Block 1 Learning Objectives

Question 1

Mitochondria

Answer 1

generates most of the ATP (chemical energy) needed to power the cells biochemical reactions

Question 2

Plasma membrane

Answer 2

cell membrane serves as a clear boundary between the internal and external environments of the cell

Question 3

Nucleus

Answer 3

repository for genetic information and as the cells control center. DNA replication, transcription and RNA processing all take place within the nucleus

Question 4

Golgi apparatus

Answer 4

helps to process and package proteins & lipid molecules. Especially proteins that are destined to be exported from the cell.

Question 5

Ribosomes

Answer 5

main site of protein synthesis within the cell, reads the mRNA sequence and translates that genetic code into a specified string of amino acids which grow into long chains that fold to form proteins

Question 6

Lysosomes

Answer 6

Primary function is to break down excess or worn out cell parts. They may also be used to destroy invading viruses and bacteria. They also aid in apoptosis as a self destruction mechanism

Question 7

Peroxisomes

Answer 7

provide a compartment for oxidation reactions and are involved in lipid biosynthesis.
In animal cells, cholesterol and dolichol are synthesized here and in the ER.
In the liver, they are involved in the synthesis of bile acids, which are derived from cholesterol

Question 8

homeostasis

Answer 8

self regulating process by which biological systems maintain stability while adjusting to changing external conditions

Question 9

Endocrine communication

Answer 9

communication over long distances thru the bloodstream

Question 10

Paracrine communication

Answer 10

neighboring cell communication

Question 11

Autocrine communication

Answer 11

cell communicating within itself

Question 12

Phospholipids (glycerophospholipids)

Answer 12

• Amphipathic (containing both hydrophilic and hydrophobic parts)
• MAIN constituent of plasma membrane
• Glycerol backbone … (see slides its all there)
• Carbon tail = hydrophobic
• Naturally form spheres that “hide: the hydrophobic tail from water

Question 13

Sphingolipids

Answer 13

Amphipathic
Sphingosine backbone (1 tail) + 1 fatty acid tail in amide linkage and polar head group

Question 14

Cholesterol

Answer 14

Sterol, impacts the fluidity of the membrane (ring structure) does not go all the way through, wedges in one of the leaflets in a particular orientation

Question 15

Which part of the plasma membrane is hydrophobic?

Answer 15

Carbon tail of bilayer

Question 16

Peripheral membrane protein

Answer 16

don’t go through the membrane, but they were anchored to another protein

Question 17

Integral membrane protein

Answer 17

proteins that go all the way or part of the way through the lipid bilayer (aka part of their structure is hydrophobic and part of their structure is hydrophilic)

Question 18

Explain the dimension of a plasma membrane and its relationship to lipid structure

Answer 18

The dimension of the lipid constituents determines the thickness of the bilayer

Question 19

Potassium inside vs. outside cell

Answer 19

high inside, low outside

Question 20

Calcium inside vs. outside cell

Answer 20

high outside, low inside

Question 21

Sodium inside vs. outside cell

Answer 21

high outside, low inside

Question 22

Cytoplasmic sodium vs extracellular sodium

Answer 22

Cytoplasmic sodium concentration is lower than extracellular concentration.

Question 23

Cytoplasmic potassium vs extracellular potassium

Answer 23

Cytoplasmic potassium concentration is higher on the inside. At any given time the potassium channels are almost always open and therefore the cell’s membrane potential is based on the potassium ions more than the other ions.

Question 24

Ion gradients

Answer 24

• Sodium-potassium pump makes these gradients happen (3 Na+ out, 2 in K in)
• The Na,K-ATPase develops and maintains steady state ion gradients for ALL cells.
• Ions are not in equilibrium bc this requires energy to maintain gradients
• Energy comes from hydrolyzing ATP

Question 25

Membrane permeability

Answer 25

• Defined by ion channels (which ones are present or open; NOT by ion concentration)
• K+ channels are present in all cells so K+ ions leak out; if you ever have to guess, go with the potassium they are usually open and plentiful!

Question 26

Steady state vs. equilibrium

Answer 26

• Steady state is when energy is put in to maintain a higher free energy state
• Equilibrium is when there is no energy put in to maintain balanced conditions

Question 27

Energy cost of maintaining ion concentration gradients

Answer 27

The energy to maintain these concentration gradients comes from hydrolyzing ATP

Question 28

Hyperpolarizing effect of closing/opening sodium or potassium channels

Answer 28

Hyperpolarizing is when the potassium channels open causing the membrane voltage to become more negative

Question 29

Depolarizing effect of closing/opening sodium or potassium channels

Answer 29

Depolarizing is when the sodium channels open causing the membrane voltage to become more positive

Question 30

Nernst equation

Answer 30

calculates the membrane potential when an ion is at equilibrium (ie when chemical and electrical forces are equal and opposite

Question 31

Goldman equation reflects the real situation where…

Answer 31

• Sodium ions and chloride ions also contribute to the membrane potential
• Ion permeabilities determine the relative influence of each ion on the membrane potential

Question 32

Two important parameters of the Goldman equation

Answer 32

ion permeabilities and ion gradients

Question 33

Voltage-gated

Answer 33

Opened by depolarization (membrane becoming less negative).

Question 34

Chemical “ligand” gated

Answer 34

Opened when a signal molecule binds to the channel protein

Question 35

Mechanically-gated

Answer 35

Open when membrane get stretched

Question 36

threshold for the neuronal action potential

Answer 36

Action potential is an all or nothing event. Must be depolarized to a specific threshold to occur.

Question 37

Absolute refractory

Answer 37

Na channels need to be reset causing a period when the membrane CANNOT be re-stimulated to produce another AP

Question 38

Relative refractory

Answer 38

K needs to be reset causing a period where another AP CAN be produced but it takes a larger than normal stimulus.

Question 39

Origin of graded potential

Answer 39

Dendrites and cell body

Question 40

Origin of action potential

Answer 40

Trigger zones and propagate along axon

Question 41

Types of graded potential channels

Answer 41

Ligand or mechanical

Question 42

Types of action potential channels

Answer 42

Voltage gated for Na and K

Question 43

Conduction of graded potentials

Answer 43

Not propagated - localized and only permits a few micrometers of communication

Question 44

Conduction of action potentials

Answer 44

Propagate → longer distance communication

Question 45

Amplitude of graded potentials

Answer 45

Varies from less than 1 mV to over 50 mV

Question 46

Amplitude of action potentials

Answer 46

All or none; about 100 mV

Question 47

Duration of graded potentials

Answer 47

Ranges from msec to several minutes

Question 48

Duration of action potentials

Answer 48

0.5 to 2 msec

Question 49

Polarity of graded potentials

Answer 49

Hyperpolarizing or depolarizing

Question 50

Polarity of action potentials

Answer 50

ALWAYS depolarizing phase followed by repolarization and return to resting MP

Question 51

Refractory period of graded potential

Answer 51

Not present → allows for spatial and temporal summation

Question 52

Refractory period of action potentials

Answer 52

Present → summation cannot occur

Question 53

Explain the two factors that influence the velocity of an action potential

Answer 53

1. Size diameter of the axon. Larger diameter axons have a higher conduction velocity, they send signals faster.
2. Myelination speeds conduction velocity.