Cell Membrane

Question 1

the cell membrane model that says the plasma membrane is neither rigid nor static in structure but is highly flexible and can change its shape and composition through time.

Answer 1

fluid mosaic model

Question 2

made of two layers of
lipids that have hydrophilic
heads and hydrophobic tails.

• Most abundant lipids in membranes
• widely accepted

Answer 2

phospholipid

Question 3

if phospholipids have hydrophilic heads and hydrophobic tails, what is it called?

Answer 3

amphiphatic

Question 4

how many heads and tails does a phospholipid have

Answer 4

1 head, 2 tails

Question 5

The ______ of a phospholipid is made of an alcohol and phosphate (PO4) group, while the ______ are chains of fatty acids. (hydrocarbon, CH3, CH2)

Answer 5

head, tails

Question 6

This head is connected to a _________ with two hydrophobic tails called fatty acids.

Answer 6

glycerol

Question 7

The cell membrane consists of a diversity of ________, __________, and __________

Answer 7

lipids, carbohydrates, proteins

Question 8

fatty acids that have single bonds (palmitic acid)

Answer 8

saturated fatty acids

Question 9

(true or false) The individual lipid molecules
are able to move in their own monolayer.

Answer 9

true

Question 10

fatty acids that have double bonds (linoleic acid)

Answer 10

unsaturated fatty acids

Question 11

movement of individual lipids in the cell membrane

Answer 11

• lateral - going from one place to another laterally (most abundant)
• rotation - the movement of lipid on its own axis
• flip flop - moving from one side to the side (not lateral, rarely occurs)
• flexion - more like a result of a movement, so that a lipid can move freely

Question 12

other than cholesterol, what helps in maintaining the membrane’s fluidity

Answer 12

the presence of double bonds

Question 13

it is an essential component of animal cell plasma membranes. it modulates the bilayer structure of biological membranes in multiple ways. It changes the fluidity, thickness, compressibility, water penetration, and intrinsic curvature of lipid bilayers.

Answer 13

cholesterol

Question 14

at warm temperature, the membrane ________, hence the cholesterol _________

Answer 14

expands, restrains movement

Question 15

at cool temperature, the membrane ________, hence the cholesterol ______________

Answer 15

compresses, maintains its fluidity by preventing tight packing

Question 16

“good” cholesterol, absorbs cholesterol and carries it back to the liver. The liver then flushes it from the body. High levels of this cholesterol can lower your risk for heart disease and stroke.

Answer 16

high-density lipoprotein

Question 17

cholesterol is only present in _______

Answer 17

animals

Question 18

sometimes called “bad” cholesterol, makes up most of your body’s cholesterol. High levels of this cholesterol raise your risk for heart disease and stroke.

Answer 18

low-density lipoprotein

Question 19

synthesized by plants only, helps maintain its temperature, helps in lowering LDL in the blood

Answer 19

phytosterol

Question 20

believed to have very similar functions to those of sterols in the membranes of animals and plants in that they can intercalate into phospholipid bilayers and modulate the fluidity of membranes by interacting with their complex lipid components. (in bacteria)

Answer 20

hopanoid

Question 21

a function of the membrane that means it can:

• keep desirable substances in the cell and also keep undesirable substances out. (acid in the stomach)
• Hydrophobic core prevents the transport of ions and polar molecules (it selects what goes in and out)

Answer 21

• define the boundaries
• act as permeability barriers

Question 22

can a small and non-polar molecule pass through the cell membrane? (O2, CO2, steroid hormones, N2)

Answer 22

yes

Question 23

can a small polar molecule pass through the cell membrane? (H2O, ethanol, glycero;)

Answer 23

yes but slow

Question 24

can a large non-polar molecule pass through the cell membrane? (Carbon Rings)

Answer 24

yes but slow

Question 25

can a large polar molecule pass through the cell membrane? (Glucose, Ions, amino acids, glucose nucleosides)

