Biology Chapter 4
Plant cells, unlike animal cells, are characterized by the presence of a ________.
cell wall and a central vacuole
In plant cells, ______ may contain organic nutrients, pigments, and poisons.
central vacuoles
The structural combination of DNA and protein forms ________.
chromatin
Based on its function in detoxifying drugs, you would expect to find a large amount of smooth ER in ______ cells. A) intestinal B) muscle C) brain D) liver
d
Chloroplast
food production
Chromosomes
genetic information
When mixed with water, phospholipids spontaneously form membranes because they ______.
have hydrophilic phosphate groups that are attracted to water and hydrophobic fatty acid tails that avoid water
One difference between eukaryotic and prokaryotic cells is that eukaryotic cells ______ prokaryotic cells.
have membrane-enclosed structures called organelles, which are lacking in
A protist that contains contractile vacuoles most likely lives ______.
in fresh water
Cytoskeleton
internal support, cilia and flagella
The most commonly used microscope, which uses visible light to view cells, is called a __________.
light microscope
Functions of the smooth endoplasmic reticulum include ________.
lipid synthesis, steroid synthesis, and drug detoxification
Based on its function in detoxifying drugs, you would expect to find a large amount of smooth ER in ______ cells.
liver
Tay-Sachs disease results from ______ lacking a specific type of lipid-digesting enzyme.
lysosomes
Cells in the thyroid gland produce and secrete thyroid hormone (a polymer of amino acids) that helps to regulate metabolism. What organelle is most likely abundant in cells of the thyroid gland?
rough endoplasmic reticulum
Cell membrane
selectively permeable
Ribosomes
site of protein synthesis
Nucleolie
site of ribosome synthesis
Which theory states that all living things are composed of cells?
cell theory
What is the size of the smallest object that can be viewed as a distinct, separate object with a light microscope?
0.2 micrometers in diameter
The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell. 1. plasma membrane 2. nucleoid region 3. ribosome 4. pili 5. cell wall
1. plasma membrane The plasma membrane is selectively permeable. Bacterial DNA is found in the nucleoid region.
In a bacterium, where are proteins synthesized? 1. ribosomes 2. nucleus 3. peroxisome 4. nucleoid region 5. capsule
1. ribosomes Ribosomes are involved in the manufacture of polypeptides (proteins).
The structure that regulates the passage of material into and out of this bacterial cell is indicated by the letter _____. http://session.masteringbiology.com/problemAsset/1100503/4/2708q.jpg 1. A 2. B 3. C 4. D 5. E
3. C The plasma membrane is selectively permeable.
_____ are surface appendages that allow a bacterium to stick to a surface. 1. Ribosomes 2. Mitochondria 3. Fimbriae 4. Flagella 5. Cell walls
3. Fimbriae Fimbriae enable bacterial cells to stick to a surface.
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell? 1. capsule 2. pili 3. cell wall 4. flagella 5. nucleoid region
3. cell wall The cell wall is a rigid supporting structure.
The endomembrane system includes ________.
Golgi apparatus, lysosomes, vacuoles, and the endoplasmic reticulum
Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of
ATP
Ribosomes
Although not membrane bound, this organelle is the site of protein synthesis.
centrioles
Always shown as a pair, next to the nucleus, and only in animal cells. Look like little, cylindrical stacks of tubes. Sometimes shown in cross section as a swirl of lines or commas.
Nucleus
This, the largest object in a eukaryotic cell, holds the cell's genetic information.
Cell Wall
Composed of cellulose, this gives plant cells stability.
Mitochondrion
Converts chemical fuel into packets of chemical energy (ATP) that can power the cell
nucleolus
Dark area(s) (nucleoli) within the nucleus. It is part of the DNA and will be mixed in with the chromatin. Each nucleus will have one to three nucleoli drawn in.
vacuole
Easily identified as a large, central, fluid filled space in a plant cell. Food vacuoles are much smaller. Contractile vacuoles are star-shaped.
Cytoplasm
Everything between the cell membrane and the nucleus. Contains all organelles and cytosol (solution in the cell).
lysosome
Found in animal cells. They are easily confused with vesicles but sometimes with various internal features such as small food particles.
