Unit 1: Chemistry and Cells Flashcards

Question

What is phase-contrast? (microscopes)

Answer 1

Variations in density within the specimen are amplified to enhance contrast in unstained cells; useful for examining living, unpigmented cells.

Answer 2

Optical modifications are used to exaggerate differences in density; image appears almost 3D.

Answer 3

Using a laser, this "optical sectioning" technique eliminates out-of-focus light from a thick sample. By capturing sharp images at many different planes, a 3D reconstruction can be recreated.

Answer 4

The SEM is especially useful for detailed study of the topography of a specimen. The electron beam scans the surface of the sample (usually coated with a thin film of gold). The beam excites electrons on the surface, and these secondary electrons are detected by a device that translates the pattern of electrons into an electronic signal sent to a video screen.

Answer 5

The TEM is used to study the internal structure of cells. The TEM aims an electron beam through a very thing section of the specimen. The specimen must be stained with atoms of heavy metals. This enhances the density of some parts of the specimen.

Answer 6

In cell fractionation, broken-up cells are placed in a tube that is spun in a centrifuge. The largest components settle on the bottom of the tube, forming a pellet. The liquid above the pellet is poured into a new tube and centrifuged again. This is repeated several times, creating a series of pellets that consist of different pieces of the specimen.

Answer 7

The attachment structures on the surface of some prokaryotes (not visible on TEM).

Answer 8

The region where the cell's DNA is located (no membrane).

Answer 9

The outer coating of many prokaryotes consisting of a capsule or a slime layer.

Answer 10

Microvilli increase the cell's surface area without increasing its volume much.

Answer 11

The nuclear envelope is a double membrane which is each a lipid bilayer separated by a space of 20-40 mm. The envelope is perforated by pore structures (around 100 mm in diameter). At the lip of each pore, the inner and outer membranes of the envelope are joined. An intricate protein called a pore complex lines each pore and regulates the entry/exit.

Answer 12

A netlike array of protein filaments (intermediate filaments in animal cells) that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.

Answer 13

The nucleolus is where rRNA is synthesized. Proteins are assembled with the rRNA are assembled into ribosomes. The ribosomes exit the nucleus via the nuclear pores.

Answer 14

- The synthesis of lipids - including steroids (sex hormones) - The metabolism of carbohydrates - The detoxification of drugs/poisons (adding hydroxyl groups to drug molecules; more drugs = proliferation of smooth ER = higher tolerance to the drugs) - The storage of calcium ions (in muscle cells, calcium ions are pumped from the cytosol into the lumen)

Answer 15

- Creates secretory proteins (most of which are glycoproteins - proteins with carbohydrates covalently bonded to them) - Membrane factory (grows in place by adding membrane proteins and phospholipids to its own membrane)

Answer 16

The cis-side usually faces the ER and receives vesicles. The trans-side gives rise to vesicles that pinch off and travel to other sites.

Answer 17

The lysosome is a membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest macromolecules (the enzymes of the lysosome work best in the acidic environments found in lysosomes). Lysosomes also play a role in phagocytosis. The food vacuole fuses with the lysosome and hydrolytic enzymes digest the food particles.

Answer 18

Cristae are the infoldings found in the inner membrane of mitochondria. They give the inner membrane a higher surface area, enhancing the productivity of cellular respiration.

Answer 19

The intermembrane space is the space between the two membranes of mitochondria. The mitochondrial matrix is the area enclosed by the inner membrane.

Answer 20

Thylakoids are the flattened interconnected sacs found in chloroplasts. Granum are stacks of thylakoids. Stroma is the fluid outside the thylakoids.

Answer 21

A family of closely related plant organelles.

Answer 22

Amylose - starch

Answer 23

It removes hydrogen atoms from certain molecules and transfer them to oxygen producing hydrogen peroxide. They have a granular or crystalline core that to be a dense collection of enzyme molecules.

Answer 24

Tubulin a dimer made of alpha-tubulin and beta-tubulin. They form a hollow tube.

Answer 25

Maintenance of cell shape; cell motility; chromosome movements in cell division; organelle movements

Answer 26

Filaments of actin

Answer 27

Maintenance of cell shape; changes in cell shape; muscle contraction; cytoplasmic streaming (movement of cytoplasm around in plant cells); cell motility; cell division (animal cells)

Answer 28

One of several different proteins (such as keratin) coiled into cables

Answer 29

Maintenance of cell shape; anchorage of nucleus and certain other organelles; formation of nuclear lamina.

