Bio Lab Exam 2

A cell placed in a solution that has less water and more solute than cytoplasm causes the cell to shrink

(hypertonic).

What is discrete?

A fixed number of outcomes is possible such that there are only whole inters possible Graphs: histograms, line-graphs, & scatterplots

So WHY will substances move from high to low concentration?

Actually, random movement is what drives diffusion! Molecules move around in all possible directions all the time. In water, in air - in every substance. The speed of the molecules in the air where you are sitting right now is about 500 meters per second!

What is quantitative or numerical data?

Data expressed not by means of a natural language but in terms of number. 2 types are continuous & discrete

qualitative (categorical) data

Data placed into categories according to specific characteristics; not in numbers but in natural language description. 2 types are ordinal & nominal

What is the definition of measures of variability or spread?

Describes how spread out or dispersed the data are.

What is data distributions?

Describes the numbers of times each possible outcomes occurs in a sample or pop'n. 2 types: bimodal & unimodal

What can you conclude about the diffusion of iodine, glucose, and starch across the selectively permeable dialysis tubing membrane?

Diffusion occurred based on a molecular size. Iodine and glucose are much smaller molecules than starch: therefore, they were able to diffuse.

What is unimodal?

Distribution has one distinct clump of data

What is a population?

Entire set of objects to be studied

What is inferential statistics?

Hypothesis testing & confidence intervals.

Diffusion is driven by this random movement of molecules. The faster molecules move, the greater the speed of diffusion. Why?

If a bunch of molecules move around randomly, they will spread out more quickly if the molecules are moving fast. Think of billiard balls. The speed of molecules-and therefore the speed of diffusion-depends on factors that can vary. Temperature and the weight of a molecule are examples of this. The type of medium also matters as we will see next.

How are you going to determine if iodine and/or starch diffuse across the dialysis tubing?

If both starch and iodine are able to diffuse across the dialysis tubing they would mix on both sides of the membrane turning both solutions dark purple. In this situation the iodine would diffuse from the beaker into the dialysis tubing with the starch.

What is normal distribution?

It's a continuous distribution that is bell-shaped.

What are the measures of central tendency?

Mean & median.

What is the median?

Middle value in data ordered by sequential rank

What is descriptive statistics?

Minimally summarized measures of center & spread from data recorded.

Did diffusion across the membrane occur for the starch solution?

No

What is continuous?

Numbers where any integer or fraction can be observed (time, height, weight)

What is measures of central tendency?

Provides info of how data clusters around some middle value

What is standard deviation?

Quantifies variation or dispersion from the avg dataset.

What is the mean or average

Sum of all individual values divided by the total number of values in the sample/pop'n

In a hypertonic solution, water mainly leaves the cell, which shrivels (crenation).

The solution has less water and so water moves out of the cell. Turgid

In a hypotonic solution, water mainly enters the cell, which may burst (lysis).

This means the solution has more water, so water moves into the cell. Flaccid

In an isotonic solution, there is no net movement of water.

This means the solution has the same concentration of water as the cell. Cells maintain normal shape and volume.

Biological membranes like cell membranes have additional factors that determine whether a substance can pass through. For example, the chemical composition of the membrane will affect the diffusion of solutes which are too large and polar, or charged.

True

Common examples include diffusion of oxygen and carbon dioxide in the respiratory system, absorption of some nutrients from the intestines, and regulation of water balance by the kidneys. Diffusion is important to living cells as a means of transporting substances across cell membranes.

True

Consider two solutions separated by a semipermeable membrane. One is 10% solute , the other is 20% solute. Water will move by osmosis into the 20% solute solution. Osmotic pressure is the amount of pressure you would have to exert on the 20% side to prevent water from entering.

True

Dialysis tubing is a selectively permeable membrane because it has pores that limit the size of molecules that can pass through it. Starch molecules are too large to pass through and will stay on the side where they were originally placed. Glucose, iodine, and water molecules are small enough to fit through the pores. If there is a concentration gradient of glucose or iodine then these molecules can diffuse down their gradients.

True

Diffusion ONLY takes place when there is a concentration gradient.

True

Diffusion can transport substances down a concentration gradient (from high to low) without the use of cellular energy. But not all substances cross cell membranes by diffusion. Some substances that cells require must be transported against a concentration gradient (from low to high) or they may be too big to pass through membranes. Others are not able to pass through due to other chemical properties

True

Diffusion is the net movement of molecules from high concentration to low. The greater the concentration gradient (difference between high and low concentration) the greater the rate of diffusion.

True

Diffusion takes place in a solution.

True

For example, if volume is equal, a 10% salt solution has lower water concentration than a 5% salt solution. More water and less solute than the solution is more dilute.

True

Here is a U-shaped tube with two substances in it. Water and some big molecule that can't move across the membrane. The water concentration is higher on the left side of the membrane Remember that molecules move about freely. Looking at the zoomed in image, we can see that there is a higher probability that a water molecule will enter a hole in the membrane from the left than from the right - simply because the water concentration is higher on the left side. On a macrolevel this means that the net-movement of water will be towards the lower water concentration. That's the simple mechanism behind osmosis.

True

If a dilute solution of iodine is added to a solution of starch, the light yellow iodine will turn a blue/black color as it reacts with the starch. If there is no starch present, the iodine keeps its light yellow color, but will just lighten in color due to dilution as it is added to the solution. This reaction of iodine with starch makes iodine a good way to test for the presence of starch.

True

In this simulation, you will examine the diffusion of iodine, starch, and glucose across an artificial membrane made of dialysis tubing. Some of these substances will move across the membrane and some will not.

True

Like all forms of diffusion, osmosis is passive, and there is a net movement from an area of high water concentration to low water concentration.

