BIOLOGY - CLUTCH CH.7 - THE...

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: FLUID MOSAIC MODEL

The cell membrane is a fluid mosaic.

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● Phospholipids and other membrane components highly mobile.

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE


● Phospholipids spontaneously assemble in aqueous environments.

EXAMPLE: ● Spontaneous assembly occurs despite entropy.

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● Cholesterol fills in gaps between phospholipids, decreasing membrane fluidity.

□ Cholesterol can interact with the aqueous environment surrounding the membrane

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE


● Proteins are integrated into the membrane via van der Waals forces.

□ Transmembrane proteins span the membrane.

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● Peripheral proteins are not integrated directly into the membrane.

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Membrane proteins have numerous functions

● Transporting substances across the membrane

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● Enzyme activity

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE


● Cell signaling – reception, transduction, and response

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● Cell recognition via glycoproteins and glycolipids

□ Glycoproteins play a major role in cell-cell recognition in the immune system

□ Glycolipids are used in determining blood type

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● Cell junctions and anchoring to the cytoskeleton or extracellular matrix

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE


● Structure of the mosaic fits function

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BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

PRACTICE: 1. Proteins in the plasma membrane are involved with all of the following except:

a. trans membrane channel c. transport

b. cell recognition d. packaging DNA

2. Which of the following does not influence membrane fluidity?

a. decrease in temperature

b. addition of cholesterol

c. hydrogen bonding of water holding the membrane together

d. the type of fatty acid used in phospholipids

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: OSMOSIS AND DIFFUSION Simple diffusion is the movement of a substance down its concentration gradient. EXAMPLE: ● Diffusion is driven by entropy EXAMPLE: ● Small and nonpolar substances can readily diffuse through the membrane.

□ Large, ionic, charged, and polar* substances cannot cross the membrane unassisted. EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: OSMOSIS AND DIFFUSION Selective permeability is largely accomplished via channel proteins and carrier proteins. ● Channel proteins form a pore that specific solutes may pass through EXAMPLE: ● Carrier proteins bind specific substances, and undergo a shape change to transport them through the membrane. EXAMPLE:

CHANNEL PROTEINS CARRIER PROTEINS

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: OSMOSIS AND DIFFUSION The cell membrane acts as a selectively permeable barrier separating the cytosol from the extracellular environment. EXAMPLE: ● Concentrations of ions and charged substances create electrical gradients. EXAMPLE: ● Electrical gradients and chemical concentration gradients coexist as electrochemical gradients. EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: OSMOSIS AND DIFFUSION Osmosis is the movement of water across a membrane from an environment of lower solute concentration to a higher one.

□ Aquaporins are channel proteins that facilitate the movement of water across the membrane EXAMPLE: ● Osmosis is NOT a type of diffusion EXAMPLE:

OSMOSIS DIFFUSION

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: OSMOSIS AND DIFFUSION Osmotic pressure drives the movement of water. ● Isotonic – concentration is the same on both sides of the membrane EXAMPLE: ● Hypertonic – concentration is greater on one side relative to the other ● Hypotonic – concentration is lower on one side relative to the other EXAMPLE: ● Osmoregulation is an organism’s regulation of its water content. Failure to do so may result in lysis.

□ Plant cells maintain turgor pressure to give their cells rigidity. EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

PRACTICE: 1. The movement solute of molecules along a concentration gradient from high to low is called:

a. active transport c. pumping b. diffusion d. osmosis

2. Osmosis requires a _______________ in order to occur. a. cell wall c. vacuole b. semi permeable membrane d. ER

3. Two solutions of salt water are at different concentrations. The one with lower concentration is ____________________ to the one with higher concentration.

a. isotonic c. hypotonic b. hypertonic d. osmosis

4. When plant cells are _________ to their environment then the turgor pressure increases.

a. hyperosmotic c. isomotic b. osmosis d. hypoosmotic

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: FACILITATED DIFFUSION

● Passive transport is the diffusion of substances via an electrochemical gradient.

□ Electrochemical gradients have an electrical and chemical concentration gradient.

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● Facilitated diffusion is the passive transport of substances that do not readily cross the membrane.

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● Carrier proteins bind a substance and change shape to carry it through the membrane.

□ The glucose transporter in red blood cells “tricks” the chemical concentration gradient.

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Ge

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: FACILITATED DIFFUSION

Channel proteins have a hydrophilic pore that allows the passage of specific molecules and ions.

● Ion channels are protein channels that allow the passage of ions

□ Cystic fibrosis is a genetic disease that can be caused due to the deletion of a single amino acid in a Cl- channel.

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● Gated channels only open when they receive a certain stimulus

□ Ligand-gated channel – opens in response to chemical stimulus

□ Voltage-gated channel – opens in response to electrical stimulus

EXAMPLE:

Ge Ge

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

PRACTICE: 1. What is required for facilitated diffusion to occur?

a. electrochemical gradient c. carrier protein

b. channel protein d. all of the above

2. Channel proteins are always open, allowing for a constant flow of solutes through them.

a. True

b. False

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: ACTIVE TRANSPORT

Active transport uses energy to move molecules or ions across the membrane

● Primary active transport uses energy directly, usually by hydrolyzing ATP to power proteins.

□ Uniporters move one substance in one direction

□ Symporters move two substances in the same direction

□ Antiporters move two substances in opposite directions

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● The Na+/K+ pump is an antiporter that uses ATP to move ions across the membrane

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● Pumps play a huge role in maintaining electrochemical gradients across the membrane

□ Proton pumps play a crucial role in the mitochondria

EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: ACTIVE TRANSPORT

● Secondary active transport uses the potential energy of one substance’s concentration gradient to transport another

substance against its concentration gradient.

● Cotransport moves the two substances in the same direction

□ The glucose/Na+ transporter takes advantage of the Na+ concentration gradient to transport glucose into the cell.

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● Countertransport moves the substances in opposite directions

□ Na+/H+ transporter takes advantage of the Na+ concentration gradient to transport H+ out of the cell.

EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

PRACTICE: 1. The type of transport that is specific, requires special carrier molecules and energy is:

a. facilitated diffusion c. active transport

b. passive transport d. endocytosis

2. Secondary active transport requires ATP

a. True

b. False

3. What is the difference between a symporter and an antiporter?

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: BULK TRANSPORT

Exocytosis is the secretion of molecules via vesicle fusion with the membrane.

Endocytosis is the process by which a cell takes in material by forming a vesicle from the membrane.

EXAMPLE: ● Phagocytosis is a form of endocytosis in which the cell reaches out pseudopodia to engulf solid material.

EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

CONCEPT: BULK TRANSPORT

● Pinocytosis is a form of endocytosis in which the cells engulfs a small droplet of solutes

□ Phagocytosis and pinocytosis are similar, but differ based on the materials being transported

EXAMPLE:

● Receptor-mediated endocytosis is a type of pinocytosis that can obtain solutes low in concentration.

□ Cholesterol is obtained by this process

EXAMPLE:

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

PRACTICE: 1. Bulk transport requires energy.

a. True

b. False

2. Phagocytosis is a type of exocytosis.

a. True

b. False

BIOLOGY - CLUTCH

CH.7 - THE MEMBRANE

BIOLOGY - CLUTCH CH.7 - THE...

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