Cell Membrane and Transport

Question 1

Phospholipid bilyaer

Answer 1

• polar heads
• non polar tails
• cell membrane is based on the bilyaer
• Various proteins and other molecules are embedded in the bilayer= fluid mosaic model
• Polar & Non-Polar substances will cross the membrane differently

Question 2

how does movement occur along a concentration gradient

Answer 2

From high to low, independent

Question 3

how do non polar substances move along the phospholipid bilayer? what about polar substances

Answer 3

non-polar: diffusion

polar+ions: channel proteins
(ex. glucose uses insulin to move across)

Question 4

How does the movement of H2O occur

Answer 4

via specific proteins: aquaporins and osmosis

solutions can be: iso-, hypo-, or hyper- tonic to the cytoplasm in the cell

Question 5

effect of temperature on diffusion

Answer 5

Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion.

Question 6

Passive transport

Answer 6

• Channels exist to move substances across membranes. Some of these channels are gated-channels opened by specific conditions or molecules

Question 7

Facilitated Diffusion

Answer 7

• Other molecules use transports that change shape to move some molecules across a membrane

Question 8

Active Transport

Answer 8

• Energy can be used by membrane proteins to change shape and force materials against a concentration gradient
• requires energy, generally the work in cells is done by ATP
• always involves carrier proteins WHERE PROTEINS CHANGE CONFORMATION WITH ATP
• Best example is the Na/K Pump

Question 9

T/F: Cholesterol and proteins float around in the phospholipid bilayer

Answer 9

True: cholesterol helps in maintaining the structural integrity and regulating the fluidity of cell membranes

proteins mediate processes in the membrane

Question 10

does passive transport require energy?

Answer 10

no

Question 11

How could cells benefit by having some molecules move against a concentration gradient?

Answer 11

because sometimes there are materials outside the cell which it needs, but they are found in lower concentration than inside the cell. In this case the cell will pay some energy to get them in against the concentration gradient.

• THIS IS ACTIVE TRANSPORT

Question 12

UNIPORT VS SYMPIPORT VS ANTIPORT

Answer 12

Uniport: independent transport of one molecule

Sympiport: when two kinds of molecules move in the same direction while diffusing through carrier proteins

Antiport: a type of transport in which two different molecules can move through a membrane in opposite directions.

Question 13

transport of sucrose

Answer 13

symport

Question 14

what type of substances need to moved across membrane AGAINST Gradients

Answer 14

• metal ion, gastric acids, glucose
• critical for a cell to maintain internal concentrations of small molecules that would otherwise diffuse across membrane

Question 15

Na/K pump

Answer 15

The Na/K is a protein that uses ATP to change it shape and move ions across membranes against concentration gradients.

Question 16

Na/K Pump process

Answer 16

1) pump binds 3 Na+ and a molecule of ATP

2) transferring phosphate group provides energy to change shape of the channel (which is the structure that holds the pump), the Na+ are driven through the channel

3) The Na+ ions are released to the outside of the membrane, and the new shape of the channel allows two new K+ to bind

4) Release of the PO4 allows the channel shape to revert to OG form, releasing the K+ ions on the inside of the membrane

Question 17

The Na/K pump is an

Answer 17

antiport

Question 18

is K+ pumped out of cells by the pump?

Answer 18

No, IT TAKES OUT 3 NA+ AND BRINGS IN 2K+
= builds up concentration gradients

Question 19

Pumps similar to the Na/K pump

Answer 19

• nerve cells to maintain concentration gradients and electrical signals
• proton pumps involved in cell respiration and photosynthesis
• calcium
• chlorine

Question 20

Coupled Transport

Answer 20

• use of an active transport to create a concentration gradient that equals out by diffusion (facilitated)

Question 21

Co Transport

Answer 21

• use one molecule to piggy-back another and get a ride inside cells by diffusion (facilitated)

Question 22

What is Endocytosis

Answer 22

Endocytosis is the process of bringing in bulk materials.