______ store the information necessary to produce proteins.
Genes
cell wall
If the cell is labeled plant, bacteria or fungi, look for a cell wall on the outside of the cell membrane. Sometimes drawn as mesh or fiber-like material.
A study conducted by the National Institutes of Health on the infectivity of methicillin-resistant Staphylococcus aureus (MRSA) stated their hypothesis as __________.
MRSA bacteria lacking the ability to produce a protein (PSM) would be less deadly than those producing it
Chloroplast
Makes food by converting light energy into chemical energy
RER
Membranes normally located just outside the nucleus and dotted with obvious ribosomes.
Golgi Apparatus
Modifies and packages proteins
cell membrane
Outermost part of cell. Can easily be confused with the cell wall (see below).
________ are the major lipids of plasma membranes.
Phospholipids
Tobacco smokers (and those exposed to tobacco smoke) are at greater risk of an ectopic (tubal) pregnancy. Based on your understanding of the structures of the cytoskeleton, what is the BEST explanation?
Tobacco interferes with the sweeping motion of cilia that aids in the movement of the egg toward the uterus.
Golgi
Proteins are absorbed, modified, packaged and distributed to their destination in this organelle.
Central Vacuole
Regulates cytoplasm composition, creates internal pressure, and stores cell compounds
ribosomes
Represented as small, free floating dots in the cytoplasm or attached to the outside of the rough ER.
Golgi apparatus
Shown further away from the nucleus than the ER, looks like stacks of pita bread with small dots (vesicles) to each side.
SER
Similar to rough ER, usually further away from the nucleus than the ER, never with dots.
Information is transferred from the nucleus to ribosomes via ______.
mRNA
Rough endoplasmic reticulum appears "rough" because __________.
many ribosomes stud the outside of the ER membrane
Vacuoles are ______.
membranous sacs
Coded genetic information is produced in the nucleus and transferred to the cytoplasm in a molecule called _____.
messenger RNA
Which of the following are the components of the cytoskeleton that help move chromosomes when cells divide?
microtubules
During a race such as a marathon, the skeletal muscle cells in your legs use a lot of energy to continually contract and power your muscles. What organelle is most likely abundant in skeletal muscle cells?
mitochondria
In addition to the nucleus, which of the following are organelles that contain their own DNA and ribosomes?
mitochondria and chloroplasts
The fluid mosaic model of the plasma membrane is characterized by __________.
molecules moving freely past one another
In some eukaryotic cells, cilia and flagella are motile, cellular appendages that aid the cell in __________.
movement
Residents of Bangladesh are thought to be developing resistance to infection by Vibrio cholera by __________.
natural selection of humans who have mutations in genes that result in cells being less susceptible to the cholera toxin
Which of the following structures manufactures the components of ribosomes?
nucleolus
Where does protein synthesis take place?
on ribosomes
The concept of a membrane as a fluid mosaic reflects the ability of ______.
phospholipids and most proteins to drift about in the plane of the membrane
Which of the following is a feature of prokaryotic cells but not eukaryotic cells?
pili
You find a cell of a type you have never seen before. The cell has both a nucleus and a cell wall. Therefore, you conclude that it is likely to be a(n) ________ cell.
plant
Mitochondria, the sites of cellular respiration, are found in __________.
plant cells and animal cells
Mitochondria
power house
Which of these distinguishes a plant cell from an animal cell?
presence of a cell wall
When using a microscope to view cells you obtained from scraping under your fingernails, you notice that the cells lack nuclei; therefore, you conclude that the cells must be a type of ________ cell.
prokaryotic
The extracellular matrix of animal cells ________.
protects and support cells
Nuclear Envelope
protects chromosomes
Which of the following is a function of the Golgi apparatus?
protein modification
Golgi
protein package and distribution center
The Golgi apparatus mainly functions to modify _____.
proteins
Which of the following are the two main components of cellular membranes?
proteins and phospholipids
Which of the following is a function of the plasma membrane?
regulate the traffic of chemicals in and out of the cell
What is the primary site of protein production in a eukaryotic cell?
ribosomes
Cellular respiration can be described as the conversion of the energy ________.
stored in food molecules to energy stored in ATP
Cell Wall
support structure (plants, bacteria & fungi)
RER
surface for protein synthesis and transport
Similar to the nucleus, chloroplasts and mitochondria are ________.
