Biology Exam 1 Flashcards

Questions and Answers

A phospholipid has a 'head' made up of a glycerol molecule attached to a single ___________, which is attached to another small molecule.

phosphate group

Because the phosphate group and its attachments are either charged or polar, the phospholipid head is _____, which means it has an affinity for water.

hydrophilic

A phospholipid also has two 'tails' made up of two ______________ molecules, which consist of a carboxyl group with a long hydrocarbon chain tail.

fatty acid

Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are __________, which means they are excluded from water.

hydrophobic Signup and view all the answers

Answer the following about nonpolar molecules:

Hydrophilic or hydrophobic? = Hydrophobic Able to cross lipid bilayer? = Can cross easily Transport protein required? = No transport protein required Signup and view all the answers

Answer the following about polar molecules:

Hydrophilic or hydrophobic? = Hydrophilic Able to cross lipid bilayer? = Have difficulty crossing the hydrophobic part of bilayer Transport protein required? = Transport protein required to cross efficiently Signup and view all the answers

Answer the following about ions:

A red blood cell placed in a hypertonic solution will shrink in a process called crenation. A red blood cell placed in a hypotonic solution will swell and potentially burst in a process called hemolysis. To prevent crenation or hemolysis, a cell must be placed in an isotonic solution such as 0.9% (m/v) NaCl or 5.0% (m/v) glucose. Indicate whether crenation, hemolysis, or neither will occur in the following solutions. Solution A: 3.21% (m/v) NaCl, Solution B: 1.65% (m/v) glucose, Solution C: distilled H2O, Solution D: 6.97% (m/v) glucose, Solution E: 5.0% (m/v) glucose and 0.9% (m/v) NaCl.

Crenation: D; A; E Signup and view all the answers

What happens when a cell is in a hypertonic solution?

The cell shrivels because of water leaving the cell; the outside of the cell is more concentrated than the inside. Signup and view all the answers

What happens when a cell is in a hypotonic solution?

The cell swells from an intake of water; the inside of the cell is more concentrated than the outside. Signup and view all the answers

What happens when a cell is in an isotonic solution?

Nothing. Signup and view all the answers

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

Osmosis. Signup and view all the answers

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?

Hypotonic. Signup and view all the answers

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

True Signup and view all the answers

Which of the following particles could diffuse easily through a cell membrane?

Oxygen Signup and view all the answers

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature. Signup and view all the answers

Osmosis is a type of diffusion.

True Signup and view all the answers

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar. Signup and view all the answers

What factors affect the membrane permeability?

Temperature; saturation of hydrocarbon tails in membrane phospholipids; amount of cholesterol in the membrane. Signup and view all the answers

Molecules always move independently from other types of molecules when passing through a membrane.

True Signup and view all the answers

When do concentration gradients exist that drive diffusion of two different types of molecules?

Only before equilibrium is reached. Signup and view all the answers

When is there a net movement of particles from one side of the membrane to the other?

Only before equilibrium is reached. Signup and view all the answers

Will one type of particle only move from one side to the other?

False Signup and view all the answers

When is there no net movement of particles?

At equilibrium. Signup and view all the answers

Which of the following molecules can cross the lipid bilayer of a membrane easily, without a transport protein or other mechanism? Select all that apply.

Lipids Signup and view all the answers

When talking about protein channels and carriers, Only Channels:

Provide a continuous pathway across the membrane; and allow water molecules and small ions to flow quickly across the membrane. Signup and view all the answers

When talking about protein channels and carriers, Only Carriers:

Undergo a change in shape to transport solutes across the membrane; and transport primarily small polar organic molecules. Signup and view all the answers

When talking about protein channels and carriers, Both Channels and Carriers:

Provide a hydrophilic path across the membrane; are integral membrane proteins; and transport solutes down a concentration or electrochemical gradient. Signup and view all the answers

When talking about endocytosis and exocytosis, Only exocytosis:

Secretes large molecules out of the cell; increases the surface area of the plasma membrane; and requires fusion of vesicles with the plasma membrane. Signup and view all the answers

When talking about endocytosis and exocytosis, Only endocytosis:

Decreases the surface area of the plasma membrane; and forms vesicles from inward folding of the plasma membrane. Signup and view all the answers

When talking about endocytosis and exocytosis, Both exocytosis and endocytosis:

Require cellular energy; and transported substances never physically cross the plasma membrane. Signup and view all the answers

Endocytosis moves materials _ a cell via _.

into....membranous vesicles Signup and view all the answers

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

phagocytosis Signup and view all the answers

Study Notes

Phospholipids

Composed of a glycerol "head" linked to a phosphate group, which is charged or polar and hydrophilic.
Two "tails" consist of fatty acid molecules with long hydrocarbon chains, making them hydrophobic and excluded from water.

