Unit 5: Membrane Structure & Function

Question 1

what makes up the cell membrane/plasma membrane?

Answer 1

it is made up of a phospholipid bilayer with cholesterol and protein embedded in it.

Question 2

what is a phospholipid made up of?

Answer 2

a phospholipid has a phosphate group and 2 fatty acid chains. the phosphate group is negatively charged/polar/hydrophilic and the fatty acid chains are uncharged/nonpolar/hydrophobic.

Question 3

what is an amphipathic molecule?

Answer 3

A molecule that contains both a hydrophilic and hydrophobic region.

Question 4

the phosphate groups are attracted to?

Answer 4

water in the intracellular fluid and extracellular fluid.

Question 5

Intracellular fluid?

Answer 5

fluid inside the cell.

Question 6

extracellular fluid?

Answer 6

fluid outside the cell membrane.

Question 7

interstitial fluid?

Answer 7

extracellular fluid not in the blood vessels.

Question 8

Fluidity of the membrane?

Answer 8

cholesterol contributes to the fluidity. an important feature of the cell membrane is the fluidity, the lipids and proteins can move but are still in place. this makes up for the fluid portion of the fluid mosaic model.

Question 9

membrane proteins?

Answer 9

there are two types of proteins that contribute to the mosaic part of the fluid mosaic model: integral proteins and peripheral proteins.

Question 10

what is an integral protein?

Answer 10

a protein that is embedded in the membrane.
- channel proteins
- glycoproteins

Question 11

what are channel proteins?

Answer 11

channel protein is an example of an integral protein which selectively allows particular materials to pass in and out of the cell

Question 12

what is a glycoprotein?

Answer 12

a glycoprotein is a protein that has carbohydrate molecules attached to it.

Question 13

what is the glycocalyx?

Answer 13

??

Question 14

what are peripheral proteins?

Answer 14

inner or outer surface of the lipid bilayer but can also be attached to the integral protein.
- they usually perform a specific function for the cell.

Question 15

What does it mean for the membrane to be selectively permeable?

Answer 15

a membrane that has selective permeability allows only substances meeting certain things to pass through.

Question 16

what substances can easily pass through the membrane?

Answer 16

small nonpolar materials such as lipids, oxygen, carbon dioxide.

Question 17

what substances have a hard time crossing?

Answer 17

glucose, amino acids, electrolytes, charged things, polar, need some assistance.

Question 18

what is passive transport?

Answer 18

movement of substances across the membrane using their own kinetic energy, no additional use of chemical energy.

Question 19

what is active transport?

Answer 19

movement of substances across the membrane using energy ATP.

Question 20

what is a concentration gradient?

Answer 20

difference in concentration of a substance across a space. substances will move from where they are more concentrated to an area where they are less concentrated.

Question 21

what is diffusion?

Answer 21

movement of particles from an area of higher concentration to an area of lower concentration. diffusion happens faster in higher temperatures.

Question 22

is there a higher or lower concentration of o2 inside or outside the cell?

Answer 22

there is a lower concentration of o2 inside the cell because cells rapidly use up oxygen during metabolism. therefore, oxygen diffuses inside the cell. opposite is for co2.

Question 23

what is facilitated diffusion?

Answer 23

diffusion process used for those substances that cannot cross the membrane due to their size, charge, or polarity.

Question 24

example of facilitated diffusion?

Answer 24

glucose: glucose is more concentrated outside of the cell but it cannot go inside the cell because it is large and it is polar. to fix this problem, a carrier protein called the GLUCOSE TRANSPORTER transfers glucose into the cell.

Question 25

carrier mediated facilitated diffusion vs channel mediated facilitated diffusion?

Answer 25

Channels are like selective tunnels allowing ions or molecules to pass based on size and charge, while carriers bind to specific molecules and transport them through a shape change.
carriers: glucose
channel: sodium ions

Question 26

does facilitated diffusion involve the use of chemical energy?

Answer 26

no, it does not because it is a passive process.

Question 27

what is osmosis?

Answer 27

osmosis is the passive movement of water across a semipermeable membrane. it includes movement of water through facilitated or simple diffusion.

Question 28

what is an isotonic solution?

Answer 28

two solutions that have the same concentration of solutes are said to be isotonic.

Question 29

what is a hypertonic solution?

Answer 29

a hypertonic solution is one that has a higher concentration of solutes than another solution. water will leave the cell and it will shrivel.

Question 30

what is a hypotonic solution?

Answer 30

a hypotonic solution is one that has a lower concentration of solutes than another. water will enter the cell and it will lyse/burst.

Question 31

homeostasis and isotonic?

Answer 31

an aspect of homeostasis is ensuring the creation of an environment in which all of the bodys cells are in an isotonic solution. kidneys work for this.

Question 32

concentration gradient in active transport?

Answer 32

atp is required to move a substance across a membrane, with the help of carrier proteins, AGAINST the concentration gradient. imagine a ball going up a slide instead of down.

Question 33

sodium potassium pump?

Answer 33

the sodium potassium pump transports sodium out of a cell while moving potassium into a cell both against their gradients.
- common in nerve cells to maintain electrical gradient.
- 3 sodium out and 2 potassium in.

Question 34

primary vs secondary active transport?

Answer 34

primary active transport uses energy directly from ATP hydrolysis to pump molecules against their concentration gradient across a membrane. Secondary active transport uses the energy stored in an ion concentration gradient (established by primary active transport) to drive the movement of other molecules against their concentration gradient.

Question 35

what is endocytosis?

Answer 35

the cells engulf the substances by wrapping their cell membrane around them forming a vesicle which allows the cell to bring in the substance.

Question 36

what is phagocytosis?

Answer 36

specialized cells like macrophages engulf LARGE particles and then it is digested and broken down inside the cell.

Question 37

what is pinocytosis?

Answer 37

cells take in extracellular fluid and dissolved molecules, helps to absorb nutrients.

Question 38

receptor mediated endocytosis?

Answer 38

cells use specific receptors on their surface to bind to particular molecules and when it binds, the cell engulfs into a vesicle. this is important for CHOLESTEROL OR HORMONES.

Question 39

what is exocytosis?

Answer 39

process of a cell exporting material out of the cell using vesicles.
- nerve cells release neurotransmitters
- endocrine cells release hormones
- immune cells release histamine