surrounded by two membranes
Which of the following parts of a cell is (are) most like the shipping center of a company?
the Golgi apparatus
Which of the following is an adaptation to increase the surface area of a part of a cell that is involved in cellular respiration?
the cristae of a mitochondrion
What is the genetic center of the eukaryotic cell?
the nucleus
What structures move proteins from the ER to the Golgi apparatus?
transport vesicles
Centrioles
used in animal cell division only
Which of the following correctly matches the organelle with its function?
vacuole ... storage
Large, Central Vacuole
water and solute compartment in plant cells
The DNA-containing region of this bacterial cell is indicated by the letter _____. http://session.masteringbiology.com/problemAsset/1100503/4/2701q.jpg 1. A 2. B 3. C 4. D 5. E
4. D The nucleoid region contains DNA.
Where is a bacterial cell's DNA found? 1. ribosomes 2. nucleus 3. peroxisome 4. nucleoid region 5. capsule
4. nucleoid region Bacteria lack a nucleus; their DNA is found in the nucleoid region.
What is the function of a bacterium's capsule? 1. protein synthesis 2. DNA storage 3. propulsion 4. protection 5. adhesion
4. protection A bacterium's capsule has a protective role.
Most human cells contain ______ chromosomes.
46
Mitochondria are found in _____. 1. animal cells only 2. plant cells only 3. all cells 4. animal cells and prokaryotic cells, but not plant cells 5. plant and animal cells
5. plant and animal cells All eukaryotic cells, including plant and animal cells, contain mitochondria.
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____. 1. translation of an RNA nucleotide sequence into a sequence of amino acids 2. linking of nucleotides to form a polypeptide 3. removal of introns from RNA and the stitching together of exons 4. translation of a DNA nucleotide sequence into a sequence of amino acids 5. transferring of information from DNA to messenger RNA
5. transferring of information from DNA to messenger RNA Transcription is the first of the two main steps of protein synthesis.
Chromosomes
Structures within the nucleus that are composed of DNA. Called chromatin in a non-dividing cell.
Mitochondria
The "Powerhouse" of the cell, this organelle is the site of cellular respiration and production of ATP.
Cytoskeleton
The "skeleton" and "muscles" of the cell, this structure is made of microtubules that also form cilia, flagella and centrioles.
Centrioles
These small microtubules are involved in animal cell division.
RER
This extensive network of membranes is studded with ribosomes and functions as a surface for protein synthesis and transport of materials.
Nuclear Envelope
This membrane holds the chromosomes within the nucleus.
Chloroplast
This organelle is green due to the presence of chlorophyll and is the site of photosynthesis.
Vacuole
This organelle is very large in plant cells and contains food, enzymes, minerals, wastes and water.
Cell Membrane
This selectively permeable structure is composed of phospholipids embedded with proteins.
SER
This set of smooth membranes functions to synthesize lipids and detoxify drugs and toxins.
Lysosome
This specialized vesicle contains digestive enzymes and is the site of hydrolysis in animal cells
In some eukaryotic cells, cilia and flagella are motile, cellular appendages that aid the cell in _____. A) movement B) cell division C) respiration D) photosynthesis
a
Nucleoli
Dark sections of DNA and proteins in the nucleus which are the site of ribosome synthesis.
vesicle
Small, fluid filled organelles in animal cells. Easily confused with the lysosome in an animal cell.
Plant Cell Wall
Strong, protective structure made from cellulose fibrils
nuclear envelope
The membrane around the nucleus. Usually with obvious nuclear pores or holes. Can be confused with the nucleus so look for labels that might apply to each part.
Rough endoplasmic reticulum appears "rough" because __________. A) many ribosomes stud the outside of the ER membrane B) of the numerous proteins produced by the rough ER C) the Golgi apparatus is associated with rough ER to produce proteins D) lysosomes are attached to the ER
a
nucleus
Usually easy to locate, the largest structure in the cell. Normally oval or round in shape. It usually has a line to the center of the circular body.
chloroplast
Usually has oval to mound shape. Membranes inside are usually stacked like papers.
chromosomes
Usually in the form of chromatin, a spaghetti like group of DNA strands. Occasionally the chromosomes are shown as X-shaped structures within the nucleus.
cytoplasm
Usually labeled with a line pointing to the inside of a cell but not to any particular structure.
mitochondria
Usually peanut or jelly bean shaped with a squiggle or worm shape within. May be confused with the chloroplast in a plant cell.
