Midterm 1 Flashcards
(248 cards)
1
Q
What are the properties of life?
A
Homeostasis, energy utilization, reproduction, order, growth & development, response to environment and evolutionary adaptation.
2
Q
Are all 7 properties of life required for something to be considered living?
A
Yes. Viruses have only a few of the properties of life and therefore are not considered to be living.
3
Q
Does all life stem from a common ancestor?
A
Yes, all forms of life come from a common ancestor.
4
Q
What are the levels of biological organization, from biggest to smallest?
A
Biosphere, ecosystem, community, population, organism, organ system, organ, tissue, cell, organelles, molecules, atoms.
5
Q
Define “energy flow”.
A
Energy flow refers to the transfer and transformation of energy that is performed by all living things. Recall that energy utilization is a property of life. It is the flow of energy through an ecosystem.
6
Q
What is the primary source of energy for all life on earth?
A
The sun.
7
Q
What are autotrophs?
A
Autotrophs are organisms that do not consume other organisms. They produce their own organic molecules (food) by means of photosynthesis, hence the name “producers”.
8
Q
What are heterotrophs?
A
Heterotrophs are organisms that cannot produce their own food. They are “consumers” in that they must consume other organisms and/or organic molecules produced by other organisms.
9
Q
Is the classic food chain model actually found in nature?
A
No, to model the actual behaviour of each organism in relation to each other organism, we’d have to draw up a complex food web.
10
Q
What is trophic structure?
A
Also referred to as an energy pyramid, it is the system of organization of organisms into different trophic levels based on the amount of energy it consumes.
11
Q
How much energy is transferred from one trophic level to the next? What happens to the rest of it?
A
Only about 10% of the energy consumed from one trophic level is passed on the next, the other 90% is lost to the environment in the form of heat.
12
Q
What is photosynthesis?
A
Photosynthesis is the transformation of solar energy to chemical energy (glucose). This chemical reaction occurs in the CHLOROPLAST of plants, algae and some bacteria.
13
Q
What is the chemical equation of photosynthesis?
A
CO2 + H2O + Solar E –> C6H12O6 (glucose) + O2
14
Q
What is cellular respiration?
A
Cellular respiration is the process of breaking down food (such as glucose) transforming it into chemical energy in the form of ATP. This chemical reaction occurs in all organisms in the MITOCHONDRIA.
15
Q
What is the chemical equation of cellular respiration?
A
C6H12O6 (glucose) + O2 –> CO2 + H2O + ATP
16
Q
What is ATP?
A
Adenosine triphosphate is the energy currency of the cell. It is not energy itself, but rather an organic compound that stores energy for cellular work.
17
Q
What does ATP consist of?
A
A nitrogenous base, a 5-carbon sugar (ribose) and 3 negatively charged phosphate groups.
18
Q
What is hydrolysis?
A
A chemical process wherein the introduction a water molecule can break down complex molecules.
19
Q
ATP is said to be a renewable source of energy in the cell. What does this mean?
A
When an ATP molecule is broken down by hydrolysis and energy is released, you are left with an inorganic phosphate and an adenosine diphosphate molecule (ADP). When the cell carries out an unrelated catabolic reaction, the energy released can be used to rebuild the “broken” ATP molecule from its components. This new energy is therefore being stored in the bonds of our newly built ATP molecule. In that sense, ATP is a renewable resource.
20
Q
What is catabolism?
A
Catabolism refers to the catabolic processes that involve a series of degrative chemical reactions that break down complex molecules into smaller units, releasing the energy stored in that molecule’s bonds. These processes are exergonic.
21
Q
What is anabolism?
A
Anabolism refers to the anabolic processes that involve a sequence of chemical reactions that synthesis molecules from smaller units, requiring an input of energy (ATP). These processes are endergonic.
22
Q
An exergonic reaction _____ energy.
A
An exergonic reaction releases energy.
23
Q
An endergonic reaction _____ energy.
A
An endergonic reaction absorbs energy.
24
Q
Using ATP as a medium, describe the cycle formed by catabolic and anabolic processes.
A
The energy released by catabolic processes is stored in the form of ATP. This energy is eventually released and used by anabolic processes to build a complex molecule from smaller units. This complex molecule is eventually broken down again by another catabolic process in which more energy is released.
25
Are Hydrogen bonds a type of covalent bond?
No, hydrogen bonds are attractive forces between two molecules resulting from the polarity of each molecule.
26
Is water polar? If so, why?
Water molecules are polar due to the unequal charge distribution of its atoms. Since the electrons spend more time around the oxygen atom than they do the hydrogen atoms, oxygen is more electronegative than hydrogen.
27
Do hydrogen bonds form between different water molecules?
Yes, the slightly H+ atoms of one water molecule is attracted to the slightly O- atom of another molecule. Each water molecule can form a maximum of 4 hydrogen bonds.
28
What is cohesion?
