B2.1

Question 1

Structure of the Lipid Bilayer

Intergral proteins?

Answer 1

• Able to be embedded throughout whole membrane due to their amphiprotic nature
• Have a hydrophobic region that is embedded in the fatty acid area of the membrane
• Ends of protein are hydrophillic

Question 2

Structure of the Lipid Bilayer

Peripheral proteins?

Answer 2

• Bound to the surface/ don’t protrude in hydrophbic region
• Don’t need to be amphipathic
• Can be found on BOTH the interior OR exterior surface, or bound to an intergral protein

Question 3

Structure of the Lipid Bilayer

Cholesterol?

Answer 3

• A chain of steriod lipids, thus sit in the hydrophobic region of the membrane of ANIMAL cell membranes
• Allow for greater fluidity by preventing the overexpanding or condensing of the membrane in extreme temperatures

Question 4

Structure of the Lipid Bilayer

Fluid Mosaic Model

Answer 4

• Presence of different proteins in non consistent pattern provides fluidity allowing the cell to change shape/ faciliates transport in and out of cell
• Shows glycoproteins and lipids

Question 5

Structure of the Lipid Bilayer

Amphipathic nature of Phospholipids

Answer 5

• Tails are non-polar and are hydrophbic
• Heads contain phosphate group (negative charge) bound to glyceral (positive charge) making it polar and hydrophillic

Question 6

Structure of the Lipid Bilayer

Selectively permeable membranes

Answer 6

• Some substances move easily though membrane
• Small non-polar substances diffuse through non-selectively but larger/ polar molcules require intergral protiens

Question 7

Structure of the Lipid Bilayer

Functions of Cell Membrane Protiens

JETRAT

Answer 7

• J - Junction, intracellular joinings/cell adhesion between cells or anchoring of the ctyoskeleton within a cell
• E - Enzyme for a metabolic pathways
• T - transport (active/passive) channels, carriers and pumps
• R - recognition
• A- Anchoring for glycoprotiens
• Transduction pathways - a receptor site for hormones to bind to/other signalling molecules

Question 8

Structure of the Lipid Bilayer

Active vs Passive Transport

Answer 8

• Passive: natural flow of particles with the concentration gradient, thus requiring no energy (straight through bilayer/through an intergral protein)
• Active: moving particles against the concentraiton gradient, thus requiring energy from ATP.

Question 9

Structure of the Lipid Bilayer

Glycoprotiens vs Glyolipids

Answer 9

• Glycolipid: if carbohydrate chains attach to the lipid tails
• Glycoprotein: attaches to a peripheral protien instead.
• Both play an important role in cell identification & adhesion

Question 10

Structure of the Lipid Bilayer

Saturated vs Unsaturated Fatty Acids in Membrane

Answer 10

• Unsaturated: the presence of DOUBLE C-C bonds creates kinks in phospholipids, preventing them form packing, especially at cooler temperatures
• Saturated: straighter, have higher melting points, creating a denser bilayer, limting expansion in higher temperatures

Question 11

Structure of the Lipid Bilayer

Cholestoral and Membrane Fluidity

Answer 11

• High Temps: Cholesterol adds stability and prevents overexpansion of the phospholipids
• Low Temps: Cholesterol prevents phospholipids from packing too tightly that fluid is reduced

Question 12

Passive Transport

Simple Diffusion?

Answer 12

• Any time a particle moves from high conc. to low conc.

Question 13

Passive Transport

Faciliated Diffusion?

Answer 13

• For larger/charged/polar particles unable to move through phospholipid, they require a membrane protien to move in or out of the cell.
• Still moves from high conc. to low conc. without energy, but are just faciliated with a protein

Question 14

Passive Transport

Osmosis?

Answer 14

• Movment of water through a semi-permeable membrane from a high water potential (hypotonic) to a low water potential (hypertonic)/ high conc. to low conc.
• Often a form of faciliated diffusion

Question 15

Passive Transport

Aquaphorins?

Answer 15

• Special protein channels that function for the transport of water
• As water is polar, the channel has a polar interior to transport it

Question 16

Passive Transport

Hypertonic?

Answer 16

• Higher concentration of solutes

Question 17

Passive Transport

Hypotonic?

Answer 17

• Lower concentration of solutes
• Surroundings of cell have fewer/lower solutes than the cell

Question 18

Passive Transport

Isotonic?

Answer 18

• Solate conc. of cell and extracellular environment are the same

Question 19

Passive Transport

How do molecules move by Simple Diffusion?

