Cell: The Unit of Life Questions and Answers

Check if the following statement is true or false.
It is okay to copy information word for word.
Completely true
True; but only if you cite.
False
Biology
Cell: The Unit of Life
Check if the following statement is true or false. It is okay to copy information word for word. Completely true True; but only if you cite. False
The liver helps us to break down medications. Therefore, liver cells (called hepatocytes) likely contain large quantities of
Rought Endoplasmic Reticulum
Golgi body
Smooth Endoplasmic Reticulum
Ribsomes
Biology
Cell: The Unit of Life
The liver helps us to break down medications. Therefore, liver cells (called hepatocytes) likely contain large quantities of Rought Endoplasmic Reticulum Golgi body Smooth Endoplasmic Reticulum Ribsomes
Polar molecules simply cannot enter into a cell due to the repellent action of the phospholipid bilayer.
True
False
Biology
Cell: The Unit of Life
Polar molecules simply cannot enter into a cell due to the repellent action of the phospholipid bilayer. True False
Much of the elegant molecular machinery that exists in every cell is dedicated to the production and utilization of the energy required for an organism to maintain the living state. How much food must an animal eat every day to maintain health? Why does the brain consume energy even when resting?
Biology
Cell: The Unit of Life
Much of the elegant molecular machinery that exists in every cell is dedicated to the production and utilization of the energy required for an organism to maintain the living state. How much food must an animal eat every day to maintain health? Why does the brain consume energy even when resting?
Why are cells are small?
They could not create enough energy to survive if they were larger.
They would be unable to move themselves through their environments if they were larger and therefore be unable to seek out the resources they need to survive.
They would be unable to move important gases and waste products across their membrances effectively if they were any larger.
They could not produce enough structural proteins for support if they were any larger.
Biology
Cell: The Unit of Life
Why are cells are small? They could not create enough energy to survive if they were larger. They would be unable to move themselves through their environments if they were larger and therefore be unable to seek out the resources they need to survive. They would be unable to move important gases and waste products across their membrances effectively if they were any larger. They could not produce enough structural proteins for support if they were any larger.
The tissue type shown in the figure is
epithelial
nervous
connective
muscular
Biology
Cell: The Unit of Life
The tissue type shown in the figure is epithelial nervous connective muscular
What is activation energy?
It is the energy that comes out of a reaction.
It is the minimum energy needed to start a reaction.
It is the maximum energy needed to slow a reaction.
It is the energy needed to open the enzyme.
It is the energy needed to switch substrates.
Biology
Cell: The Unit of Life
What is activation energy? It is the energy that comes out of a reaction. It is the minimum energy needed to start a reaction. It is the maximum energy needed to slow a reaction. It is the energy needed to open the enzyme. It is the energy needed to switch substrates.
What does the science root word "synthesis" mean?  
A. to build or make
B. to spin quickly
C. to make
incorrectly/fake
Biology
Cell: The Unit of Life
What does the science root word "synthesis" mean? A. to build or make B. to spin quickly C. to make incorrectly/fake
describe ONE mechanism by which a virus can turn a normal cell into a cancer cell.
Biology
Cell: The Unit of Life
describe ONE mechanism by which a virus can turn a normal cell into a cancer cell.
Cellulose is the most abundant natural biopolymer. 
