Mastering Bio 07 : Lipids and Membrane Structure

A food company hydrogenated a barrel of fat. The treatment ... (a) made the fat less fluid (b) made the fat less saturated (c) lengthened the fat tails (d) put more bends (kinks) in the fat tails Both (a) and (d).

(a) made the fat less fluid (Hydrogenation removes double bonds, so the tails can straighten.)

What do fats, steroids, and waxes have in common? (a) Moderate polarity (b) Low solubility in water (c) They occur in membranes Both (a) and (c) Both (b) and (c).

(b) Low solubility in water (Low water solubility is the trait that defines lipids)

What holds phospholipids together in a bilayer formation? 1. hydrophilic and hydrophobic interactions with water 2. ionic interactions between phospholipid tails 3. covalent bonds between polar heads 4. interaction of cis-double bonds in tails with polar heads

- hydrophilic and hydrophobic interactions with water (The hydrophobic tails interact with each other and are repelled by water, while the heads are hydrophilic and are attracted to water. This dual nature causes groups of phospholipids to assemble into distinct layers to minimize tail contact with water and maximize head contact with water)

What functional feature(s) does the phosphate group contribute to the structure of a phospholipid?

1. place to attach another small charged molecule 2. negative charge to interact with water (he phosphate attaches to the glycerol and provides a place for another small molecule to attach to the phospholipid. The phosphate has a charge, so it interacts with polar water molecules.)

How many fatty acids are in a phospholipid?

2 (Two fatty acids are attached to the glycerol and make up the tails of the phospholipid)

Which molecule is less soluble in water--a fat or a phospholipid? Why?

A fat molecule is less soluble in water because it has three non-polar fatty acids and no polar or charged head like a phospholipid has (The replacement of one of the fatty acids with a polar chemical group makes phospholipids more soluble in water than fats.)

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans? a. Amphipathic nature b.Permeability c. Solubility in water d. Hydrophobic nature

Amphipathic nature

How are phospholipids in a biological membrane structured?

Biological membranes are made of phospholipids that have assembled with the polar heads facing out to interact with the water, and the non-polar tails pushed together in the interior of the membrane.

The presence of many C-C and C-H bonds causes fats to be ... (a) rich in energy (b) insoluble in water (c) low in energy Both (a) and (b) Both (b) and (c).

Both (a) and (b) (The many C-C and C-H bonds make fats nonpolar and insoluble in water. They can also be oxidized, releasing much energy)

Triglycerides vary with respect to the number of ... (a) hydrocarbon tails (b) C atoms in the tails (c) double bonds in the tails Both (b) and (c) All of the above.

Both (b) and (c). (Tail lengths of 16 to 22 are common. There may be from 0 to 6 double bonds.)

In what way do the membranes of a eukaryotic cell vary? 1. Certain proteins are unique to each membrane 2. Only certain membranes of the cell are selectively permeable 3. Phospholipids are found only in certain membranes 4. Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.

Certain proteins are unique to each membrane

There is a greater concentration of solute outside the cell. Is this hypotonic or hypertonic?

Hypertonic

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell? a. Isotonic b. Hypertonic c. Hypotonic d. Osmotic

Hypotonic (The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.)

Which of the following particles could diffuse easily through a cell membrane? 1. Oxygen (O2) 2. Sodium ion (Na+) 3. Glucose 4. Hydrogen ion (H+)

Oxygen (O2) (Small nonpolar molecules such as oxygen can diffuse across cell membranes)

A white blood cell engulfing a bacterium is an example of _____.

Phagocytosis (occurs when a cell engulfs a large particle)

Which of these is NOT a lipid? 1. cholesterol 2. RNA 3. wax 4. phospholipid 5. steroids

RNA (it's a nucleic acid)

Cholesterol helps to stabilize the structure of the plasma membrane. True or False

TRUE

Phospholipids can be recognized by the presence of a head and two tails. True or False

TRUE

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

TRUE (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail)

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? 1. The double bonds block interaction among the hydrophilic head groups of the lipids 2. The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly 3. Unsaturated fatty acids are more nonpolar than saturated fatty acids 4. Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly.

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly

How do phospholipids interact with water molecules? 1. Phospholipids do not interact with water because water is polar and lipids are nonpolar 2. The polar heads interact with water; the nonpolar tails do not 3. The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract) 4. Phospholipids dissolve in water.

The polar heads interact with water; the nonpolar tails do not.

What is a function if transport proteins?

The protein is allowing solute molecules to enter the cell

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

The two sides of a cell membrane face different environments and carry out different functions

What do DNA, proteins, and fats have in common? They contain nitrogen. They contain phosphorus They contain carbonyl groups They are polymers They are polar.