Cohesion is water's ability to link together by forming hydrogen bonds between its molecules. This makes water more structured than other liquids and gives it a higher surface tension.
29
What is adhesion?
Adhesion is water's ability to form hydrogen bonds with a substance other than water (such as vessel walls in plants).
30
Both _____ and _____ allow for the upward transport of water in plants.
Both cohesion and adhesion allow for the upward transport of water in plants.
31
What is a hydrophilic substance?
A hydrophilic substance is a substance that can dissolve in water, such as ionic compounds and polar covalent compounds.
32
What is a hydrophobic substance?
A hydrophobic substance is a substance that cannot dissolve in water, such as non-polar covalent compounds.
33
Polymers are formed from _____.
Polymers are formed from monomers.
34
What are monomers?
The term monomer is used to define small molecules that can bind with similar molecules to former a larger, more complex molecule (a polymer). These are the building blocks for biological macromolecules such as DNA, RNA, proteins and carbohydrates.
35
How are polymers formed?
Polymers are formed by a dehydration / condensation reaction, wherein a water molecule is removed to form a new bond. More specifically, an H+ atom is removed from the end of a short polymer and combines with a hydroxide molecule (HO-) that is removed from an unlinked monomer, forming an H2O molecule. The monomer can join add itself to the end of the short polymer, forming a longer polymer.
36
How are polymers broken down?
Polymers are broken down by a hydrolysis reaction, wherein the insertion of a water molecule between a polymer and one of its monomers causes them to separate.
37
What is a carbohydrate?
A carbohydrate is a biomolecule consisting of carbon, hydrogen and oxygen atoms. The term refers to simple sugars (monomers) and their polymers. Carbohydrates serve as fuel for cells and as a carbon source to build other molecules.
38
What is the general formula for monosaccharides? What is its most common variant?
The general formula is (CH2O)n, where n is a whole number other than 0. The most common variant is (CH2O)6 = C6H12O6 (glucose).
39
What two forms can sugars be found in?
Either in linear form or in ring form.
40
What is the most common form a sugar can be found in? Why?
In nature, sugars are most commonly found in ring forms since this is the form they naturally take when in an aqueous solution.
41
What is a disaccharide?
A disaccharide is the name given to two sugar monomers (two monosaccharides) joined together by a glycosidic linkage.
42
What is a polysaccharide?
Polysaccharides range from a few hundred to tens of thousands of sugar monomers (monosaccharides) joined together by glycosidic linkages.
43
What is cellulose?
Cellulose is a polysaccharide consisting of beta-glucose subunits. It reinforces plant cell walls (structural support) and cannot be digested by most animals due to the fact that we do not have the enzyme that can break down beta-glycosidic bonds (the type of linkage found between joined beta-glucose molecules).
44
What is starch?
Starch is a polysaccharide consisting of alpha-glucose subunits. It is slightly branched (new branch about every 20 subunits) and acts as energy storage for plants when an excess of glucose is produced.
45
What is glycogen?
Glycogen is a polysaccharide consisting of alpha-glucose subunits. It is found in animals and is more branched than starch (new branch about every 10 subunits). Like starch, it also functions as energy storage.
46
What is chitin?
Chitin is type of polysaccharide found in the cell walls of some fungi and in the exoskeletons of animals such as lobsters, crabs and beetles (structural support).
47
Are lipids polymers?
Lipid molecules cannot link to one another to form polymers. They are the only biological macromolecules that behave this way.
48
Are lipids hydrophilic?
No, lipids are hydrophobic, meaning that they are insoluble in water.
49
What are fats / triglycerides / triacylglycerols made up of?
Fats are made up of a glycerol molecule (a 3 carbon alcohol) and 3 fatty acids (long hydrocarbons with a carboxyl group at one end).
50
How are fats / triglycerides / triacylglycerols formed?
Each fatty acid is linked to the glycerol molecule by a dehydration/condensation reaction. The linkage between them is known as an ESTER LINKAGE.
51
What is an Ester linkage?
An ester linkage is the name given to the bonds between a fat's glycerol and its three fatty acids.
52
Why part of a fat / triglyceride / triacylglycerol makes it hydrophobic?
Fats are hydrophobic due to the hydrocarbon chains within each fatty acid.
53
What is a saturated fat / triglyceride / triacylglycerol?
A saturated fat means that the fat's fatty acids are are saturated with hydrogen atoms (they contain as many H atoms as they can). This means there isn't a single C=C double bond, which in turn means that there isn't a bend in any of the chains either causing them to be solid at room temperature. Saturated fats are found in animal sources.
54
What is an unsaturated fat / triglyceride / triacylglycerol?
An unsaturated fat means that there is at least one C=C double bond in one of its fatty acids. This means there is a bend in at least one of the fatty acids, causing the sample to be liquid at room temperature. Unsaturated fats are found in plant and fish sources.
55
What are the 3 primary functions of fats / triglycerides / triacylglycerols?
