Key Concepts in Biology: Structure, Function, and Processes

What are the main differences between DNA and RNA?

DNA is double-stranded, contains deoxyribose sugar, and uses thymine as a base, while RNA is single-stranded, contains ribose sugar, and uses uracil instead of thymine.

What are the four levels of protein structure?

1. Primary: sequence of amino acids; 2. Secondary: alpha helices and beta sheets formed by hydrogen bonds; 3. Tertiary: 3D shape due to interactions among R groups; 4. Quaternary: multiple polypeptide chains interacting.

How does temperature or pH affect protein shape and function?

Changes in temperature or pH can denature proteins, altering their shape and potentially leading to loss of function.

What are the six most common elements in macromolecules?

Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.

In which macromolecules is sulfur and phosphorus primarily found?

Sulfur is primarily found in proteins, while phosphorus is primarily found in nucleic acids and phospholipids.

What are the differences between glycogen, starch, and cellulose?

Glycogen is used for energy storage in animals, starch is used for energy storage in plants, and cellulose provides structural support in plant cell walls.

What distinguishes saturated fats from unsaturated fats?

Saturated fats have no double bonds between carbon atoms and are typically solid at room temperature, while unsaturated fats contain one or more double bonds and are usually liquid.

What is the significance of hydrogen bonds in water molecules?

Hydrogen bonds form due to the attraction between the partial positive charge of hydrogen and the partial negative charge of oxygen, contributing to water's unique properties.

What is the difference between dehydration synthesis and hydrolysis?

Dehydration synthesis joins monomers to form polymers by removing water, while hydrolysis breaks down polymers into monomers by adding water.

What is the general structure of an amino acid?

An amino acid consists of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a unique R group (side chain).

What determines the unique properties of an amino acid?

The unique R group (side chain) of each amino acid determines its specific properties.

What are the major functions of macromolecules?

Carbohydrates provide energy, lipids store energy and form membranes, proteins perform various functions including catalysis, and nucleic acids store and transmit genetic information.

How do the properties of water support life on Earth?

Water's high specific heat, cohesion, adhesion, and solvent properties support various biological processes essential for life.

What are the functions of the nucleus, ER, Golgi apparatus, and mitochondria?

Nucleus: stores genetic information; Rough ER: synthesizes proteins; Smooth ER: synthesizes lipids; Golgi apparatus: modifies and packages proteins; Mitochondria: produces ATP.

What is the endosymbiotic theory?

The endosymbiotic theory suggests that eukaryotic cells evolved from prokaryotic cells through a symbiotic relationship, supported by evidence such as double membranes and DNA similarities.

What is water potential and how is it calculated?

Water potential is the measure of the potential energy in water, calculated as the sum of solute potential and pressure potential, predicting water movement in plants.

What are the types of passive transport?

Types of passive transport include simple diffusion, facilitated diffusion, and osmosis, where particles move from high to low concentration without energy use.

What is the difference between active and passive transport?

Active transport requires energy to move substances against their concentration gradient, while passive transport does not require energy and moves substances down their gradient.

What is the role of aquaporins in cells?

Aquaporins are channel proteins that facilitate the rapid transport of water across cell membranes; their removal can lead to decreased water permeability.

What are the components of a cell membrane?

Cell membranes consist of a phospholipid bilayer, proteins, cholesterol, and carbohydrates, each contributing to membrane fluidity and function.

What happens to a cell in hypertonic and hypotonic solutions?

In hypertonic solutions, cells lose water and may shrivel; in hypotonic solutions, cells gain water and may swell or burst.

What types of molecules pass through a cell membrane most easily?

Small, nonpolar molecules pass through most easily, while large or charged molecules pass through least easily.

What is the pathway of a protein produced by bound ribosomes on the rough ER?

Proteins synthesized by bound ribosomes enter the rough ER, are modified, packaged into vesicles, and sent to the Golgi apparatus for further processing.

What is the importance of the active site of enzymes?

The active site of enzymes is crucial for binding substrates and catalyzing reactions; changes to the active site can impair enzyme function.

What factors can affect enzyme activity?

Factors include temperature, pH, substrate concentration, and the presence of inhibitors or activators.

What is the purpose of designing an investigation to test enzyme activity?

To identify and explain independent, dependent, and controlled variables, and establish a control group.

What do living things not defy according to the second law of thermodynamics?

They do not defy the principle that energy systems tend to move towards increased entropy.

What are the inputs and outputs of the Light Dependent Reactions?

Inputs: Light energy, water; Outputs: ATP, NADPH, oxygen.

Where do the Light Dependent Reactions occur?

In the thylakoids of chloroplasts.

What is the main purpose of the Light Dependent Reactions?

