Week Two Review Notes Flashcards

Question

What structure helps animal cells divide but is absent in plant cells?

Answer 1

Centrioles – they organize spindle fibers in animal cells.

Answer 2

Rapid cell division – can be a sign of growth, repair, or cancer.

Answer 3

A chemical or physical agent that causes changes (mutations) in DNA, potentially leading to cancer.

Answer 4

A gene that, when mutated or overexpressed, promotes uncontrolled cell division and contributes to cancer development.

Answer 5

The spread of cancer cells from the original tumor to form secondary tumors in other tissues or organs.

Answer 6

UV radiation, tobacco smoke, X-rays

Answer 7

Function: Prevent uncontrolled cell division by: - Repairing damaged DNA - Initiating apoptosis (programmed cell death) if damage is too severe - Inhibiting progression through the cell cycle Famous example: TP53, which codes for p53 protein. p53 halts the cycle at G1/S if DNA is damaged, allowing time for repair. Mutation effect: If inactivated by mutation, cells may divide uncontrollably → tumor formation. 📌 Think of tumor suppressors as the "brakes" of the cell cycle.

Answer 8

⚡ Proto-oncogenes Function: Promote normal cell division and growth. These genes encode: - Growth factors - Receptors - Cell signaling molecules Oncogenes: When mutated or overexpressed, proto-oncogenes become oncogenes, which lead to excessive cell division. Examples: RAS gene, MYC gene 📌 Think of proto-oncogenes as the "accelerator" – when stuck down, cells divide too fast.

Answer 9

🧬 Animal Cells: Cleavage Furrow Formation Occurs after telophase to split the cytoplasm. Steps: 1. Actin and myosin microfilaments assemble beneath the plasma membrane at the equator. 2. These filaments form a contractile ring. 3. The ring contracts, pulling the membrane inward. 4. A cleavage furrow forms — a visible indentation. The membrane pinches in completely, dividing the cell into two daughter cells. 📌 Easy way to remember: “Animals pinch in two.”

Answer 10

Plant cells have a cell wall, so they can’t pinch like animals. Steps: 1. Vesicles from the Golgi apparatus carry cell wall materials (like cellulose). 2. These vesicles accumulate at the center of the cell — where the metaphase plate was. 3. Vesicles fuse together to form the cell plate. The cell plate grows outward toward the existing cell walls. 4. The membranes of the vesicles become new plasma membranes for each daughter cell. 5. Cellulose is deposited to form the new cell wall between the two cells. 📌 Easy way to remember: “Plants build a wall.”

Answer 11

🔗 Cohesion Water molecules stick to each other due to hydrogen bonding. Important for transport in xylem in plants — water forms a continuous column. 🧠 Think: "Co-stick" = sticking together.

Answer 12

🧲 Adhesion Water molecules stick to other polar surfaces (like cell walls). Helps in capillary action, drawing water up narrow tubes in plant stems.

Answer 13

🔹 Monosaccharides (single sugars) Basic unit of carbs Examples: Glucose (C₆H₁₂O₆) – main energy source Galactose, fructose 🧠 Function: Rapid energy source – easily absorbed and used in respiration.

Answer 14

🔗 Disaccharides Two monosaccharides joined via condensation reaction (forms a glycosidic bond) Examples: Glucose + fructose → sucrose Glucose + glucose → maltose

Answer 15

🛢️ Triglycerides 1 glycerol + 3 fatty acids (joined by condensation) Used for long-term energy storage, insulation, and protection Hydrophobic → stored in fat droplets

Answer 16

1 glycerol + 2 fatty acids + phosphate group Key component of cell membranes Amphipathic: Hydrophilic head Hydrophobic tails

Answer 17

A1: α-glucose

Answer 18

A2: α-glucose

Answer 19

A3: β-glucose

Answer 20

A4: 1,4 glycosidic bonds (unbranched, helical)

Answer 21

A5: Both 1,4 and 1,6 glycosidic bonds (branched)

Answer 22

A6: Glycogen is more highly branched, with 1,6 bonds occurring more frequently.

Answer 23

A7: More branches provide more terminal ends for quick glucose release — ideal for animal energy demands.

Answer 24

A8: Cellulose has 1,4 β-glycosidic bonds with alternating flipped β-glucose molecules, forming straight, unbranched chains.

Answer 25

A9: Hydrogen bonds between adjacent chains form microfibrils, providing strength to plant cell walls.

Answer 26

A10: Energy storage in plants

Answer 27

A11: Energy storage in animals, mainly in liver and muscle cells

Answer 28

A12: Structural support in plant cell walls

Answer 29

A13: Starch and glycogen are digestible. Cellulose is not — humans lack the enzyme cellulase.

Answer 30

A14: Amylose, a component of starch

Answer 31

A15: Cellulose – due to hydrogen-bonded microfibrils

Answer 32

A17: Glycogen, due to its high degree of branching

Answer 33

A18: It's insoluble, compact, and doesn't affect osmotic balance.

