Tuesday, September 30, 2008

Finishing up 7.3 and Starting 36.1

7.3 Continued

In cotransport, an ATP pump that transports a specific solute indirectly drives the active transport of other substances. In this process, the substance that was initially pumped across the membrane will do work, providing energy for the transport of another substance against its concentration gradient, as it leaks back across the membrane w/its concentration gradient.

Large molecules are moved across the cell membrane through exocytosis and endocytosis. In exocytosis, vesicles from the cell's interior fuse w/the cell membrane expelling their contents to the exterior. In endocytosis, the cell forms new vesicles from the plasma membrane; this is basically the reverse of exocytosis, and this process allows the cell to take in macromolecules.

There are three types of endocytosis:

1. Phagocytosis (remember: phag = to eat) occurs when the cell wraps pseudopodia around the substance and packages it within a large vesicle formed by the membrane.

2. In pinocytosis (remember: pino = to drink), the cell takes in small droplets of extracellular fluid in small vesicles. Pinocytosis is not specific – no target molecules are taken in, in this process.

3. Receptor-mediated endocytosis is a very specific process. Certain substances (ligands) bind to specific receptors on the cell's surface (these receptors are usually clustered in coated pits), and this causes a vesicle to for around the substance and then to pinch off into the cytoplasm.


For review, here is a brief outline of cellular transportation:

I. Passive Transport

A. Diffusion

i. High to low concentration

ii. MOST molecules that can diffuse are nonpolar and hydrophobic

B. Facilitated Diffusion

i. Transport proteins

a. Channel proteins

b. Carrier proteins

ii. High to low

C. Osmosis

i. Water

ii. Selectively permeable membrane

iii. Hypotonic to hypertonic

II. Active Transport

A. ATP required

i. Low to high

B. Primary Active Transport

i. Sodium-potassium pump (3:2 ratio of Na to K)

C. Cotransport

III. Other

A. Exocytosis

B. Endocytosis

i. Phagocytosis

ii. Pinocytosis

iii. Receptor-mediated



Chapter 36

Resource Acquisition and Transport in Vascular Plants

Section 1

An Overview of Transport Mechanisms in Plants:

Three kinds of transport occur in plants:

1. The uptake and loss of water and minerals from individual cells, for instance in a root cell or leaf cell.

2. Transport of substances short distances, from cell to cell

3. Transport of sap within the xylem and phloem, throughout the entire plant

In plants, the uptake of water across cell membranes occurs through osmosis, the passive transport of water across a membrane.

The water potential is defined as the combined effects of solute concentration and the pressure that the cell wall contributes.

Turgor pressure is the pressure exerted against the cell wall when the cell is filled w/water.

Aquaporins are the channels in the plant cell walls specifically designed for the passage of water. How might this affect osmosis?

Plants have a tonoplast surrounding their vacuoles; the tonoplast regulates molecules going into and out of the vacuole.

The symplast is a continuation of cytoplasm that is connected by plasmodesmata between cells.

The apoplast is the nonliving continuum that is formed by the extracellular pathway formed by the continuous matrix of cell walls.


Thursday, September 25, 2008

New videos and info for Chapter 7

I am posting videos, images, and sample questions for Chapter 7 as extra info and as a review!

An overview video on the structure of the plasma membrane: Click on the link below:

Passive vs. Active Transport

A video on Osmosis, click on link:


Diffusion models

For those of you who were questioning how exocytosis and endocytosis affected the size of the plasma membrane, this animation should answer your question.


A few questions to ponder:

1. The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?

a.distilled water b. 0.4 M c. 0.8 M d. 1.0 M e. none of the above

2. If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?

a. The red blood cell would burst, and the plant cell would shrink.
b. Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.
c. Seawater is isotonic to both cells. There will be no change in water content of the cells.
d. Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure.
e. The red blood cell would shrink, and the plant cell would gain water.

3. Imagine two solutions separated by a selectively permeable membrane that allows water to pass, but not sucrose or glucose. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change?

a. Nothing happens because the two solutions are isotonic to one another.
b. Water enters the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose.
c. Water leaves the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose.
d. The sucrose solution is hypertonic and will gain water because the total mass of sucrose is greater than that of glucose.
e. After the sucrose dissociates to two monosaccharides, water will be osmotically drawn to that side of the membrane.

4. A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?

a. osmosis b. passive transport c.exocytosis
d.active transport e. endocytosis

Wednesday, September 24, 2008

Section 7.3

Things you must learn:
* Diffusion is of the Solute
* Osmosis is of the water

1. Problems using diffusion and osmosis

The solutions in the two arms of the U-tube are separated by a membrane that is permeable to water and glucose but not sucrose. Side A is half filled with a solution of 2M sucrose and 1M glucose. Side B is half-filled with 1M sucrose and 2M glucose. Initially, the liquid levels on both sides are equal.

