Chapter 9 - Membranes Flashcards by Reginald S

Membranes

Living membranes are structurally organized to

Separate the inside of the cell from the outside

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Membranes

What are living membranes?

Plasma membranes of cells

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Membranes

Proteins embedded in the living membrane allow

Passage of specific molecules into and out the cell

2. Communication between cells and with the environment

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Membranes

True or False

Biochemical organization of plasma membranes are well established

False

biochemical organization of plasma membranes are not well established

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Membranes

Cell membranes contain 4 main components which are

Phospholipid bilayer

Transmembrane proteins

Interior protein network

Cell surface markers

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Membrane: Phospholipid bilayer

Composed of three main types of lipids which are

Glycerol Phospholipids

Sphingolipids

Sterols (cholesterol)

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Membranes: Phospholipid Bilayer

Cell membrane composed of

Phospholipids

Sphingolipids

Cholesterol

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Membranes : Phospholipid bilayebranes

Phospholipids and/or sphingolipids form

A bilayer, aka non polar fatty acid chain pointing inward, polar head group pointing outwards

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Membranes: phospholipid bilayer

Have diverse head groups that can be positively and negatively charged ,
Or just primarily negatively charged

Glycerol phospholipids

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Membranes : phospholipids

Phospholipids can have different fatty acid chain length and composition, with it being either saturated or cis - unsaturated (T/F)

True

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Membranes: Phospholipid bilayer

Generally contain saturate fatty acid chain aka (hydrocarbon)

Sphingolipids

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Membranes: Phospholipid bilayer

Cell membranes cannot be differently structured (T/F)

False

Different lipid and or protein composition

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Membranes: Phospholipid bilayer

What forms spontaneously due to the tendency of water molecules to form the maximum number of hydrogen bonds

Phospholipid bilayer

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Membranes: Phospholipid bilayer

When placed in water, spontaneously forms bilayer

Nonpolar group orient to each mother while polar head groups orient towards charge water molecules

Phospholipid

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Membrane: phospholipid bilayer

Is a lipid bilayer stable?

Yes because waters affinity for hydrogen bonding never stops to

Hydrogen bonding of water holds a membrane together

Phospholipid bilayer is fluid

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Membranes

Membrane fluidity of a cell varies with or is determined by the (lipid) composition of the membrane itself (T/F)

True

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Membranes : Phospholipid bilayermbranes

Describe Fluid Mosaic Model

Globular proteins embedded in the lipid bilayer are/ inserted into the lipid bilayer

Nonpolar Amino Acids are in contact with the nonpolar interior, aka fatty acids

Polar (amino Acids) portions , aka hydrophilic heads protrude out from membrane surface (polar exterior)

These proteins can float around the plasma membrane due to the nature of the nonpolar and polar contacts

Creates barrier for all elements inside and outside the cell

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Membranes: Phospholipid bilayer

Saturated fatty acids

Mono cis - saturated fatty acids

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Membranes: Phospholipid bilayer

What type of fatty acid chain results in a thicker membrane

Unsaturated fatty acid chain

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Membranes: Phospholipid bilayer

What type of fatty acid leaves more space for cholesterol?

Why is cholesterol important?

Unsaturated fatty acids

Gives membranes it’s fluidity

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Membranes: Phospholipid bilayer

Endoplasmic Reticulum membrane is composed of_________________

and had very little_______________

Unsaturated phospholipids

Cholesterol

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Membranes: phospholipid bilayer

Is the plasma membrane thinner than the endoplasmic reticulum?

No.

The endoplasmic reticulum(20 amino acids) is thinner than the plasma membrane (thick; 25amino acids)

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Membranes: proteins

Allows certain molecules to enter or exit the cells

Transporters

Membranes: proteins

Perform chemical reactions on the interior surface of the plasma membrane

Enzymes

Membranes: proteins Detects external chemical signal

Cell surface receptors

Membranes: proteins Pro retina that identify the cell type as "self vs no self"

Cell surface identity markers

Membranes: proteins Proteins that allow two cells to stick together

Cell to cell adhesion molecules

Membranes: proteins Proteins that allow a cell to be anchored to the cytoskeleton

Attachments to cytoskeleton

Membranes: proteins Proteins can be anchored to phospholipids via

Hydrophobic heads

Membranes: proteins Proteins that can span the lipid bilayer _____________ The part of the protein that extends through the lipid bilayer and is in contact with the non polar interior are ___________ or ___________

Transmembrane proteins A helices or B-pleated sheets

Membranes: proteins Membrane spanning region is called ___________ This region anchors_____________

