Chapter 3: Cells Flashcards
What is a cell?
This is a living structural and functional unit enclosed by a membrane
What are the three main parts of a cell?
Plasma membrane
Cytoplasm
Nucleus
Describe the structure of the plasma membrane
This makes the cell’s flexible outer surface, which separates the internal and external environment
It is made up of a lipid bilayer which itself is made up of (2x) phospholipids, cholesterol, and glycolipids
What are the two types of proteins in the plasma membrane?
Integral and peripheral
What are the roles of the plasma membrane?
Regulates flow of materials in and out of the cell
Key role in communication among cells and between cells in external environment
What are integral proteins?
These are proteins that extend through the lipid bilayer. These proteins allow small and medium-sized water-soluble materials to cross through the membrane
What are peripheral proteins
These are proteins that loosely attach to the exterior or interior surface of the membrane
How is the plasma membrane selectively permeable?
The lipid bilayer is permeable to water and non-polar molecules like fatty acids, O2, CO2, etc. but is impermeable to ions and large, uncharged polar molecules like glucose and amino acids.
Large molecules like proteins usually require transport via vesicles to travel through the plasma membrane
What are the proteins in the plasma membrane that determine the membrane’s function?
Receptors
Ion channels
Carrier proteins/transporters
Enzymes
Cell identity markers
What is cholesterol used for in the plasma membrane?
This binds with adjacent phospholipids to help make the phospholipid bilayer stronger
It also maintains fluidity in cell membranes at normal body temperatures
What is extracellular fluid? Give some examples
This is the fluid outside of cells. This includes interstitial fluid, blood plasma, and lymph
What is interstitial fluid?
This is a type of extracellular fluid found between cells in tissues
What is blood plasma?
This is a type of extracellular fluid found in blood vessels
What is lymph?
This is a type of extracellular fluid found in lymphatic vessels
What are the methods for which substances move across the plasma membrane?
Passive transport and active transport
What is passive transport?
This is when a substance moves down its concentration gradient through the membrane, only using its own kinetic energy.
Simple diffusion and osmosis
What is active transport?
This is when a substance is pushed through the membrane against its concentration gradient. This requires cellular energy, usually from ATP
Define diffusion
This is a passive process in which a substance will move due to its kinetic energy, travelling from high concentration to low concentration
What is simple diffusion?
This is when substances diffuse across a membrane through the lipid bilayer.
What is facilitated diffusion
This is when a substance can’t move through the membrane via simple diffusion or a passive process.
An integral membrane protein helps the substance move across the membrane. The protein will be either a membrane channel or carrier
Describe the facilitated diffusion of potassium ions
Gated ion channels are present in the plasma membrane that allows intracellular K+ ions to move out into the cell (following concentration gradient) when the gate is open.
Describe the facilitated diffusion of a glucose molecule
The glucose transporter, the carrier protein, is an integral protein which teeters back and forth. In one position, the carrier protein is open to the extracellular fluid, where glucose can onto slots of the carrier protein. The protein will undergo a change in shape, causing it to open to the intracellular fluid, allowing glucose to enter the cell, following its concentration gradient
Describe how water moves in osmosis
Water will move from an area of higher water concentration to an area of lower concentration. Or it will move from an area of lower solute concentration to higher solute concentration.
Describe what will happen next in this experiment:
A selectively permeable membrane that permits water but not sucrose molecules to pass is filled with a 20% sucrose 80% water solution. The upper part of the cellophane sac is wrapped tightly about a stopper through which a glass tube is fitted.
The sac is placed into a beaker containing 100% water
Because the cellophane is selectively permeable to water only, the amount of sucrose inside the sac will not change, but water from the beaker will move into the cellophane because of the higher solute concentration in the sac. Volume in the sac will increase, while the volume of water in the beaker itself will drop
What is an isotonic solution?
This is when the concentrations of solutes are the same on both sides of a membrane.
Any solution in which cells maintain their normal shape and volume is called an isotonic solution
What is a hypotonic solution?
This is a solution that has a lower concentration of solutes, thus a higher concentration of water.