Initially in terms of tonicity, the solution in Side A with regards to that is Side B is isotonic. (3M for each).
After the system reaches equilibrium, what changes are observed?
Diffusion .5M glucose B-->A osmosis water B-->A

The solutions in the arms of the U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 glucose and 0.5M of NaCl, and Side B is filled with a solution of 0.8M glucose and 0.4M NaCl. Initially, the volume in both arms is the same.

At the beginning of the experiment Side A is hypo to Side B. Side A after 3 days, 0.5 NaCl B --> A and Water A-->B

2. Notes from the reading (because of the shortened schedule we did not have the chance to cover all of Sec. 7.3 and will finish on Tuesday)

Ions have both a chemical and a voltage gradient across the membrane, and this causes an ELECTRICHEMIC GRADIENT. The inside of the cell is slightly more negative than the outside, so that membrane potential favors the movement of citations (positively charged ions) into the cell

The sodium potassium pump works by exchanging sodium Na+ for potassium K+ across the cell membrane; it exchanges 3 Na+ ions for 2 K+ ions, so for each round of the pump, there is a net transfer of one positive from the cell interior to the exterior. This type of pump, called ELECTROGENIC PUMP, generates voltage across the membrane.

<-- Osmotic Gradient

Vocabulary to review from this section:
Diffusion: the movement of molecules of any substance so that they spread out evenly into the available space
Concentration Gradient:
the region along whicht the density of a chemical substance decreases
Passive Transport:
the diffusion of a substance across a biological membrane
the diffusion of water across a selectively permeable membrane
the ability of a solution to cause a cell to gain or lose water
Isotonic: having the same solute concentration as another solution, thus having no effect on passage of water into or out of the cell.
comparing two solutions, referring to the one with greater solute concentration Hypotonic: comparint two solutions, referring to the one with less solute concentration

That's all ladies! Have a great weekend! Get some rest, go to your conferences, study for our quiz on Monday, tell your parents you love them, and above all keep yourselves very safe!!!

Tuesday, September 23, 2008

Chapter 7 Movement Through Membranes

Movement Through Membranes

I. Passive
A. Diffusion
1) Osmosis
B. Facilitated
1) Carrier
II. Active
Hydrocarbons, carbon dioxide, and oxygen are hydrophobic substances that can pass easily across the cell membrane.
Ions and polar molecules cannot pass easily across the membrane. The former substances move across the membrane through passive diffusion. In passive diffusion, the substance will travel from where it is more concentrated to where it is less concentrated, diffusing down its concentration gradient. This type of diffusion requires that no work be done, and it relies only on the thermal motion energy intrinsic to the molecule in question. The term passive diffusion is used because the cell expends no energy in moving the substance.

The word for the passive transport of water is osmosis. In osmosis, water flows from the hypotonic solution (the solution with lower solute concentration) to a hypertonic solution (one with a higher solute concentration). Another form is an isotonic solution where both concentrations are equal. Animal cells want to be in an isotonic solution whereas plant cells prefer a slightly hypotonic solution to keep their cell walls rigid.

Hydrophilic substances get across the membrance through transport proteins. Transport proteins work in two ways:
1) They provide a hydrophilic channel through which the molecules can pass
2) They bind loosely to the molecule and carry them through the membrane

The process by which ions and hydrophilic substances diffuse across the cell membrance with the help of transport proteins is called facilitated diffusion. Transport proteins are specific for the substances they transport.

In active transport, substances can be moved against their concentration gradient. Not surprisingly, in this type of transport, the cell must expend energy. This type of transport is crucial for cells to be able to maintain sufficient quantities of substances that are relatively rare in their enviornment.

Specific tansmembrance proteins are responsible for active transport and ATP supplies the energy for this type of transport. ATP transfers one of its phospates to the transport protein, which might be responsible for making the protein change its shape to allow for the passage of the substance.
Things to Look Forward To Tomorrow:
1) Quiz!
2) More on Active Transport
3) What a sodium potassium pump actually is
4) Last day before our fabulous 5 day weekend!!!

Monday, September 22, 2008

Chapter 7 (7.1 Notes)


Membranes are of the utmost importance to the cell as a whole, and to many of the organelles contained in the cell, because they act as selective barriers to let in only the substances that each cell or specific organelle needs to function properly.

