Biology 1 Exam 2 Study Notes

• Study notes for Biology 1 Exam 2

Cellular Respiration

• Humans obtain energy from food
• The ultimate energy source in this food originates from the sun, captured during photosynthesis
• Producers (autotrophs) create their own food
• Consumers (heterotrophs) obtain energy by consuming other organisms
• Photosynthesis occurs in chloroplasts
• The waste products of photosynthesis are oxygen and water
• Plants do perform cellular respiration
• Aerobic means with oxygen
• Anaerobic means without oxygen
• Electron carriers/shuttles include NADH and FADH2.
• Cellular respiration includes Glycolysis, the Citric Acid Cycle, and the Electron Transport Chain

Glycolysis

• Glycolysis takes place in the cytoplasm
• Glycolysis requires an initial investment of energy in the form of 2 ATP
• Glycolysis involves the breakdown of glucose into pyruvate and yields 2 ATP (net), 2 NADH, and 2 pyruvate molecules per glucose molecule

Citric Acid Cycle

• The Citric Acid Cycle occurs in the mitochondrial matrix
• Pyruvic acid is converted into acetyl-CoA before entering the citric acid cycle.
• The citric acid cycle involves the input of acetyl-CoA, which combines with oxaloacetate to form citrate, and ultimately regenerates oxaloacetate to continue the cycle
• The Citric Acid Cycle produces ATP, NADH, FADH2, and releases carbon dioxide.

Electron Transport Chain

• The Electron Transport Chain (ETC) takes place in the inner mitochondrial membrane
• The ETC involves the transfer of electrons from NADH and FADH2 through a series of protein complexes, creating a proton gradient across the inner mitochondrial membrane
• The ETC produces ATP and water.
• The final electron acceptor within the ETC is oxygen
• ATP synthase uses the proton gradient generated by the ETC to synthesize ATP through chemiosmosis
• During cellular respiration, carbons in glucose are oxidized to form carbon dioxide
• The electron transport chain (ETC) produces the most ATP

Fermentation

• Fermentation differs from cellular respiration as it doesn't use oxygen and doesn't involve the citric acid cycle or ETC
• Organisms perform fermentation when oxygen is unavailable or when they lack the necessary enzymes for cellular respiration
• The byproduct of fermentation in human muscle cells is lactic acid, which causes muscle fatigue

Photosynthesis

• Photosynthesis contributes to plant growth through the production of glucose
• Photosynthesis takes place in chloroplasts, specifically in the thylakoid membranes (light-dependent reactions) and the stroma (Calvin cycle
• Plants obtain water through their roots via osmosis from the soil
• Plants obtain CO₂ from the air through stomata located on their leaves
• The photosynthesis equation is: 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
• Chlorophyll is the green pigment in plants that absorbs light energy to initiate photosynthesis

Chlorophyll

• Light is a packet of energy called a photon
• When light hits an object, plants reflect the color that you see allowing white light to illuminate plants

Two Steps of Photosynthesis

• Photosynthesis occurs in two stages: light-dependent reactions and the Calvin Cycle

Light Reaction

• The electrons and O₂ gas originate from the splitting of water molecules (photolysis) in the light-dependent reactions
• Electrons are excited when light energy is absorbed by chlorophyll, boosting them to a higher energy level
• The light-dependent reactions involve the input of light energy and water
• The light-dependent reactions produce ATP, NADPH, and oxygen.
• The electron transport chain is a series of protein complexes that transfer electrons and generate a proton gradient to produce ATP

Calvin Cycle

• The light reactions of photosynthesis provide ATP and NADPH for the Calvin Cycle
• The Calvin cycle results in the production of glucose.
• Electron transport chain is found in both cellular respiration and in the light reactions of photosynthesis
• Different types of photosynthesis exist due to adaptations to different environmental conditions, such as C4 and CAM photosynthesis

Cellular Reproduction

• Cellular reproduction occurs for growth, repair, and reproduction
• Chromosomes are structures made of DNA and proteins that contain genetic information
• Chromatin is a complex of DNA and proteins (histones) that form chromosomes
• Homologous chromosomes are pairs of chromosomes with the same genes but potentially different alleles
• Haploid cells contain one set of chromosomes (n), while diploid cells contain two sets (2n)
• Sister chromatids are identical copies of a chromosome formed during DNA replication
• Histones are proteins around which DNA is wrapped to form chromatin
• Asexual reproduction involves one parent and results in genetically identical offspring
• Sexual reproduction involves two parents and results in genetically diverse offspring

Cell Cycle

• The cell cycle includes interphase (G1, S, G2 phases) and mitosis (cell division)
• Interphase is the stage when the cell grows, replicates DNA (S phase), and prepares for division

Mitosis

• Mitosis is the process of cell division that results in two identical daughter cells

Prophase

• Chromosomes condense, and the nuclear envelope breaks down in prophase

Metaphase

• Chromosomes line up at the metaphase plate during metaphase

Anaphase

• Sister chromatids separate and move to opposite ends of the cell during anaphase

Telophase/Cytokinesis

• Chromosomes decondense, a nuclear envelope reforms, and the cell divides into two separate cells (cytokinesis)
• Sex chromosomes determine an individual's sex

Sex Chromosomes

• Typical males have XY sex chromosomes
• Typical females have XX sex chromosomes
• Autosomes are chromosomes that are not sex chromosomes

Meiosis

• Meiosis is a type of cell division that produces gametes (sex cells)

Gametes

• Gametes are haploid (n)
• Meiosis results in the reduction of the number of chromosomes
• Crossing over is the exchange of genetic material between homologous chromosomes, resulting in recombinant DNA
• Independent assortment is the random arrangement and separation of chromosomes during meiosis
• Nondisjunction is the failure of chromosomes to separate properly during meiosis, leading to gametes with an abnormal number of chromosomes
• Mitosis results in two identical daughter cells, while meiosis results in four genetically diverse gametes
• Karyotypes are used to analyze an individual's chromosomes and can reveal chromosomal abnormalities

Patterns of Inheritance

• Heredity is the passing of traits from parents to offspring
• Genetics is the study of heredity and variation
• Gregor Mendel is the father of genetics
• Gregor Mendel performed his research on pea plants

Mendel's Research

• Genes are units of heredity that determine traits
• Traits are characteristics or features that are inherited
• Purebred individuals have homozygous alleles for a specific trait
• Hybrids are individuals with heterozygous alleles for a specific trait
• A cross is the mating of two individuals to produce offspring
• The law of segregation states that allele pairs separate during gamete formation
• Dominant alleles mask the expression of recessive alleles
• Alleles are alternative forms of a gene
• Homozygous individuals have two identical alleles for a gene
• Heterozygous individuals have two different alleles for a gene
• Punnett squares are used to predict the possible genotypes and phenotypes of offspring in a monohybrid cross
• The law of independent assortment states that genes for different traits are inherited independently of each other
• Genotype is the genetic makeup of an individual
• Phenotype is the observable characteristics of an individual
• A test-cross is used to determine the genotype of an individual with a dominant phenotype by crossing it with a recessive individual

Human Genetics

• Genetic testing is the analysis of an individual's DNA to identify genetic variations associated with diseases or traits
• Incomplete dominance is a pattern of inheritance where the heterozygous phenotype is intermediate between the two homozygous phenotypes
• Co-dominance is a pattern of inheritance where both alleles are expressed equally in the heterozygous phenotype Blood types are examples of co-dominance Sex-linked genes are genes located on the sex chromosomes, such as the X chromosome