What is a hypertonic solution?
This is a solution that has a higher concentration of solutes, thus a lower concentration of water.
What is osmotic pressure?
This is the pressure that a solution containing solute particles that are impermeable to a membrane exerts on that membrane
If a red blood cell is placed in a hypotonic solution, what will happen to the cell?
Because the solute concentration is higher in the cell, water will flow into it, causing hemolysis
If a red blood cell is placed in a hypertonic solution, what will happen to the cell?
Because the solute concentration is higher in the solution, water will be drawn out of the cell, causing crenation.
How does ATP facilitate active transport?
The energy derived from splitting ATP changes the shape of a carrier protein called a pump, causing the substance to move across a membrane against its concentration gradient
Describe the steps of the sodium potassium pump
3 Na ions from the cytosol will bind to the inside surface of the Na-K pump, triggering ATP to bind as well
ATP is split into ADP and phosphate, with the energy release causing the pump to change shape, moving Na outside of the pump. Phosphate will bind to the inner side of the pump at the same time.
2 K ions from extracellular fluid will bind on the outside surface of the pump and cause the Phosphate from earlier to be released
The release of Phosphate causes the pump to return to its original shape, moving K into the cell
What is a vesicle?
This is a small round sac that is made from existing membrane that buds off
What is endocytosis?
This is when materials move into the cell via vesicle formation from the membrane
What is exocytosis?
This is when materials move out of the cell by fusion of a vesicle with the membrane
What are the types of endocytosis?
Phagocytosis and bulk-phase endocytosis (pinocytosis)
What is phagocytosis?
This is when large solid particles like bacteria, viruses, or dead cells, are taken in by the cell
What is bulk-phase endocytosis or pinocytosis?
This is also known as “cell drinking,” and is when cells take up tiny droplets of extracellular fluid
What are the steps of phagocytosis?
A particle binds to a plasma membrane receptor
Projections of the plasma membrane called pseudopods extend from the cell and surround the particle
Ends of the pseudopods fuse together to form a vesicle called a phagosome that then enters the cytoplasm
The phagosome fuses with one or more lysosomes, which contain lysosomal enzymes that break down the ingested material
Undigested material may remain indefinitely in a vesicle called a residual body, or be exerted by the cell
What is a residual body in a cell?
This is a vesicle that contains undigested material that has been phagocytosed
What is the purpose of pinocytosis?
This is done to extract solutes dissolved in extracellular fluid. Cells are able to extract amino acids and fatty acids in this way
Which molecules are capable of simple diffusion?
Because they need to cross the plasma membrane easily, they must be lipid-soluble molecules.
Oxygen
Carbon dioxide
Fat soluble vitamins like A, D, E, and K
The polar molecules water and urea are capable of simple diffusion
Which molecules undergo facilitated diffusion
ions such as K, Cl, Na, and Ca
Simple sugars such as glucose, fructose, and galactose
Some vitamins
Which substances undergo active transport?
Ions such as Na, K, Ca, H, I, and Cl
Which substances undergo phagocytosis?
Bacteria, viruses, and aged or dead cells
Which substances undergo pinocytosis or bulk-phase endocytosis
Solutes in extracellular fluid
Which substances undergo exocytosis?
Neurotransmitters
Hormones
Digestive enzymes
What is the cytoskeleton of a cell for?
This provides structural framework and generates movements
What is the cytoskeleton comprised of?
This is made of a network of 3 different types of protein filaments
Microfilaments
Intermediate filaments
Microtubules
What is the cytoplasm?
This is everything in the cell except for the nucleus. It includes the cytosol and the organelles
Describe microfilaments
These are the thinnest elements of the cytoskeleton. They make up microvilli which are key for absorption.
Microfilaments are also involved in muscle contraction, cell division, and cell locomotion.
Name some microfilament-assisted movements
Migration of embryonic cells during development,
Invasion of tissues by white blood cells to fight infection
Migration of skin cells during wound healing
Describe intermediate filaments
These are thicker than microfilaments and thinner than microtubules. They are found in areas of the cell subject to tension, like stretching.