Energy storage, fats contain twice as much energy per gram as polysaccharides; fats protect internal organs; fats prevent heat loss.
56
What are phospholipids made up of?
Phospholipids consist of a glycerol molecule, 2 fatty acids, a negatively charged phosphate group and a small hydrophilic group attached to the phosphate.
57
How are phospholipids amphipathic?
Phospholipids are amphipathic because they have both hydrophilic (phosphate group) and hydrophobic (fatty acid chains) regions.
58
What are micelles?
When phospholipids are submerged in water, they form aggregates called micelles wherein the hydrophilic heads are pointing outwards while the hydrophobic tails are sequestered. This is due to the amphipathic nature of phospholipids.
59
What is the primary function of phospholipids?
Phospholipids are the primary component of the cell membrane. Cell membranes are primarily comprised of a phospholipid bilayer, wherein the hydrophilic heads form the outer and inner edges while the hydrophobic tails form the core.
60
What do all steroids have in common in their composition.
All types of steroids consist of 4 fused Carbon rings.
61
Why is cholesterol significant as a steroid? (not to do with its role in the cell membrane).
Cholesterol is the starting compound for other steroids, such as estradiol, testosterone, progesterone and cortisol.
62
What does a hormonal protein do?
Hormonal proteins coordinate an organisms cellular activity.
63
What does a receptor protein do?
Receptor proteins react to chemical stimuli.
64
What does a contractile/motor protein do?
Contractile and motor proteins are responsible for movement.
65
What do structural proteins do?
Structural proteins act as support for things such as our hair.
66
What does an enzymatic protein do?
Enzymatic proteins (enzymes) selectively accelerate chemical reactions.
67
What does a defensive protein do?
Defensive proteins offer protection against disease (antibodies).
68
What does a storage protein do?
Storage proteins store amino acids.
69
What does a transport protein do?
Transport proteins aid in the transport of substances.
70
Proteins are polymers, the monomers of which are _____ _____.
Proteins are polymers, the monomers of which are amino acids.
71
How many different amino acids are there for all known living things?
There are 20 different amino acids for all known living things.
72
What do all amino acids have in common?
They all have a common sequence of atoms called a backbone. The variable side chain is what gives each amino acid its uniqueness.
73
Is a polymer of amino acids a protein?
Not necessarily. A polymer of amino acids is called a polypeptide. Under specific conditions, that polypeptide assumes a function and becomes a protein.
74
Can a protein consist of one of more polypeptides?
Yes, a protein can consist of one of more polypeptides.
75
In a protein / polypeptide, what are the bonds between amino acids called?
The bonds between amino acids are called peptide bonds.
76
When amino acids form a polypeptide, their common sequences of atoms become the _____ _____.
When amino acids form a polypeptide, their backbones link to become the polypeptide backbone,
77
How many amino acids are there in a polypeptide?
Polypeptides can range from only a few amino acids in length to thousands of amino acids in length.
78
What aspect of a protein determines its function?
The 3D structure (shape) of a protein is what determines its function.
79
What is protein denaturation?
When heated, a protein will collapse, losing its 3D shape and as a result, it will no longer be able to perform its function. Chemicals such as alcohol can also denature proteins.
80
What are the two types of nucleic acids?
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
81
What does DNA do?
Deoxyribonucleic Acid stores heritable information.
82
How is DNA organized?
DNA is organized into chromosomes which are made up of 100s to 1000s of genes.
83
What are genes?
A gene is the basic physical and functional unit of heredity. Each of these segments of DNA act as instructions to build a specific protein.
84
DNA directs its own synthesis through the process of _____.
DNA directs its own synthesis through the process of replication.
85
DNA directs the synthesis of RNA through the process of _____.
DNA directs the synthesis of RNA through the process of transcription.
86
What are the 3 types of RNA?
Messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).
87
What does mRNA do?
Messenger RNA directs the synthesis of a protein through the process of translation.
88
What does tRNA do?
Transfer RNA acts as a amino acid delivery vehicle during the process of protein synthesis.
89
What does rRNA do?
Ribosomal RNA makes up the structure of the Ribosome.
90
Nucleic acids are polymers, the monomers of which are _____.
Nucleic acids are polymers, the monomers of which are nucleotides. In other words, nucleic acids are polynucleotides.
91
What are nucleotides comprised of?
A nitrogenous base, a pentose sugar and a phosphate attached to carbon 5 of sugar (5').
92
What are the two types of nitrogenous bases?
Purines and pyrimidines.
93
What are the pyrimidines?
Cytosine, Thymine and Uracil (U replaces T in RNA).
94
What are the purines?
Guanine and adenine.
95
What's different in the structure between DNA and RNA.
DNA's pentose sugar has one less oxygen atom (deoxyribose) than RNA's pentose sugar (ribose).
96
Describe the synthesis of a nucleic acid.
