BSC2010 Exam #2

Which of the following types of molecules are the major structural components of the cell membrane?

phospholipids and proteins

______helps to stabilize the structure of the plasma membrane.

cholesterol

Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane?

water, glucose, hydrogen ion

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

There is a greater concentration of solute outside the cell.

hypertonic solution

A cell will gain ____ when placed in a hypotonic solution.

water

A cell will lose water when placed in a ______ solution.

hypertonic

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

the types of transport proteins in the membrane

Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.

lipids, carbon dioxide, water, oxygen

Which of the following molecular movements is due to diffusion or osmosis?

When a plant cell is placed in concentrated salt water, water moves out of the cell.

The contents of a red blood cell are _____ to distilled water.

hypertonic

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?

Water molecules move between the two solutions, but there is no net movement of water across the membrane.

Which of the following factors does not affect membrane permeability?

The polarity of membrane phospholipids

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar.

True or false? Osmosis is a type of diffusion.

true

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature

Which of the following particles could diffuse easily through a cell membrane?

Oxygen (O2)

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

true

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic

large molecules assembled from glycerol and fatty acids by dehydration reactions

fats

bond between hydroxyl carboxyl groups

ester linkage

three fatty acids joined to gylcerol by ester linkages

triacylglycerol

nonpolar C-H bonds in the long hydrocarbon skeleton makes fats ____

hydrophobic

hydrocarbons are hydrophobic because C-H bonds are non-polar

true or false

true

fatty acids can vary by

-length

-# and location of double bonds

-saturated vs. unsaturated

saturated fatty acid

no C-C double bonds

-hydrogen at every possible location

-straight chain

-solid at room temp

-cardiovascular disease

lipids

-ester linkage

-hydroxyl/carboxyl

proteins

-peptide bond

-carboxyl/amino

carbohydrates

-glycosidic linkage

-hydroxyl/hydroxyl

unsaturated fatty acids

-one or more C-C double bonds

-formed by removal of H atoms from the carbon skeleton

-kinked structure at double bond

-liquid at room temp

-better for cardiovascular health

fats are used for?

energy storage

insulation

cushion vital organs

functions of other lipids

humans and other mammals store fats as long-term energy reserves in ____

adipose tissue

____ are major components of cell membranes

phospholipids

phospholipids

-glycerol

-2 fatty acids

-phosphate group at 3rd position of glycerol

-phosphate group is negatively charged (functional groups)

-other smaller groups may be attatched to the phosphate group

hydrocarbon chain of fatty acid is ___

hydrophobic

charges make phosphate group, etc ___

hydrophilic

___ molecules- both hydrophobic and hydrophilic characters

amphipathic

arrangement of membrane phospholipids

-hydrophobic "tails" from core

-hydrophillic "heads" on outside

. Barrier between cell and external environment

. Barrier between cell and internal organelles

lipid bilayer

membranes are ___ and ___

fluid

mobile

membrane liquid bilayer stays together through ___ interactions.

-non-covalent (weak)

hydrophobic

lipid bilayer membranes are "fluid" because membrane molecules move (diffuse) laterally in the membrane

true or false

true

fluidity is affected by ___ and ___

composition and temperature

membranes with ____ fatty acids are more fluid

unsaturated

the structure of phosphlipid hydrocarbon "tails" in a lipid bilayer membrane does not influence the membrane's function

true or false

false

____ affects membrane fluidity

-reduces fluidity at warm temps

-maintains fluidity at cool temps

cholesterol

lipids with a carbon skeleton consisting of four fused carbon rings

-include cholesterol and certain hormones

steroids

-component of cell membranes

-precursor from which all other steroids are synthesized

cholesterol

cholesterol is always "bad" for your health

true or false

false

separates the living cell from its nonliving surroundings

plasma membrane

membranes allow some substances to cross more easily than others

selective permeability

____ are mosaics

-collage of diff. proteins embedded in the fluid matrix of the lipid bilayer

membranes

what is a fat or triacylglycerol?

a lipid made of 3 fatty acids and glycerol

what are the similarites and differences between a triacuglycerol molecule and a phospholipid molecule?