True

Molecules move all the time and diffusion is the net movement of molecules from a region of higher concentration to one of lower concentration.

True

Molecules move around randomly and at a high speed.

True

Selectively permeable membranes have characteristics which allow some molecules, but not others, to pass. For example, dialysis tubing has small "pores" that limit the movement of molecules above a certain size.

True

Smaller substances will diffuse across the artificial membrane made of dialysis tubing, while larger substances will not.

True

Substances that cannot diffuse through membranes may be transported using other mechanisms. Most require the use of cellular energy (ATP) and so are considered active transport mechanisms.

True

Tea with two spoonfuls of sugar is more concentrated than tea with one spoonful.

True

The concentration of a solution is commonly described in terms of the amount of solute it contains.

True

The tonicity of a solution gives information about potential cell volume changes if cells are placed in that solution.

True

Water moves by osmosis from an area of high water concentration to an area of low water concentration. By definition, the water must pass through a semi-permeable membrane. This means the membrane is permeable to water, but not all solutes.

True

You will place glucose and starch inside dialysis tubing and then place the tubing in a beaker containing iodine and water. You will then observe and record your observations after 10 minutes.

True

Did diffusion across the membrane occur for the glucose solution?

Yes

Did diffusion across the membrane occur for the iodine solution?

Yes

Tonicity is a comparison of the relative concentrations of two solutions separated by

a selectively permeable membrane.

Osmotic pressure is defined as the pressure that must be applied to

a semi-permeable membrane to oppose or prevent osmosis.

What are the two types of data distribution?

bimodal & unimodal

When the solute concentration is unequal, we say that a________________exists.

concentration gradient.

Water moves freely by osmosis across cell membranes, based on:

concentration gradients.

Iodine by itself is brown. When it interacts with starch, iodine turns

dark purple.

The rate of diffusion may be influenced by

density of media, concentration gradient, temperature, molecular size, and membrane permeability.

A concentration gradient is present when there is a

different concentration of solutes within a solution.

What is bimodal?

distribution has 2 distinct clumps of data

What is a value?

each measurement or observation

In some types of media such as gas, solvent molecules are widely spaced, and solute moves more freely and therefore also FASTER. Faster movement means faster diffusion. Therefore lower density of molecules means

faster diffusion, all things equal.

In diffusion, molecules move from

high concentration to low concentration.

Like all other cases of diffusion, water moves by osmosis from an area of

high water concentration to low.

What is a null hypothesis?

hypothesis that states there is no relationship/pattern between the independent & dependent

Placing a cell in a solution that has more water and less solute than cytoplasm causes a cell to swell as water goes into the cell

hypotonic & turgid

Whether diffusion occurs in a gas, a semi-solid or a liquid, the basic mechanism is the same:

individual molecules move around randomly, therefore groups of molecules tend to spread out as much as possible.

An isotonic environment

is balanced so water enters and leaves cells at the same rate.

Diffusion

is the net movement of a solute from an area of higher concentration to an area of lower concentration.

There are 3 types of osmotic environments:

isotonic, hypotonic, and hypertonic.

A solution is created when two substances are

mixed and one is dissolved in the other.

Diffusion of these substances across the dialysis tubing will depend on

molecular size.

Osmosis is passive, meaning that

no cell energy is used in the process.

What is a statistic?

numerical characteristic of a sample from the population

What is a parameter?

numerical characteristics of population

Diffusion is the result of the random movement

of molecules.

Recall how water concentration is related to solute concentration in a solution. The more solute that is in solution, the less water it contains. The greater the concentration gradient of water across a membrane, the faster

osmosis occurs.

A membrane is called selectively permeable if it allows some substances to

pass through while preventing others from doing so.

Osmosis and diffusion are both_________ transport processes during which water moves from areas where solutes are less concentrated to areas where they are more concentrated.

passive

The energy that drives diffusion comes from the kinetic energy in molecules. Because of this kinetic energy, the molecules of all matter are in constant motion. Diffusion across cell membranes does not require the use of cellular energy. Because of this, diffusion is called a__________ proces.

passive

Tonicity is related to solute content and membrane permeability to those solutes. When working with cells, the tonicity of a solution gives information about

potential changes in cell volume that occur when cells are placed in that solution.

What is standard error?

quantifies the variation in means from multiple datasets or a sample distribution of original dataset.

Elodea cells have a

rigid cell wall that helps them keep their shape even when water moves into or out of them.

Osmosis is the diffusion of water across a

semi-permeable membrane.

Diffusion happens in the same way in

semisolids, liquids, and gases.

A hypertonic environment tends to cause a cell to

shrivel or collapse as water exits the cell.

Concentration tells us how much

solute there is in a solution.

In a solution, the substance which there is most of is called the solvent. The other substances in the solution are called

solutes.

What are the measures of variability?

standard deviation & standard error

What is a sample?

sub-collection of objects from population

A hypotonic environment tends to cause a cell to

swell as water enters the cell (turgid)

What is data?

systematically recorded info

What does a low standard deviation indicate?

that the data is close to the mean

What does a high standard deviation indicate?

that the data points are spread out over a large range

What is a variable?

the object being controlled, manipulated, measured, or observed. There are two main types independent & dependent.

An isotonic solution will preserve cell volume because

there will be no net movement of water into or out of the cell.

Diffusion takes place when solute concentration is______ within a solution.

unequal

When thinking about osmosis, it is important to think in terms of the concentration of the solvent, water. The more solute a solution contains, the lower the concentration of

water.

Ordinal

when categories are in a particular order (large med & small)

Nominal

when categories have no natural ordering

Tonicity is the relative concentration of a solution compared to the concentration of cytoplasm. The tonicity of a solution tells you whether a cell placed in that solution

will shrink, swell, or stay the same.