Which of the following molecules can diffuse directly through the lipid bilayer of cell membranes?
A. steroid hormones
By definition, biomolecules must _____.
C. contain carbon
Hydrophobic molecules are _____.
A. lipophilic
DNA is _______________ into RNA.
C. transcribed
Which of the following may be found in cell membranes?
E. all of the above
Protein synthesis requires the participation of which of the following organelles?
C. nucleus
A protein is coded in the DNA by a _____.
B. gene
Only the sense strand of DNA codes for a protein.
Direct electrical and metabolic coupling between cells is facilitated by _____.
B. gap junctions
Coupling between cells requires a direct pathway for the transfer of ions or other molecules.
DNA replication occurs during which phase of the cell cycle?
A. S
Cell division can be divided into two phases: ___________ and cytokinesis.
D. mitosis
Anaphase and telophase are phases within mitosis. Interphase is the period between cell divisions.
Starch is a polysaccharide found in animal tissue.
a. True
b. False
b. False
In RNA, adenine forms covalent bonds with thymine.
a. True
b. False
b. False
Fibrous proteins are often structural elements in cells.
a. True
b. False
a. True
Mitochondrial DNA is inherited through the maternal line.
a. True
b. False
a. True
Skin and muscle cells contain large numbers of intermediate filaments.
a. True
b. False
a. True
The cell membrane is considered to be fluid because the phospholipids and other molecules in the membrane are not linked by chemical bonds.
a. True
b. False
a. True
A functional protein is translated from introns joined together in an mRNA molecule.
a. True
b. False
a. False
The first amino acid of a protein is always glutathione.
a. True
b. False
b. False
A protein without a leader sequence will remain in the nucleus after translation.
a. True
b. False
b. False
In contrast to DNA, mRNA molecules tend to be short-lived.
a. True
b. False
a. True
desmosome
filamentous junction between two adjacent cells that provides a strong physical linkage between them; enables tissues to withstand stretching without cells being torn apart from one another
disaccharide
carbohydrate consisting of two monosaccharides covalently bonded together
eicosanoids
modified fatty acids (all derived from arachidonic acid) that function in intercellular communication
endoplasmic reticulum
elaborate network of membranes inside cells that enclose a single interior compartment; includes rough endoplasmic reticulum and smooth endoplasmic reticulum
fatty acids
long hydrocarbon chains with a carboxyl group at on end
gap junctions
areas where two adjacent cells are connected together by membrane proteins called connexons that form small channels between the cells, enabling ions and small molecules to move freely between them
gene
section of DNA that codes for a particular protein or proteins
genetic code
the correspondence between DNA triplets and specific amino acids that governs the expression of all genetic information
golgi apparatus
an organelle consisting of membrane-bound flattened sacs called cistern that process molecules synthesized in the endoplasmic reticulum and prepare them for transport
glycogen
a glucose polymer found in animal cells; functions as an energy store
glycerol
three-carbon alcohol that functions as the backbone of a triglyceride or phospholipid
glucose
most common monosaccharide; provides important source of cellular energy
helicase
enzyme that causes a section of DNA to unwind during replication
hydrolysis
use of water to split another molecule
interphase
period in the life cycle of the cell during which it is carrying on its normal physiological functions
intermediate filaments
fibrous proteins with a diameter between that of microfilaments and microtubules; stronger and more stable than microfilaments
integral membrane proteins
proteins that are tightly embedded within the lipid bilayer
inclusions
cytosolic particles composed of triglycerides or glycogen; serve as energy stress for cellular metabolism
law of complementary base pairing
states that whenever two strands of nucleic acids are held together by hydrogen bonds,
G-C, A-T in DNA (A-U in RNA)
leader sequence
initial sequence of amino acids that is present in a newly synthesized polypeptide chain and function in directing the fate of the final protein
lipids
biomolecules that contain primarily carbon and hydrogen atoms linked together by non polar covalent bonds
lysosomes
small spherical membrane-bound organelles congaing numerous degradative enzymes; involved in the breakdown of unneeded intracellular material or foreign matter that has been taken into the cell
microtubules
the largest-diameter protein filaments of the cytoskeleton, composed of long, hollow tubes made of tubulin
microfilaments
the smallest-diameter protein filaments of the cytoskeleton
metabolism
sum of all the chemical reactions that take place in the body
messenger RNA (mRNA)
molecule that carries genetic information from the nucleus to the cytoplasm; contains the code for the amino acid sequence of a protein
meiosis
a series of two cell divisions that generate daughter cells (gametes) with half the normal chromosome number; involved in gametogensis
microvilli
projections of the plasma membrane that increase its surface area; often found in epithelial cells specialized for transport
monosaccharide
simple sugar composed of a single unit
mitosis
the type of cell division that yields two daughter cells containing the normal number of chromosomes; necessary for the growth and replacement of cells
mitochondrial matrix
the innermost compartment in mitochondria, bounded by the inner mitochondrial membrane; contains the krebs cycle enzymes
nuclear envelope
barrier that separates the nucleus from the cytoplasm; consists of two membranes
nucleotide
a biomolecule containing one or more phosphate groups, a 5-C carbohydrate, a nitrogenous base; involved in energy exchange and in the storage and transmission of genetic information in cells
nucleic acids
polymers of nucleotides that function in the storage and expression of genetic information; see DNA and RNA
nuclear pores
pore in the nuclear envelope that allow selective movement of molecules between the nucleus and cytoplasm
organelles
plasma membrane
phospholipid
peroxisomes
spherical membrane-bound organelles that function in the degradation of molecules such as amino acids, fatty acids, and toxic foreign matter
