverts blood away from the skin and holds it deeper in the body so that less heat is radiated from the surface of the body.

Would the polar part of a molecule mix well with water? Why or why not

Water is a charged molecule in other words water is a polar molecule. This means it has a negative end and a positive end. In the phospholipid molecule in model 1 there is a negatively charged oxygen atom attached to the phosphorus molecule. This negatively charged oxygen will be attracted to the positively charged parts of the water , so this molecule and other molecules that are polar mix well with water

Consider the feedback loop that cools the body when it is too warm. Identify the "stimulus" and the "response" in that feedback loop.

When body is too warm the stimulus is the rising temperature and the response is sweating and diverting blood to the surface of the body.

You've probably heard the saying "a vicious cycle" used before. Do you think this relates more to positive or negative feedback loops?

When the stimulus amplifies the response and the response amplifies the stimulus and this repeats until everything is super intense and outside of normal ranges, this is positive feedback. "Vicious cycles" are based on positive feedback. Here's an example: let's suppose you have two friends that don't get along. Friend 1 insults Friend 2, and so Friend 2 insults back. This angers Friend 1 who further insults Friend 2. Each become angrier and angrier insulting more and more until things spiral out of control and we've got a vicious cycle that is amplifying itself. In a negative feedback cycle, Friend 2 would simply walk away or turn the other cheek after receiving an insult from Friend 2, and this negative feedback would prevent the vicious cycle from even beginning. It would negate the situation instead of amplifying it.

When there is a difference in concentration of a particular particle on either side of the plasma membrane, a BLANK exists

When there is a difference in concentration of a particular particle on either side of the plasma membrane, a CONCENTRATION GRADIENT exists

Explain the effect of ingesting an extremely large amount of water at the level of the brain cells

When you drink a large amount of water in a very short period of time, you dilute the blood. This makes the blood hypotonic to the cells of the body, including brain cells. In an attempt to establish equilibrium, water will begin moving into the cells, causing them to swell. This can damage brain and other cells of the body to the extent that death ensues.

Define signal

a gesture, action, or sound that is used to convey information or instructions

Define response

a reaction to something

Define stimulus

a thing that rouses activity or energy in someone or something; a spur or incentive

What is the gap between the proteins called?

channels

describe the shape and structure of the epithelial tissue: cubiodal

cubiodal cells are roughly cube-shaped cells

Embedded proteins are often found spanning the membrane of a cell or organelle. These proteins serve as BLANK for specific molecules to travel through the membrane, either into or out of the cell.

embedded proteins serve as CHANNELS for specific molecules to travel through the membrane, either into or out of the cell

what are the four primary tissue types

epithelial, connective, muscular, and nervous

Hypertonic cells show

hypertonic cells show a net decrease in water. the cells have decreased in size

Define hypothalamus

hypothalamus senses that temperature is too low or too high. Sends out signals to either heat or cool the body. Overall it monitors temperatures.

hypotonic cells show

hypotonic cells show a net increase in water. The cells have increased in size

isotonic cells show

isotonic cells show no net change in water. There is no change in the size or shape of the cell

define osmosis

osmosis is the diffusion of water across the plasma membrane

are the tails of phospholipids polar or nonpolar

the tails of phospholipids are nonpolar

Define thermoregulation

thermoregulation is how the body regulates its internal temperature