BLG 143 Lecture Notes - Lecture 12: Facilitated Diffusion, Phospholipid, Amphiphile

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12 Jan 2017

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Phospholipids: amphipathic lipid molecule; part hydrophobic, part hydrophilic. Diffusion: ions and molecules diffuse spontaneously from high [ ] to low [ ]. Osmosis: water moving across plasma membrane, high to low. Membrane proteins: responsible for passage of ions, large and/or polar molecules in and out. Separates cell from external environment; life from non-life. Descendents of first-life molecule were protected by membrane that separated it from hostile environment: kept toxicants out. ii) reactants collided more frequently; more [ ] of reactants = more products. Phospholipids are the most common molecule in membrane. Lipid: c-containing compounds found in organisms; non-polar + hydrophobic. Have major hydrocarbon (molecules with only h and c) component: fatty acid, a hydrocarbon chain bonded to carboxyl. Isopropene and fatty acids: key building block in lipids. 3 types of lipid in cells: 1) fats 2) steroids 3) phospholipids. Lipids are defined by solubility rather than structure. Triglyceride (fat): 3 fatty acids + glycerol by ester linkage through condensation.

Related Questions

It's a pretty elementary concept, and when I first learned of itI don't think I had the foundations to even think of such aquestion, but I found myself the other day thinking about theamphipathic nature of the phospholipids in the plasma membrane andwhy it might be that lipid-soluble molecules don't stay in betweenthe layers (of the bilayer).

I know that simple diffusion is a response to a concentrationgradient, but consider a case where equilibrium is being restoredand lipid-soluble molecules are diffusing from whateverextracellular matrix through the membrane and into the cytosol.Towards the end of this process, when equilibrium is nearlyrestored and the last few molecules are making their way into thecell, the rate of diffusion for these last couple molecules will beslower than those that diffused when the concentration differencewas greater. Since the polar heads on the outside and inside of thebilayer are hydrophilic but the inner part, where the fatty acidtails are, is hydrophobic, what drives a molecule to leave thecozy, accepting, lipophilic environment of the middle (of thebilayer) to cross through the cytosolic-side rejecting polar headsand enter the cytosol?

I understand that initially these molecules were moving into thecell in response to a difference in intracellular vs extracellularconcentration, but I'm asking whether we would ever see a casewhere the gradient is nearly zero and a molecule in transit simplydecides to reside in between the layers instead of crossing all theway into the cell; as if moving through the cytosolic polar headside is not worth the effort to reduce a nearly-zero gradient tozero.

Please ask me if I can clarify my question in any way -- I'mfinding it difficult to phrase. I asked my professor (who has herdoctorate in toxicology & pharmacology) and she understood whatI was asking but didn't have an answer.

Please help! Not sure about these questions..thanks

Which can cross the phospholipid bilayer of a membrane without assistance from transport proteins?

	A.	Ions such as Na+.
	B.	Small hydrophobic molecules such as O2.
	C.	Small hydrophilic molecules such as glucose.
	D.	Any small molecule or ion.

QUESTION 2

Which transport process requires a cell to expend energy?

	A.	Moving a solute up its concentration gradient.
	B.	No transport processes require energy.
	C.	Moving a solute either up or down its concentration gradient.
	D.	Moving a solute down its concentration gradient.

QUESTION 3

Imagine a cell whose membrane is permeable to water, but impermeable to solute X. If solute X is more concentrated outside the cell than inside, which way will water move by osmosis?

	A.	Water will not move in either direction, in or out of the cell.
	B.	Water will move equally in both directions, in and out of the cell.
	C.	Water will leave the cell.
	D.	Water will enter the cell.

QUESTION 4

The cellular structure that encloses the DNA/genes is the

		ribosome.
		plasma membrane.
		nucleus.
		mitochondrion.

QUESTION 5

The part of metabolism that builds larger, more complex molecules or structures from smaller, simpler components is

	A.	anabolism.
	B.	catabolism.
	C.	catalysis.
	D.	hydrolysis.

QUESTION 6

In an exergonic reaction

	A.	the reactants have more energy than the products, so energy is absorbed.
	B.	the reactants have more energy than the products, so energy is released.
	C.	the reactants have less energy than the products, so energy is released.
	D.	the reactants have less energy than the products, so energy is absorbed.

Question 401 pts

Kinetic energy is the stored energy that can be used for motion.

True

False

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Question 411 pts

When an electron is transferred from one atom to another, and the two atoms are then electrically attracted to one another, a(n) ________________ bond is formed.

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Question 421 pts

Changing the number of ____________ of an atom would change the chemical properties of the atom.

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Question 431 pts

Forming molecules and breaking down molecules in biological organisms usually requires the use of _________ to help the reaction proceed faster.

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Question 441 pts

Organic molecules have a core composed of .

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Question 451 pts

The building blocks of carbohydrates are

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Question 461 pts

Water molecules crossing a membrane from high to low concentration is .

active transport

cell fate

facilitated diffusion

osmosis

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Question 471 pts

Choose the membrane molecule responsible for the passage of polar molecules and ions into and out of the cell.

phospholipids

transmembrane channel proteins

cell surface proteins

carbohydrate chains

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Question 481 pts

The simplest cells are .

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Question 491 pts

Which of the following membrane bound organelles are found inside bacterial cells:

nucleus

organelles are not found in prokaryotic cells

mitochondria

chloroplasts

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Question 501 pts

Which of the following is a specialized components of the cell, is associated with the rough endoplasmic reticulum, and is responsible for making proteins.

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Question 511 pts

Proteins are sorted, modified, and packaged by the _____________ and later transported to the outside of the cell.

ribosomes

golgi bodies (golgi apparatus)

nucleus

mitochondria

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Question 521 pts

Dehydration synthesis is a process of linking two smaller subunits together to form a polymer. Which of the following statements below is true of dehydration synthesis?

Oxygen is consumed.

A water molecule is removed from the molecules.

A water molecule is added to the molecules

Carbon dioxide is given off.

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Question 531 pts

Proteins are made up of _________ held together by peptide bonds.

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Question 541 pts

Which of the following gives an amino acid its properties?

NH2

R Group or functional group

COOH

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Question 551 pts

The final three-dimensional shape of a protein that includes the bonding of two or more polypeptide chains is call its _____ structure.

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Question 561 pts

How do DNA and RNA differ?

all statements are differences between DNA and RNA.

DNA is double stranded while RNA is single stranded.

They have different sugars.

Thymine is present in DNA but not in RNA.

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Question 571 pts

Which of the following is a component of a DNA nucleotide?

phosphate

a nitrogen containing base

All are components of a nucleotide.

5-carbon sugar

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Question 581 pts

Cell membranes are made up of several different types of molecules. Select the membrane molecule below that is made up of a polar region and two non-polar fatty acid tails.

transmembrane proteins

carbohydrate chains

phospholipids

cell surface proteins

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Question 591 pts

Two organelles which are believed to have once been free-living bacterial cells are ____________ and ______________.

chloroplasts and mitochondria

golgi apparatus and endoplasmic reticulum

ribosomes and nucleolus

peroxisomes and lysosomes

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Question 601 pts

The is an extensive system of internal membranes responsible for producing carbohydrates and lipids.

smooth endoplasmic reticulum

rough endoplasmic reticulum

nucleolus

mitochondria

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BLG 143 Lecture Notes - Lecture 12: Facilitated Diffusion, Phospholipid, Amphiphile

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