Chapter 5 - Membrane Structure

Question 1

What is selective permeability?

Answer 1

Selective permeability is easy permeability for some but not all substances.

Question 2

Why is selective permeability important to cells?

Answer 2

It allows them to control what substances go in and out during chemical exchanges

Question 3

What does amphipathic mean?

Answer 3

Has both a hydrophilic and hydrophobic side

Question 4

T or F: The tails of a phospholipid are hydrophobic

Answer 4

True

Question 5

What is the role of cholesterol in the cell membrane?

Answer 5

Provides fluidity - restricts movement at high temperatures so they stay together, hinders close phospholipid packing at cold temperatures - keeps it from becoming a gas/being too fluid or from solidifying

Question 6

Cells can change the ratio of saturated to unsaturated fatty acid tails in their phospholipid bilayers based on their environment. how is this good?

Answer 6

they can maintain the optimal amount of membrane fluidity - if it’s too cold, add more unsaturated, if it’s too hot, add more saturated

Question 7

Why add saturated fats in hot weather?

Answer 7

They can pack together more tightly because of their lack of a double bond, so they can solidify more easily and aren’t excessively fluid

Question 8

Why add unsaturated fats in cold weather?

Answer 8

They can’t pack together as tightly because they have a double bond between carbons, forming a kink. This means they don’t solidify as easily.

Question 9

What does a glycoprotein look like and do?

Answer 9

It’s on the extracellular part of the bilayer and it looks like a super dead tree. It’s used for cell to cell signals, identification, and form holding cells together

Question 10

What does an integral protein look like/do?

Answer 10

It allows the passage of hydrophilic substances into the bilayer. It has hydrophobic and hydrophilic regions to keep it stuck in there and allow hydrophilic stuff to pass through.

Question 11

What does a peripheral protein look like/do?

Answer 11

It’s kind of a blob that’s stuck onto the phospholipid bilayer. It supports, communicates, has enzymes, and plays a role in molecule transfer.

Question 12

What does cholesterol in the phospholipid bilayer do?

Answer 12

It maintains fluidity

Question 13

What do the phospholipids in the phospholipid bilayer look like and do?

Answer 13

o== they are amphipathic and make up the bilayer and make it semipermeable and protect the cell

Question 14

What does the hydrophilic region of the phospholipid bilayer do?

Answer 14

Defense, cell comms, lets them not be like “ew get away from me” in an aqueous environment, electrostatic interactions with water

Question 15

What does the hydrophobic region of a phospholipid bilayer do?

Answer 15

good pbarrier for charged and polar substances because they can’t pass through easily

Question 16

Why are some regions of membrane proteins hydrophilic and hydrophobic?

Answer 16

corresponds with bilayer + stuff it’s transporting

Question 17

Describe the transport function of a membrane protein.

Answer 17

Moves charged particles in and out of the cell, is specific

Question 18

Describe the enzymatic activity function of a membrane protein.

Answer 18

catalyzes chemical reactions

Question 19

describe the signal transduction function of a membrane protein.

Answer 19

has a binding site with complimentary shape with a chemical messenger like a hormone - may make the protein change shape to send message inside by binding to a cytoplasmic protein (I just know this will be your favorite card, sarah)

Question 20

describe the cell to cell recognition function of membrane proteins

Answer 20

they’re like id tags where they’re recognized by membrane proteins of other cells, but they’re kinda short lived.

Question 21

describe the intercellular joining feature of membrane proteins

Answer 21

membrane proteins of adjacent cells may hook together in various kinds of junctions (gap or tight) and it holds cells together and is less short lived

Question 22

Describe the attachment to cytoskeleton and ECM function of membrane proteins

Answer 22

Elements of the cytoskeleton may noncovalently bond to membrane proteins. this helps maintain cell shape, stabilizes their location, and can coordinate extra and intra cellular changes.

Question 23

Where are phospholipids made?

Answer 23

Endoplasmic reticulum (i would say smooth)

Question 24

What is the process for getting membrane parts made and to the membrane?

Answer 24

membrane components synthesized in er (both), transported to golgi apparatus, modified, transported to plasma membrane in vesicles (which have their own plasma membrane lol) and are secreted into the plasma membrane.

Question 25

Why can oxygen and carbon dioxide diffuse easily through the lipid bilayers while glucose and water need to use proteins to cross the cell membrane?

Answer 25

Oxygen and CO2 are small and nonpolar. Glucose and water are hydrophilic and polar, so they get repelled by the tails. Also glucose is kinda big.

Question 26

What channel protein transports water?

Answer 26

Aquaporin

Question 27

Describe a channel protein.

Answer 27

Channel proteins act as a tunnel that molecules like water can use to pass through a membrane. They have hydrophilic channels (though that might depend on what it’s transporting). Sometimes they’re gated, sometimes not.