The pentose sugar of one nucleotide connects to the phosphate group of another nucleotide. This leads to the formation of a SUGAR PHOSPHATE BACKBONE.
97
What is the linkage between the pentose sugar of one nucleotide and the phosphate of another nucleotide called?
A phosphodiester bond.
98
DNA consists of two strands wrapped into a _____ _____.
DNA consists of two strands wrapped into a double helix.
99
How are DNA's two strands held together?
DNA's two strands are held together by hydrogen bonds between their nitrogenous bases.
100
Adenine binds with _____.
Adenine binds with thymine (or uracil, in RNA).
101
Guanine binds with _____.
Guanine binds with cytosine.
102
How many hydrogen bonds are there between adenine and thymine?
There are two hydrogen bonds between A & T.
103
How many hydrogen bonds are there between guanine and cytosine?
There are 3 hydrogen bonds between G & C.
104
DNA strands are joined in an _____-_____ manner.
DNA strands are joined in an anti-parallel manner. They are parallel but run in opposite directions.
105
What protein a gene will produce depends on what?
The sequence of nitrogenous bases will determine what the gene will produce. Two genes will have different sequences.
106
RNA is single stranded, does this mean that it does not form hydrogen bonds between 2 sets of nitrogenous bases?
RNA is single stranded, but it can fold and complement itself or bind to regions of complementarity on other RNA strands.
107
What are the characteristics of a eukaryotic cell?
Such as animal and plant cells, eukaryotic cells have a nucleus and membrane bound organelles.
108
What are the characteristics of a prokaryotic cell?
Such as bacteria and archaea, prokaryotic cells store their DNA in a region called the nucleoid and don't have membrane bound organelles (less compartmentalized).
109
The chloroplast and central vacuole are only found in _____ _____.
The chloroplast and central vacuole are only found in plant cells.
110
Do only plant cells have a cell wall?
No, while animal cells do not have a cell wall, ALL prokaryotic cells (bacterial and archaea) do.
111
Which are smaller, prokaryotic cells or eukaryotic cells?
Prokaryotic cells (1 - 10 micrometers) are often about 10x smaller than eukaryotic cells (10 - 100 micrometers).
112
What characteristic of a cell decreases as volume increases?
The surface area to volume ratio of a cell decreases as its volume increases.
113
Why are cells so small?
If the volume of a cell is too large, its surface area would not be large enough to meet the metabolic requirements of the cell. Several small cells will exchange materials better than one large cell because of their high surface area to volume ratio.
114
Biological membranes are formed primarily from a phospholipid bilayer, however these can also contain _____ and _____.
Biological membranes are formed primarily from a phospholipid bilayer, however these can also contain proteins and lipids.
115
Biological membranes from a barrier that is _____ permeable.
Biological membranes from a barrier that is selectively permeable. Only some things can cross.
116
Describe the orientation of phospholipids in biological membranes.
The hydrophilic heads are pointed outside and inside the cell, while the hydrophobic tails are sequestered within the membrane (between the heads).
117
What is the endomembrane system?
The endomembrane system refers to specific components of the cell that are all interrelated, either directly through physical contact or indirectly through vesicles.
118
What are the components of the endomembrane system?
The nuclear envelope, the endoplasmic reticulum (smooth and rough), the Golgi apparatus, the lysosome, vacuoles and plasma membrane.
119
Describe the nucleus.
The nucleus is membrane bound and contains chromatin (DNA + histone proteins). Within the nucleus, DNA replicates itself and directs the synthesis of mRNA.
120
Describe the nuclear envelope / nuclear membrane.
The nuclear envelope is a DOUBLE phospholipid bilayer (4 layers of phospholipids). The fusion of both bilayers is what forms nuclear pores, through which large molecules, such as mRNA can pass. There is a network of proteins on the nuclear side (inside) called the NUCLEAR LAMINA which maintain the shape of the nucleus.
121
What is chromatin?
Chromatin is the “disorganized” form of DNA. Chromosomes are made up of chromatin (DNA and histone proteins).
122
What is the nucleolus?
The nucleolus is a region found within the nucleus where rRNA synthesis takes place.
123
What is the endoplasmic reticulum and where is it located?
The ER is an extensive membranous network of tubules and sacs that are continuous with the nuclear envelope. It is therefore located right next to the nucleus.
124
Describe the smooth ER (SER).
The SER synthesizes lipids, participates in carbohydrate metabolism, aids in drug and poison detoxification and stores Ca2+ in the muscle cells. The SER lacks ribosomes and therefore cannot synthesize proteins.
125
Describe the rough ER (RER).
The RER has ribosomes on its surface, hence the name. It therefore synthesizes SECRETED proteins (proteins that leave the cell) as well as proteins that will find themselves within the plasma membrane. The RER equally produces membrane for its own structure that can be added to other members of the endomembrane system.
126
What are ribosomes comprised of and what do they do?
Ribosomes are composed of rRNA and ribosomal proteins. They synthesize proteins.
