Bio Orals

What are the characteristics of life?

1) Order - hierarchy (all life made of cells; organized levels - organellese, cells, tissues, organs, organ systems

2) Respond to stimuli (plants leaning towards sun, fleeing danger)

• organisms detect and react to internal or external changes (stimuli) like light, temperature, or hunger, crucial for survival, adaptation, finding resources

3) Reproduction - create new, similar organisms + pass on DNA

4) Growth + Development - based on genes

5) Homeostasis - maintain stable internal environment (critical for fxn)

6) Metabolism - chemical rxns in organisms critical for life

• catabolism: break down for energy

• anabolism: use energy to buiild

7) Evolution

What is adhesion? What is cohesion? What is surface tension?

• Cohesion: attraction between water molecules - stick together due to H-bonding (H+ to O-)

• Adhesion: water molecules and other molecules

• Surface tension: due to cohesion; liquid’s surface resists rupture when placed under tension

What are the four macromolecules?

1) Carbohydrates: monosaccharide (monomer)

• body’s main energy source; store energy as glycogen/starch; sturctural support as cell walls (cellulose, chitin)

2) Lipids: glycerol + fatty acids

• hydrophobic/nonpolar; cell membrane; long-term source of energy (stored in adipose; over double energy of carbs); thermal insulation; steroid hormones (sex hormones, cortisol; myelin sheath on neurons

3) Proteins: amino acids

• muscle, hair, collagen; enzymes; protein channels; receptors; hemoglobin; peptide hormones (insulin, glucagon)

4) Nucleic Acid (DNA + RNA): nucleotides

• store, transmit, and express genetic information

Eukaryotes vs Prokaryotes (SIMILIARITIES)

• ribsomes

• cytoplasm

• DNA

• cell membrane

• Protein Synthesis: Both use DNA, RNA, and ribosomes to create proteins.

• Energy Production: Both need energy, though eukaryotes use mitochondria and prokaryotes use their cell membrane/cytoplasm. 

Eukaryotes vs Prokaryotes (DIFFERENCES)

• Prokaryotes:

  • bacteria + archaea (domains)

  • unicellular

  • cell walls (most)

  • no membrane-bound organelles

• Eukaryotes:

  • Domain: Eukarya

  • Kingdoms: Animalia, Plantae, Fungi, and Protista

  • Some cell walls: plants, fungi, and certain protists (specifically algae

  • nucleus + membrane-bound organelles

What are the main cell organelles?

• Cytoplasm: Jelly-like substance filling the cell, site of glycolysis (the first stage of cellular respiration), protein synthesis (translation), and glycogen synthesis

• Nucleus: holds DNA (nucleolus: makes ribosomes)

• Endoplasmic Reticulum

  • Rough: makes proteins (destined for secretion or membrane insertion)

  • Smooth: makes lipids, detoxifies, stores Ca2+

• Golgi Apparatus: receives proteins and lipids from the endoplasmic reticulum (ER), modifies, sorts, and packages them into vesicles for transport to destinations like lysosomes, the plasma membrane, or secretion outside the cell

• Lysosomes: digest macromolecules (proteins, fats, nucleic acids, carbohydrates) (autophagy), recycle nutrients for metabolism, break down waste + foreign invaders, maintain homeostasis

• Vacuoles: storage and support center by holding water, nutrients, and waste

What are the six kingdoms of life?

1. Archaebacteria (Archaea): Single-celled prokaryotes (no nucleus) often living in extreme environments (heat, salt, no oxygen).

2. Eubacteria (Bacteria): True bacteria, single-celled prokaryotes found everywhere, important for digestion and illness, and industrial uses.

3. Protista (Protists): A diverse group of mostly single-celled eukaryotes (with nuclei) like algae and protozoa, with varied nutrition.

4. Fungi (Fungi): Multicellular (mostly) eukaryotes that absorb nutrients (heterotrophs), like mushrooms, yeasts, and molds.

5. Plantae (Plants): Multicellular eukaryotes that make their own food (autotrophs) through photosynthesis.

6. Animalia (Animals): Multicellular eukaryotes that ingest food (heterotrophs) and lack cell walls. 

Cell-signalling

• Ligand binds to receptor protein

• Ligand-gated ion channel

• Voltage-gated ion channel

• Types of signalling: autocrine, endocrine, paracrine (nearby but not touching), gap junctions (touching cells, cytoplasm connected)

How/why does ATP release energy?

• ATP hydrolysis: h2o breaks bond between phosphates → releases energy (ATP→ ADP+Pi)

• Exergonic (releases energy) reaction

• ATP is unstable; ADP is more stable

  • ATP's three negatively charged phosphate groups repel each other intensely

Describe cellular respiration.