True
False
Biology
Cell: The Unit of Life
Cellulose is the most abundant natural biopolymer. True False
exons:
are not a part of the "mature" mRNA that undergoes translation
are binding sites for repressors; therefore exons are involved in controlling gene expression
are found in eukaryotic cells only
do not contain codons or information about proteins; they are removed from the mRNA during splicing/editing process
Biology
Cell: The Unit of Life
exons: are not a part of the "mature" mRNA that undergoes translation are binding sites for repressors; therefore exons are involved in controlling gene expression are found in eukaryotic cells only do not contain codons or information about proteins; they are removed from the mRNA during splicing/editing process
which of the following is WRONG (or false):
When bacteriophage DNA is inserted into bacterial chromosome, viral genes that specify viral structural proteins are expressed, resulting in making new viruses
prophage is viral DNA inserted into bacterial chromosome
the choices in this question have to do with the lysogenic life cycle/lysogeny
acquiring prophage may cause recipient bacteria to make toxins or express genes on the prophage that do not specify viral structural proteins
Prophage may leave the bacterial chromosome
Biology
Cell: The Unit of Life
which of the following is WRONG (or false): When bacteriophage DNA is inserted into bacterial chromosome, viral genes that specify viral structural proteins are expressed, resulting in making new viruses prophage is viral DNA inserted into bacterial chromosome the choices in this question have to do with the lysogenic life cycle/lysogeny acquiring prophage may cause recipient bacteria to make toxins or express genes on the prophage that do not specify viral structural proteins Prophage may leave the bacterial chromosome
nucleocapsids/nucleoproteins are:
same as capsomeres
the protein box PLUS the nucleic acid of the virus
attachment molecules of viruses
same thing as (refers to) the nucleic acid of the virus
ONLY the "protein box" portion of the virus
found in naked viruses
membrane that surrounds the viral nucleic acid
Biology
Cell: The Unit of Life
nucleocapsids/nucleoproteins are: same as capsomeres the protein box PLUS the nucleic acid of the virus attachment molecules of viruses same thing as (refers to) the nucleic acid of the virus ONLY the "protein box" portion of the virus found in naked viruses membrane that surrounds the viral nucleic acid
you added cell-free DNA molecules containing a gene that codes for an exotoxin to bacteria in broth. After incubation, the bacteria in broth now make the exotoxin (whereas they did not before). What caused this?
bacteria picked up DNA using its pili/fimbriae
bacteria picked up the DNA but there was Nrecombination
conjugation
transduction
transformation
Biology
Cell: The Unit of Life
you added cell-free DNA molecules containing a gene that codes for an exotoxin to bacteria in broth. After incubation, the bacteria in broth now make the exotoxin (whereas they did not before). What caused this? bacteria picked up DNA using its pili/fimbriae bacteria picked up the DNA but there was Nrecombination conjugation transduction transformation
new viral components (parts) are made during which stage of the viral life cycle?
release
entry
uncoating
assembly/maturation
biosynthesis
attachment
Biology
Cell: The Unit of Life
new viral components (parts) are made during which stage of the viral life cycle? release entry uncoating assembly/maturation biosynthesis attachment
What are the two different sex chromosomes for humans?
A. X and Y
B. A and B
C. M and F
Biology
Cell: The Unit of Life
What are the two different sex chromosomes for humans? A. X and Y B. A and B C. M and F
Sister chromatids are attached at the center point called
a. Centrosome
b. Centriole
C. Centromere
d. Centroid
Biology
Cell: The Unit of Life
Sister chromatids are attached at the center point called a. Centrosome b. Centriole C. Centromere d. Centroid
2. The following is the longest phase of mitosis
a. Prophase
b. Metaphase
c. Anaphase
d. Telophase
Biology
Cell: The Unit of Life
2. The following is the longest phase of mitosis a. Prophase b. Metaphase c. Anaphase d. Telophase
John wants to see if fat guys bounce higher on a trampoline. He gets five guys to test: Bill=100 pounds, Tom=130 pounds, Matt 150 pounds, Tim=180 pounds, and Phil=200 pounds. They each jump off a ten-foot ledge onto a trampoline while John checks to see how high they bounce. What is the independent variable in this experiment? 
The weight of the jumpers 
The bounciness of the trampoline 
The height the jumpers go 
The 10 ft. drop
Biology
Cell: The Unit of Life
John wants to see if fat guys bounce higher on a trampoline. He gets five guys to test: Bill=100 pounds, Tom=130 pounds, Matt 150 pounds, Tim=180 pounds, and Phil=200 pounds. They each jump off a ten-foot ledge onto a trampoline while John checks to see how high they bounce. What is the independent variable in this experiment? The weight of the jumpers The bounciness of the trampoline The height the jumpers go The 10 ft. drop
During which stage of team development do members endorse the group's decision?
social stage
reinforcement stage
orientation stage
conflict stage
emergence stage
Biology
Cell: The Unit of Life
During which stage of team development do members endorse the group's decision? social stage reinforcement stage orientation stage conflict stage emergence stage
Numeric and measurable types of data such as height, age, scores, cost are considered what type of data?
quartile
quiet
qualitative
quantitative
Biology
Cell: The Unit of Life
Numeric and measurable types of data such as height, age, scores, cost are considered what type of data? quartile quiet qualitative quantitative
What does it mean when a cell has an infection? 