They contain carbonyl groups

Which of the following statements concerning unsaturated fats is true? (a)They are more common in animals than in plants (b)They generally solidify at room temperature (c)They contain more hydrogen than do saturated fats having the same number of carbon atoms (d)They have double bonds in the carbon chains of their fatty acids (e)They have fewer fatty acid molecules per fat molecule.

They have double bonds in the carbon chains of their fatty acids

Why are covalent interactions between the phospholipid and protein components of the membrane least important in holding components of a biological membrane?

This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.

True or false? Osmosis is a type of diffusion.

True

Are these statements true about fluid mosaic structures? 1. Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. 2. The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center. 3. The diverse proteins found in and attached to membranes perform many important functions.

YES. Membranes consist of diverse proteins suspended in and attached to a phospholipid bilayer. Kinks in the unsaturated fatty acid tails of some phospholipids keep the membrane fluid, and a mosaic of proteins perform a variety of functions.

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say? a. Not so. Fats are small enough to travel easily without help. b. Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids. c. Right. Fats are too polar to travel alone in water. d. Yes. Nonpolar molecules aren't compatible with water. e. You have it backwards. Fats help phospholipids to travel.

Yes. Nonpolar molecules aren't compatible with water. (Water rejects nonpolar molecules such as fats, so fats travel inside particles that are coated with polar parts of phospholipids and proteins.)

Phospholipids structures are composed of what?

a phosphate group, a glycerol, and fatty acids

Signaling proteins are part of signal transduction pathways that transmit external chemical signals into the cell.

a receptor protein that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell

A function of cholesterol that does not harm health is its role _____. - as the primary female sex hormone - as a component of animal cell membranes - the most abundant male sex hormone - All of cholesterol's effects cause the body harm - in calcium and phosphate metabolism

as a component of animal cell membranes

Glycoprotein is made up of?

carbohydrate and a protein

Saturated fats ________. 1. are generally liquid at room temperature 2. contain more hydrogen than unsaturated fats that consist of the same number of carbon atoms 3. have multiple double bonds in the carbon chains of their fatty acids 4. are more common in plants than in animals

contain more hydrogen than unsaturated fats that consist of the same number of carbon atoms

In fat synthesis,________and fatty acids combine to make fats plus________. glycerol; water esters; water esters; phosphate phosphate; glycerol glucose; phosphate

glycerol; water (Water is a by-product of the reaction that makes ester links between glycerol and fatty acids)

In the reaction that builds a fat,________ groups react with ________ groups. sulfhydryl; carboxyl carboxyl; amino hydroxyl; phosphate hydroxyl; carboxyl phosphate; amino

hydroxyl; carboxyl

You know that this cell is in a(n) _____ solution because it _____.

hypertonic solution ... lost water (A cell will lose water when placed in a hypertonic solution)

You know that this cell is in a(n) _____ solution because the cell _____.

hypotonic ... swelled (A cell will gain water when placed in a hypotonic solution)

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles (The prefix "endo-" means "inward.")

Which of these can RAPIDLY pass directly through the phospholipids of the plasma membrane, without the help of a transport protein? 1. lipid soluble molecule 2. water 3. glucose 4. hydrogen ion

lipid soluble molecule (Small, nonpolar, lipid-soluble molecules can pass rapidly through the phospholipids of the plasma membrane. Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of the membrane. To move rapidly through the membrane, they must pass through membrane transport proteins)

What characteristic do all lipids have in common?

none of them dissolves in water - Almost all the covalent bonds in lipids are nonpolar, causing their solubility in water to be extremely low. Lipids are hydrophobic substances.

Which of these is rich in unsaturated fats? 1. beef fat 2. lard butter 3. olive oil 4. a fat that is solid at room temperature

olive oil

What is the diffusion of water across a selectively permeable membrane.

osmosis

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis (is the passive transport of water)

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid (Pinocytosis is "cell drinking.")

The most unsaturated fats have ... the most double bonds the highest ratio of H to C the fewest double bonds the shortest hydrocarbon tails the longest hydrocarbon tails.

the most double bonds (Every double bond is a place where hydrogen could be added)

Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

the similarity of the drug molecule to other molecules that are transported into the target cells (If the target cells have transport proteins that specifically bind to certain molecules, they may bind with and transport a drug that is similar in structure)

The permeability of a biological membrane to a specific polar solute depends primarily on which of the following? See Concept 7.2 (Page)

the types of transport proteins in the membrane (The lipid bilayer will be impermeable or very poorly permeable to polar or charged solutes. The presence of the correct transport protein will determine the permeability.)