Bio 3 Exam 1

The resting potential of a typical eukaryotic cell is _______ mV.

-60

N-linked oligosaccharides are added in the _______ and modified in the _______.

ER; Golgi

Which interaction is MOST important in enhancing the solubility of macromolecules in water?

H bonds

Which of the following are involved in forming the tertiary structure of proteins?

H bonds Hydrophobic interactions Ionic bonds

The light microscope was used to observe the cellular structure of cork by _______, who named the chambers "cells."

Hooke

Which of the following is not a destination for vesicles leaving the Golgi apparatus?

Mitochondria

Which of the following classes of amino acids is buried within the folded structure of the protein?

Nonpolar

The MOST electronegative atoms typically present in biological molecules are ____ and ____.

O, N

Organisms that evolved the ability to use H2O as a donor of electrons and hydrogen for the photosynthetic conversion of CO2 to organic compounds radically changed Earth by producing

O2

In the "pulse-chase" experiment, Palade and colleagues studied the pathway taken by newly secreted proteins in pancreatic acinar cells by labeling them with radioactive amino acids, removing unused label, and determining their location within the cells at various time points. Which sequence represents the correct order in which the proteins were identified?

Rough ER → Golgi apparatus → secretory vesicles

The major model of vesicle fusion holds that actual fusion of a vesicle with its target membrane is driven by the interaction of pairs of proteins called vesicle and target

SNAREs.

What is the primary reason that mammalian red blood cells are used in the study of the plasma membrane

They lack nuclei and membrane-bounded organelles.

Most laboratories make use of cultured cells to study human disease. What makes these cultured cells such useful models?

They provide a continuous and uniform source of new cells.

Which statement about transmembrane proteins is true?

They usually have one or more α helices spanning the membrane bilayer

The sugar groups of glycolipids and glycoproteins are found on the outer surface of the plasma membrane

True

Transmembrane proteins in the plasma membrane are synthesized on the rough ER

True

The feature that most clearly distinguishes eukaryotes from prokaryotes is the presence of _______ in eukaryotic cells.

a nucleus

The pH of endosomes and lysosomes is

acidic.

Molecules that traverse a membrane against their concentration gradient do so by _______ transport.

active

Active transport differs from facilitated diffusion in that

active transport involves the transport of molecules up their concentration gradient.

Molecules that are partly water-soluble and partly water-insoluble are

amphipathic

Cholesterol is present in the membranes of all

animal cells

Plasma membrane phospholipids are

asymmetrically distributed between the two membrane halves.

Enzymes affect the transition state of a chemical reaction by

binding to substrate(s). providing a surface on which reactions converting substrate to product can occur more rapidly. altering the conformation of substrate(s) to approach that of the transition state.

Amino acids:

can form peptide bonds are composed of a central carbon surrounded by an amino group, a carboxyl group, a hydrogen atom, and a variable side chain can have side chains that are polar, nonpolar, or with unique properties

While small, uncharged molecules can diffuse through the hydrophobic core of a phospholipid bilayer, larger polar molecules such as glucose must enter cells by binding to

carrier proteins that facilitate the passage of specific molecules across membranes.

Lysosomal proteins are initially incorporated into _______ vesicles

clathrin-coated

The major site at which membrane lipids are synthesized is the

cytosolic side of the ER membrane.

Cholesterol affects membrane fluidity by

decreasing membrane fluidity at high temperatures and increasing membrane fluidity at low temperatures

Integral membrane proteins are those that

directly associate with membrane lipids

In the fluid mosaic model of biological membrane structure, transmembrane proteins are

embedded nearly randomly in the lipid bilayer.

Organelles such as mitochondria and chloroplasts are thought to have originated in eukaryotic cells via a process called

endosymbiosis

The trans-Golgi network is the

exit part of the Golgi where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs

The lumen of the ER is equivalent topologically to the

extracellular space.

The MOST stable atoms and thus those that are typically nonreactive are the atoms that have _______.

full outer shells

Lipids with unsaturated fatty acids

increase fluidity of membranes.

Introducing a double bond into a fatty acid puts a(n) _______ into the conformation of the molecule.

kink

Common factors affecting membrane fluidity include

length of phospholipid fatty acid chains. temperature. number of double bonds in the fatty acid chains

A signal sequence in a polypeptide chain targets all but _______ proteins to the rough ER surface.

mitochondrial

Phospholipids in a membrane commonly

move laterally in the plane of the bilayer. rotate within the bilayer.

A few sugars joined together are called a(n)

oligosaccharide

The ingestion of large particles by cells is a form of endocytosis known as

phagocytosis

Cell membranes are composed principally of

phospholipids

What kind of bond results from an unequal sharing of electrons?

polar covalent bond

Proteins must have more than one _______ to have a quaternary structure.

polypeptide chain

Fluorescent-labeled antibodies are used on cells primarily to locate a specific

protein

If secretory proteins are isolated from secretory vesicles and injected into the cytosol, they will

remain in the cytosol until they are degraded.

Most plasma membrane proteins in higher eukaryotic cells are synthesized on

rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus

The plasma membrane functions as a

selective barrier to the passage of molecules. site for the uptake of macromolecules into the cell. site for cell-cell interactions.

Channels form pores through which molecules of appropriate size and charge can cross a membrane. By contrast, carrier proteins

selectively bind the molecule to be transported, change configuration, and release it on the other side

As they emerge from the ribosome, signal sequences are recognized and bound by a(n)

signal recognition particle (SRP).

Phospholipid bilayers are permeable only to molecules that are _______ and _______.

small; uncharged

Newly synthesized membrane lipids are found in both halves of a membrane bilayer because they are

synthesized on one surface and flipped to the other surface by flippases

Where are hydrophobic interactions MOST likely to occur?

the core of a water-soluble protein

Most cellular lipids are synthesized in

the endoplasmic reticulum.

Free ribosomes in the cytosol and ribosomes bound to the ER membrane have

the same types of large and small subunits.

Passive transport across a membrane refers to

transport in the energetically favorable direction

Active transport is transport in an energetically

unfavorable direction, always coupled to another reaction or source of energy.

Clathrin-coated vesicles are involved in

uptake of extracellular molecules by endocytosis and the transport of molecules from the trans-Golgi network to the lysosomes.

A feature common to most transmembrane proteins is a(n)

α-helical region of about 20 to 25 hydrophobic amino acids.