A. An invader is kept out of the cell by the cell membrane. 
B. An invader has been denied entry into the cell by the cell membrane. 
C. An invader has found its way into the cell.
Biology
Cell: The Unit of Life
What does it mean when a cell has an infection? A. An invader is kept out of the cell by the cell membrane. B. An invader has been denied entry into the cell by the cell membrane. C. An invader has found its way into the cell.
Some ribosomes are free-floating in the cell. Others are bound to an organelle. Where are the bound ribosomes found? 
A. floating in the cytoplasm 
B. attached to the endoplasmic reticulum 
C. attached to the cell wall
Biology
Cell: The Unit of Life
Some ribosomes are free-floating in the cell. Others are bound to an organelle. Where are the bound ribosomes found? A. floating in the cytoplasm B. attached to the endoplasmic reticulum C. attached to the cell wall
Cyanide, azide, and carbon monoxide interfere with the
activity of _
heme
ALL OF THESE
Complex IV
iron
Biology
Cell: The Unit of Life
Cyanide, azide, and carbon monoxide interfere with the activity of _ heme ALL OF THESE Complex IV iron
Kevin is in high school. First period is chemistry, and he has a quiz in class tomorrow. Kevin is really
trying hard to remember all the new information he has learned today so he does well on his quiz
tomorrow. Kevin also has a history class third period where he had learned about famous historical
explorers. The next day on his chemistry quiz he was asked for the name of the element with an
atomic number of 27. Instead of "cobalt" the only name that was running through his head was John
Cabot (an Italian explorer). What is this condition that poor Kevin has faced?
Proactive interference
Serial Learning
Retroactive Learning
Similarity
Biology
Cell: The Unit of Life
Kevin is in high school. First period is chemistry, and he has a quiz in class tomorrow. Kevin is really trying hard to remember all the new information he has learned today so he does well on his quiz tomorrow. Kevin also has a history class third period where he had learned about famous historical explorers. The next day on his chemistry quiz he was asked for the name of the element with an atomic number of 27. Instead of "cobalt" the only name that was running through his head was John Cabot (an Italian explorer). What is this condition that poor Kevin has faced? Proactive interference Serial Learning Retroactive Learning Similarity
Choose the correct option among the following 
(1) Lyophilic sols are reversible sols 
(2) Lyophilic sols are more stable than lyophobic sols 
(3) Lyophilic colloids are used to protect lyophobic colloids 
(4) All of these
Biology
Cell: The Unit of Life
Choose the correct option among the following (1) Lyophilic sols are reversible sols (2) Lyophilic sols are more stable than lyophobic sols (3) Lyophilic colloids are used to protect lyophobic colloids (4) All of these
This cell type contains lysozomes that enable the breakdown of bacteria through phagocytosis. The cell has a multilobed nucleus and visible cytoplasmic granules. This cell type is the most abundant leukocyte, comprising 50% to 70% of all leukocytes. 
This cell type secretes chemicals that destroy large pathogens that cannot be phagocytized. The cell has a bilobed nucleus with visible cytoplasmic granules. This cell type constitutes 2% to 4% of all leukocytes.
This cell type secretes histamine as part of the inflammatory response and can secrete heparin, which prevents blood coagulation. The nucleus is often hidden by large, casily visible granules. This cell type is the rarest, comprising less than 1% of all leukocytes.
This cell type can be classified into subclasses with specialized functions, such as producing antibodies or attacking infected cells. The nucleus is circular, ovoid, or slightly dimpled in one side. This cell type constitutes 25% to 33% of all leukocytes.
This cell type can differentiate into a macrophage. The cell is large and has a nucleus that is large, clearly visible, and kidney-shaped. This cell type constitutes 3% to 8% of all leukocytes.
Biology
Cell: The Unit of Life
This cell type contains lysozomes that enable the breakdown of bacteria through phagocytosis. The cell has a multilobed nucleus and visible cytoplasmic granules. This cell type is the most abundant leukocyte, comprising 50% to 70% of all leukocytes. This cell type secretes chemicals that destroy large pathogens that cannot be phagocytized. The cell has a bilobed nucleus with visible cytoplasmic granules. This cell type constitutes 2% to 4% of all leukocytes. This cell type secretes histamine as part of the inflammatory response and can secrete heparin, which prevents blood coagulation. The nucleus is often hidden by large, casily visible granules. This cell type is the rarest, comprising less than 1% of all leukocytes. This cell type can be classified into subclasses with specialized functions, such as producing antibodies or attacking infected cells. The nucleus is circular, ovoid, or slightly dimpled in one side. This cell type constitutes 25% to 33% of all leukocytes. This cell type can differentiate into a macrophage. The cell is large and has a nucleus that is large, clearly visible, and kidney-shaped. This cell type constitutes 3% to 8% of all leukocytes.
