1.3 Cells Review

Question 1

What are the similarities among living cells?

Answer 1

Structural features
-all cells are surrounded by a plasma membrane
-all cells has genetic information nucleic acids to transfer heritable information from one generation to the next)
-metabolic processall living cells produce ATP and
use its energy to drive metabolic processes.)
-Genetic process All living things use ribosomes and transfer RNA
molecules during the conversion of the DNA code to protein)
-signaling all living things use small ions, like calcium, for communication purposes).

Question 2

How is bacteria classified?

Answer 2

Genetic information. shape ( spheres, rod shapes, and spiral bacteria) and their affinity to take up certain diagnostic stains.

Question 3

What is a cytoskeleton?

Answer 3

The cytoskeleton is a system of protein filaments (actin filaments (microfilaments),
microtubules, inermediate filaments) in the cytosol of eukaryotic cells that give a cell the
shape and the capacity for movement.

How many? (3 types) the actin microfilament system, the
intermediate filament system that has larger filaments than actin, and microtubules which are the
largest filaments in cells term of their diameter

Question 4

What does amphipathic mean? What kind of molecules are ampiphatic?

Answer 4

• LIPIDS
• It has dual solubility/two domains

The domain that’s called the head, is polar, meaning that the atoms which make up
this domain don’t share electrons freely between them. The imbalance creates regions of positive
and negative charge, which then interacts with water, which is also positively and negatively
charged. Therefore, the head of a lipid molecule is soluble in water, a characteristic known as
hydrophilic. Lipids also have a number of tail regions which are nonpolar, there can be one or
several. Tails are made up of long chains of carbon, linked together by single or double bonds
and the remaining bonds are made with hydrogen. The lipid tails are therefore hydrocarbons.

Question 5

What is the difference between unsaturated and saturated lipids?

Answer 5

If
every bond possible is made with a hydrogen atom, the molecule is said to be saturated.
However, if some of the carbon-carbon bonds are double bonds, a region with fewer linked
hydrogens is created and the molecule is then said to be unsaturated.

Question 6

What are the three most common lipids? p

Answer 6

phosphoglycerids, sphingolipids and sterols.

Question 7

What are glycolipids?

Answer 7

Glycolipids are

molecules created by linking a carbohydrate molecule to the polar head group of a lipid. Coat nerve cells

Question 8

How are phosphoglycerides distinguished?

Answer 8

by their head groups (choline vs, ethanolamine, vs serine)

-phosphatidylcholine, phosphatidyl-serine and phosphatidyl-ethanolamine

Question 9

Which phosphoglyceride has the only negative side?

Answer 9

Phosphotadyl-serine

Question 10

Why two phosphoglycerides are found in the cytosolic side of a cell?

Answer 10

phosphptadyl-serine and phospho-ethanolamine

Question 11

Which phosphoglyceride is found mostly on extracellylar face of cell?

Answer 11

phosphatidyl-choline

Question 12

Why do the cytosolic face of a cell membranes tend to be negatively charged?

Answer 12

b/c phosphotadyl-serine the only lipid with a negative charge tends to be on the cytosolic face in healthy cells. becomes exoplasmic when it dies.

Question 13

How are sphingosine fomred? Which one is the most common?

Answer 13

Sphingosine is built by the addition of the amino acid serine, to a 15 carbon unsaturated fatty
acid chain. One of the most common sphingolipids is sphingomyelin, which is abundant in the
myelin membranes surrounding nerve cell processes.

Question 14

Why do several types of structures

form spontaneously from mixtures of lipids and water? What kind of structures form?

Answer 14

-Because the hydrocarbon tail of lipids is excluded from water

-If a chamber is experimentally created
with two aqueous compartments, lipids will form a bilayer between them, in which polar head
groups face each compartment and the tails are all facing each other

-Small, spherical arrays of lipids can also be formed spontaneously and these are called
micelles. they are formed most easily by lipids having only one
hydrocarbon tail.

-liposomes

Question 15

Why is flip-flop of lipids rare?

Answer 15

because this would involve moving the polar head group of a lipid through
the nonpolar region occupied by the hydrocarbon tails

Question 16

What three factors that can affect the fluidity of biological
membranes?

Answer 16

• Temperature (low = gel-like and high= fluid like). Phase transition temperature (Tm) temp at whic half of the membrane is in the gel phase or half of the membrane is in the fluid phase.
• unsaturated vs saturated (double bonds vs single bonds). Length
• Abundance of sterols

Question 17

at temperatures where a membrane is fluid what does cholesterol do the the membrane fluidity?