They help hold organelles like the nucleus in place
And they help attach cells to one another
Describe Microtubules
These are the largest cytoskeletal component. They are long hollow tubes that help determine cell shape and function for movement of organelles within a cell (like secretory vesicles) and migration of chromosomes during cell division.
They are also responsible for movements of cilia and flagella
What are organelles?
These are specialized structures in cells that have characteristic shapes and functions
What is the centrosome?
This is an organelle near the nucleus.
What is the centrosome made of?
It is made from two centrioles and pericentriolar materials.
What are centrioles?
These are cylindrical structures composed of nine clusters of three microtubules (triplets) that are arranged in a circular pattern.
What is the pericentriolar matrix?
This is the area surrounding the centrioles which contain hundreds of ring-shaped proteins called tubulins.
What is the importance of tubulins (in centrosomes)
These are the organizing centers for growth of the mitotic spindle (key in cell division), and microtubule formation in non-dividing cells
What are ribosomes?
These are the sites of protein synthesis in the cells.
They are named after their high content of ribonucleic acid (RNA)
What is the endoplasmic reticulum?
This is a network of folded membranes of flattened tubules
What is the rough ER?
This part of the endoplasmic reticulum extends from the nuclear envelope and holds many ribosomes
(It extends into the smooth ER)
What is the function of the rough ER?
Its key function is to synthesize proteins
What is the smooth ER?
This is the part of the endoplasmic reticulum extending from the rough ER and lacks ribosomes.
What is the function of the smooth ER?
Its key function is to synthesize fatty acids and steroids like estrogens and testosterone
It is also important for inactivating or detoxifying several drugs and harmful substances in the liver.
Describe the structure of ribosomes
These consist of two subunits - a large and small
Where are ribosomal subunits synthesized and assembled?
These are made in the nucleolus of the nucleus. They then exit the nucleus and are assembled in the cytoplasm to become a functional unit.
What is the difference in function between free ribosomes and ribosomes on the ER?
Free ribosomes make proteins used in the cytosol whereas rough ER ribosomes are used to make proteins for specific organelles, insertion into the plasma membrane, or export out of the cell.
What is the sarcoplasmic reticulum?
This is the form of smooth endoplasmic reticulum in muscle cells.
Calcium ions are stored in these for muscle contraction
What is the Golgi complex?
This is an organelle that proteins are transported to after synthesis in the rough ER
Describe the structure of the Golgi compelx
This is made of 3 to 20 cisterns - flattened membranous sacs with bulging edges, that are piled onto each other. Cells usually have several Golgi complexes. Cells that secrete proteins have more extensive complexes.
What are the functions of the Golgi Complex?
Modifies and packages proteins
Sorts proteins and packs into vesicles to be sent either to extracellular fluid, plasma membrane, or other organelles like lysosomes
What are lysosomes?
These are membrane enclosed vesicles that can contain digestive enzymes
What are peroxisomes?
These are lysosomes that contain several oxidases used to oxidize several organic substances
What are proteasomes?
These are lysosomes that destroy unneeded, damaged, or faulty proteins
Where is the site of most ATP production?
The mitochondria
How many mitochondria are usually seen in cells? List 3 areas where cells have many mitochondria
Between 100 to 1000, depending on how active the cell is.
The muscles, liver, and kidneys have many mitochondria
What is a mitochondrial cristae?
This is an arrangement of folds from the inner mitochondrial membrane
What is the mitochondrial matrix?
This is the large central fluid-filled cavity of the mitochondrion which is enclosed by the inner membrane
Which of the following can make proteins?
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Mitochondria
Both the rough ER and mitochondria are capable of making proteins. There are some ribosomes in mitochondria that allow them to create some proteins
Where in the mitochondria is most ATP generated?
On the inner facing surface of the cristae.
What is the nucleus?
This is a spherical or oval structure, usually being the most prominent feature of a cell
Describe how many nuclei can be found in cells
Most body cells have a single nucleus, but mature red blood cells have none, while skeletal muscle cells and some others have several
What is the nuclear envelop?