127
What are the two types of ribosomes and what types of proteins do they synthesize?
Free ribosomes, found in the cytoplasm, synthesize cytosolic proteins. Bound ribosomes, found on the RER synthesize membrane-bound proteins and secreted proteins.
128
Where do newly synthesized membrane bound proteins and newly synthesized secreted proteins go?
Newly synthesized proteins depart from the ER in transport vesicles which bud from the ER itself. These vesicles then fuse with the Golgi apparatus.
129
What does the Golgi apparatus consist of?
The Golgi apparatus consists of flattened membranous sacs called cisternae.
130
What does the Golgi apparatus do to proteins it receives from the ER?
Proteins are modified by adding and removing carbohydrate groups (glycoproteins). The Golgi apparatus also sorts and packages proteins to send them to a destination either within the cell or out of it. Proteins are packaged into transport vesicles.
131
What is a lysosome?
Lysosomes are membrane enclosed sacs of hydrolytic enzymes and very acidic pH.
132
What does a lysosome do? Why? (3)
Lysosomes carry out intracellular digestion (during phagocytosis) by fusing to the food vacuole and they digest damaged organelles and macromolecules for recycling. They do these things to protect the cell, to maintain it and to recycle its components (autophagy).
133
What is phagocytosis / endocytosis (same thing)?
Phagocytosis is when the cell membrane engulfs a food particle, creating a food vacuole within the cell that contains the food particle. Lysosomes then break down that food.
134
What is autophagy?
Autophagy is when a lysosome fuses with a vesicle containing one or more damaged organelles in order to break these down and to recycle any monomers.
135
What is a vacuole?
A vacuole is a membrane bound sac.
136
What are the 3 types of vacuoles?
Food vacuole (protozoa), contractile vacuole (fresh water protozoa) and central vacuole.
137
What do food vacuoles do?
Similar to lysosome, these allow digestion of food particles in protozoa (single celled, animal-like organism).
138
What do contractile vacuoles do?
Contractile vacuoles can be found in freshwater protozoa for OSMOREGULATION. They pump water out of the cell as to not burst (lyse).
139
What does the central vacuole do?
Primarily found in plant eukaryotes, central vacuoles store nutrients/waste, they sequester harmful compounds and maintain pressure within the cell.
140
What are the membrane bound organelles that aren't a part of the endomembrane system?
The other membrane bound organelles are the mitochondria, chloroplasts and peroxisomes.
141
What does the mitochondria do?
The mitochondria is the site of cellular respiration in all eukaryotic cells, it produces ATP in the presence of oxygen. The number of mitochondria per cell varies depends on cellular activity.
142
Describe the structure of the mitochondria.
The mitochondria has a DOUBLE phospholipid bilayer, forming two fluid filled spaces. The outer membrane is highly permeable to small molecules and ions, the inner membrane is folded into CRISTAE which increases surface area. The inner membrane contains enzymes involved in cellular respiration. Within the inner membrane is the mitochondrial space (matrix), which is filled with DNA, ribosomes and enzymes.
143
What do chloroplasts do?
In plant cells, the chloroplast is the site of photosynthesis. Like the mitochondria, it is surrounded by a double phospholipid bilayer. It is this organelle that gives plants their green colour because it contains chlorophyll, a green pigment.
144
Describe the structure of the chloroplast.
The inner bilayer surrounds a fluid, STROMA that contains DNA, ribosomes and enzymes involved in photosynthesis. The stroma also contains THYLAKOIDS, which are membranous sacs containing chlorophyll. Thylakoids are stacked into GRANA (multiple GRANUM).
145
What do peroxisomes in animal cells do?
In animals, peroxisomes contain enzymes that carry out detoxification reactions (such as alcohol detoxification) as well as enzymes for the breakdown of fatty acids which serve as fuel for cellular respiration.
146
What do peroxisomes do in plant cells?
In plants, there are specialized peroxisomes called glyoxysomes that contain enzymes for the breakdown of stored fats in germinating seeds.
147
Describe the structure of a peroxisome.
Peroxisomes are surrounded by a single phospholipid bilayer and they contain oxidative enzymes.
148
What is the cytoskeleton?
It is the cells skeleton, a dynamic network of protein fibers found in the cytoplasm.
149
What are the 3 types of fibers that make up the cytoskeleton?
From thickest to thinnest, the three types of fibers that make up the cytoskeleton are microtubules, intermediate filaments and actin filaments/microfilaments.
150
Describe the structure and function of mircotubules.
Microtubules are tubes made from TUBULIN monomers. Theses are responsible for organelle and chromosome movement as well as cell motility (cilia and flagella).
151
What is cilia and flagella?
A cilium is an organelle that is short, many can be found on the cells surface and it moves like an oar. A flagellum is longer and demonstrates a wave-like motion. There is usually only 1 for a given cell (such as sperm). Both of these are responsible for movement of the cell.
