Module 3: Cells Flashcards
1
Q
What are the three principal parts of the generalized cell?
A
Plasma membrane, cytoplasm (cytosol and organelles), nucleus
2
Q
What is the plasma membrane composed of and what does it surround?
A
Composed of a liquid bilayer consisting of phospholipids, cholesterol and glycolipids with various proteins inserted. It surrounds the cytoplasm.
3
Q
What are the types of lipids in the plasma membrane ?
A
Phospholipids, cholesterol and glycolipids
4
Q
What are the functions of the plasma membrane ?
A
- Acts as a barrier separating inside and outside of the cell
- Controls the flow of substances into and out of the cell
- Helps identify the cell to other cells like immune cells
- Participates in intercellular signaling
5
Q
What are the types of proteins in the plasma membrane ?
A
Peripheral (loosely attached to the exterior) and integral (extend into or through the lipid bilayer)
6
Q
What is selective permeability ?
A
The property of the plasma membrane to allow some substances to move in and out of the cell and restrict some others
7
Q
What is the lipid bilayer permeable to ?
A
Water and non-polar molecules like fatty acids, fat-soluble vitamins, steroids, oxygen and carbon dioxide
8
Q
What is the lipid bilayer not permeable to ?
A
Ions, charged molecules, and large uncharged molecules like glucose and amino acids
9
Q
What are the functions of integral proteins and what is the main type of protein ?
A
Integral proteins are mainly glycoproteins and they can serve as channels (pores), transporters (carriers), receptors (recognition sites) or enzymes
10
Q
What are the functions of peripheral proteins ?
A
Enzymes or cytoskeletal anchors
11
Q
What is the use of cholesterol in the plasma membrane ?
A
Stabilize the membrane and reduce its fluidity
12
Q
What is the role of transporter proteins in the plasma membrane ?
A
They increase the permeability of the membrane to molecules that cannot cross the lipid layer by changing shape as they move a substance from one side to the other
13
Q
What is the role of receptor proteins in the plasma membrane ?
A
They recognize and bind to a specific molecule that governs some cellular function
14
Q
What is the role of membrane glycoproteins and glycolipids in the plasma membrane ?
A
They are cell identity markers, they enable the cell to recognize other cells of its own kind during tissue formation
15
Q
Name the types of extracellular fluid and their location
A
Insterstitial fluid (between cell tissues), plasma (blood plasma in blood vessels), cerebrospinal (within and around the brain and spinal cord) and lymph (in lymphatic vessels)
16
Q
What portion of body fluid is in intracellular fluid ?
A
2/3
17
Q
What is a concentration gradient ?
A
A difference of concentration between two areas
18
Q
What are the criteria to classify transport process ?
A
Active, passive or vesicular
19
Q
What are the types of passive transport used by the living cells (are they mediated or non-mediated) ?
A
- Diffusion through lipid bilayer (non-mediated)
- Diffusion through a channel (non-mediated)
- Facilitated diffusion (mediated)
20
Q
Define diffusion
A
The random mixing of particles that occurs in a solution
21
Q
What factors influence diffusion ?
A
- Steepness of the concentration gradient
- Temperature
- Size or mass of the diffusing substance
- Surface area
- Diffusion distance
22
Q
What is simple diffusion ?
A
When molecules diffuse across the lipid bilayer
23
Q
What molecules can diffuse by simple diffusion through the lipid bilayer ?
A
Non-polar hydrophobic molecules such as respiratory gases, lipids, small alcohols and ammonia. Water and urea as well.
24
Q
What processes are allowed by simple diffusion through the lipid bilayer ?
A
Gas exchange, absorption of some nutrients and excretion of some wastes
25
What is facilitated diffusion ?
When a solute binds to a specific transporter on one side of the membrane and is released on the other side after the transporter undergoes a conformational change
26
What substances move across the plasma membrane by facilitated diffusion ?
Glucose, fructose and some vitamins
27
What are ion channels ?
They are integral proteins that are specific and selective and may be gated or open all the time
28
What is osmosis ?
Osmosis is a pasive process in which there is a net movement of water through a selectively permeable membrane. Water moves from a high water concentration area to a low water concentration area.