This is a double membrane of the nucleus that separates the nucleus and cytoplasm
What are nuclear pores?
These are holes in the nuclear envelop that control movement of substances between the nucleus and cytoplasm
What are nucleoli?
These are spherical bodies within the nucleus that hold clusters of protein, DNA, and RNA, and is the site of ribosome assembly
What controls a cells structure and directs most of its activities?
Genes do this in the nucleus
How many chromosomes are present in a somatic cell?
46 chromosomes are present
What is chromatin?
This is the apparent granular mass of chromosomes when the cell is not dividing
What is a genome?
This is the total genetic information carried in a cell
What are cilia and flagella?
These are motile cell surface projections with an inner core of microtubules
What are the functions of cilia and flagella?
Cilia move fluids over a cell’s surface
A flagellum moves an entire cell
What are stem cells?
These are unspecialized cells that can divide for indefinite periods and give rise to specialized cells
What is a totipotent stem cell? Give examples
This is a cell that has the potential to form an entire organism.
Zygotic cells and cells from a four-day old embryo are totipotent
What is a pluripotent stem cell? Give examples
These are stem cells that can give rise to many but not all different types of cells.
These include five-day old embryo cells
What is a multipotent stem cell? What is its main purpose?
These stem cells divide into cells with a specific function and create a closely related family of cells.
These mainly maintain or repair tissue
What is an oligopotent stem cell? Give examples
This is a type of stem cell that can create a few different cell types.
These include myeloid cells, and lymphoid cells (develop into different types of blood cells)
What is a unipotent stem cell? Give examples
This produces only one type of cell, but can renew itself, distinguishing it from non-stem cells.
These include stem keratinocytes in the skin or satellite cells in muscles
Describe the steps of protein synthesis
Information in a specific region of DNA is transcribed in the nucleus to make a specific molecule of RNA
RNA moves out of the nucleus via pores and into the cytoplasm
RNA attaches to a ribosome where the information from the RNA is translated into a specific order of amino acids
What enzyme catalyzes the transcription of DNA?
This is done by RNA polymerase. It must be instructed where to start and end
What is a promoter?
This is a special sequence of nucleotides on DNA located near the beginning of a gene and is where RNA polymerase attaches to
What is messenger RNA
This is a type of RNA that directs synthesis of protein
What is ribosomal RNA?
This is a type of RNA that joins with ribosomal proteins to make ribosomes
What is transfer RNA?
This is a type of RNA that binds to an amino acid and amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation.
What are the three kinds of RNA made from DNA?
Messenger (mRNA), ribosomal (rRNA), and transfer (tRNA)
What is a terminator?
This is a special nucleotide sequence on the DNA that specifies the end of the DNA. When RNA polymerase reaches this point, it will detach from both the DNA and the transcribed RNA molecule
What is transcription?
This when genetic information in the DNA strand is copied into a complementary sequence in the RNA strand
What is translation?
This is when mRNA associates with ribosomes and directs the synthesis of a protein by converting the sequence of nucleotides in mRNA into a specific sequence of amino acids
Describe the steps of translation
mRNA binds to small ribosomal subunit at the mRNA binding site.
Initiator tRNA binds to the start codon (AUG) on mRNA to begin translation
Large ribosomal subunit attaches to small ribosomal subunit-mRNA complex to make a functional ribosome. The initiator tRNA fits into the P-site of the large subunit. One end of the tRNA has an anticodon attaching to mRNA, and the other end has a specific amino acid
Another tRNA approaches and its anticodon attaches to mRNA at the A-site of the large subunit. The amino acid held on the P-site tRNA creates a peptide bond with the A-site tRNA, and it is released from the P-site tRNA
Ribosome shifts by one codon so that the previous P-site tRNA moves to the E-site, and the previous A-site tRNA moves to the P-site.
The now empty tRNA at the P-site then exits the ribosome.
The cycle continues until the ribosome reaches a stop codon on the mRNA.
What is a polyribosome?
This is a group of ribosomes that are all attached to the same mRNA. They all move together at the same time to create large amounts of protein synthesis from each mRNA.
What is cell division?