Question 28

Describe a carrier protein.

Answer 28

Carrier proteins change shape to let contents in or out and can act as barriers since they don’t let things just go whooshing on through.

Question 29

How do ions like H+ get through the membrane?

Answer 29

Active transport with a protein because there is no way in heck that charge will be allowed by the tails.

Question 30

Define diffusion

Answer 30

net movement of particles form an area of high to low concentration down the concentration gradient

Question 31

define concentration gradient

Answer 31

a region of space over which the concentration of a substance changes (high and low)

Question 32

define passive transport

Answer 32

a substance diffuses down its concentration gradient across a membrane

Question 33

define osmosis

Answer 33

net movement of water from an area of higher water potential/lower solute concentration to an area of lower water potential/high solute concentration - diffusion but water

Question 34

define isotonic

Answer 34

solution with same concentration of solute and water (as whatever you put in it, not like 1 part solute to 1 part water)

Question 35

define hypertonic

Answer 35

solution with a high solute and low water concentration

Question 36

define hypotonic

Answer 36

a solution with a high water and low solute concentration

Question 37

define turgid

Answer 37

sturdy/stiff - this is what happens when the vacuole pushes against the cell wall, causing high turgor pressure.

Question 38

define flaccid

Answer 38

floppy and limp - the cytoplasm and vacuole start pulling away from the cell wall (membrane comes too) and turgor pressure decreases

Question 39

define plasmolysis

Answer 39

wilting - the cytoplasm and vacuole really pull away from the cell wall and there’s practically no turgor pressure.

Question 40

What happens to a plant and animal cell in a hypotonic solution?

Answer 40

Plant cell - turgid because turgor pressure is high and the cell wall is pushed against.
Animal cell - lysed (burst) and spherical before that because there’s too much water inside and no cell wall to hold it in

Question 41

What happens to a plant and animal cell in an isotonic solution?

Answer 41

Animal cell - bioncave/perfectly happy if not a blood cell because water goes in and out at the same rate
Plant cell - flaccid (but not that flaccid) because there isn’t enough water in that thing to keep turgor pressure up

Question 42

What happens to a plant and animal cell in a hypertonic solution?

Answer 42

Plant cell - gets plasmolyzed because too much water is leaving and the cell membrane (and everything inside) is pulling away from the cell wall
Animal cell - gets cretnated/shriveled because not enough water

Question 43

What prevents lysis in plant cells?

Answer 43

cell walls

Question 43

What prevents lysis in freshwater protista LIKE THE PARAMECIUM???

Answer 43

ALL HAIL PARAMECIUM
They have a contractile vacuole that pumps out water from the PARAMECIUM’s body

Question 44

Describe facilitated diffusion and give examples

Answer 44

Molecules diffuse across the phospholipid membranes with the assistance of channel and carrier proteins. For example, water uses facilitated diffusion with aquaporins.

Question 45

Would CO2 use facilitated diffusion to leave a cell?

Answer 45

No. It’s small and nonpolar and can diffuse through the membrane without a protein.

Question 46

How is ATP used in active transport?

Answer 46

Energy in the form of ATP is expended to move a substance against their concentration gradient

Question 47

Describe the sodium potassium pump.

Answer 47

3 sodium ions pumped out with atp! This makes it want 2 potassium ions pumped in without the need for more ATP! I know we established that these proteins are specific so it’s pretty cool! Here’s the even cooler part! Sodium wants to go in bc gradient and charge difference, but potassium’s gradient and charge difference conflict! So, it follows the ion charge until the concentration is REALLY strong! Then, it kinda stops moving (or goes in and out at the same rate) and establishes the K+ equilibrium potential! (which is sometimes the membrane potential)

Question 48

How is glucose transported through a membrane?

Answer 48

Facilitated diffusion with carrier protein

Question 49

How is water transported through a membrane?

Answer 49

Facilitated diffusion with channel protein

Question 50

How is sodium transported through a membrane?

Answer 50

active transport with a carrier protein (some need energy and shouldn’t quite be thought of in the same way as others)

Question 51

How is oxygen transported through a membrane?

Answer 51

Simple diffusion

Question 52

Describe exocytosis

Answer 52

vesicle that wants to leave cell gets transported to the edge, fuses to it, opens up, lets the stuff out, and joins the membrane or pinches off and leaves.

Question 53

Describe endocytosis

Answer 53

Includes phagocytosis (big) and pinocytosis (small) - stuff outside membrane comes close to cell membrane, membrane invaginates (makes dimple), pinches it off with stuff inside with the help of specialized proteins, and then the particles make their way into the cell in their brand new vesicle.

Question 54

Are endocytosis and exocytosis active or passive?

Answer 54

Active - require energy

Question 55

What is cytosol?

Answer 55

Cytoplasm goo.