29
What is osmotic pressure ?
The pressure applied by a solute on a membrane through which it cannot pass
30
What is the tonicity of a solution ?
It relates to how the solution influences the shape of body cells
31
Define isotonic solution and what would happen to a red blood cell in such a solution
A solution in which the solute concentration is the same as one in the cell. The red blood cell would maintain its shape
32
Define hypotonic solution and what would happen to a red blood cell in such a solution
A solution with lower concentration of solutes (higher concentration of water) than the cytosol inside the cell. Water molecules will tend to go inside the cell, which will swell. The process is called hemolysis.
33
Define hypertonic solution and what would happen to a red blood cell in such a solution
A solution with higher concentration of solutes (lower concentration of water) than the cytosol inside the cell. Water molecules will tend to go outside of the cell, which will shrink. The process is called crenation.
34
Define active transport
An active process in which cellular energy is used to transport substances across the membrane against a concentration to an area of high concentration.
35
How does active transport occur?
Energy derived from splitting ATP changes the shape of a carrier protein called a pump, which moves a substance across a cellular membrane against its concentration gradient.
36
Describe the sodium-potassium pump process
1. Three sodium ions in the cytosol bind to the protein
2. The sodium binding triggers the splitting of ATP into ADP plus phosphate group, which also becomes attached to the protein. This chemical reaction changes th shape of the pump protein, expelling the three sodium ions into the extracellular fluid. The changed shape of the protein favors the binding of two potassium ions.
3. The binding of the K+ causes pump protein to release the phosphate group and get back to its original shape.
4. As the pump protein changes back to its shape, it releases the two potassium ions into the cytosol. It is ready again to bind to sodium ions.
37
What is a vesicule ?
A small round sac formed by budding off from an existing membrane
38
What are the functions of vesicules ?
- Transport substances from one structure to another within cells
- Take in substances from extracellular fluid
- Release substances into extracellular fluid
39
What is endocytosis ?
When materials move into a cell in a vesicule formed from the plasma membrane because they are too large to enter by active transport or diffusion
40
What is exocytosis ?
Movement of substances out of a cell in secretory vesicules that fuse with the plasma membrane and release their contents into the extracellular fluid
41
What are the three types of endocytosis ?
Phagocytosis and bulk-phase endocytosis (pinocytosis) and receptor mediated endocytosis
42
What is phagocytosis ?
Movement of a solid particle such as bacteria, viruses, aged or dead cells into a cell after pseudopods engulf it. Only occurs in phagocytes, cells that are specialized to engulf and destroy bacteria and foreign substances
43
What is bulk-phase endocytosis ?
Movement of extracellular fluid into cell by unfolding of plasma membrane. The plasma membrane folds and becomes a vesicule with the solutes from the extracellular fluid in it.
44
In what cells is exocytosis particularly important ?
Secretory cells that release digestive enzymes, hormones, mucus or other secretions and nerve cells that release neurotransmitters
45
What is the cytoplasm ?
All the cellular contents between the plasma membrane and the nucleus. Includes cytosol and organelles
46
What is the cytosol ?
It's the intercellular fluid, the liquid portion of the cytoplasm that surrounds the organelles.
47
What is the cytosool composed of ?
75-90% water, proteins, carbohydrates, lipids and inorganic subtances.
48
What is the use of the cytosol ?
It is the medium in which many reactions occur. Chemicals can be in solution or in colloidal form (suspended).
49
What are the different organelles ?
Cytoskeleton (microfilaments, intermediate filaments and microtubules), centrosomes, cilia, flagella, ribosomes, endoplasmis reticulum, Golgi complex, lysosomes, nucleus, perixosomes, proteasome and mitochondria
50
What is the cytoskeleton and what are its different parts ?
It is a network of several kinds of protein filaments that extend throughout the cytoplasm and provide a structural framework for the cell. It is composed of microfilaments, intermediate filaments and microtubules.
51
What is the role of microfilaments and what are they composed of ?
Providing mechanical support and helping generate movement. They are composed of actin.
52
What is the role and composition of intermediate filaments ?
Intermediate filaments are found in parts of the cell subject to tension. They help hold organelles in place and help attach cells to one another. They are composed of many types of proteins.