This is the process whereby cells reproduce themselves when they are damaged, diseased, or worn out
What are the two types of cell division?
Reproductive cell division and somatic cell division
What is reproductive cell division?
This is aka meiosis. It produces gametes (sperm and oocytes)
What is somatic cell division?
This is when a cell divides into two identical cells
What is the cell cycle?
This is the sequence of changes that a cell goes through from the time it forms until it duplicates its contents and divides into two cells
What are the two major phases of the cell cycle in somatic cells?
Interphase and mitotic
What is the interphase phase of the cell cycle?
This is the phase of when a cell is not dividing. DNA replicates itself at this phase
What is the mitotic phase of the cell cycle?
This is the phase of when a cell is dividing. This is when the nucleus and cytoplasm splits into 2 cells. It is divided into four stages
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is the largest single cell in the body?
This is the oocyte. It has a diameter of 140 micrometers
What is the diameter of a red blood cell?
It is 8 micrometers in diameter
What is aging?
This is a normal process accompanied by a progressive alteration of the body’s homeostatic adaptive responses.
There are observable changes in structure and function and increases vulnerability to environmental stress and disease
What is gerontology?
This is the study of the process and problems associated with aging
What is prophase?
This is when chromatin condense into chromosomes visible under a light microscopes. Each prophase chromosome at this point is made up of a pair of identical, double-stranded chromatids.
Tubulins in the pericentriolar material of the centrosomes start to form the mitotic spindle.
Microtubules lengthen between the centrosomes push them to opposite poles of the cell.
While the spindles are pushing the centrosomes to opposite ends, they also attach to the kinetochores of the chromosomes, allowing for the movement of chromosomes during cell division.
The spindles eventually extend from pole to pole.
Nucleolus and nuclear envelope break down
What is a centromere?
This is a constricted region of the chromosome that holds the chromatid pair together
What is the kinetochore?
This is the protein complex outside of each centromere which the mitotic spindles connect to
What happens during interphase?
This is when the cell replicates its DNA, and creates more organelles and cytosolic components to prepare for cell division.
What is metaphase?
This is when the centromeres of the chromatid pairs are aligned along the microtubules at the center of the mitotic spindle. This line down the middle where the centromeres align is called the metaphase plate
What is anaphase?
This is when the centromeres split, allowing the two members of each chromatid pair to move to opposite poles of the cell. When the chromatid pair are split, each pair is then called a chromosome again.
What is telophase?
This is the final stage of mitosis, which begins after chromosomal movement stops. The chromosomes uncoil and go back to threadlike chromatin form when they are opposite ends of the cell. A new nuclear envelope forms around each mass of chromatin, the nucleoli appear in each pole, and the mitotic spindle eventually breaks up.
What is cytokinesis?
This is when the cell is dividing its cytoplasm and organelles. It begins late in anaphase with the formation of a cleavage furrow. Microfilaments in the cleavage furrow pull the plasma membrane progressively inward, pinching the cell in the center like a belt, and splitting it in two. After the process, there are two equivalently sized and identical cells with copied chromosomes. When this ends, interphase begins.
What is a cleavage furrow?
This is a slight indentation of the plasma membrane that extends around the center of the cell
What is the increase in the size of cells without cell division called?
Hypertrophy
What is the loss of tissue differentiation and function that is characteristic of most malignancies?
Anaplasia
What is is the transformation of one type of cell into another?
Metaplasia
What is the tonicity of most intravenous solutions with respect to blood cells?
Isotonic
What other organelle besides the nucleus contains DNA?
Mitochondrion
What is the polar portion of a cholesterol molecule that forms hydrogen bonds with the polar heads of neighbouring phospholipids and glycolipids?
This is made up of an OH group
What are the three main components of the lipid bilayer portion of a plasma membrane?
Phospholipids, cholesterol, and glycolipids
What is the site of synthesis of rRNA and assembly of rRNA and proteins into ribosomes?
The nucleolus
What is the transport process that moves substances through cells using endocytosis on one side of a cell and exocytosis on the opposite side of the cell
Transcytosis