Molecular Properties

Non-polar molecules are hydrophobic, easily crossing lipid bilayers without transport proteins.
Polar molecules are hydrophilic, struggle to cross lipid bilayers, and require transport proteins for efficient passage.
Ions are also hydrophilic, facing similar challenges as polar molecules when crossing membranes.

Tonicity and Cell Behavior

Hypertonic solutions cause red blood cells to shrink (crenation) due to water loss.
Hypotonic solutions result in swelling and potential bursting of cells (hemolysis).
Isotonic solutions maintain cell integrity with no net water movement; solutions like 0.9% NaCl or 5% glucose exert equal osmotic pressure as the cell interior.

Water Movement

Osmosis is the process by which water crosses selectively permeable membranes.
A red blood cell in a salt solution that bursts is in a hypotonic environment.

Membrane Permeability Factors

Factors influencing membrane permeability include temperature, saturation of hydrocarbon tails, and cholesterol levels in the membrane.
Lipids are mostly non-polar, whereas sugars are polar, serving as key differentiators between these two classes of biomolecules.

Diffusion and Equilibrium

Concentration gradients exist pre-equilibrium, driving the diffusion of different types of molecules.
There is net particle movement from one side of the membrane to another only before equilibrium is reached.
No net movement of particles occurs at equilibrium, with independent movement of different molecules.

Protein Transport Mechanisms

Channels provide continuous pathways for small ions and water to cross membranes quickly.
Carriers change shape to transport small polar organic molecules across the membrane.
Both channels and carriers offer hydrophilic pathways, serve as integral membrane proteins, and facilitate transport down gradients.

Endocytosis and Exocytosis

Exocytosis secretes large molecules out of cells, increases plasma membrane surface area, and involves vesicle fusion with the membrane.
Endocytosis decreases plasma membrane surface area and creates vesicles through inward folding.
Both processes require energy and do not involve the physical crossing of substances through the plasma membrane.

Special Cases

Endocytosis can bring materials into cells via membranous vesicles.
An example of phagocytosis is a white blood cell engulfing a bacterium.

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Biology Exam 1 Flashcards

Questions and Answers

A phospholipid has a 'head' made up of a glycerol molecule attached to a single ___________, which is attached to another small molecule.

Because the phosphate group and its attachments are either charged or polar, the phospholipid head is _____, which means it has an affinity for water.

A phospholipid also has two 'tails' made up of two ______________ molecules, which consist of a carboxyl group with a long hydrocarbon chain tail.

Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are __________, which means they are excluded from water.

Answer the following about nonpolar molecules:

Answer the following about polar molecules:

Answer the following about ions:

What happens when a cell is in a hypertonic solution?

What happens when a cell is in a hypotonic solution?

What happens when a cell is in an isotonic solution?

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

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?

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

Which of the following particles could diffuse easily through a cell membrane?

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Osmosis is a type of diffusion.

How can a lipid be distinguished from a sugar?

What factors affect the membrane permeability?

Molecules always move independently from other types of molecules when passing through a membrane.

When do concentration gradients exist that drive diffusion of two different types of molecules?

When is there a net movement of particles from one side of the membrane to the other?

Will one type of particle only move from one side to the other?

When is there no net movement of particles?

Which of the following molecules can cross the lipid bilayer of a membrane easily, without a transport protein or other mechanism? Select all that apply.

When talking about protein channels and carriers, Only Channels:

When talking about protein channels and carriers, Only Carriers:

When talking about protein channels and carriers, Both Channels and Carriers:

When talking about endocytosis and exocytosis, Only exocytosis:

When talking about endocytosis and exocytosis, Only endocytosis:

When talking about endocytosis and exocytosis, Both exocytosis and endocytosis:

Endocytosis moves materials _____ a cell via _____.

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

Study Notes

Phospholipids

Molecular Properties

Tonicity and Cell Behavior

Water Movement

Membrane Permeability Factors

Diffusion and Equilibrium

Protein Transport Mechanisms

Endocytosis and Exocytosis

Special Cases

Studying That Suits You

Description

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