Chapter 5

Question 1

What are the type of tails in phospholipids?

Answer 1

Hydrocarbon tails, hydrophobic , lipid

Question 2

Can phospholipid tails affect the what?

Answer 2

Fluidity of the membrane/viscosity

Question 3

How do phospholipid tails affect membrane fluidity?

Answer 3

Their tails are made out of lipids/fats. If it’s unsaturated fat, it has kinks that make the membrane more fluid/lower viscosity. If it’s saturated fat, it can pack together tightly and have less fluid/more viscosity.

Question 4

What is cholesterol, how does it affect the membrane?

Answer 4

Most common STEROID in the body, it’s a type of fat. Steroids are non-polar and have a ring structure. When cold, phospholipids move close together (like penguins). When hot, they spread apart. Both movements decrease the membrane’s ability to transport molecules, so cholesterol preventes these phospholipids from moving too much, which stabilizes the membrane. Opposite effect of temperature.

Question 5

What type of structure does Cholesterol have? Draw it out.

Answer 5

Ring structure,

Question 6

Can proteins move within the bilayer?

Answer 6

Yes, they can rotate and move laterally.

Question 7

What is the mouse experiment?

Answer 7

Merged membrane proteins of a mouse and human together. When cells fused, the membrane proteins of two cells became uniformly distributed over cell surface. Proves proteins can move around bilayer.

Question 8

Hydrophobic molecules are ___ soluble. Can they pass easily through membrane? Give examples of hydrophobic molecules.

Answer 8

lipid soluble, and non polar molecule (doesn’t mix with water). SMALL Can pass easily and rapidly through membrane. Ex: small lipids and steroids, O2, CO2.

Question 9

Oxygen is hydrophobic or hydrophilic? Explain

Answer 9

Hydrophobic because it’s nonpolar. Nonpolar = hydrophobic. Non-polar because it’s 2 oxygens, so equal electronegativities.

Question 10

Which 2 molecules are amphipathic? Draw a picture of both and label the polar hydrophilic head and nonpolar hydrophobic tail.

Answer 10

Steroids (cholesterol) and phospholipids.

Question 11

Why can’t polar molecules easily cross membrane? Give examples.

Answer 11

Polar molecules must break their interactions with water to enter the hydrophobic interior of the bi-layer, which is energetically unfavorable and requires energy output. ex: amino acids, glucose, nucleotides. Most amino acids have to be transported across bc they are polar (charged) and repelled. Glucose is also polar. Nucleotides are negatively charged. No charged molecules allowed.

Question 12

What are transport proteins? What do they allow in?

Answer 12

The door to a cell, help molecules cross the membrane. Allows hydrophilic (polar) substances that are excluded from the membrane interior to cross.

Question 13

What are the 2 main factors that determine passage across a membrane?

Answer 13

Size (small) and solubility (lipid soluble, water soluble needs an ion channel)

Question 14

Difference between transport proteins, carries, and channels.

Answer 14

There are two classes of membrane transport proteins—carriers and channels. Carries are active and passive, channels are only passive.

Question 15

What molecules rarely cross a lipid bilayer, regardless of their size?

Answer 15

Large charged polar (hydrophilic) molecules (ions) because charges are repelled by hydrophobic tails .
Charged molecules like ions repel uncharged molecules within hydrophobic tails, cannot pass.

Question 16

sidedness meaning, effect?

Answer 16

Membranes have distinct inside and outside faces (batman 2 face), affects the movement of proteins synthesized in the endomembrane system.

Question 17

membrane asymmetry meaning

Answer 17

The cell membrane comprises two sides. One side faces the cell cytoplasm that contains water and other biomolecules like proteins. The other side faces the extracellular matrix produced by the material released from the cell. The two sides of the plasma membrane have different lipid & protein composition.

Question 18

Endomembrane system, what is included?

Answer 18

Composed of the different membranes in the cytoplasm within a EUKARYOTIC cell. basically the organelles, and organelles are wrapped in their own tiny phospholipid membrane as well. Nucleus, endoplasmic reticulum (ER), golgi apparatus, and lysosomes. where MEMBRANE PROTEINS are synthesized (ER and golgi)

Question 19

Give functions of all organelles found in the endomembrane system.

Answer 19

Nucleus: stores DNA of cell, where DNA replication, transcription and RNA processing take place. ER: smooth ER creates/stores lipids and steroids, rough synthesizes proteins.
Golgi: factory where proteins from the ER are further processed and sorted for transport to their destinations.
Lysosome: digestive system of cell, breakdown macromolecules (CLPN)

Question 20

Passive transport. what are the 2 types?

Answer 20

diffusion of a substance across a membrane with no energy needed. 1. Diffusion: tendency for molecules to spread out evenly into available space (AIR FRESHNER), substances DIFFUSE down their concentration gradient to reach equilibrium. 2. Osmosis: movement of WATER across membrane between 2 solutions. affected by the concentration gradient of dissolved substances. water moves from low solute to high solute concentration (or high water concentration to low water concentration)

Question 21

Tonicity

Answer 21

ability of a solution to cause a cell to lose or gain water, impacts cells without cell walls (aka animal cells), ISONTONIC & HYPOTONIC

Question 22

isotonic

Answer 22

concentration of solutes is same as inside the cell, no net movement of water

Question 23

hypertonic

Answer 23

concentration of solutes outside cells is greater than inside cell, cell will lose water because water moves from areas of high water concentration to low water concentration

Question 24

Hypotonic

Answer 24

concentration of solutes outside cells is less than inside cells, cell will gain water because water moves from areas of high water concentration to low water concentration.