Answer 25

no, needs transmembrane proteins

Question 26

Molecules that require energy expenditure
for them to be transported across the membrane

Answer 26

polar molecules, large molecules (glucose, amino acids, nucleic acids, proteins)

Question 27

Molecules that are free to move across the membrane

Answer 27

lipids, alcohol, small molecules (oxygen, nitrogen, CO2, water)

Question 28

The plasma membrane forms the physical barrier between the cytoplasm and extracellular space, allowing for _______________ necessary for life to occur
(thylakoid in the chloroplast that is in charge of light-dependent reaction of photosynthesis)
(energy transduction - one type of energy is converted into another type)

Answer 28

biochemical reaction

Question 29

Cells in multicellular organisms are in ________ with other cells

In plants, this is done through __________
(example: bladder, for urine, membrane maintains elasticity?)

Answer 29

contact, plasmodesmata/gap junctions

Question 30

apoplastic pathway in plants

Answer 30

water is transported from root hair to xylem through the cell wall of intervening cells.

Question 31

symplastic pathway in plants

Answer 31

water moves across the symplast, which consists of the cytoplasm and plasmodesmata (minute connections between the cytoplasm of adjacent cells).

Question 32

cell membrane contains the protein molecules that act as _______ to detect extracellular signals

Answer 32

receptors

Question 33

a protein receptor that keeps you awake

Answer 33

caffeine

Question 34

a protein receptor that makes you sleep

Answer 34

adenosine

Question 35

the cell membrane has ________________ - proteins that transport substances across biological membranes.
- can either be channel or carrier protein
- water - aquaporin

Answer 35

transport proteins

Question 36

a _______________ has a channel through which a water molecule or a specific molecule can pass

Answer 36

channel protein

Question 37

a _______________ alternates between two shapes, moving a solute across the membrane during the shape change

Answer 37

carrier protein

Question 38

membrane proteins

Answer 38

transport, adhesion, recognition, receptor

Question 39

______________ fasten adjacent cells together in animal tissues.

Answer 39

adhesion proteins

Question 40

_____________ proteins help in recognition when
the body is being invaded by pathogens so that
the necessary immune response may be
triggered. (glycoprotein, glycolipid)

Answer 40

recognition

Question 41

_____________have certain shapes that allow only specific molecules to bind to them. they transmit information to the cell by sensing the presence or absence of their cognate ligands, a process that often involves complex, multi-step pathways.

Answer 41

receptor proteins

Question 42

integral membrane proteins found in all living organisms from bacteria to humans. they are mainly involved in the transmembrane diffusion of water as well as various small solutes in a bidirectional manner are widely distributed in various human tissues

they transport water across cell membranes in response to osmotic gradients created by active solute transport.

Answer 42

aquaporin

Question 43

a type of membrane protein that is permanently attached to the biological membrane. they reside within the bilayer membranes that surround cells and organelles, playing critical roles in the movement of molecules across them and the transduction of energy and signals.

function:
- channeling or transporting molecules across the membrane. Others as cell receptors.

Answer 43

integral membrane protein

Question 44

membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins or penetrate the peripheral regions of the lipid bilayer.

• allows cells to coordinate and communicate using networks of proteins and reactions.

Answer 44

peripheral membrane protein

Question 45

the third major component of plasma membranes. In general, they are found on the outside surface of cells and are bound either to (peripheral) proteins (forming glycoproteins) or to lipids (forming glycolipids).

these carbohydrates form distinctive cellular markers, sort of like molecular ID badges, that allow cells to recognize each other. These markers are very important in the immune system, allowing immune cells to differentiate between body cells, which they shouldn’t attack, and foreign cells or tissues, which they should. (for recognition)

Answer 45

carbohydrates

Question 46

The phospholipid bilayer is ____________________ because it only allows certain substances into cells while keeping others out. The size and the chemical nature of the molecules are important determiners of the permeability of the membrane to certain substances.

Answer 46

selectively permeable