Transmembrane domain Integral membrane proteins

Membranes: proteins Can span the lipid bilayer and FORM pores

Proteins formed from ß-sheets

Transport through membranes 1. Transport can be _________ or ____________. 2. ____________ transport does not expend energy 3. _____________ expends energy

1. Passive or Active 2. Passive 3. Active

Transport through membranes : passive transport Movement of molecules from higher concentration to lower concentration until equilibrium is reached Nonpolar molecules can move freely through the nonpolar bilayer

Diffusion

Transport through membranes 1. Polar molecules need specific protein membranes to allow for diffusion to occur ( channel proteins & carrier proteins) 2. The diffusion of molecules or ions through carrier proteins or ions channels Requires a concentration gradient, but not any input of energy

Facilitated diffusion

Transport through membranes : passive transport A difference between the concentration on the inside of the membrane and that on the outside Allows ion and molecules to pass through membrane easily

Concentration gradient

Transport through membranes : facilitated diffusion A transmembrane protein with a hydrophilic interior that provides aqueous channel allowing diffusion of species that cannot cross the membrane Usually allows passage for K+, Na+, Ca+

Channel protein

Transport through membranes : facilitated diffusion A membrane protein that binds to a specific molecule that cannot cross the membrane and allows passage through membrane

Carrier protein

Transport through membranes : facilitated diffusion Possesses a hydrated interior that spans the membrane, ions can diffuse through the channel in either direction, depending on the relative concentration across the membrane

Ion channels

Transport through membranes : passive transport Adds PHOSPHATE GROUP to GLUCOSE once it enters a cell , to keep glucose concentration levels low Increases inward diffusion of glucose Glucose transporter binds(carrier protein) glucose on extracellular side, then releases it in the intracellular side

Red blood cells

Transport through membranes : passive transport Diffusion of water molecules down their concentration gradient Concentration of solutes(ions) determines direction of water movement

Osmosis

Transport through membranes: Passive Transport—> Osmosis 1. More solutes/higher concentration = 2. Less solutes/ less concentration = 3. Equal solutes/ same concentration =

1. Hypertonic 2. Hypotonic 3. Isotonic

Transport through membranes: Passive transport Aquaporins

Proteins that form channels that allows water transport

Transport through membranes : passive transport Concentration of all solutes in a solution determines the____________

Osmotic concentration

Transport through membranes : passive When water changes the shape of the cell The amount of water that enters the cell depends on the difference in solute concentration between the cell and the extracellular fluid.

Osmotic pressure

True or false Diffusion, facilitated diffusion and osmosis are passive transport process that move materials down their concentration gradient

True

Transport through membranes : Expenditure of energy, typically from ATP Moves substances ACROSS a cell membrane UP their concentration gradients What am I?

Active transport

Transport through membranes : Active Transport Carrier protein that transports one type of molecule

Uniporters

Transport through membranes: Active Transport Carrier proteins that transport 2 molecules in the SAME DIRECTION

Symporters

Transport through membranes : Active Transport Carrier proteins that transport 2 molecules in OPPOSITE DIRECTIONS

Antiporters

Transport through membranes—> Active Transport: uses ATP to move molecules up their concentration gradient Best Example: Na+/ K+ pump - cell has a lot of K+, little Na+ 1. Describe the steps for this pump.

1. Carrier in membrane binds intracellular sodium 2. ATP phosphorylates protien with bound sodium 3. Phosphorylation causes conformational change in protein, reducing its affinity for Na+. Na+ then diffuses out 4. This confirmation has higher affinity for K+. Extracellular potassium binds to exposed sites 5. Binding of potassium causes dephosphorylation of protein 6. Dephosphorylation of protein triggers change back to original conformation, with low affinity for K+, K+ diffuses into the cell, and the cycle repeats

Transport through membranes: Active Transport Glucose (uses N+ gradient) Molecules moved against their concentration gradient by using the energy stored in a gradient of a different molecule Uses energy of N+ moving down concentration gradient to couple to glucose transport

Coupled transport

Bulk Transport -> 2 Processes 1. Into the cell = 2. Out the cell =

1. Endocytosis | 2. Exocytosis

How do large polar molecules, or substances cells require for growth get into cells?

Bulk Transport - endocytosis - exocytosis

Bulk Transport In this process the plasma membrane envelopes food particles and fluids Things are transported out of the cell in bulk via vesicles Vesicles fuse with plasma membrane, spilling its contents into the extracellular space Used to release hormones, neurotransmitters, enzymes, and other substances

Endocytosis

Bulk Transport: endocytosis Cell use three major types of endocytosis which are :

Phagocytosis - "eats cell" - fragments of organic matter, includes other cells Pinocytosis - drinks, or engulfs liquids Receptor-mediated endocytosis - Molecules bind to receptors on cell surface, which are then taken up by the cell