Answer 34

🔗 Peptide Bond Formation (Condensation Reaction): Peptide bond forms between the amino group of one amino acid and the carboxyl group of another. Water (H₂O) is released → it's a condensation reaction. 🧪 Reaction: Amino acid 1+Amino acid 2→Dipeptide+H Many amino acids = polypeptide

Answer 35

- Sequence of amino acids in a polypeptide. - Determined by DNA and held by peptide bonds.

Answer 36

- Local folding of chain due to hydrogen bonding. Common patterns: α-helix β-pleated sheet

Answer 37

3D shape of the entire polypeptide. Stabilized by: - Hydrogen bonds - Ionic bonds - Disulfide bridges (covalent, strong) - Hydrophobic interactions

Answer 38

- When a protein has two or more polypeptide chains (e.g., hemoglobin). - May involve prosthetic groups (non-polypeptide parts like iron in hemoglobin). 🧠 Protein shape = function!

Answer 39

Transport protein for oxygen in red blood cells

Answer 40

Antibodies; identify and neutralize pathogens

Answer 41

🔸 2. Antiparallel Strands in DNA Double Helix DNA is made of two strands running in opposite directions → antiparallel One strand runs 5' → 3', the other runs 3' → 5' Strands are held together by hydrogen bonds between complementary bases The structure is a double helix, discovered by Watson & Crick using Rosalind Franklin’s X-ray diffraction data

Answer 42

📌 Phosphodiester bonds connect nucleotides along a strand

Answer 43

📌 Hydrogen bonds connect bases between strands

Answer 44

- Unwinds the double helix - Breaks hydrogen bonds between base pairs - Creates a replication fork

Answer 45

- Adds complementary nucleotides to the exposed strands - Always works 5’ → 3’ direction - On one strand (leading) it adds nucleotides continuously - On the lagging strand, it adds nucleotides in Okazaki fragments (discontinuous)

Answer 46

🔹 The Setup: Bacteria grown in heavy nitrogen (¹⁵N) so their DNA became heavier Then transferred to light nitrogen (¹⁴N) medium and allowed to replicate 🔹 Observations: After 1 generation: DNA was of intermediate density (not all light or heavy) After 2 generations: 50% light, 50% intermediate DNA 🔹 Conclusion: Confirms semi-conservative model of DNA replication

Answer 47

1. Denaturation (95°C): DNA strands are separated by heating Annealing (50–65°C): 2. Primers bind to the start of the DNA segment to be copied 3. Extension (72°C): Taq DNA polymerase adds nucleotides to build new strands

Answer 48

- Function: Adds complementary nucleotides to the new DNA strand. - Works in the 5’ → 3’ direction only. - Main enzyme for synthesizing the leading and lagging strands. 🧠 Adds bases starting at RNA primer.

Answer 49

- Function: Removes RNA primers and replaces them with DNA nucleotides. 🧠 It cleans up and fills the gaps left after RNA primers are removed.

Answer 50

- Function: Synthesizes short RNA primers to provide a starting point for DNA polymerase III. - These primers are needed because DNA polymerase can’t start a strand on its own. 🧠 RNA primer = “starter line” for replication.

Answer 51

Function: Joins Okazaki fragments together on the lagging strand by forming phosphodiester bonds. Seals any breaks in the sugar-phosphate backbone. 📌 Think of it as the “glue” enzyme.

Answer 52

- Converts DNA --> RNA 🧩 Purpose: To copy the genetic code from DNA into a single-stranded mRNA molecule, so it can leave the nucleus and go to a ribosome.

Answer 53

🔄 Steps of Transcription: 1. Initiation: RNA polymerase binds to promoter on DNA Unwinds small section of DNA 2. Elongation: RNA polymerase builds mRNA strand using the antisense strand as template (3' → 5') mRNA is made 5' → 3' 3. Termination: RNA polymerase reaches terminator sequence → stops mRNA strand detaches and DNA re-zips 🧠 Only one DNA strand (template/antisense) is used to make mRNA.

Answer 54

- Converts mRNA --> protein 🧩 Purpose: To convert the message in mRNA (a sequence of codons) into a chain of amino acids → which folds into a protein!

Answer 55

1. Initiation: Ribosome binds to mRNA tRNA with anticodon UAC binds to start codon (AUG) Brings first amino acid = methionine 2. Elongation: Next tRNA binds to next codon Ribosome forms peptide bond between amino acids Ribosome shifts (translocates) → new codon enters A-site 3. Termination: Stop codon is reached No matching tRNA → ribosome releases polypeptide

Answer 56

Codon = 3 bases on mRNA Each codon codes for 1 amino acid

Answer 57

A change in the DNA base sequence that can affect the protein made.

Answer 58

🧬 Example: Sickle Cell Anemia - Mutation: DNA base changes from A to T - mRNA codon changes from GAG (glutamic acid) to GUG (valine) - Causes abnormal hemoglobin → sickle-shaped red blood cells → health issues