Based on its function in detoxifying drugs, you would expect to find a large amount of smooth ER in ______ cells. A) liver B) muscle C) intestinal D) brain
a
Functions of the smooth endoplasmic reticulum include ______. A) lipid synthesis, steroid synthesis, and drug detoxification B) lipid synthesis, protein synthesis, and drug detoxification C) lipid synthesis, steroid synthesis, and protein synthesis D) steroid synthesis, protein synthesis, and drug detoxification
a
The concept of a membrane as a fluid mosaic reflects the ability of ______. A) phospholipids and most proteins to drift about in the plane of the membrane B) most proteins but not phospholipids to drift about in the plane of the membrane C) phospholipids but not proteins to drift about in the plane of the membrane D) carbohydrates to drift into and out of the membrane structure
a
The electron microscope has been particularly useful in studying bacteria because __________. A) bacteria are so small B) electrons can penetrate tough bacterial cell walls C) bacteria move so quickly they are hard to photograph D) bacteria are distinguished by differences in individual macromolecules
a
Tobacco smokers (and those exposed to tobacco smoke) are at greater risk of an ectopic (tubal) pregnancy. Based on your understanding of the structures of the cytoskeleton, what is the best explanation? A) Tobacco interferes with the sweeping motion of cilia that aids in the movement of the egg toward the uterus. B) Tobacco smokers tend to get pregnant when they are younger. C) Tobacco interferes with the functioning of the flagella propelling sperm. D) Tobacco interferes with the transfer of oxygen to the uterus, thereby forcing the zygote to implant in a fallopian tube.
a
What are the primary sites of protein production in a eukaryotic cell? A) ribosomes B) the nucleus C) the Golgi apparatus D) vacuoles
a
What is the smallest entity that exhibits all the characteristics of life? A) a cell B) tissues C) organelles D) macromolecules
a
When mixed with water, phospholipids spontaneously form membranes because they ______. A) have hydrophilic phosphate groups that are attracted to water and hydrophobic fatty acid tails that avoid water B) have hydrophilic fatty acid tails that are attracted to water and hydrophobic phosphate groups that avoid water C) have hydrophilic heads that are attracted to their hydrophobic tails D) are both fluid and mosaic
a
When using a light microscope to view a cell you obtained from scraping under your fingernails, you notice that the cell lacks a nucleus; therefore, you conclude that the cell must be a type of ______ cell. A) prokaryotic B) eukaryotic C) fungal D) plant
a
Which of the following is a characteristic of chloroplasts that suggests that they might have evolved from free-living bacteria? A) Chloroplasts have their own DNA. B) Chloroplasts have cell walls. C) A single, highly folded plasma membrane surrounds chloroplasts. D) Chloroplasts contain pigments.
a
Which of the following structures manufactures the components of ribosomes? A) nucleolus B) cytoplasm C) endoplasmic reticulum D) nucleus
a
Within the nucleus of a cell, long DNA molecules and associated proteins form fibers called _____. A) chromatin B) ribosomes C) cell junctions D) nuclear envelope
a
What is the smallest entity that exhibits all the characteristics of life?
a cell
The nuclear envelope is composed of ______.
a double membrane
Bacteria do not contain
a nucleus
Microtubules are associated with ________.
all of the answer choices
Some ribosomes are suspended in the cytosol of a cell, whereas other ribosomes _______.
are attached to the outside of the nucleus
A hormone that will be secreted from a cell is manufactured by ribosomes ________.