Answer 30

A region that is often located near the nucleus and organizes microtubules. - Composed of a pair of centrioles which is each composed of 9 sets of triplet microtubules arranged in a ring

Answer 31

Microtubules

Answer 32

Motile cilia and flagella: 9 doublets of microtubules arranged in a ring with 2 single microtubules in the center. "9+2" pattern Nonmotile cilia: Same as motile cilia, but lacking the 2 microtubules in the center. "9+0" pattern

Answer 33

A structure that anchors the microtubule assembly of a cilium or flagellum. Structurally similar to a centriole (microtubule triplets in a 9 + 0 pattern)

Answer 34

Large motor proteins that attach along each outer microtubule doublet. A typical dynein protein has two "feet" that "walk" along the microtubule of the adjacent doublet, using ATP for energy.

Answer 35

The primary cell wall is the first cell wall a young plant secretes which is relatively thin and flexible. When the cell matures and stops growing, it strengthens its wall. Some plants cells do this by simply secreting hardening substances into the primary wall. Others add a secondary cell wall. The secondary wall is often deposited in several laminated layers and has a strong and durable matrix that affords the cell protection and support.

Answer 36

Middle lamella is a thin layer rich in sticky polysaccharides called pectin. It glues adjacent cells together and is between the primary and secondary cell walls.

Answer 37

A small core protein with many carbohydrate chains covalently atached

Answer 38

Cell-surface receptor proteins that bind on their cytoplasmic side to associated proteins attached to microfilaments and transmits signals between the ECM (extracellular matrix) and the cell.

Answer 39

A junction that occurs at the plasma membranes of neighboring cells that are tightly pressed against each other, bound by specific proteins. This prevents leakage of extracellular fluid.

Answer 40

Junctions that function like rivets, fastening cells together. Intermediate filaments made of keratin proteins anchor desmosomes in the cytoplasm.

Answer 41

Junctions that provide cytoplasmic channels from one cell to an adjacent cell (similar to plasmodesmata in plants).

Answer 42

Desmosomes

Answer 43

The nuclear matrix is an intricate meshwork of proteins spread throughout the nucleus. The matrix plays a role in essential nuclear functions, which include gene expression, RNA splicing, RNA export, and nuclear protein import and export.

Answer 44

Secretory cells

Answer 45

Fat-storing tissues in plant seeds. They convert fatty acids into sugar.

Answer 46

Glucose, galactose

Answer 47

Carbonyl in the middle of the chain Fructose

Answer 48

Glycosidic linkages

Answer 49

Heavily branched

Answer 50

α-glucose has an H on top and an OH on the bottom of Carbon 1, while ß-glucose has an OH on top and an H on the bottom of Carbon 1. ß glucose is more stable and harder to break down in humans' digestive systems. In cellulose, every ß glucose is upside down.

Answer 51

An ester linkage

Answer 52

Peptide bonds. In a peptide bond, the O double-bonded to the C of the carboxyl group and the N from the amine group are on opposite sides.

Answer 53

An alpha carbon has an amine group (NH2) and a carboxyl on the other. An H is attached above the alpha carbon, and an R group is attached below the alpha carbon.

Answer 54

Storage, enzymes, defensive, transport, hormones, receptors, motor, structure

Answer 55

The xth amino acid and the (x+4)th amino acid. Ex. Between the 1st amino acid and 5th amino acid.

Answer 56

2 rings, Guanine and Adenine

Answer 57

1 ring, Cytosine, Uracil, Thymine

Answer 58

A pathway in which a substance is broken down into smaller parts

Answer 59

A pathway in which a substance is formed from smaller parts

Answer 60

1. Energy is not created or destroyed 2. Entropy continuously increases

Answer 61

The total energy of a system

Answer 62

Something that is thermodynamically favorable. Either enthalpy decreases or entropy increases.

Answer 63

When there is a net release of free energy, -ΔG

Answer 64

When there is a net consumption of free energy, +ΔG

Answer 65

The transfer of a phosphate group

Answer 66

Phosphorylation makes a molecule less stable, so there is more free energy. This also converts ATP to ADP.