53
What is the role and composition of microtubules ?
They help determine cell shape and function in intracellular transport of organelles and the migration of chromosomes during cell division. They are formed of tubulin.
54
What is the centrosome ?
A dense area near the nucleolus containing two centrioles at right angles to one another and a pericentriolar matrix. It serves as a center for organizing microtubules in interphase cells and the miotic spindle during cell division.
55
What are cilia ?
Numerous, short, hair-like projections extending from the surface of a cell, which functions to move materials over the surface of cells located in the lining of the respiratory tract and fallopian tubes.
56
What are the main components of cilia and flagella ?
Microtubules
57
What is a flagella ?
A structure similar to cilia, but longer, and can move an entire cell. Only example in humans is the tail of the sperm.
58
What is a ribosome composed of and what is its main function ?
Ribosomes are tiny spheres that consist of ribosomal RNA and several ribosomal proteins forming a large and a small subunit. They are the sites of protein synthesis.
59
Where can ribosomes be found ?
Mostly in the endoplasmic reticulum and some are free (in clusters or singly)
60
What is the endoplasmic reticulum ?
A network of folded membrane that form flattened sacs or tubules called cisterns.
61
Describe rough ER
It is continuous with the nucleus membrane and has a outer surface studded with ribosomes.
62
Describe smooth ER
It extends from the rough ER to form a network of membrane tubules, but it does not contain ribosomes on its membrane surface.
63
What are the functions of rough ER ?
To synthetize secretory proteins and membrane molecules (glycoproteins and phospholipids)
64
What are the functions of smooth ER ?
Synthetize fatty acids and steroids, detoxify chemicals in the liver and store and release calcium ions in muscle cells.
65
What is the difference between free ribosomes and ribosomes located in the ER ?
Ribosomes associated with ER synthetize proteins destined for insertion in the plasma membrane or secretion from the cell. Free ribosomes synthetize proteins used in the cytosol.
66
What is the Golgi complex ?
It's the first step for delivering of proteins made in the ER. It consists of 4 to 6 stacked, flattened membraneous sacks (cisterns)é The cisterns are separated in cis medial and trans sections.
67
What are the functions of the Golgi complex ?
- Modifies, sorts, packages and transports proteins received from the rough ER.
- Form secretory vesicules that discharge processed proteins via exocytosis
- Form transport vesicules that ferry lipids to the plasma membrane or molecules to other organelles like lysosomes
68
What are lysosomes ?
Membrane-enclosed vesicules that form in the Golgi complex and contain many digestive enzymes.
69
What are the functions of lysosomes ?
- Allow the final products of digestion such as monosaccharides, faty acids and amino acids to be transported into the cytosol (intracellular digestion)
- Digestion of worn-out organelles (autophagy)
- Digestion of cellular contents (autolysis) during embryological development and extracellular digestion
70
What are peroxisomes ?
Small structures similar to lysosomes, but with enzymes like catalase that use molecular oxygen to oxidize various organic substances. It can be for normal substances like amino acids, or toxic substances.
71
What are proteasomes ?
Tiny barrel-shaped structures that get rid of proteins inside the cell by cutting them into peptides.
72
What is the structure of a mitochondrion ?
A double membrane. A smoothe outer membrane and a folded inner membrane arranged in cristae. The large central fluid-filled cavity of a mitochondrion is the mitochondrial matrix.
73
What is the role of mitochondria and how do they achieve it ?
Mitochondria are the site of ATP production in the cell through catabolism of nutrient molecules. The elaborate fold of the cristae provides an enormous surface for chemical reactions with surface enzymes and matrix enzymes.
74
How do mitochondria replicate ?
They self-replicate using their own DNA
75
How many nucleus does a cell have ?
Most have one, some have none (red blood cells) and some have many (skeletal muscle fibres)
76
What are the main structures of the nucleus ?
The nuclear envelope (double membrane), perforated by nuclear pores, the nucleoli and genetic material.
77
What are the levels of DNA packaging ?
Nucleosomes, chromatin fibres, chromatids and chromosomes.
78
How many chromosomes do the cells have ?
46 arranged in 23 pairs
79
What are the functions of the nucleus ?