152
Describe the structure and function of microfilaments.
Microfilaments are made from actin proteins. They permit muscle contraction, cell motility (pseudopodia) and cell division. These are equally responsible for cytoplasmic streaming (they move fluid throughout the cell to circulate its contents).
153
What are pseudopodia?
A pseudopodium is the name given to the protrusions formed by the cell membrane (arms) during phagocytosis.
154
Describe the structure and function of intermediate filaments.
Intermediate filaments consist of a divers class of proteins, depending on cell type. These fix organelle location and gives the nucleus its shape and rigidity as part of the nuclear lamina.
155
What task do all types of cytoskeleton fibers accomplish?
The microtubules, intermediate filaments and actin filaments all offer support in maintaining the cell shape.
156
What is the function of the cell wall?
In plant cells, the cell wall's rigidity maintains the cell shape and prevents excess water uptake.
157
What is the cell wall composed of?
This depends on the specific organism. A bacterium's cell wall is made up of PEPTIDOGLYCAN. In plants and protists (algae), cell walls are made up of cellulose. In fungi, cell walls are made of chitin.
158
Membranes that surround organelles separate the _____ from the _____.
Membranes that surround organelles separate the LUMEN (inside) from the cytosol (outside).
159
The cell membrane separates all that is _____ from all that is _____.
The cell membrane separates all that is INTRACELLULAR from all that is EXTRACELLULAR.
160
What is lateral diffusion?
The phospholipids and proteins of membranes perform lateral diffusion when they move from side to side. This lateral movement is common and is what gives cell membranes their fluidity.
161
What is flip-flopping?
Phospholipids of a membrane perform a flip-flop when a phospholipid pointing outwards switches places with a phospholipid pointing inward (towards the cell). This type of movement is very rare.
162
What is the fluid mosaic model?
The fluid mosaic model is a description of membranes, describing it as being fluid (its components are capable of lateral diffusion) and a mosaic of different lipids, proteins and carbohydrates.
163
What are the two main types of membrane proteins?
The two types of membrane proteins are peripheral proteins and integral proteins.
164
Describe peripheral proteins.
Peripheral proteins are not imbedded in the membrane, they reside on its surface and are therefore easy to remove. They also lack hydrophobic sequences.
165
Describe integral proteins.
Integral proteins are embedded within the membrane (transmembrane proteins). For this reason they are difficult to remove and have hydrophobic regions.
166
Why do integral proteins have hydrophobic regions?
A hydrophobic region is necessary in order to coexist and interact with the interior of the membrane, which is also hydrophobic.
167
Do integral proteins extend all the way through the membrane?
Not necessarily, an integral protein may only extend partway into the membrane interior. Regardless, the region in contact with the hydrophobic interior of the membrane must also be hydrophobic, and the region in contact with the aqueous environment must also be aqueous.
168
Why do some transmembrane proteins have a hydrophilic channel going through them?
Some transmembrane proteins have a hydrophilic channel going through them to allow the transport of polar substances across the membrane, such as water.
169
What are the different functions of membrane proteins?
Transport, Enzymatic, Signal transduction, Cell-Cell recognition, Intercellular joining & Stabilization of membranes.
170
What are glycoproteins?
Membrane proteins with carbohydrate groups attached to them.
171
What are glycolipids?
Membrane lipids with carbohydrate groups attached to them.
172
In what way is a membrane asymmetrical?
The inner layer is not the same as the outer layer, membranes have sidedness, meaning there is an inside and an outside.
173
What increases the fluidity of a membrane?
Heat and shorter, unsaturated phospholipids increase fluidity.
174
What is cholesterols role in the membrane?
Cholesterol acts as a fluidity buffer. It keeps membranes from becoming too fluid when the temperature increases and keeps it from becoming too rigid when the temperature decreases.
175
What is the benefit of a fluid membrane?
Fluidity in the membrane allows for movement and the formation of pseudopodia.
176
Describe diffusion as a form of membrane transport.
Diffusion is a form of PASSIVE TRANSPORT, meaning there is no energy required. This occurs when substances naturally move down their concentration gradient (from high to low concentration).
177
Describe facilitated diffusion.
Facilitated diffusion, like simple diffusion, does not require energy. However, it does require a channel or carrier. This means that solute is moving down its concentration gradient but is either a large polar or ionic compound and therefore needs an integral protein to provide a corridor of passage across the membrane.
178
What is an aquaporin molecule?
Also called water channels, aquaporins are transmembrane proteins that allow the passage of water across a membrane. Waters polarity is what makes it so difficult for it to traverse the membrane. It is an example of facilitated diffusion.
179
Describe active transport.
For solutes to move up the concentration gradient (from low to high concentration), energy and an integral membrane protein is required. The carrier protein in this type of transport undergoes a conformational change using an input of energy from ATP.
180
What is bulk transport?