In eukaryotic cells, ribosomes are found both free in the cytosol and attached to the endoplasmic reticulum (ER). Proteins produced on the attached ribosomes are delivered to the ER, while proteins produced on free ribosomes are delivered to the cytosol. Briefly explain in one or two sentences the two processes in terms of the following: ONE ultimate destination of a protein produced on an attached ribosome, and ONE general function of the protein (You do not need to identify the specific protein.) • ONE ultimate destination of a protein produced on a free ribosome,
Biology
Cell: The Unit of Life
In eukaryotic cells, ribosomes are found both free in the cytosol and attached to the endoplasmic reticulum (ER). Proteins produced on the attached ribosomes are delivered to the ER, while proteins produced on free ribosomes are delivered to the cytosol. Briefly explain in one or two sentences the two processes in terms of the following: ONE ultimate destination of a protein produced on an attached ribosome, and ONE general function of the protein (You do not need to identify the specific protein.) • ONE ultimate destination of a protein produced on a free ribosome,
Which among the following is considered the basic unit of life?
Cells
Tissues
Organs
Organ systems
Biology
Cell: The Unit of Life
Which among the following is considered the basic unit of life? Cells Tissues Organs Organ systems
The body's functions are all done by __ tissues.
same
similar
only one type of
different
tissues.
Biology
Cell: The Unit of Life
The body's functions are all done by __ tissues. same similar only one type of different tissues.
The diagrams below display different types of cells as viewed by a microscope under low magnification.
These diagrams demonstrate how cells can be differentiated by their
A. modes of locomotion.
B. means of replication.
C. sizes and densities.
D. cell structures.
Biology
Cell: The Unit of Life
The diagrams below display different types of cells as viewed by a microscope under low magnification. These diagrams demonstrate how cells can be differentiated by their A. modes of locomotion. B. means of replication. C. sizes and densities. D. cell structures.
Which of the following pairs is mismatched?
A) Mitochondria-ATP production
B) Golgi complex - modification and packaging of newly made proteins
C) Rough endoplasmic reticulum - protein synthesis
D) Nucleus - location of genetic information
E) Lysosome - photosynthesis
Biology
Cell: The Unit of Life
Which of the following pairs is mismatched? A) Mitochondria-ATP production B) Golgi complex - modification and packaging of newly made proteins C) Rough endoplasmic reticulum - protein synthesis D) Nucleus - location of genetic information E) Lysosome - photosynthesis
Which of the following is not true of prokaryotic cells?
A) They usually have a cell wall.
B) They reproduce by binary fission.
C) They may move using cilia.
D) They may be motile by means of flagella.
E) They possess a plasma membrane.
Biology
Cell: The Unit of Life
Which of the following is not true of prokaryotic cells? A) They usually have a cell wall. B) They reproduce by binary fission. C) They may move using cilia. D) They may be motile by means of flagella. E) They possess a plasma membrane.
Which of the following is NOT able to readily diffuse across the plasma membrane without the aid of a transport protein?
carbon dioxide
small hydrophobic molecules
oxygen
large polar molecules
small ions
Biology
Cell: The Unit of Life
Which of the following is NOT able to readily diffuse across the plasma membrane without the aid of a transport protein? carbon dioxide small hydrophobic molecules oxygen large polar molecules small ions
You have a DNA sequence that codes for a protein and is 105 nucleotides long.
A frameshift mutation occurs at the 85th base in the nucleotide sequence. How
many amino acids will be still be correct in this protein?
