BIO QUIZ #2

Question 1

Phospholipid is made of…

Answer 1

• a polar head (hydrophilic) composed of a glycerol and phosphate molecule
• 2 non-polar tails (hydrophobic) made out of fatty acids/hydrocarbon chains

Question 2

A phospholipid is…

Answer 2

Because phospholipids contain both hydrophilic (water-loving) and lipophilic (fat-loving) regions, they are classed as amphipathic

Question 3

Head

Answer 3

• again, a phosphate group attached to glycerol
• hydrophilic = water-loving = attracts water molecules

Question 4

Tail

Answer 4

made of fatty acids/hydrophilic = water fearing / can be saturated or unsaturated

Question 5

Saturated Tails (creates a straight chain)

Answer 5

has as much hydrogen as possible to bond w carbon, meaning there are less double bond between carbon atoms/decreases flexibility & increases density/increases MP & FP *(straight tails = close together = stronger IMF)

Question 6

Unsaturated Tails (creates a kinked chain)

Answer 6

has less hydrogen present to bond w/ carbon, so there are more double bonds between carbon atoms/increases flexibility & decreases density/decreases MP and FP (kinked tails = not close together = weaker IMF)

Question 7

NOTE: The ideal ratio of saturated to unsaturated fatty acids depends on the temperatures that a cell experiences.

Question 8

THE LIPID BILAYER IS SELECTIVELY PERMEABLE AND?

Answer 8

the membrane core is hydrophobic!/hydrophilic substances have low permeability like large polar molecules, charged molecules, & ions/hydrophobic substances pass through easily/permeability also depends on size (water vs. glucose - larger)

Question 9

more on the plasma membrane’s selective barrier nature

Answer 9

the cell can decide what goes in and out of it through simple diffusion and active transport/the selection differs depending on what the cell needs/NOTE: the cell CANNOT stop small hydrophobic particles from diffusing across the membrane

Question 10

EMERGENT PROPERTY OF PHOSPHOLIPIDS (working together)

Answer 10

When put into water, phospholipids self-organize to keep their heads wet and their tails dry.

Question 11

FLUID MOSAIC

Answer 11

• membrane is referred to as a fluid mosaic in which proteins move within the layers of lipids
• fluid part is the phospholipid bilayer; mosaic of proteins
• overall, DYNAMIC

Question 12

Why is it fluid?

Answer 12

• phospholipid bilayer is flexible, allows cellular shape to change
• membrane lipids and some proteins can drift laterally across the membrane (proteins drift slower than lipids/some proteins are attached to the cytoskeleton and cannot move far)
• individual phospholipids are not bonded to each other

Question 13

integral vs. peripheral proteins

Answer 13

integral proteins pass through the lipid bilayer at least once and act as ion channels/pump proteins; partially hydrophobic, can be embedded in one or more phospholipid layers, some are transmembrane w/ hydrophilic ends

peripheral proteins are attached to the surface of the phospholipid bilayer; hydrophilic surface/ca be attached to integral proteins or in the peripheral regions of the bilayer

Question 14

glycoprotein vs. glycolipid

Answer 14

Glycoprotein = a protein which has a carbohydrate molecule covalently bonded to it
Glycolipid = the carbohydrate is attached to a lipid in the membrane
Both involved in cell recognition and adhesion; found in the outer surface of the plasma membrane

Question 15

What are the functions of membrane proteins (JET RAT)

Answer 15

Junction - serves to connect and join cells together (cell adhesion/intercellular joinings)

Enzymes (immobolized) - act as a catalyst for metabolic reactions on or in the cell membrane (electron transport chain)

Transport - responsible for facilitated diffusion using protein channels and active transport using protein pumps

Recognition - acts as a marker for cellular identification

Anchorage (cell adhesion) - attached to the cytoskeleton or extracellular matrix

Transduction (hormone-binding site) - acts as a receptor for peptide-based hormones (like insulin)

Question 16

endomembrane system and membrane fluidity

Question 17

Cholesterol structure

Answer 17

• one polar OH group allows cholesterol to attach to phospholipid heads
• the hydrocarbon tail links with the phospholipid tails b/c they are both hydrophobic

Question 18

Cholesterol is…

Answer 18

amphipathic & a type of lipid; part of a group called steroids

Question 19

Only found in…

Answer 19

animal cells, where they function to maintain integrity and mechanical stability; not found in plants cells b/c they have a rigid cell wall made of cellulose

Question 20

CHOLESTEROL’S ROLE IN FLUIDITY

Answer 20

1. Restricts movement of phospholipids and other molecules - decreases fluidity
2. Disrupts the regular packing structure of hydrocarbon tails of phospholipids; increases fluidity as cholesterol prevents the tails from crystallizing and hence behaving as a solid
3. Reduces permeability for hydrophilic substances like sodium and hydrogen.