Answer 17

At temperatures where
a membrane is fluid, cholesterol reduces membrane fluidity because it counteracts the effect of
the unsaturated hydrocarbon tail. However, because the rigid sterol ring structure inhibits close
contact of lipids, cholesterol can also prevent gelling of membranes and therefore the addition of
cholesterol actually lowers the phase transition temperature of a membrane.

Question 18

How are lipids rafts produced?

Answer 18

functionally specialized domain are lipid rafts. adding the addition of one part cholesterol to a homogeneous cell

Question 19

What is the dual role of cholesterole?

Answer 19

Membranes are less permeable

-Membranes are less fluid at high temps, but also gel at lower temps

Question 20

What is glycosylation?

Answer 20

mono or poly
saccharides are added to the lipid. In animal cells, these glycolipids are modifications of
sphingosine.

Question 21

how are Gangliosides formed?

Answer 21

formed by linking sphingosine to a more complex polysaccharide. One or more of the polysaccharide units is always a sialic acid in gangliosides.

Question 22

How can proteins interact with membranes?

Answer 22

Integral proteins: transmembrane proteins (hydrophobic interactions attach it to membrane)

Anchored proteins: cytosolic and non-cytosolic (attached through covalent attachment to glycolipids)

Peripheral proteins: cytosolic and non-cytosolic ( loosely
attached, either to the lipid membrane surface or to another more tightly associated protein)

Question 23

Channel forming proteins are usually what kind of protein?

Answer 23

Integral/transmembrane

beta barrels and
they allow regulated movement of material through a pore that’s in the middle of the barrel

Question 24

y, proteins found on the outside of cells are frequently

found attached to what lipid?

Answer 24

GPI (GPI link)

Question 25

How do one distinguish between peripheral proteins and integral proteins?

Answer 25

Peripheral proteins are released by high concentration of salt, which disrupts ionic
interactions

Detergents are needed to release integral proteins and hydrocarbon-anchored protein

Question 26

If membrane proteins are glycosylated, carbohydrates will be on what side of the cell?

What if they have disulfide?

Answer 26

exoplasmic. With disulfide also on the exoplasmic. Sulfhydryl groups in cytosol side do not form disulfide bonds b/c cytosol is a reducing environment

Question 27

What is the cell fusion method?

Answer 27

type of
experiment that can be used to study the movement of proteins within a membrane. Two
different types of cells, each with unique membrane associative proteins are fused to create a
single, larger cell. Initially, proteins unique to the individual cells are found in localized areas of
the fused cell, but they rapidly disperse over the entire cell surface.

Question 28

What are the three ways to study movement of proteins?

Answer 28

cell fusion

-frap and flip

Question 29

Describe FRAP

Answer 29

With this
method, the area that is bleached is small and the larger surrounding cell contains large amounts
of unbleached protein. Immediately after the bleaching event, the bleached area would have no
proteins that were fluorescent, however over time, the bleached proteins begin to move out of the
bleached zone and unbleached subunits move into it and you can monitor this recovery of
fluorescence in the bleached area with a video camera.

the recovery curve eventually reaches its initial value, before bleaching,
which means that the area of the bleach was relatively small and the movement of the proteins
was not restricted in any way.

Question 30

Describe FLIP

Answer 30

With this
method, one area of the cell is bleached over and over, and the intensity of fluorescence in a
neighboring area is monitored, instead of the fluorescence in the area that’s being bleached. If
fluorescently labeled proteins can move between the two regions, there’s going to be a gradual
loss of fluorescence in the area that’s not being bleached and this is because the subunits are
moving into that bleached area and being bleached. If all of the fluorescently labeled proteins in
a cell move freely, they will all eventually move into that area and be bleached and the entire cell
will eventually become dark, as shown in this diagram. The method does have some advantages
over FRAP. For example, the fluorescent proteins which are being looked at or measured are not
the ones that are being exposed to the potentially damaging laser light.

Question 31

cells have several strategies of further restricting the movement
of proteins to form specialized domains. What are these strategies?

Answer 31

aggregation
tethered from the outside
tethered from the inside
tethered to another cell

proteins may selfaggregate , or be linked together on either the outside or inside of cells by
other proteins. Proteins can also be localized at contact points between
cells, like that shown in or between a cell and the surface that it’s attached to (tight junctions)

lipid rafts can also restrict movement of proteins

and corrals also restrict movement corrals are created by cytoskeleton filament protiens

Question 32

In terms of concentration how does material move across membrane?

Answer 32

things to move across the membrane, from where
they are more concentrated, to where they are less so. This movement requires no energy, but it
is also uncontrolled.