attached to the endoplasmic reticulum
A major difference between prokaryotic and eukaryotic cells is that __________. A) prokaryotic cells have cell walls; eukaryotic cells do not B) eukaryotic cells have membrane-bound organelles; prokaryotic cells do not C) eukaryotic cells are older than prokaryotic cells in an evolutionary sense D) prokaryotic cells are larger than eukaryotic cells
b
A plant cell has a versatile compartment that stores organic nutrients, absorbs water, and contains poisons that protect against plant-eating animals. This compartment is the _____. A) cristae B) central vacuole C) chloroplast D) food vacuole
b
In addition to the nucleus, which of the following are organelles that contain DNA? A) lysosomes and ribosomes B) mitochondria and chloroplasts C) mitochondria and ribosomes D) endoplasmic reticulum and Golgi apparatus
b
The Golgi apparatus mainly functions to modify _____. A) mRNA B) proteins C) the nucleolus D) Genes
b
The nuclear envelope is composed of ______. A) chromatin B) a double membrane C) DNA D) carbohydrates
b
What type of microscope would be best for studying the detailed structure of the surface of a plasma membrane? A) transmission electron microscope B) scanning electron microscope C) light microscope D) both a light microscope and an electron microscope
b
Which cellular organelle is required for photosynthesis in eukaryotic cells? A) mitochondrion B) chloroplast C) Golgi apparatus D) lysosome E) nucleus
b
Which of the following are components of the cytoskeleton that help move chromosomes when cells divide? A) actin filaments B) microtubules C) intermediate filaments D) myosin filaments
b
Which of the following is a function of the plasma membrane? A) protein synthesis B) regulate the traffic of chemicals into and out of the cell C) lipid synthesis D) all of the above
b
Which of these distinguishes a plant cell from an animal cell? A) presence of a nucleus B) presence of a cell wall C) presence of a plasma membrane D) ability to metabolize E) ability to reproduce
b
Which organelle plays a role in intracellular digestion? A) chloroplast B) lysosome C) plasmodesma D) Golgi apparatus E) ribosome
b
______ store the information necessary to produce proteins. A) Ribosomes B) Genes C) Carbohydrates D) Lysosomes
b
Which one of the following groups is composed of prokaryotic cells?
bacteria
The electron microscope has been particularly useful in studying bacteria because __________.
bacteria are so small
Over 100 years ago, microbiologist Paul Ehrlich talked about his concept of the ideal antibiotic as a "magic bullet" that could kill harmful bacteria but have minimal side effects for the infected person. How do antibiotics accomplish this goal?
by targeting structures found only in bacterial cells and not the host cells
A hormone that will be secreted from the cell is manufactured by ribosomes _____. A) attached to the Golgi apparatus B) attached to the plasma membrane C) attached to the endoplasmic reticulum D) inside the nucleus
c
Functions of the smooth endoplasmic reticulum include ______. A) lipid synthesis, steroid synthesis, and protein synthesis B) lipid synthesis, protein synthesis, and drug detoxification C) lipid synthesis, steroid synthesis, and drug detoxification D) steroid synthesis, protein synthesis, and drug detoxification
c
Similar to the nucleus, chloroplasts and mitochondria are ______. A) green B) manufactured by the nucleolus C) surrounded by two membranes D) able to synthesize lipids
c
Which of the following is a characteristic of mitochondria that suggests that they might have evolved from free-living bacteria? A) Mitochondria have cell walls. B) Mitochondria rely upon proteins as their source of energy. C) Mitochondria have their own DNA. D) The plasma membrane of a mitochondrion, forming the surface of this organelle, is the site of many important steps of cellular respiration.
c
Which one of the following lists the steps involved in the production of new proteins in the appropriate order and correctly describes each step? A) mRNA travels from nucleus to cytoplasm...DNA transfers information to mRNA...ribosomes translate mRNA into proteins B) ribosomes translate proteins into mRNA...mRNA travels from nucleus to cytoplasm...DNA transfers information from mRNA C) DNA transfers information to mRNA...mRNA travels from nucleus to cytoplasm... ribosomes translate mRNA into proteins D) DNA transfers information to mRNA...mRNA travels from cytoplasm to nucleus... ribosomes translate mRNA into proteins E) DNA reads information from mRNA...mRNA travels from nucleus to cytoplasm... ribosomes translate mRNA into proteins
c
Cytoplasm
cell contents
A plant cell has a versatile compartment that stores organic nutrients, absorbs water, and contains poisons that protect against plant-eating animals. This compartment is the _____.
central vacuole
Which plant organelle is responsible for photosynthesis?
chloroplast
Within the nucleus of a cell, long DNA molecules and associated proteins form fibers called _____.