EX. SARS-CoV2 virus is being brought into cells, SARS-CoV2 uses endocytosis to trick cells into bringing it in so it can infect the cell

Question 23

Phagocytosis

Answer 23

Phagocytosis brings in large solids (cell eating)

Question 24

pinocytosis

Answer 24

pinocytosis brings in small amounts of fluid from outside (cell drinking)

Question 25

Exocytosis

Answer 25

fusion of substances with the cell membrane to form vesicles that need to be taken back into the cell

Question 26

FLUID MOSIAC MODEL COMPONENTS AND FUNCTIONS

Answer 26

peripheral protein- support, communication, enzymes, and molecule transfer

cholesterol- maintaining the structural integrity and regulating the fluidity of cell membranes

cytoskeleton- it spatially organizes the contents of the cell; it connects the cell physically and biochemically to the external environment; and it generates coordinated forces that enable the cell to move and change shape.

cytoplasm- medium for chemical reactions

ogliosaccharides- cell adhesion and cell recognition, method of communication to help our body identify our own cells

glycolipid- maintain membrane stability but also facilitates cell-cell communication acting as receptors, anchors for proteins and regulators of signal transduction

extracellular fluid carbohydrate- denotes all body fluid rates outside of cells

glycoprotein- enable cells to recognize another cell as familiar or foreign, which is called cell-cell recognition. They also help cells attach to and bind other cells, which is called cell adhesion.

glycoprotein: enable cells to recognize another cell as familiar or foreign, which is called cell-cell recognition. They also help cells attach to and bind other cells, which is called cell adhesion

trans membrane protein- controlling signal transmission, transport of nutrients and other soluble molecules, and energy conversion across organelles and cells

Question 27

how would the cell membrane differ based on diff environmental conditions?

Answer 27

cold for ex.
- less kinetic energy means you need more channels and more cholesterol to 1) keep MORE molecules moving along when they can’t diffuse and aren’t as fast
2) have MORE cholesterol to maintain that fluidity within the cell

Question 28

how do enzymes attract substrates

Answer 28

intermolecular forces, randomness

Question 29

what is the structure of aquaporins

Answer 29

polar head

• the amino acids inside are both acids and bases polar for the h2o to pass, finding their way based on concentration gradient

Question 30

difference between a channel and carrier protein

Answer 30

channels- are always open, more of a tunnel for molecules to pass along on

carrier proteins- have moments of opening and closing, and are actually transporting molecules across, transmembrane

Question 31

coenzymes vs cofactors

Answer 31

coenzymes (organic): bind loosely to enzyme
cofactors (inorganic): don’t tend to bind to enzyme

• iron for ex. facilitates the transport, transitional tissue storage, and cellular use of oxygen for hemoglobin, making it a cofactor of hemoglobin, it makes the process of creating it easier without it binding to anything

Question 32

are aquaporins always open

Answer 32

yes, they are uniport channels

Question 33

why/when would something need to move against the concentration gradient?

Answer 33

needing higher amounts of concentrations of a particular molecule needed and choosing to wisely waste ATP on it,

for ex. Active transport proteins ensure that glucose moves into the intestinal cells, and cannot move back into the gut, glucose is required for fuel

Question 34

what will enzymes do when they separate from substrate

Answer 34

redox, phosphorylations, etc.

Question 35

proton pump

Answer 35

use of ATP to remove protons from inside of the cell to the outside, leading the inside of the plasma membrane negatively charged

UNIPORT

Question 36

co transport example

Answer 36

sucrose and proton: coupled transport, plants cells use the protons to drive sucrose nutrients alongside into the cell, therefore the sucrose is piggybacking from the protons efforts to diffuse down the concentration gradient maintained by the proton pump

Question 37

what would happen if na/k pump stopped working

Answer 37

cell would swell up, becoming hypotonic and dying from lysis because there isn’t homeostatic desires being met with the salt balancing out.

Question 38

reviewed fluid mosaic model**

Answer 38

• cholesterol maintaining fluid flow
• proteins determine most functions:
  peripheral proteins: not embedded in lipid bilayer at all
  integral/transmembrane channel proteins: penetrate into the lipid bilayer

proteins in membrane do the following:
- transport
- mediate enzyme activity
- signal transduction
- intercellular joining
- cell-cell recognition
- attachment to the cytoskeleton and ECM

• outer surface has carbohydrate, oligosaccharides lay on exterior and detect other body cells