Answer 67

They lower the activation energy of a reaction

Answer 68

The shape of the enzymes changes, and the enzyme helps facilitate the reaction (can be holding the reactants in place, creating a microenvironment, etc.)

Answer 69

Competitive and non-competitive. The competitive inhibitor binds to the active site and prevents the substrate from binding there. The noncompetitive inhibitor binds to a different site on the enzyme; it doesn't block substrate binding, but it causes other changes in the enzyme so that it can no longer catalyze the reaction efficiently.

Answer 70

When the activity of an enzyme is regulated by another molecule

Answer 71

When a substrate binding to a multi-subunit enzyme triggers shape change in all subunits. Amplifies response of enzyme to substrates

Answer 72

The activity of the enzyme is suppressed by its product

Answer 73

They allow it to be more rigid (Seen in warmer environments)

Answer 74

They allow it to be more fluid (Seen in colder environments)

Answer 75

It restrains phospholipid movement at high temperatures, but also lowers the temperature required for solidification.

Answer 76

Proteins that penetrate the hydrophobic interior of the lipid bilayer

Answer 77

A protein that spans the whole membrane

Answer 78

Proteins that aren't embedded in the cell membrane

Answer 79

A solution that is less concentrated in something (ex. salt).

Answer 80

A solution that is more concentrated in something (ex. salt).

Answer 81

Hypotonic. It allows them to remain turgid (water pressure pressing their cell walls)

Answer 82

The plant becomes flaccid.

Answer 83

The plant cell shrivels. This occurs in a hypertonic solution.

Answer 84

It lyses (bursts open)

Answer 85

It shrivels up

Answer 86

Channel proteins: Molecule or ion channels (are often gated by ligand or voltage) Carrier proteins: Bind to specific solutes and transfer them across the membrane

Answer 87

Transport that moves solute against its concentration gradient. It requires ATP. It can maintain membrane potential

Answer 88

Proton pumps use ATP to pump a molecule/ion (say Na+) against its concentration gradient outside the cell. When the molecule/ion naturally diffuses back in, it brings another molecule with it (say glucose).

Answer 89

The secretion of vesicles through the cell membrane

Answer 90

Phagocytosis - The cell takes in a large particle via a vesicle Pinocytosis - The cell takes in many "gulps" of vesicles Receptor-mediated endocytosis - Receptors to specific substrates cluster in coated pits (takes in cholesterol)

Answer 91

Receptor, transduction, response

Answer 92

Long-distance signaling (with hormones)

Answer 93

- Embryonic development - Immune response

Answer 94

A binding molecule that leads to a change in the shape of the receptor

Answer 95

It attaches to a GPCR which causes the activation of adenylate cyclase (by the alpha subunit). Adenylate cyclase then takes ATP and produces cAMP (cyclic adenosine monophosphate). cAMP (the secondary messenger) then activates Protein Kinase A, which then stimulates the breakdown of glycogen.

Answer 96

V0 (or d[P]/dt) = (Vmax[s])/(Km + [s]) Where V0 is current rate of reaction, Vmax is maximum rate of reaction and Km is a constant

Answer 97

Lower Km, Same Vmax The concentration of the substrate at which half of the active sites of the enzyme are occupied by the substrate changes (is lower) The maximum velocity achieved stays the same On a graph, the curve/slope of the line is different, but the peak is the same.

Answer 98

Same Km, Lower Vmax The concentration of the substrate at which half of the active sites of the enzyme are occupied by the substrate is the same The maximum velocity is lower On a graph, the curve/slope would look very similar, while the peak would be lower.

Answer 99

When a ligand binds to a GPCR, it undergoes a conformational change (its shape changes), and it binds to the G-protein, activating it and causing the GTP to bump out the GDP. This causes the alpha subunit to dissociate from the beta and gamma subunits. The alpha subunit (and the beta/gamma dimer both) can regulate protein functions. The target protein can relay signals via 2nd messengers. The GTP is then hydrolyzed back to GDP (the RGS (regulation of G-protein signaling) protein can accelerate this).