Membranes are primarily made up of phospholipids and proteins (though carbohydrates are crucial to membranes, too) held together by weak interactions that cause the membrane to be fluid. In the fluid mosaic model of the cell membrane, the membrane is fluid, and the proteins are embedded in or associated with the phospholipid bilayer.

There are both integral proteins and peripheral proteins in the cell membrane.
  • Integral proteins are those that are completely embedded in the membrane, some of which are transmembrane proteins that span the membrane completely.
  • Peripheral proteins are loosely bound to the membrane's surface.
Carbohydrates on the membrane are crucial in cell-cell recognition (which is necessary for proper immune function) and in developing organisms (for tissue differentiation). Cell surface carbohydrates--many of which are oligosaccharides--vary from species to species and are the reason that blood transfusions must be type-specific.

Notes from the book:
  • Like all biological membranes, the plasma membrane exhibits selective permeability; that is, it allows some substances to cross it more easily than others.
7.1: Cellular Membranes are fluid mosaics of lipids and proteins
  • A phospholipid is an amphipathic molecule, meaning it has both a hydrophilic region and a hydrophobic region (In a phospholipid, the head is hydrophilic, and the the tail is hydrophobic).
Membrane Models: Scientific Inquiry
  • Lipids and proteins have the ability to drift laterally within the membrane.
The Fluidity of Membranes
  • A membrane remains fluid as a temperature decreases, until finally the phospholipids settle into a closely packed arrangement and the membrane solidifies.
  • The membrane remains fluid to a lower temperature if it is rich in phospholipids with unsaturated carbon tails. Because of kinks in the tail where double bonds are located, unsaturated hydrocarbons cannot pack as closely together and this makes the membrane more fluid.
  • **Cholesterol, which is wedged between phospholipid molecules in the plasma membranes of animal cells, can be thought of as a "temperature buffer" for the membrane, because it hinders the close packing of phospholipids, lowering the temperature required for the membrane to solidify.**

This diagram explains membrane protein functions. You may want to look over synthesis of membrane components and their orientation on the resulting membrane.

Friday, September 19, 2008

Evolution Connection!

This is the first post of two different types I will frequently post on the blog. One type of post is on Evolution Connection-- A major theme in AP Biology. The other type of question is on Science, Ethics and Technology.

For those of you wanting to stretch yourself, I am posting two questions which relate to chapter 6 on the cell. If you would like to "answer" these questions, please do so by posting a response. Please remember that there can be many answers.

1. Which aspects of cell structures best reveal evolutionary unity?

2. What are some examples of specialized modifications?

Have Fun!
Today In Biology We...
  1. took a quiz
  2. Curtis lied about the quiz result charts being fixed
  3. got our labs back
  4. learned about the one tracked minds of boy's sperm
  5. took some notes
  6. played a fun revealing-thinger game

Here are the notes that we took today!


cytoskeleton- a network of fibers throughout the cytoplasm that forms a dynamic framework for support and movement and regulation.
  • gives mechanical support to the cell and helps maintain its shape.
  • enables a cell to change shape in an adaptive manner
  • associated with motility by interacting with specialized proteins called motor molecules
  • plays a regulatory role bu mechanically transmitting signals from cell's surface to it's interior

The 3 types of fibers in the cytoskeleton are shown above in the beautiful picture and explained below

microtubules- straight hollow fibers about 25nm in diameter and 200nm in length; constructed from the globular proteins called tubulin. Examples would include:
  • centrioles: pair of cylindrical structures located in the centrosomes of an animal cell, composed of nine sets of triplet microtubules arranged in a ring.

  • cilia and flagella: locomotor oraganelles found in eukaryotic cells that are formed from a specialized arrangement of microtubules.

microfilaments- also called actin filaments; provide cellular support; participate in muscle contraction; and responsible for localized contraction of cells
  • helps with the elongation and contaction of psuedopodia druring amoeboid movement
intermediate filaments- (8-12nm) between microtubules and microfilaments; constructed from keratin subunits; fix organelle position; reinforce cell shape; bear tension


Plant cells produce coats external to the plasma membrane.

cell wall-protects the plants and gives support; contains cellulose

extracellular matrix- (EMC) meshwork of marcomolecules outside the plasma membrane of animal cells, locally secreted by cells; provides support and anchorage fro the cells

plasmodesmata- channels that perforate plant cell walls through which cytoplasmix strands communicate between adjectent cells.

tight junction-intercellular junction that holds cells together tightly enough to black transport of substances through the intercellular space.

desosomes- intercellular junctions that rivet cells together into strong sheets, but still permit substances to pass freely

gap junction-intercellular junction specialized fro material transport etween the cytoplasm of adjacent cells.