Bulk transport is a type of active transport, wherein a vacuole containing large macromolecules/particles or large amounts of smaller molecules are brought into the cell.
181
What is osmosis?
Osmosis is the diffusion of water across a semi-permeable membrane (only water can pass). Under such conditions, water will move from low to high concentrations. Osmosis continues until both solutions are isotonic.
182
What does it mean if solution A is isotonic to solution B?
It means that solution A and solution B have the same concentration.
183
What does it mean if solution A is hypotonic to solution B?
It means that solution A has a lesser concentration than solution B.
184
What does it mean if solution A is hypertonic to solution B?
It means that solution A has a greater concentration than solution B.
185
Why do animal cells prefer being in an isotonic solution?
In a hypotonic solution, animal cells enlarge until they burst (lysis) and in a hypertonic solution, these cells shrivel. Only in an isotonic solution do these cells not suffer any consequences.
186
Why do plant cells prefer being in a hypotonic solution?
A plant cell's cell wall prevents lysis, and so the cell is turgid and happy. In an isotonic solution, cells lose mechanical support, becoming flaccid and in a hypertonic solution, the cell becomes PLASMOLYZED, which is lethal.
187
What are the two types of bulk transport?
Exocytosis, when molecules are secreted out of the cell and endocytosis, when molecules move into the cell.
188
Are secreted proteins being brought to the plasma membrane a form of bulk transport?
Yes, secreted proteins being sent from the Golgi apparatus to be secreted from the cell is an example of exocytosis.
189
What are the two types of endocytosis?
The two types of endocytosis are phagocytosis and pinocytosis.
190
Describe phagocytosis.
A particle is engulfed by pseudopodia, creating a food vacuole that then fuses with a lysosome which allows the digestion of the engulfed particle.
191
Describe pinocytosis.
Pinocytosis is when extracellular fluid is gulped by the cell in tiny vesicles. Due to the "food" being a concentrated solution, pinocytosis can be thought of as "cell-drinking".
192
What are the two steps of gene expression?
The two steps of gene expression are transcription (DNA to mRNA) and translation (mRNA to polypeptide).
193
In transcription, the mRNA grows in what direction?
mRNA is synthesized in the 5' to 3' direction.
194
What enzyme catalyzes mRNA synthesis?
RNA polymerase is the enzyme that catalyzes transcription.
195
Where does transcription occur in eukaryotic cells?
Transcription occurs in the nucleus, the mRNA is then exported to the cytoplasm for translation.
196
What are the template and coding strands?
During transcription, the template strand is the DNA strand complementary to the newly made RNA. The other strand is called the coding strand because the newly made RNA will have the same sequence as the coding strand, not the template strand. And so it is the gene on the coding strand that will be expressed.
197
What are triplets of nucleotides on the mRNA strand called?
Triplets of nucleotides on the mRNA are called codons.
198
Describe translation.
mRNA attaches to ribosomes, ribosomes read the mRNA and tRNA molecules bring over specific amino acids and ribosomes catalyze the formation of peptide bonds between them.
199
Describe the structure of a tRNA molecule.
At the top of a tRNA molecule is the amino acid attachment site. Which amino acid is attached depends on the anticodon, which is a sequence of 3 bases located at the bottom of the tRNA molecule. These 3 bases are complementary to a codon on the mRNA strand.
200
What does a genetic code dictionary do?
A genetic code dictionary tells you which CODONs on an mRNA strand code for which amino acids.
201
Does the start codon, AUG, code for an actual amino acid?
Yes, AUG denotes the beginning of a polypeptide and codes for the Met amino acid, meaning that all polypeptides begin with a Met amino acid.
202
Do any of the three stop codons code for an actual amino acid?
No, when a stop codon is reached, a release factor binds to the stop CODON and the ribosome leaves the mRNA.
203
What are polyribosomes?
Polyribosomes are a cluster of ribosomes simultaneously translating copies of mRNA, this type of activity can be found in both bacterial and eukaryotic cells.
204
How is protein synthesis different in prokaryotic cells?
In prokaryotic cells, translation can happen at the same time as transcription. Ribosomes can read an mRNA strand as it's being synthesized by RNA polymerase.
205
What are mutations?
Mutations are any change to sequence of bases in DNA.
206
Why do most mutations not change anything?
Most mutations don't change anything because multiple similar CODONS code for the same amino acids. However, certain mutations can lead to disease.
207
What are the 3 purposes of cell division?
Growth & development, tissue renewal and reproduction.
208
The cell is in interphase __-__% of the time and in the mitotic phase only __-__% of the time.
The cell is in interphase 90-95% of the time and in the mitotic phase only 5-10% of the time.
209
What are the three sub phases of interphase?
G1 (growth phase 1), S phase (DNA synthesis) and G2 (growth phase 2).
210
What occurs in G1 of interphase?
In growth phase 1, the cell grows and its organelles duplicate.
211
What occurs in S phase of interphase?