84
28
85
All of them. Frameshift mutation are silent
Biology
Cell: The Unit of Life
You have a DNA sequence that codes for a protein and is 105 nucleotides long. A frameshift mutation occurs at the 85th base in the nucleotide sequence. How many amino acids will be still be correct in this protein? 84 28 85 All of them. Frameshift mutation are silent
What of the following statements are tenets of cell theory?
all living organisms are composed of cells
all cells come from pre-existing cells
all cells have DNA contained within a nucleus
all cells have a cell wall composed of cellulose
cells are the structural and organizational unit of life
Biology
Cell: The Unit of Life
What of the following statements are tenets of cell theory? all living organisms are composed of cells all cells come from pre-existing cells all cells have DNA contained within a nucleus all cells have a cell wall composed of cellulose cells are the structural and organizational unit of life
What is the sequence of organelles for a protein to be synthesized and secreted out of an Eukaryotic cell?
Rough ER-> Golgi apparatus > Plasma membrane
Smooth ER-> Plasma membrane-> Food vacuole
Nucleus -> Cytoplasm Plasma membrane
Mitochondria -> Chloroplast -> Peroxisome
Biology
Cell: The Unit of Life
What is the sequence of organelles for a protein to be synthesized and secreted out of an Eukaryotic cell? Rough ER-> Golgi apparatus > Plasma membrane Smooth ER-> Plasma membrane-> Food vacuole Nucleus -> Cytoplasm Plasma membrane Mitochondria -> Chloroplast -> Peroxisome
This organelle packages proteins for dispersal throughout the cell
mitochondrion
golgi apparatus
peroxisome
contractile vacuole
lysosome
Biology
Cell: The Unit of Life
This organelle packages proteins for dispersal throughout the cell mitochondrion golgi apparatus peroxisome contractile vacuole lysosome
Which of the following describes the difference between phagocytosis and receptor mediated endocytosis?
A. only phagocytosis is mediated by vesicles
B. only receptor-mediated endocytosis is mediated by vesicles
C. only phagocytosis is described as bulk transport
D. only receptor-mediated endocytosis is highly specific in transporting molecules
Biology
Cell: The Unit of Life
Which of the following describes the difference between phagocytosis and receptor mediated endocytosis? A. only phagocytosis is mediated by vesicles B. only receptor-mediated endocytosis is mediated by vesicles C. only phagocytosis is described as bulk transport D. only receptor-mediated endocytosis is highly specific in transporting molecules
You are interested in a water-soluble protein that functions within the ER lumen. Given that information, which of the following statements can't be true about your protein of interest?
Answers A-D
A This protein contains a hydrophobic stop-transfer sequence in addition to its N-terminal signal sequence
B Although synthesis of the protein begins on a ribosome in the cytosol, the ribosome is brought to the ER membrane to complete Sanatation
C The signal sequence from the protein will be cleaved by a signal protaase (peptidase)
D The protein has an N-terminal signal sequence that binds to a Signal Recognition Particle (SRP) in the cytosal
Biology
Cell: The Unit of Life
You are interested in a water-soluble protein that functions within the ER lumen. Given that information, which of the following statements can't be true about your protein of interest? Answers A-D A This protein contains a hydrophobic stop-transfer sequence in addition to its N-terminal signal sequence B Although synthesis of the protein begins on a ribosome in the cytosol, the ribosome is brought to the ER membrane to complete Sanatation C The signal sequence from the protein will be cleaved by a signal protaase (peptidase) D The protein has an N-terminal signal sequence that binds to a Signal Recognition Particle (SRP) in the cytosal
In contrast to phospholipids, the transport
of fatty acids across membranes is much
more rapid (less than a second). Propose
an explanation for this observation.
Biology
Cell: The Unit of Life
In contrast to phospholipids, the transport of fatty acids across membranes is much more rapid (less than a second). Propose an explanation for this observation.
What would be the term for something that allows some molecules to get through a membrane and keeps others out? 
A. Insoluble permeability 
B. Soluble permeability 
C. Selective solubility 
D. Selective permeability
Biology
Cell: The Unit of Life
What would be the term for something that allows some molecules to get through a membrane and keeps others out? A. Insoluble permeability B. Soluble permeability C. Selective solubility D. Selective permeability
When the genetic code is transcribed from DNA to mRNA which nitrogenous base never appears in RNA and is replaced with uracil? 
A. Adenine 
B. Thymine 
C. Guanine 
D. Cytosine
Biology
Cell: The Unit of Life
When the genetic code is transcribed from DNA to mRNA which nitrogenous base never appears in RNA and is replaced with uracil? A. Adenine B. Thymine C. Guanine D. Cytosine
During photosynthesis, radiant or light energy is converted into what kind of energy?