Okay that's it! Don't forget about your vocab this weekend!

Thursday, September 18, 2008

Chapter 6.2 Notes and Review

Today in class we took our 6.1 quiz on microscopes and the structure and functions of the cell's organelles. Don't forget...Quiz tomorrow on 6.2! Here are the notes we took today:

Other Membranous Organelles

Perxisome: membrane bound organelles that contain specialized teams of enzymes for specific metabolic pathways; all contain peroxide-- producing oxidases
-Breakdown of purines-- the G&A--nitrogen base!
-Produce hydrogen preoxide and break down hydrogen peroxide in plants
-In the liver, peroxisomes enzymatically transfer H from poisons to oxygen

*Mitochondria and chloroplasts are the main energy transformers of cells*

Mitochondria: organelles, which are the sites of cellular respiration, a catabolic oxygen-requiring process that uses energy extracted from organic macromolecules to produce ATP.
Two membranes that have their own unique combination of proteins embedded in phospholipids bilayer:
Outer membrane: highly permeable to solutes, but it blocks passage of proteins and other macromolecules
Inner membrane: contains embedded enzymes that are involved in cellular respiration. 
The membrane's many infoldings or cristae increase the surface area available for these reactions to occur

The inner and outer membranes divide the mitochondrion into two internal compartments:
Intermembrane space: narrow region between the inner and outer mitochondrial membranes
Mitochondrial Matrix:compartment enclosed by the inner mitochondrial membranes; contains enzymes

Plastids: a group of plants and algal membrane bound organelles that include amyloplasts, chromoplasts, and chloroplasts.
Amyloplasts: colorless plastids that store starch; found in roots and tubers
Chromoplasts: plastids containing pigments other than chlorophyll; responsible of the color of fruits, flowers and autumn leaves
Chloroplasts: chlorophyll- containing plastids, which are the sites of photosynthesis

Chloroplasts are divided into 3 functional compartments by a system of membranes

Intermembrane space: separates the double membrane
Tylakoid space: segregates the interior of the chloroplast into two compartments:
Thylakoid space: space inside the thylakoid
Stroma: viscous fluid outside the thylakoids
Thylakoid: Flattened membranous sacs inside the chloroplast
*Think Pancakes!*

Here are a couple multiple choice questions to prepare for the quiz tomorrow!

Which structure is not apart of the endomembrane system?
a) nuclear envelope
b) chloroplast
c) Golgi apparatus
d) plasma membrane
e) ER

Which structure is common to  plants and animals cells?
a) chloroplasts
b) wall made of cellulose
c) central vacuole
d) mitochondrion
e) Centriole

Which of the following is present in prokaryotic cells?
a) mitochondrion
b) ribosome
c) nuclear envelope
d) chloroplasts
e) ER

ANSWERS: b, d, b

Wednesday, September 17, 2008

Chapter 6: The Cell

Endomembrane System

The Endomembrane System includes many membranes of eukaryotic cells:

-nuclear envelope
-endoplasmic reticulum
-golgi apparatus
-plasma membrane (related)

The membranes may be interrelated
directly through physical contact or indirectly through vesicles.

Vesicles are membrane-enclosed sacs that are pinched off pinched off portions of membranes moving from the sight of one membrane to another.

The Endoplasmic Reticulum is an extensive membranous network of tubules and sacs (cisternae) which sequesters its internal lumen (cisternal space) from the cytosol. Two types of ER:

-smooth ER: synthesis of lipids, phospholipids & steroids, carbohydrate metabolism, detoxify drugs & poisons, store calcium for muscle contraction -found in liver

-rough ER: continuous with outer membrane of nuclear envelope, manufactures secretory proteins & membrane
-glycoprotein: protein covalently bonded to carbohydrate
-oligosaccharide: small polymer of sugar units
-transport vesicle: membrane vesicle in transit from one part of the cell to another

Golgi Apparatus are organelles made of stacked, flattened membranous sacs (cisternae), that modify, store, and route products to the ER. Some characteristics include:

-distinct polarity: opposite ends differ in thickness & composition
-cis face
receives and trans face pinches off vesicles for transport to other sites

A Lysosome is a membrane-enclosed bag of hydrolytic enzymes that digest all major classes of macromolecules. Some characteristics include: -optimal pH is about 5 -enzymes include lipases, carbohydrates, proteases, & nucleases
-pinch off from trans face of golgi apparatus

Tuesday, September 16, 2008

Chapter 6: A Tour of the Cell

A Concept map for cells!