chromatin
Nucleus
control center
The function of the chloroplast is to __________.
convert light energy to chemical energy
In eukaryotic cells, what name is given to the region between the nucleus and the plasma membrane?
cytoplasm
the term used to indicate the part of a eukaryotic cell where organelles are suspended in fluid is _____.
cytoplasm
Cellular respiration can be described as the conversion of the energy ______. A) stored in ATP to energy used to do work B) of sunlight to energy stored in organic compounds C) stored in ATP to energy stored in food molecules D) stored in food molecules to energy stored in ATP
d
Coded genetic information is produced in the nucleus and transferred to the cytoplasm in a molecule called _____. A) extracellular matrix B) ribosome C) chromatin D) messenger RNA
d
Information is transferred from the nucleus to ribosomes via ______. A) DNA B) smooth endoplasmic reticulum C) rough endoplasmic reticulum D) mRNA
d
Microtubules are associated with ______. A) cilia B) cell shape C) flagella D) all of the above
d
Mitochondria, the sites of cellular respiration, are found in __________. A) bacteria B) animal cells and bacterial cells, but not in plant cells C) plant cells only D) plant cells and animal cells E) animal cells only
d
The endosymbiotic theory states that __________; one piece of evidence supporting this theory is the fact that __________. A) the first hereditary material was RNA ... mitochondria and chloroplasts have heredity based on RNA B) the genomes of complex animals came in part from the genomes of invading pathogens ...the human genome contains the complete genomes of 120 viruses and 10 bacteria C) two organisms live in close association ...the two participating individuals are two different species D) mitochondria and chloroplasts originated as ingested prokaryotes ...mitochondria and chloroplasts have their own DNA
d
The figure below shows a Paramecium, a single-celled freshwater protist. The hairlike structures visible on the Paramecium allow it to move. These structures are ______. A) flagella B) microfilaments C) intermediate filaments D) cilia
d
The fluid mosaic model of the plasma membrane is characterized by __________. A) attachment to the cell wall in animal cells B) the presence of the cell's genetic information C) a bilayer composed of carbohydrate D) molecules moving freely past one another
d
The nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles make up the __________. A) nucleolus B) rough ER C) extracellular matrix D) endomembrane system
d
The term used to indicate the part of a eukaryotic cell where organelles are suspended in fluid is _____. A) nuclear membrane B) phospholipid bilayer C) extracellular matrix D) cytoplasm
d
What evidence suggests that mitochondria might have evolved before chloroplasts? A) Mitochondria can sometimes divide to produce chloroplasts. B) Some mitochondria have chloroplasts inside of them. C) Only mitochondria have their own DNA. D) Almost all eukaryotes have mitochondria but only some cells have chloroplasts.
d
What structures move proteins from the ER to the Golgi apparatus? A) transport proteins B) nucleolus C) central vacuole D) transport vesicles
d
Which of the following are the two main components of cellular membranes? A) proteins and nucleotides B) phospholipids and nucleotides C) carbohydrates and nucleotides D) proteins and phospholipids
d
Which of the following is a function of the Golgi apparatus? A) protein synthesis B) drug detoxification C) digestion of organic matter inside the cell D) protein modification
d
Which of the following is an adaptation to increase the surface area of a part of a cell that is involved in cellular respiration? A) the endoplasmic reticulum B) the outer membrane of a chloroplast C) the grana of a chloroplast D) the cristae of a mitochondrion
d
SER
detoxification/ lipid synthesis
If a cell's lysosomes burst, the cell would ______.
digest itself
Lysosomes are responsible for ______.
digestion of organic matter inside the cell
Lysosome
digestion/hydrolysis
Which of the following is stored in the lysosomes of the cell?
digestive enzymes
Most of the DNA in a eukaryotic cell is in _____. A) the cytoplasm B) the mitochondria C) the cytoskeleton D) the endomembrane system E) the nucleus
e
Which one of the following groups is composed of prokaryotic cells? A) animals B) fungi C) plants D) protists E) bacteria
e
The nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles make up the __________.
endomembrane system
A major difference between prokaryotic and eukaryotic cells is that __________.
eukaryotic cells have membrane-bound organelles; prokaryotic cells do not