- Contain genes
- Control cell structure
- Direct cellular activities
- Produce ribosomes in nucleoli
80
What is the role of proteins ?
Determine the physical and chemical characteristics of a cell
81
Give a summary of protein fabrication.
1. DNA contained in genes provide the instructions for making proteins.
2. To synthetize a protein, the information contained in a specific region of DNA is first transcribed to produce a specific molecule of RNA.
3. The RNA then attaches to a ribosome, where the information contained in the RNA is translated into a corresponding specific sequence of amino acids, to form a new protein molecule.
82
What are the three types of RNA made from DNA ?
Messenger RNA, ribosomal RNA and transfer RNA
83
What is the role of each RNA type ?
- Messenger RNA directs synthesis of a protein
- Ribosomal RNA joins with ribosomal proteins to make ribosomes
- Transfer RNA binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation.
84
Define transcription
It is the process by which the genetic information encoded in DNA is copied onto a strand of mRNA.
85
What is the enzyme that catalyzes transcription ?
RNA polymerase
86
What happens when the RNA polymerase reaches the terminator in transcription ?
It detaches from the transcribed RNA molecule and the DNA strand. Once synthetized, RNA leave the nucleus through a nuclear pore. In the cytoplasm, they participate in the next step of protein synthesis, translation.
87
What is translation ?
The process of reading the mRNA nucleotide sequence to determine the amino acid sequence of the protein
88
What are the 7 translation steps ?
1. Initiator tRNA attaches to a start codon
2. Large and small ribosomal subunits join to form a functional ribosome and intiator tRNA fits into P site
3. Anticodon of incoming tRNA pairs with next mRNA codon at A site
4. Aminoacid on tRNA at P site forms a peptide bond with amino acid at A site
5. The two-peptide protein created from the formation of the peptide bond becomes attached to tRNA at A site
6. Risobome shifts by one codon : tRNA previously at P site enters E site and is released from ribosome; tRNA previously at A site is now at P site.
7. Protein synthesis stops when the ribosome reaches stop codon on mRNA
89
What is cell division, in general ?
It is the process by which cells reproduce themselves. It consists of nuclear division (mitosis and meiosis) ad cytoplasmic division (cytokinesis).
90
What is the difference between somatic cell division and reproductive cell division ?
Somatic cell division results in an increase of body cells and involves a nuclear division called mitosis.
Reproductive cell division results in the production of sperm and eggs and involves a nuclear division called meiosis.
91
What are the two major periods of somatic cell life?
Interphase, when a cell is not dividing and miotic phase, when a cell is dividing
92
What is observable in a cell during interphase ?
A defined nuclear envelope, a nucleolus, chromatin.
93
What life processes are carried on during interphase ?
Every life process except cell division
94
What is the miotic phase composed of ?
Mitosis (nuclear division) and cytokinesis (cytoplasmic division)
95
What is mitosis ?
Distribution of two sets of chromosomes, one set into each of the separate nuclei
96
What are the stages of mitosis ?
Prophase, metaphase, anaphase and telophase.
97
What happens during prophase ?
Chromatin condenses into chromosomes, composed of two identical chromatids, held together by a centromere. Later, the pericentriolar matrix of the two centrosomes start to form an assembly of microtubules called miotic spindle. The lenghtening of microtubules pushes centrosomes to each poles of the cell, and nucleolus and nuclear envelope start to break down.
98
What happens during metaphase ?
The centromeres of the chromatid pairs are aligned along the microtubules of the miotic spindle at its exact center, in a plane called metaphase plate
99
What happens during anaphase ?
The centromeres split, separating the two members of each chromatid pair, which move to opposite sides of the cell. Once separated, the chromatids are called chromosomes.
100
What happens during telophase ?
After the chromosomal movement stops, telophase begins. The identical set of chromosomes uncoil and revert to chromatin form. A new nuclear envelope forms around each chromatin mass, nucleioli appears, and the miotic spindle breaks up.
101
What is cytokinesis and when does it occur?
The division of the cytoplasm and organelles of a parent cell. The process begins at late anaphase or early telophase, with the formation of a cleavage furrow. When cytokinesis is complete, interphase begins.