Question 21

cholesterol in our blood stream

Answer 21

Fats and cholesterol cannot dissolve in the bloodstream and so are packaged with proteins (to form lipoproteins) for transport
Low density lipoproteins (LDLs) carry cholesterol from the liver to the body (hence raise blood cholesterol levels)
High density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal (hence lower blood cholesterol levels)

The mix of fatty acids consumed as part of a diet directly influences the levels of cholesterol in the bloodstream:
Saturated fats increase LDL levels within the body, raising blood cholesterol levels
Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels
Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels

High cholesterol levels in the bloodstream lead to the hardening and narrowing of arteries (atherosclerosis)
When there are high levels of LDL in the bloodstream, the LDL particles will form deposits in the walls of the arteries
The accumulation of fat within the arterial wall leads to the development of plaques which restrict blood flow
If coronary arteries become blocked, coronary heart disease (CHD) will result – this includes heart attacks and strokes

Question 22

gated ion channels

Answer 22

Some channels in the cell membrane are “gated”: they open/close as a response to something
Neurons have voltage- gated ion channels that respond to changes in potential

more on slide!

Question 23

Endocytosis

White blood cells can engulf bacteria when fighting infection.
Single celled organism like amoeba can engulf bacteria as a food source.

Answer 23

the process by which large substances (or bulk amounts of smaller substances) enter the cell without crossing the membrane

Question 24

Endocytosis explained

Answer 24

The invagination of the membrane creates a flask-like depression which envelopes the extracellular material / the invaginated membrane is then sealed off to form an intracellular vesicle containing the material

Question 25

types of endocytosis

Answer 25

• Phagocytosis: the process by which solid substances are ingested (transported to lysosomes)
• Pinocytosis: the process by which liquid/dissolved substances are ingested (faster entry than through protein channels)
• Receptor-mediated endocytosis: molecules attach to receptors, and when the appropriate amount/combo has been reached, a coated vesicle is created

Question 26

plays an important role in…

Answer 26

nutrition and immunity as well as membrane recycling

NOTE: lysosomes break down and thus disarm many kinds of foreign and potentially pathogenic (cause disease) materials that get into the cell through such extracellular sampling.

Question 27

Exocytosis (releasing hormones/waste)

Answer 27

the process by which large substances LEAVE the cell without crossing the membrane using active transport

1. a vesicle is formed from the Golgi apparatus
2. the vesicle moves towards the membrane and fuses with it
3. Secretion of the vesicle contents

Question 28

Endomembrane system

Answer 28

Functions: exocytosis/transport vesicles/production of lysosomes

The endomembrane system is a group of membranes and organelles in eukaryote cells work together to transport, package and modify proteins. / Creates compartmentalization within cells allowing for cell specialization. / Secreted materials leave the cell through the vesicles.

Question 29

Endomembrane System Pathway

Answer 29

1. Nucleus (transcription DNA to mRNA)
2. rER (translation mRNA to proteins)
3. sER (packages proteins into vesicles)
4. Vesicles (move the proteins towards the Golgi)
5. Golgi modifies proteins
6. Secretory vesicles (secrete); move the vesicles towards the plasma membrane
7. Exocytosis - vesicles fuse with the membrane and the proteins are released

Question 30

SODIUM-POTASSIUM TRANSPORT

Answer 30

• Exchange transport: 3 Na+ out, 2 K+ in
• Net movement: +outside, -in
• Generates electrical potential across membrane (-40 to -70 vM)
• This resting potential is necessary for the function of neurons
• Requires active transport - ATP (needs energy for moving substances from low to high concentration)

STEPS:
1. The interior of the pump is opened to the inside of the axon; 3 Na+ enter the pump and attach to its binding sites
2. ATP transfers one phosphate group from itself to the pump; this changes its shape and closes the interior of the pump.
3. The interior of the pump is opened to the outside of the cell, and so the 3 Na+ are released
4. 2 K+ enter the pump and attach to its binding sites.
5. The binding of K+ cause the release of the phosphate molecule; this changes the pump’s shape - opens interior of pump to the inside of axon
6. 2 K+ are released into the axon. Now, more sodium ions enter the pump again.

Question 31

recall simple diffusion, osmosis, facilitated diffusion, and active transport