1. Glycolysis (cytoplasm): glucose → 2 pyruvate + 2 ATP + 2 NADH

2. Pyruvate processing (mitochondria matrix): 2 pyruvate → 2 acetyl CoA + 2 NADH + CO2

3. Citric Acid Cycle (mitochondria matrix): 2 acetyl CoA → 2 ATP + 6 NADH + 2 FADH2 + CO2

4. Electron Transport Chain (inner mitochondrial membrane): electrons from NADH + FADH2 move through protein complexes, releasing energy + pumping protons into intermembrane space (creates proton gradient); following concentration gradient, protons return to matrix through ATP Synthase (ADP + Pi → ATP)

   1. 26-34 ATP from ETC

   2. 30-38 in total (cellular respiration)

   3. Process = oxidative phosphorylation using ETC

Describe photosynthesis.

1) Light-dependent reaction

• occurs in thylakoid (in chloroplast)

• chlorophyll captures light; h2o splits; electrons go through protein complexes (similar to ETC) → ATP + NADPH + O2 produced

2) Light-independent reaction (Calvin Cycle)

• occurs in stroma

• CO2 enters through stomata; fixed CO2, ATP, electrons from NADPH → glucose

  • remember: fixed = incorporated into organic molecules

Basic structure of DNA

• double helix

• sugar phosphate backbone

• nitrogenous base

• hydroxyl (-OH) → 3’

• phosphate - 5’

• compacted DNA (wrapped around histones) = chromosomes

  • humans : 46 chromosomes; 23 sets

Describe DNA replication.

• occurs during interphase

• Helicase: breaks H-bonds between strands

• Topoisomerase: prevents supercoiling downstream

• Primase: lays down RNA primer

• DNA Polymerase: builds complementary strand 5’→ 3’ (moving on template strand 3’→5’)

• Ligase: glues okazaki fragments on lagging strand together (Polymerase has to keep building 3’→5’ so it keeps moving forward to new RNA primers)

Describe Gel Electrophoresis.

• separates by size of DNA (-) fragments

• 1) fill wells in agarose gel w/ DNA

  • DNA is cut by restriction enzymes at specific spots

• 2) Run electric current (DNA→ + side); shorter fragments move quicker/further

• 3) Visualize using dye or comparing to DNA ladder

• Purpose: comparing likeness between DNA samples

Describe PCR (Polymerase Chain Reaction)

• Purpose: to rapidly amplify (create millions to billions of copies of) a specific, targeted segment of DNA

• 1) Denaturation: heat to separate strands of DNA

• 2) Annealing: cool; primers bind to complementary sequences on template strands

• 3) Elongation: add DNA polymerase to make complementary strands

• repeat many times

• Why: diagnosing infectious diseases (e.g., COVID-19, HIV), forensic DNA profiling, genetic research, paternity testing, and detecting mutations or pathogens - turns an undetectable amount of genetic material into a large enough sample for analysis

Describe Cell Cycle.

• Interphase:

  • G1: cell grows

    • G1 checkpoint: Is cell growing enough? Is DNA damaged? Does it have resources needed?

  • S: replicates DNA

  • G2: cell grows

    • G2 checkpoint: Was the DNA replicated correctly? Is it growing correct?

• M Phase:

  • Mitosis: cell division

    • Metaphase Checkpoint: Are the chromosomes lined up correctly + attached to spindle?

• G0:

  • cells are functioning but not prepared to divided (due to lack of resources or cell type doesnt divide(neurons))

• **Regulators:

  • CDK: activated by binding of Cyclin; phosphorylate target proteins to drive cell cycle forward

  • P53: pauses cell cycle if DNA is damaged. Repairs or apoptosis.

Describe all steps of Mitosis.

• Parent to Daughter Cells: One parent cell produces two genetically identical diploid daughter cells.

• Prophase: Chromatin condenses into chromosomes, spindles form, and the nuclear envelope breaks down.

• Metaphase: Chromosomes align at the cell's equator (middle), and spindles attach.

• Anaphase: Sister chromatids separate and are pulled to opposite poles.

• Telophase: Nuclear envelopes reform around the two sets of chromosomes.

• Cytokinesis: Cytoplasm divides, resulting in two distinct daughter cells. 

• * End up with diploid cells: two complete sets of chromosomes (one from each parent)

Describe all steps of meiosis.

• Meiosis: produces four genetically distinct haploid daughter cells

  Prophase I: homologous chromosomes pair up (synapsis)
  • Crossing over: exchange of genetic material between homologous chromosomes

  Metaphase I: homologous pairs (tetrads) line up in the middle
  • Independent assortment: homologous pairs line up randomly

  Anaphase I: homologous chromosomes are pulled apart

  Telophase I: nuclei reform

  Cytokinesis I: cytoplasm divides

  Prophase II: similar to mitosis

  Metaphase II: chromosomes line up in the middle

  Anaphase II: sister chromatids are pulled apart

  Telophase II: nuclei reform

  Cytokinesis II: cytoplasm divides