In S phase, chromosomes replicate.
212
What occurs in G2 of interphase?
In growth phase 2, tubulin and actin proteins are made and the cell checks that everything is ready to enter mitosis.
213
What are sister chromatids?
When a chromosome is duplicated, the duplicated chromosomes remains attached at the CENTROMERE and are called sister chromatids.
214
What are kinetochores?
Kinetochores are proteins at the centromere, where mitotic spindle microtubules attach.
215
During DNA replication, what enzyme separates the two DNA strands?
Helicase is the enzyme responsible for unwinding and separating the two DNA strands.
216
During DNA replication, what enzyme makes the new DNA?
DNA polymerase is the enzyme that builds new DNA strands complementary to the two original strands in the 5' to 3' direction.
217
Mitosis is the division of the cell's nucleus. What are the 5 stages of mitosis?
Prophase, Prometaphase, Metaphase, Anaphase, Telophase.
218
Describe prophase.
Chromosomes condense, mitotic spindle forms and centrosomes move apart.
219
Describe prometaphase.
Nuclear envelope breaks down, spindle fibers attach to chromosomes at kinetochores.
220
Describe metaphase.
Chromosomes line up at the metaphase plate (center of the cell) in single file.
221
Describe anaphase.
Sister chromatids are pulled apart to opposite sides of the cell.
222
Describe telophase.
Spindle fibers disassemble, nuclear envelope reforms and chromosomes uncoil.
223
Describe cytokinesis.
In animal cells, this occurs by cleavage. A cleavage furrow is created by a ring of actin microfilaments that pinches inward until the cell divides into two. In plant cells, vesicles containing cell wall material line up in the middle of the cell and fuse together, forming a cell PLATE. The cell plate eventually combines with the wall of the parent cell and forms the new cell wall.
224
The centrosome consists of a _____ pair.
The centrosome consists of a centriole pair.
225
In what phase of mitosis does the cell plate begin to form in plant cells?
The cell plate begins to form in telophase.
226
Describe binary fission.
In prokaryotes, after chromosomes replicate, each copy moves to opposite ends of the cell, the cell grows in size and then splits into two.
227
Where does meiosis take place?
Meiosis takes place in specialized cells within the testes and ovaries (the GONADS).
228
Homologous chromosomes consist of 1 _____ and 1 _____ chromosome.
Homologous chromosomes consist of 1 paternal and 1 maternal chromosome.
229
How many sets of chromosomes do human somatic cells have?
Human somatic cells are diploid, meaning they have 2 sets of chromosomes.
230
How many sets of chromosomes do human gametes have?
Human gametes are haploid, meaning they have 1 set of chromosomes.
231
What is fertilization?
Fertilization is when 2 haploid gametes fuse to form a diploid cell (ZYGOTE).
232
What are the 4 phases of meiosis 1?
Prophase 1, metaphase 1, anaphase 1 and telophase 1. These are followed by cytokinesis 1.
233
What are the 4 phases of meiosis 2?
Prophase 2, metaphase 2, anaphase 2 and telophase 2. These are followed by cytokinesis 2.
234
Describe prophase 1.
Chromosomes condense, mitotic spindle forms, centrosomes move apart and nuclear envelope fragments.
Then, homologous chromosomes pair up, forming tetrads through SYNAPSIS. Crossing over occurs.
235
Describe metaphase 1.
Tetrads line up at the metaphase plate, chromosomes are in double file.
236
Describe anaphase 1.
Homologous chromosomes are pulled apart to opposite sides of the cell.
237
Describe telophase 1.
Spindle fibers disassemble, nuclear envelope reforms, chromosomes decondense.
238
Describe cytokinesis 1.
Separation into 2 haploid cells.
239
Describe prophase 2.
Mitotic spindle forms, chromosomes decondense, centrosomes move apart, nuclear envelope fragments.
240
Describe metaphase 2.
Chromosomes line up at the metaphase plate in single file.
241
Describe anaphase 2.
Sister chromatids are pulled apart into opposite sides of the cell.
242
Describe telophase 2.
Spindle fibers disassemble, nuclear envelope reforms and chromosomes decondense.
243
Describe cytokinesis 2.
Separation of the initial diploid cell into 4 haploid cells.
244
What are the 3 mechanisms of genetic variation?
Independent assortment, crossing over and random fertilization.
245
Describe independent assortment.
The random orientation of tetrads at the metaphase plate mean than meiosis 1 daughter cells have 50/50 chance of receiving either the paternal chromosome or maternal chromosome for each chromosome.
246
Describe crossing over.
Crossing over during prophase 1 creates RECOMBINANT CHROMOSOMES. These chromosomes have a mix of paternal and maternal genes.
247
Describe random fertilization.
Any sperm can fertilize any egg. 8 million sperm x 8 million eggs = about 70 trillion possibilities.
248
What one thing drives all genetic variation?
Mutation drives all genetic variation.