Answer 100

They have 7 transmembrane alpha helices (that is why they are also called "7 transmembrane receptors"

Answer 101

G-proteins that associate with GPCRs are heterotrimeric meaning that they have 3 different subunits. The first subunit is called alpha, the second beta, and the third gamma. The alpha and gamma subunits are attached to the cell membrane, (by lipid anchors) while the beta subunit is attached to the gamma subunit. A G-protein can either be on or off depending on whether GTP (guanosine triphosphate) or GDP (guanosine diphosphate) is bound to the alpha subunit, respectively.

Answer 102

An enzyme that catalyzes the transfer of a phosphate group to another molecule/protein (ex. insulin)

Answer 103

It is a protein complex with a signal-binding site and tyrosine attached to it.

Answer 104

When a signaling molecule attaches to the signal binding sites, 2 separate polypeptides (of RTK) will come together and become an unphosphorylated dimer (with activated tyrosine regions). Each tyrosine attaches a phosphate onto a tyrosine on the opposite side (as it is a dimer). When all the tyrosines have a phosphate attached to them, this dimer becomes phosphorylated. A relay protein will then bind to phosphate on a tyrosine region, undergo a conformational change, and lead to a cellular response. There can be multiple cell responses all from one signaling molecule.

Answer 105

Proteins that bring 2 or more proteins together in a relatively stable configuration.

Answer 106

- Only allows ions in when a ligand binds to it - Closes when the ligand unbinds

Answer 107

Because steroids are fat-soluble, they can pass directly through the membrane. When inside the cell, they bind to receptors in the cytoplasm. This hormone-receptor complex enters the nucleus and binds to genes, acting as a transcription complex stimulating the creating of mRNA.

Answer 108

Protein kinases phosphorylate proteins with Pi (phosphate) from ATP

Answer 109

A chain of events in which one protein/enzyme phosphorylates another, producing ADP.

Answer 110

An enzyme that removes a phosphate from a phosphorylated molecule. This helps "reset" a phosphorylation cascade.

Answer 111

cAMP and Ca2+

Answer 112

Any cell in an organism that is not a reproductive cell

Answer 113

An organism's reproductive cell(s)

Answer 114

A duplicated chromosome (in the shape of an X). NOT mother and father chromosomes. Sister chromatids are identical and attached by cohesin protein complexes.

Answer 115

The part of a chromosome which attaches to the spindle fiber. It is made of repetitive sequences and the attachment to the microtubules are facilitated by proteins which recognize this repetitive sequence.

Answer 116

The mitotic (M) phase

Answer 117

The cell rapidly grows and protein/organelle production occurs

Answer 118

The cell grows and copies its chromosomes. This accounts for around half the cycle in the average cell.

Answer 119

The cell grows and gets ready for cell division

Answer 120

The chromatin condenses (visible under an LM), the nucleoli disappear, and the mitotic spindle of microtubules begins to form.

Answer 121

The step that follows mitosis, where the cytoplasm is divided and 1 cell becomes 2 cells.

Answer 122

Asters ("stars")

Answer 123

The nuclear envelope fragments and the microtubules extending from each centrosome can now invade the nuclear area. The chromosomes become even more condensed. A kinetochore forms at the centromere of each chromatid (2 per chromosome) and some of the microtubules attach to the kinetochores, becoming "kinetochore microtubules", which move the chromosomes. Nonkinetochore microtubules lengthen the cell.

Answer 124

A specialized protein structure that forms at the centromere of each chromatid during prometaphase.

Answer 125

The centrosomes are now at opposite poles of the cell, and the chromosomes have all arrived at the metaphase plate (a plate along the middle of the cell).

Answer 126

The cohesin proteins connecting the two sister chromatids of each pair are cleaved. Each chromatid becomes an independent chromosome. The kinetochore microtubules shorten, moving the daughter chromosomes toward opposite ends of the cell (at a rate of 1 µm/min). Nonkinetochore microtubules lengthen, elongating the cell.

Answer 127

Two daughter nuclei start forming in the cell (nuclear envelopes arise from the fragments from the parent cell's nuclear envelope). Nucleoli reappear and the chromosomes become less condensed. Any remaining spindle microtubules are depolymerized.

Answer 128

A subcellular region containing a pair of centrioles. It organizes microtubules, but is not essential for cell division.,

Answer 129

A motor protein walks the chromosome backward, as the microtubule depolymerizes at its kinetochore end, releasing tubulin subunits.

Answer 130

A shallow groove in the cell surface near the old metaphase plate

Answer 131

On the cytoplasmic side of the cell is a ring of actin filaments working with molecules of myosin. Actin and myosin work together, causing the ring to contract (like a drawstring), and splitting the cell in 2.

Answer 132

In telophase, vesicles from the Golgi Apparatus move via microtubules to the middle of the cell where they gather to form a cell plate. The cell plate enlarges until it fuses with the surrounding membrane. This creates two cells. A cell wall is then created between the two cells.

Answer 133

Binary fission

Answer 134

A specific place on a bacterial chromosome where replication begins. When replication begins, it produces two origins (like opening a ziplock bag) and as the chromosome continues to replicate, one origin moves rapidly toward the opposite end of the cell.

Answer 135

An actin-like protein.

Answer 136

A tubulin-like protein pinches the cell membrane inward.

Answer 137

Chromosomes are attached to the nuclear envelope and microtubules pass through cytoplasmic tunnels in the nuclear envelope to facilitate division.

Answer 138

The nuclear envelope remains intact and the microtubules form a spindle within the nucleus. Microtubules separate the chromosomes, and the nucleus splits into two daughter nuclei.

Answer 139

A control point where stop and go-ahead signals can regulate the cycle. It prevents errors in the end products of mitosis

Answer 140

G1, G2, and M phases

Answer 141

Cyclin-dependent kinases When a cyclin is present, it activates the CDK giving the "go-ahead" signal for the cell cycle

Answer 142

MPF is the cyclin-CDK complex that promotes the entrance into mitosis from the G2 phase by phosphorylating multiple proteins needed during mitosis (condensins for chromatin condensation, lamins for the degradation of the nuclear envelope, etc.). It is activated at the end of G2 by a phosphatase which removes an inhibitory phosphate group added earlier.

Answer 143

It phosphorylates inhibitory sites on myosin, which prevents cytokinesis. When MPF activity falls at anaphase, the inhibitory sites are dephosphorylated, and cytokinesis proceeds.

Answer 144

When anaphase-promoting complex (APC) marks cyclin B (the cyclin of MPF) for degradation in a negative feedback loop. This begins shortly after the onset of anaphase.

Answer 145

The G1 checkpoint (also called "restriction point" in mammalian cells) determines whether a cell will complete the cell cycle and divide, or else it will exit the cycle, switching into a non-dividing state called the G0 phase.

Answer 146

Enough MPF (maturation promoting factor) must be produced

Answer 147

Anaphase must wait for assembled sister chromatids

Answer 148

It stops cells with DNA damage from proceeding in the cell cycle

Answer 149

A protein released by certain cells that stimulates other cells to divide.

Answer 150

An external physical factor on cell division in which crowded cells stop dividing.

Answer 151

A property most animal cells exhibit: to divide the cell must be attached to something (ex. like the inside of a flask or the extracellular matrix of a tissue)

Answer 152

When cells acquire the ability to divide indefinitely, causing them to behave in cell division like cancer cells.

Answer 153

A catabolic pathway in which oxygen is consumed as a reactant along with organic fuel.

Answer 154

Organic compounds + oxygen -> carbon dioxide + water + energy

Answer 155

It loses electrons

Answer 156

It gains electrons (its charge is being reduced)

Answer 157

The reactant that ends up accepting the electron. It oxidizes the reducing agent.

Answer 158

The react that ends up losing the electron. It reduces the oxidizing agent.

Answer 159

(nicotinamide adenine dinucleotide) It is an electron accepter and functions as an oxidizing agent (it becomes NADH). "Electron shuttle"

Answer 160

The cytoplasm. It can happen with or without oxygen.

Answer 161

The mitochondria

Answer 162

The mitochondria

Answer 163

ATP formed directly in a few reactions of glycolysis and the citric acid cycle (NOT oxidative phosphorylation)

Answer 164

Energy investment and energy payoff. The cell uses 2 ATP in the investment phase but ends up generating 2 NADH, 2 Pyruvate, and 4 ATP in the payoff phase (net 2 ATP).

Answer 165

Glucose first gets a phosphate attached to it (from one of the investment ATPs; makes it more chemically reactive). It then is converted to fructose (6-phosphate). Another phosphate gets attached to it (from the 2nd ATP), making fructose 1,6-biphosphate. The 6-carbon sugar molecule is then cleaved into two 3-carbon sugars: G3P and DHAP. G3P is used as soon as it forms and DHAP is converted into G3P (this equation never reaches equilibrium). G3P is then oxidized by the transfer of electrons to NAD+ forming NADH (two molecules). Using the energy from this exergonic redox reaction, a phosphate group is attached to the oxidized substrate making a high-energy product. One phosphate from this product (1,3-bisphosphate-glycerate) is transferred to ADP (substrate-level phosphorylation; this yields 2 ATP in total). At some point, a molecule called phosphoenol-pyruvate is formed. A phosphate group is transferred from PEP to ADP (forming in a total of 2 ATP molecules). This results in pyruvate being created (twice).

Answer 166

CO2 is removed, and the remaining two-carbon fragment is oxidized, forming NADH from NAD+.

Answer 167

The Krebs cycle

Answer 168

CoA is the input, and 2 CO2, 3 NADH, 1 FADH2, and 1 ATP are produced.

Answer 169

Acetyl CoA reacts with oxaloacetate to become citrate. After a series of reactions, products are released and oxaloacetate is the end result (ready to react with the next acetyl CoA).

Answer 170

In the inner membrane of the mitochondrion in eukaryotic cells and the cell membrane in prokaryotic cells.

Answer 171

Electron carriers alternate between reduced and oxidized states as they accept and then donate electrons, releasing free energy at each step. The last electron carrier is oxygen (very electronegative).

Answer 172

This small hydrophobic molecule is the only member of the electron transport chain that isn't a protein/doesn't belong to a protein complex. It acts as an electron transporter.

Answer 173

An electron carrier with a heme prosthetic group (has an iron atom that accepts and donates electrons).

Answer 174

An enzyme that makes ATP from ADP and inorganic phosphate. It works like an ion pump running in reverse. ATP synthase uses the energy of an existing ion gradient to power ATP synthesis.

Answer 175

The intermembrane space of the mitochondria has a high concentration of H+ ions. The H+ ions flowing down their gradient enter a channel in a stator (part of ATP synthase), which is anchored in the membrane. H+ ions enter binding sites within a rotor (another part of ATP synthase), changing the shape of each subunit so that the rotor spins within the membrane. Each H+ ion makes one complete turn before leaving the rotor and passing through a second channel in the stator into the mitochondrial matrix. The spinning of the rotor also causes an internal rod to spin, which activates catalytic sites on a knob below it that produces ATP from ADP and inorganic phosphate.

Answer 176

The process in which energy is stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work.

Answer 177

The electron transport. The chain uses the exergonic flow of electrons from NADH and FADH2 to pump H+ across the membrane.

Answer 178

4 ATPs by substrate-level phosphorylation (2 from glycolysis and 2 from the Krebs cycle), 26-28 ATP from oxidative phosphorylation. At the end of the citric acid cycle, either 8 NADH and 2 FADH2 are produced or 6 NADH and 4 FADH2 (6 NADH from the Krebs cycle, 2 FADH2 from the Krebs cycle, and 2 NADH from glycolysis which can be converted into FADH2).

Answer 179

Anaerobic respiration uses the electron transport chain, while fermentation does not.

Answer 180

A way of harnessing chemical energy without cellular respiration.

Answer 181

Substrate-level phosphorylation

Answer 182

Pyruvate (from glycolysis) is converted to ethanol (an alcohol) in two steps. CO2 is first released from pyruvate, and then the resulting product is reduced by NADH to ethanol. This generates the supply of NAD+ needed for the continuation of glycolysis. Many bacteria carry our alcohol fermentation under anaerobic conditions.

Answer 183

Pyruvate is reduced directly by NADH to form lactate as an end product (no release of CO2). Human muscle cells utilize lactic acid fermentation when oxygen is scarce.

Answer 184

Organisms that carry out only fermentation or anaerobic respiration.

Answer 185

Organisms (including yeasts and many bacteria) can make enough ATP to survive using either fermentation or respiration.

Answer 186

A process by which the amino groups of amino acids are removed.

Answer 187

Breaks the fatty acids of fats down to two-carbon fragments, which enter the Krebs cycle as acetyl CoA.

Unit 1: Chemistry and Cells Flashcards

(220 cards)