Question 25

Cell wall function

Answer 25

maintain water balance, or cell will shrivel/burst

Question 26

Facilitated Passive Transport/Facilitated diffusion, what are the 2 types of facilitated transport proteins?

Answer 26

the process of moving molecules from high to low concentration across a membrane by using a protein channel in the membrane. Does not use energy but relies on a protein to facilitate movement. type of integral membrane protein that spans the entirety of the cell membrane. How ions and small polar molecules that cannot pass the membrane diffuse such as carbohydrates, amino acids, nucleosides, and ions. 2 types are channel and carries proteins. No energy needed, only concentration gradient.

Question 27

what are carbohydrates, amino acids, nucleosides, and ions? Draw out each.

Answer 27

Carb=sugar/saccharide, amino acids=proteins, nucleosides=DNA. each are charged and cannot pass through membrane by itself. require facilitated diffusion which requires no energy but needs transmembrane protein.

Question 28

transmembrane protein

Answer 28

any protein that spans the entire cell membrane

Question 29

integral proteins

Answer 29

penetrate the hydrophobic core of the lipid bilayer, TRANSMEMBRANE protein. move molecules across

Question 30

Channel protein, give examples

Answer 30

made up of HYDROPHILIC/polar amino acids, attract ions/polar molecules (like attracts like), some are gated and only open with a signal ex: AQUAporins: H20, Muscle cells: gated ion channels that allow muscle contraction when oepned

Question 31

Carrier Proteins. give example

Answer 31

specific to a single substance, bind to that substance, change shape and carries it to other side., can do passive and active IMPORTANT EXAMPLE: glucose transport protein (GLUTS)

Question 32

active transport

Answer 32

uses energy (ATP form) to move solutes AGAINST gradient (low to high)

Question 33

how does ATP power active transport?

Answer 33

shifting a phosphate group from ATP to the transport protein. results in conformational change in the transport protein that translocates the solute across the membrane.

Question 34

sodium potassium pump

Answer 34

an ACTIVE transport system, requires energy. animal cells have higher K+ and lower Na+ inside cell, uses ATP to pump 3 Na+ out and 2 K+ in (GOING AGAINST GRADIENT)

Question 35

steps of sodium potassium pump

Answer 35

1. high concentration of K+ and low Na+ inside cell, 3 Na binds to pump 2. ATP transfer phosphate group to pump, causing protein to change shape 3. releases Na+ ions outside cell 4. 2 K+ from outside cell can now bind to pump, releases phosphate 5. K+ released inside cell, binding site changes to accommodate Na+ again.

Question 36

electrochemical gradient (watch video)

Answer 36

caused by the electrical concentration gradient of ions across a membrane, a difference of charge across membrane. why our nerves work, its the driving force across a plasma membrane that dictates whether an ion will move in or out of cell

Question 37

electrogenic pump, give example (watch video)

Answer 37

transport protein that generates the voltage across a membrane, active (low to high), ex. proton pump, sodium potassium pump, an ION pump that generates charge as a result of its activity, proton pump uses ATP (active) to pump hydrogen ions out of the cell, makes inside of cell negative, balances pH. ions moving up a gradient take energy. Why are protons pumped? The electrochemical gradient generated by proton pumping provides energy required for the transport of these molecules, DIFFERENT CHARGE INSIDE AND OUTSIDE

Question 38

membrane potential

Answer 38

voltage difference across a membrane, electricity comes rom setting up electrochemical gradient, maintains and functions nervous system

Question 39

Cotransport (secondary active transport), give example

Answer 39

form of active transport, when active transport of a specific solute indirectly drives the active transport of another solute, transported in OPPOSITE directions, proton sucrose contransporter, protons cannot move if sucrose doesn't move at the same time, uses stored potential energy from H+

Question 40

Draw active vs passive transport

Answer 40

Active: diffiusion, osmosois, facilitated diffusion Active transport: H+ pump, sodium potassium pump

Question 41

Bulk transport

Answer 41

ACTIVE TRANSPORT, transports large quantities of materials and food particles across membrane. occurs by exocytosis (exit cell) and endocytosis (enter cell) help Large proteins cross membrane

Question 42

exocytosis

Answer 42

exit cell, transport vesicles travel to the membrane, fuse with it, and release their contents. usually secreting waste, active transport, needs energy

Question 43

endocytosis

Answer 43

enter cell, cell takes in macromolecules CLPN, by forming new vesicles from the plasma membrane, brings into cell, active transport

Question 44

3 types of endocytosis DRAW EACH

Answer 44

1. phagocytosis: surround food, form vesicle around it, and bring into cell 2. pinocytosis: "pina colada" brings in small molecules, cell drinking 3. receptor -mediated endocytosis: SPECIFIC, brings small molecules into the cell, attracts specific molecules (ligands) with receptors, coated pits recognize the specific molecule, brings into cell, how insulin and other hormone proteins are brought into the cell

Question 45

6 major functions of membrane proteins, draw and explain each

Answer 45

1. transport 2. enzymatic activity 3. signal transduction 4. cell-cell recognition 5. intercellular joining 6. attachment to the cytoskeleton and extracellular matric (ECM)

Question 46

Cell cell recognition

Answer 46

Cell's ability to distinguish one type of neighboring cell from another through carbohydrates in the membrane

Question 47

enzymatic activity

Answer 47

a protein built into the membrane with active site exposed, carry out chemical reactions like an enzyme, substrate binds to the enzyme, enzyme releases products into same outside side of cell

Question 48

signal transduction

Answer 48

signaling molecule binds to receptor transduces signal from outside to inside, amplifies original signal

Question 49

intercellular joining

Answer 49

membrane proteins hook together to other cells' membrane proteins, help form tissues

Question 50

attachment to cytoskeleton and ECM

Answer 50

maintains shape of cell