A Tour of the Cell: How We Study Cells

Light microscopes (LSs) are used to observe most plant and animal cells, bacteria, and some organelles like mitochondria and nuclei, although most cell organelles are too small to be seen with a light microscope. With these instruments, scientists can observe things from 1 mm in size.

Electron microscopes are used to study objects from about 0.1 nm to 100mm in size. They function by focusing a beam of electrons either through the specimen or onto its surface. There are two kinds of EMs: transmission electron microscope (TEMs) and scanning electron microscopes (SEMs)

A Panoramic View of the Cell

The best way to remember the main facts about prokaryotes and eukaryotes is to study a table of their major characteristics:


Prokaryotic Cells

Eukaryotic Cells

Plasma membrane



Cytosol with organelles







No (It had a Nucleoid)



1-10 micrometers

10-100 micrometers

Internal membranes



Prokaryotic cells include bacteria and archaebacteria, where as eukaryotic cells are animal and plant cells. Some details to remember about prokaryotes include:

  • No membrane bound nucleus—instead chromosomes grouped together in region called the Nucleoid
  • No membrane bound organelles
  • Smaller than eukaryotes
  • Consist of bacteria and archaebacteria

Some details to remember about eukaryotic cells include:

  • Membrane bound nucleus, which contains cell’s chromosomes
  • Membrane bound organelles in cytoplasm
  • Much larger that prokaryotes
  • Eukaryote cells make up the kingdoms protista, fungi, plantae, and animalia

The Nucleus and Ribosomes, the Endomembrane system, other membranous organelles, and the cytoskeleton.

Nucleus: A generally conspicuous membrane bound cellular organelle in a eukaryotic cell; contains most of the genes that control the entire cell.

Nuclear Envelope: A double membrane which encloses the nucleus in a eukaryotic cell.

Chromatin: Complex of DNA and histone proteins, which makes up chromosomes in eukaryotic cells; appears as a mass of stained material in nondivded cells.

Chromosomes: long threadlike association of genes composed of chromatin and found in the nucleus of eukaryotic cells.

Nucleolus: Roughly spherical region in the nucleus of nondividng cells, which consists of nucleolar organizers and Ribosomes in various stages of production.

Nuclear Organizers: Specialized regions of the same chromosomes, with multiple copies of genes for rRNA synthesis.

Ribosome: A cytoplasmic organelle that is the site for protein synthesis

Free Ribosomes: Ribosomes suspended in the cytosol

Attached Ribosomes: Attached to the outside of the endoplasmic reticulum (ER)

Monday, September 15, 2008

Ch. 6 Vocabulary And Roots


Centrosome: A structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. The centrosome has two centrioles.

Chromatin: The complex of DNA and proteins that makes up a eukaryotic chromosome. When a cell is not dividing, it exists in dispersed form, in long, thin fibers.

Crista: An infolding of the inner membrane of mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP.

Chromosome: A cellular structure carrying genetic materials, found in the nucleus of eukaryotic cells. Has one long protein ans associated proteins.

Contractile Vacuole: A membranous sac that helps move excess water out of certain fresh water protists.

Desmosome: A type of intercellular junction in animal cells that functions as a rivit.

Dyneim: In cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent doublet.

Gap Junction: A type of intercellular junction in animals that allows the passage of materials between cells.

Granum: A stack of membrane-bounded thylakoids in the chloroplast. Function in the light reactions of photosynthesis.

Microfiliment: A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton. Causes cell contraction.

Microtubule: A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in the cilia and flagella.

Middle Lamella: In plants, a thin layer of adhesive extracellular material, primarily pecting, found between the primary walls of adjacent young cells.

Mitochondrial Matrix: The compartment of mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.

Nucleoid: A dense region of DNA in a prokaryotic cell.

Peroxisome: An organelle containing enzymes that transfer hydrogen from various substrates to oxygen producing and the degrading hydrogen peroxide (H2O2).

Phagocytosis: A type of endocytosis in which large particulate substances are taken up by a cell.

Plasmodesma: An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.

Primary Cell Wall: In plants, a relatively thin and flexible layer first secreted by a young cell.

Secondary Cell Wall: In plants, a strong and durable matrix, often deposited in several laminated layers fort cell protection and support.

Stroma: Within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in synthesis of organic molecules from CO2 and H2O.

Thylakoid: A flattened membranous sac inside ta chloroplast. Interconnected system and contain molecular "machinery" used to convert light energy to chemical energy.

Tight Junction: A type of intercellular junction in animal cells that prevents the leakage of material between cells.

Tonoplast: A membrane that binds the chief vacuole of a plant cell.
























Tour of an Animal Cell Video: