What interactions stabilize alpha-helices and beta-sheets in proteins?

Hydrogen bonds between backbone carbonyl (C=O) groups and backbone N–H groups.

What are the three chemical components of a nucleotide?

A pentose sugar (ribose or 2-deoxyribose), a nitrogenous base, and one or more phosphate groups.

What is the stoichiometric ion exchange ratio of the sodium-potassium pump (Na+/K+ ATPase) per hydrolyzed ATP?

Pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, making it an electrogenic pump.

Which two metabolic functions are carried out by peroxisomes in animal cells?

They oxidize fatty acids, including very-long-chain fatty acids, and use catalase to break down hydrogen peroxide (H2O2).

What are monosaccharides, and is (CH2O)n a universal carbohydrate formula?

Monosaccharides are single sugar units, such as glucose, that can build larger carbohydrates. Many simple sugars fit (CH2O)n, but modified sugars and polysaccharides need not.

What are the three main filament classes of the animal-cell cytoskeleton?

Actin microfilaments, intermediate filaments such as keratin filaments, and microtubules made from alpha/beta-tubulin dimers.

Why can human digestive enzymes break down starch but not cellulose?

Starch has alpha-1,4 links and, in amylopectin, alpha-1,6 branches; amylases and other digestive enzymes act on it. Humans lack cellulase for cellulose's beta-1,4-linked glucose chains.

Where do most rRNA production and early ribosome assembly occur in an animal cell?

In the nucleolus. The 5S rRNA is made elsewhere in the nucleus and later incorporated into assembling ribosomal subunits.

Why is a typical membrane phospholipid amphipathic?

It has a polar, hydrophilic head and nonpolar, hydrophobic tails, so different parts interact differently with water.

In which directions do most kinesins and cytoplasmic dynein move along microtubules?

Most kinesins move toward the plus end; cytoplasmic dynein moves toward the minus end. Movement toward the cell center or periphery depends on microtubule orientation.

How do the usual sugars and bases of RNA and DNA differ?

RNA has ribose with a 2'-OH group and normally uses uracil; DNA has 2-deoxyribose with 2'-H and normally uses thymine instead of uracil.

What linkage joins monosaccharides in a disaccharide?

A glycosidic bond. Hydrolysis of this bond uses water to separate the sugar units.

How do simple diffusion and facilitated diffusion differ?

Simple diffusion passes through the lipid bilayer; facilitated diffusion uses channels or carriers. Both are passive, with net movement down concentration gradients or, for ions, electrochemical gradients.

What four groups are attached to the alpha-carbon of a typical amino acid?

An amino group, a carboxyl group, a hydrogen atom and a side chain (R). Protonation depends on pH; proline's side chain also bonds to the amino nitrogen.

Which organelle digests macromolecules using enzymes that work in an acidic lumen?

The lysosome, whose internal pH is typically around 4.5–5.0.

Which atoms are joined by a peptide bond between amino acids?

The carbonyl carbon from the carboxyl group of one amino acid bonds to the amino nitrogen of the next.

What interactions can stabilize the tertiary structure of a globular protein?

The hydrophobic effect, hydrogen bonds, salt bridges and van der Waals interactions; some proteins also have covalent disulfide bonds between cysteines.

What are the structural components of a triglyceride molecule?

One glycerol molecule esterified to three fatty acid chains.

What nuclear feature distinguishes bacterial cells from typical eukaryotic cells?

Bacteria lack a membrane-bound nucleus; their chromosomal DNA lies in a nucleoid region.

How does cholesterol buffer fluidity in animal-cell membranes?

At higher temperatures it restrains phospholipid movement; at lower temperatures it interferes with tight packing, helping the membrane remain fluid.

How does a red blood cell respond to hypertonic and hypotonic solutions?

In a hypertonic solution, net water loss makes it shrink. In a hypotonic solution, net water entry makes it swell; sufficient swelling can cause it to rupture (hemolysis).

How do rough and smooth endoplasmic reticulum differ?

Rough ER has bound ribosomes and helps synthesize and fold proteins entering the secretory pathway. Smooth ER lacks bound ribosomes and participates in lipid synthesis, detoxification and Ca2+ storage, depending on cell type.

Why do saturated fatty acids generally melt at higher temperatures than comparable cis-unsaturated fatty acids?

Their straighter chains pack more closely, strengthening intermolecular attractions. Cis double bonds introduce bends that disrupt packing; the comparison assumes similar chain lengths.

In simple Michaelis–Menten kinetics, how does reversible competitive inhibition affect apparent Km and Vmax?

Apparent Km increases while Vmax is unchanged. A sufficiently high substrate concentration can overcome the inhibition in this model.

What are the three core tenets of classical cell theory?

Living organisms consist of one or more cells; cells are the basic structural and functional units of life; new cells arise from existing cells.

How does secondary active transport differ from ATP-driven primary active transport?

ATP-driven primary transport directly couples ATP hydrolysis to uphill transport. Secondary transport couples the downhill movement of one solute to the uphill movement of another, using an existing electrochemical gradient.

Why is the inner mitochondrial membrane extensively folded into cristae?

To increase the surface area available for electron transport chain complexes and ATP synthase enzymes.

How does pure noncompetitive inhibition affect apparent Km and Vmax in the Michaelis–Menten model?

Vmax decreases while Km is unchanged. This ideal case assumes equal inhibitor affinity for free enzyme and the enzyme–substrate complex; allosteric inhibition does not automatically follow this pattern.

Why is ATP hydrolysis to ADP + Pi favorable under typical cellular conditions?

ADP and Pi are collectively stabilized relative to ATP and water by factors including hydration, resonance and reduced charge repulsion. The actual ΔG depends on concentrations and conditions; breaking a bond alone requires energy.

Which lipid features and environmental factor influence membrane fluidity?

Fatty-acid chain length and unsaturation, sterol content, and temperature. Shorter chains and cis double bonds generally increase fluidity at a given temperature.

How do enzymes accelerate reactions without changing equilibrium?

They lower the activation free-energy barrier for forward and reverse reactions. They do not change the equilibrium constant or the overall reaction free-energy change under the same conditions.

What is the primary function of the Golgi apparatus?

Modifying, sorting, packaging, and tagging proteins and lipids from the ER into vesicles for secretion or delivery to other organelles.

Cell Biology & Biomolecules

32 review cards on organelles, membrane transport, biomolecules and enzyme activity, including introductory enzyme kinetics. Assumes basic biology and chemistry.

Level: basic
Languages: en → en
Cards: 32
Markdown: Cell Biology & Biomolecules (.md)

Flashcards (32)