Answer 19

• Must be small to get through phopholipid heads
• Should be non-polar due to non-polar central region of the membrane
• E.g., Oxygen and CO2

Question 20

Passive Transport

Carrior proteins vs Channel proteins

Both are membrane proteins for charged/polar particles

Answer 20

• Charged or polar molecules move passivley through membrane proteins
• CHANNEL: have a polar core creating space for polar and charged particle to move
• CARRIER: change shape as molecule moves through it.

Question 21

Passive Transport

Sodium-Potassium Pump and Active Transport

What is it, what does it do?

Answer 21

• Moves particles against the concentration gradient
• SP-pump is a protein pump that uses energy (ATP) to convert between two shapes
• Allows for 3Na+ ions to move out and 2K+ ions to move in.

Question 22

Active Transport

Endocytosis?

Answer 22

• Materials enter the cell by pushing through the plasma membrane, pulling a part with it creating a vesicle
• This requires energy, can be used to bring in large solid particles (phagocytosis) or a volume of liquid containing solutes (pinocytosis)

Question 23

Active Transport

Exocytosis?

Answer 23

• Used for particles to be removed from the cell
• E.g., in unicellular organisms to expel water in a contracile vacuole to manage osmotic balance.
• Used to export protein products –> the vesicle is made by the golgi apparatus and fuses with membrane for export

Question 24

Active Transport

Gated ion channels?

Answer 24

• Allow for diffusion in or/and or of the cell based on the conc. gradient
• Relevant because ions are charged
• Gate ion channels allow channels to be opened for diffusion to be turned on at a specific time
  See action potentials in C2

Question 25

# Active Transport Indirect Active Transport? | /Secondary transport

Answer 25

* ATP is used to move one substance but a **Second substance** can then move as a result of the active transport. * E.g., H+ requires energy but when a conc. of it has been accumulated, it moves back down passively and something else can move with it.

Question 26

# Active Transport Cell-Adhesion molecules

Answer 26

* Cells are connected to one another witihin tissues in multicellular organisms in what is called cell-to-cell junctions. * Creating these junctions relies on **Cell Adhesion Molecules (CAMS)** which are proteins embedded in the membrane and protrude out towards other cells. * Two CAMS join to create junctions, helping create complex cellular arrangements in tissues.

Question 27

# Active Transport What is the role of the Golgi Apparatus for Exocytosis?

Answer 27

* Proteins are made at the roughER and are packaged into a vescile and moved to the ER where they're modified, then the **membrane of the golgi pushes through to create vesicles** that transport the protein products to the membrane * At the membrane, the vesicle **fuses with the cell membrane**, becoming apart of it and **expelling the protiens** (exocytosis) out of the cell.

Question 28

# Active Transport Neurotransmitter Gated vs Voltage Gates Ion Channels

Answer 28

* Neurons fire based on the movement of ions - hence, for regulation, ion channels are gated and normally closed, relying on two signals to open. * **In Neurotransmitter/Ligand Gated**: a chemical messenger faciliates opening of channel. * **In Voltage Gates ion Channel**: the gates are based on charge differences between interal and external envrionemnts, whereby a change (from an aciton potential) causes the opening.

Question 29

# Active Transport How is the Sodium Potassium Pump an Exchange Transporter?

Answer 29

* Because one protein moves sodium outside of the cell and potassium inside the cell. * When the pump changes shape/conformation to **release Na ions, the K ions enter** at the same time. * Then it conforms back, **releasing K and able to collect Na**

Question 30

# Active Transport What's the role of ATP for the Sodium Potassium Pump?

Answer 30

* Responsible for creating the shape change that **closes the pump** on the **inside** and faciliates the **reopening on the outsde**. * ATP is used --> phosphate group binds to outside of the pump (hydrolysis) * When potassium then **Enters**, once sodium is **Expelled**, that causes the **lone phosphate to deatch** triggering the next shape change, and thus one ATP can generate the entire cycle.

Question 31

# Active Transport What are sodim-dependent glucose contransporters? | A form of secondary active transport

Answer 31

* The sodium-potassium pump uses active transport to move sodium into the **extracellular space** where the **glucose-needing transporting resides** * Once Na+ conc. is established, it moves via a channel that moves **glucose as well as sodium** * Hence, no ATP is used for the transport of glucose, but was used for the transport of sodium, thus indirectly still energy demanding.

Question 32

# Active Transport What are the uses of cell adhesion molecules? | CAMs

Answer 32

* CAMs help create juntions between cells, used to make **specialized tissue** in multicellular organisms, enabling cells to funciton as units. * Purpose can vary - some facilate/prevent movement * Can also be protective when tumors form by preventing cells breaking away (metastasis)/cancer to other areas.