-tria- has 3 fatty acid chains

-phospholipid has 2 fatty acid chains

-both formed starting with glycerol

-phospholipid has the phosphate group instead of a 3rd hydrocarbon.

what is meant by "fluid mosaic" model of cell membranes?

-"fluid"- refers phospholipids being able to diffuse around and move around freely in their half of the liquid bilayer. not covalently attatched to the adjacent phospholipids.

. extremely unlikely that a phosphoplipid would flip over to other half of bilayer

. proteins in membrane can also move around

-"mosaic"- diff kinds of proteins. phospholipds are not all same. some have diff. tails. could be saturated/unsaturated. could have diff. # of double bonds. all different molecular arrangements that add variety. VARIETY

according to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

they can move laterally along the plane of the membrane

fluid mosaic model of membrane structure

-hydrophilic regions of proteins and phospholipids in maximum contact with water.

-hydrophobic regions in nonaqueous environment

lipids can move ___ and ____ throughout the membrane

laterally and rapidly.

-can do so because they are small molecules

membrane proteins move ___

slowly.

-because they are large molecules

some proteins

-move in a directed manner

-never move at all

membranes have distinct inside and outside faces.

two membrane layers may differ in:

-lipid composition

-orientation of proteins

-outer surface also has carbohydrates

____ begins during synthesis of new membrane

ex. some plasma membrane proteins reinforce cell shape

asymmetry

_____ are important for cell-cell recognition

membrane carbohydrates

cells can distinguish one type of neighboring cell from another

-important for orginization of cells as tissues and organs during development (nervous system)

-important for rejection of foreign cells in immune system

molecules in membrane are modified with carbohydrates

-glycoproteins

-

the inside face of a cells membrane is chemically similar to the outside because membrane molecules easily flip from one side to the other

true or false

both statements false

all of an organisms chemical reactions--> an emergent property

metabolism

alteration of molecules in steps

metabolic pathway

-chem. reactions are organized into metabolic pathways

breakdown of complex molecules

-release energy

catabolic pathways

build complex molecules

-consume energy

anabolic pathways

-energy released by catabolic pathways drives anabolic pathways

glycogen formation in muscle of the liver is an example of anabolic metabolism

true or false

true

study of energy transformations

thermodynamics

first law of thermodynamics

energy can be transferred or transformed, but cannot be created or destroyed

second law of thermodyamics

every energy transfer or transformation increases the disroder (entropy) of the universe

entropy

measure of disorder or randomness

much of the increased entropy of the universe takes the form of increasing ____

heat

free energy change(DeltaG)

portion of a system's energy that is able to perform work

-at equlibrium deltaG=0 (cell is dead...)

biological structures (cells, organs, organisms) form spontaneously

true or false

false

exergonic reaction can proceed __-

spontaneously

-(deltaG <0) is negative

endergonic reaction cannot proceed ____

spontaneously

(deltaG >0) positive

open systems

can exchange energy (and often matter) with their surroundings -system does not reach equlibrium

what are living organisms?

open systems

whole goal of metabolism is to produce?

ATP

____ synthesizes most of our ATP for us

mitochondria

ATP

energy for cellular work

what makes up ATP?

hydroxyl

adenine

ribose

phosphate

___ drives cellular work, transport, mechanical work, chemical.

ATP

changes reaction rate without being consumed (changed)

catalyst

___ are biological catalysts

enzymes

a catalytic protein

enzyme

a catalytic RNA

ribozyme

enzymes speed reactions by lowering

Ea (activation energy)

enzymes do not change ___

deltaG

enzymes are ____ specific

substrate

reactant that binds to an enzyme

substrate

substrate binds to ____ of enzyme

active site

-structure of active site --> specific for substrate bindingcatalysis

substrate converted to ___(may be reversible)

products

____ is an enzymes catalytic center

active site

substrates are typically held in the active site by ___ interactions

weak

catalysis

-thousands of reactions per second

-involves -R groups of a few amino acids at active sire

-enzymes unaffected by the reaction :reusable (catalyst!)

most metabolic enzymes catalyze reactions in ____

both forward and reverse directions