Biology
Cell: The Unit of Life
During photosynthesis, radiant or light energy is converted into what kind of energy?
A 40-year-old man is brought to the emergency department because of lethargy, confusion, and a fainting episode 2 hours ago. He was alert after he regained consciousness. Over the past 2 months he has gained more than 10 kg (22 lb). He takes no medications. The patient's father has a history of recurrent stomach ulcers despite multiple medications. Laboratory studies show a glucose concentration of 45 mg/dL and an increased C-peptide concentration.
The hormone that is most likely causing this patient's symptoms is originally synthesized in which of the following structures?
A Free ribosomes
B Mitochondria
C Rough endoplasmic reticulum
D Secretory granules
E Smooth endoplasmic reticulum
Biology
Cell: The Unit of Life
A 40-year-old man is brought to the emergency department because of lethargy, confusion, and a fainting episode 2 hours ago. He was alert after he regained consciousness. Over the past 2 months he has gained more than 10 kg (22 lb). He takes no medications. The patient's father has a history of recurrent stomach ulcers despite multiple medications. Laboratory studies show a glucose concentration of 45 mg/dL and an increased C-peptide concentration. The hormone that is most likely causing this patient's symptoms is originally synthesized in which of the following structures? A Free ribosomes B Mitochondria C Rough endoplasmic reticulum D Secretory granules E Smooth endoplasmic reticulum
When using a compound light microscope, the most common reason for staining a specimen being observed is to ...
keep the organism from moving around
determine the effects of chemicals on the organism
make the view more colorful and interesting
reveal details that are otherwise not easily seen
Biology
Cell: The Unit of Life
When using a compound light microscope, the most common reason for staining a specimen being observed is to ... keep the organism from moving around determine the effects of chemicals on the organism make the view more colorful and interesting reveal details that are otherwise not easily seen
The cancer drug Taxol interferes with the separation of chromosomes during anaphase of mitosis. The likely mechanism of Taxol's action is 
(A) interference with the synthesis of cyclin- Cdk complexes. 
(B) prevention of kinetochore microtubule breakdown. 
(C) excitation of inhibitory transcription factors. 
(D) methylation of select areas of DNA on metaphase chromosomes. 
(E) blockage of spindle formation from microtubule organizing centers.
Biology
Cell: The Unit of Life
The cancer drug Taxol interferes with the separation of chromosomes during anaphase of mitosis. The likely mechanism of Taxol's action is (A) interference with the synthesis of cyclin- Cdk complexes. (B) prevention of kinetochore microtubule breakdown. (C) excitation of inhibitory transcription factors. (D) methylation of select areas of DNA on metaphase chromosomes. (E) blockage of spindle formation from microtubule organizing centers.
Which of the following descriptions best identifies Streptococcus?
rod-shaped bacteria connected in a bunch
rod-shaped bacteria connected in a line
Osphere-shaped bacteria connected in a bunch
sphere-shaped bacteria connected in a line
thick rigid spiral-shaped bacteria
Biology
Cell: The Unit of Life
Which of the following descriptions best identifies Streptococcus? rod-shaped bacteria connected in a bunch rod-shaped bacteria connected in a line Osphere-shaped bacteria connected in a bunch sphere-shaped bacteria connected in a line thick rigid spiral-shaped bacteria
Choose the four (4) features that plant cells have that animal cells do not.
Nucleus
Cell Wall
Plasmodesmata
Flagella
Chloroplasts
Lysosomes
Mitochondria
Centrosomes
Central Vacuole
Biology
Cell: The Unit of Life
Choose the four (4) features that plant cells have that animal cells do not. Nucleus Cell Wall Plasmodesmata Flagella Chloroplasts Lysosomes Mitochondria Centrosomes Central Vacuole
Which of the following is TRUE about cell membranes?
Proteins increase the mechanical strength of the cell membrane
Phospholipids make up the cell membrane
Cholesterol acts as floating doors, enabling substances in and out of the cell
The hydrophobic tail is oriented to face the outside of the cell membrane
Biology
Cell: The Unit of Life
Which of the following is TRUE about cell membranes? Proteins increase the mechanical strength of the cell membrane Phospholipids make up the cell membrane Cholesterol acts as floating doors, enabling substances in and out of the cell The hydrophobic tail is oriented to face the outside of the cell membrane