#	Front (Term / Question)	Back (Definition / Answer)
1	What interactions stabilize alpha-helices and beta-sheets in proteins?	Hydrogen bonds between backbone carbonyl (C=O) groups and backbone N–H groups.
2	What are the three chemical components of a nucleotide?	A pentose sugar (ribose or 2-deoxyribose), a nitrogenous base, and one or more phosphate groups.
3	What is the stoichiometric ion exchange ratio of the sodium-potassium pump (Na+/K+ ATPase) per hydrolyzed ATP?	Pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, making it an electrogenic pump.
4	Which two metabolic functions are carried out by peroxisomes in animal cells?	They oxidize fatty acids, including very-long-chain fatty acids, and use catalase to break down hydrogen peroxide (H2O2).
5	What are monosaccharides, and is (CH2O)n a universal carbohydrate formula?	Monosaccharides are single sugar units, such as glucose, that can build larger carbohydrates. Many simple sugars fit (CH2O)n, but modified sugars and polysaccharides need not.
6	What are the three main filament classes of the animal-cell cytoskeleton?	Actin microfilaments, intermediate filaments such as keratin filaments, and microtubules made from alpha/beta-tubulin dimers.
7	Why can human digestive enzymes break down starch but not cellulose?	Starch has alpha-1,4 links and, in amylopectin, alpha-1,6 branches; amylases and other digestive enzymes act on it. Humans lack cellulase for cellulose's beta-1,4-linked glucose chains.
8	Where do most rRNA production and early ribosome assembly occur in an animal cell?	In the nucleolus. The 5S rRNA is made elsewhere in the nucleus and later incorporated into assembling ribosomal subunits.
9	Why is a typical membrane phospholipid amphipathic?	It has a polar, hydrophilic head and nonpolar, hydrophobic tails, so different parts interact differently with water.
10	In which directions do most kinesins and cytoplasmic dynein move along microtubules?	Most kinesins move toward the plus end; cytoplasmic dynein moves toward the minus end. Movement toward the cell center or periphery depends on microtubule orientation.
11	How do the usual sugars and bases of RNA and DNA differ?	RNA has ribose with a 2'-OH group and normally uses uracil; DNA has 2-deoxyribose with 2'-H and normally uses thymine instead of uracil.
12	What linkage joins monosaccharides in a disaccharide?	A glycosidic bond. Hydrolysis of this bond uses water to separate the sugar units.
13	How do simple diffusion and facilitated diffusion differ?	Simple diffusion passes through the lipid bilayer; facilitated diffusion uses channels or carriers. Both are passive, with net movement down concentration gradients or, for ions, electrochemical gradients.
14	What four groups are attached to the alpha-carbon of a typical amino acid?	An amino group, a carboxyl group, a hydrogen atom and a side chain (R). Protonation depends on pH; proline's side chain also bonds to the amino nitrogen.
15	Which organelle digests macromolecules using enzymes that work in an acidic lumen?	The lysosome, whose internal pH is typically around 4.5–5.0.
16	Which atoms are joined by a peptide bond between amino acids?	The carbonyl carbon from the carboxyl group of one amino acid bonds to the amino nitrogen of the next.
17	What interactions can stabilize the tertiary structure of a globular protein?	The hydrophobic effect, hydrogen bonds, salt bridges and van der Waals interactions; some proteins also have covalent disulfide bonds between cysteines.
18	What are the structural components of a triglyceride molecule?	One glycerol molecule esterified to three fatty acid chains.
19	What nuclear feature distinguishes bacterial cells from typical eukaryotic cells?	Bacteria lack a membrane-bound nucleus; their chromosomal DNA lies in a nucleoid region.
20	How does cholesterol buffer fluidity in animal-cell membranes?	At higher temperatures it restrains phospholipid movement; at lower temperatures it interferes with tight packing, helping the membrane remain fluid.
21	How does a red blood cell respond to hypertonic and hypotonic solutions?	In a hypertonic solution, net water loss makes it shrink. In a hypotonic solution, net water entry makes it swell; sufficient swelling can cause it to rupture (hemolysis).
22	How do rough and smooth endoplasmic reticulum differ?	Rough ER has bound ribosomes and helps synthesize and fold proteins entering the secretory pathway. Smooth ER lacks bound ribosomes and participates in lipid synthesis, detoxification and Ca2+ storage, depending on cell type.
23	Why do saturated fatty acids generally melt at higher temperatures than comparable cis-unsaturated fatty acids?	Their straighter chains pack more closely, strengthening intermolecular attractions. Cis double bonds introduce bends that disrupt packing; the comparison assumes similar chain lengths.
24	In simple Michaelis–Menten kinetics, how does reversible competitive inhibition affect apparent Km and Vmax?	Apparent Km increases while Vmax is unchanged. A sufficiently high substrate concentration can overcome the inhibition in this model.
25	What are the three core tenets of classical cell theory?	Living organisms consist of one or more cells; cells are the basic structural and functional units of life; new cells arise from existing cells.
26	How does secondary active transport differ from ATP-driven primary active transport?	ATP-driven primary transport directly couples ATP hydrolysis to uphill transport. Secondary transport couples the downhill movement of one solute to the uphill movement of another, using an existing electrochemical gradient.
27	Why is the inner mitochondrial membrane extensively folded into cristae?	To increase the surface area available for electron transport chain complexes and ATP synthase enzymes.
28	How does pure noncompetitive inhibition affect apparent Km and Vmax in the Michaelis–Menten model?	Vmax decreases while Km is unchanged. This ideal case assumes equal inhibitor affinity for free enzyme and the enzyme–substrate complex; allosteric inhibition does not automatically follow this pattern.
29	Why is ATP hydrolysis to ADP + Pi favorable under typical cellular conditions?	ADP and Pi are collectively stabilized relative to ATP and water by factors including hydration, resonance and reduced charge repulsion. The actual ΔG depends on concentrations and conditions; breaking a bond alone requires energy.
30	Which lipid features and environmental factor influence membrane fluidity?	Fatty-acid chain length and unsaturation, sterol content, and temperature. Shorter chains and cis double bonds generally increase fluidity at a given temperature.
31	How do enzymes accelerate reactions without changing equilibrium?	They lower the activation free-energy barrier for forward and reverse reactions. They do not change the equilibrium constant or the overall reaction free-energy change under the same conditions.
32	What is the primary function of the Golgi apparatus?	Modifying, sorting, packaging, and tagging proteins and lipids from the ER into vesicles for secretion or delivery to other organelles.