To capture energy from sunlight to create ATP and NADPH.

What role do chlorophyll pigments play in photosynthesis?

They absorb light energy to excite electrons in Photosystems II and I.

What is created as a result of the electron transport chain in the Light Dependent Reactions?

A high concentration of H+ ions inside the thylakoid, forming an electrochemical gradient.

How is ATP produced during the Light Dependent Reactions?

H+ ions leave the thylakoid through ATP Synthase, driving the production of ATP.

What are the inputs and outputs of the Light Independent Reactions (Calvin Cycle)?

Inputs: ATP, NADPH, carbon dioxide; Outputs: G3P (Glyceraldehyde 3-phosphate), which can be converted to glucose.

Where do the Light Independent Reactions occur?

In the stroma of chloroplasts.

What is the significance of the proton gradient in cellular processes?

It is used to produce ATP and can also be used for other cellular functions.

What happens if the proton gradient is not functioning?

ATP production would be significantly reduced, affecting energy availability for the cell.

What is the main goal of Glycolysis?

To convert glucose into pyruvate, producing 2 ATP and 2 NADH in the process.

Where does Glycolysis occur?

In the cytosol.

What is produced during the Krebs Cycle?

NADH, FADH2, ATP, and carbon dioxide as a byproduct.

Where does the Krebs Cycle take place?

In the mitochondrial matrix.

What is the primary function of the Electron Transport Chain (ETC)?

To transfer electrons from NADH and FADH2 to oxygen, producing water and ATP.

What is unique about fermentation?

It allows ATP production without oxygen, using alternative electron acceptors.

What are the byproducts of Alcohol and Lactic Acid Fermentation?

Alcohol fermentation produces ethanol and carbon dioxide; Lactic acid fermentation produces lactic acid.

What is the role of NADH and FADH2 in cellular respiration?

They carry electrons to the Electron Transport Chain for ATP production.

What is the significance of ATP in cellular metabolism?

ATP releases energy when converted to ADP, fueling metabolic processes.

How does the process of endosymbiosis relate to photosynthesis?

It explains how photosynthesis evolved in eukaryotic cells from prokaryotic ancestors.

What process creates a proton gradient in the mitochondria?

As electrons are passed down the electron transport chain, H+ ions are brought into the mitochondrial intermembrane space from the mitochondrial matrix.

What is the significance of the proton gradient in mitochondria?

It creates a high concentration of H+ in the intermembrane space and a low concentration in the matrix, which drives ATP synthesis.

How is ATP formed from ADP and inorganic phosphate in mitochondria?

H+ ions pass through ATP Synthase, using the energy from the proton gradient to convert ADP + P into ATP.

What is oxidative phosphorylation?

It is the process of ATP formation that occurs as a result of the proton gradient created during electron transport.

What are the products of fermentation?

Fermentation produces either alcohol and CO2 or lactic acid, depending on the organism.

What is the difference between fermentation and anaerobic respiration?

Fermentation does not require oxygen and does not go through the Krebs cycle or electron transport chain, while anaerobic respiration does.

What are paracrine and endocrine signaling?

Paracrine signaling involves local cell communication, while endocrine signaling involves hormones traveling through the bloodstream to distant targets.

What is the difference between hydrophilic and hydrophobic ligands?

Hydrophilic ligands cannot cross the cell membrane and bind to receptors on the cell surface, while hydrophobic ligands can cross the membrane and bind to intracellular receptors.

How are signals amplified in cell signaling?

Signals are amplified through a cascade of reactions, where one molecule activates multiple downstream molecules.

What role do enzymes play in the activation and deactivation of signaling molecules?

Enzymes can activate or deactivate signaling molecules, such as kinases that add phosphate groups and phosphatases that remove them.

What happens if a receptor protein's shape is mutated?

A mutation that changes the shape of the receptor protein may prevent it from binding its ligand, disrupting the signaling pathway.

What are G-protein coupled receptors (GPCRs)?

GPCRs are cell surface receptors that, upon ligand binding, activate G-proteins to initiate a signaling cascade.

What are Tyrosine kinase receptors?

Tyrosine kinase receptors are membrane receptors that, when activated by a ligand, phosphorylate tyrosine residues on themselves and other proteins.

What are Ligand gated ion channels?

Ligand gated ion channels are membrane proteins that open in response to the binding of a ligand, allowing ions to flow across the membrane.

What is negative feedback in biological systems?

Negative feedback is a regulatory mechanism where a change in a variable triggers a response that counteracts the initial change.

What is positive feedback in biological systems?

Positive feedback is a process where a change in a variable triggers a response that enhances the initial change.

What occurs during the G1 phase of the cell cycle?

During G1, the cell grows and prepares for DNA replication.

What happens during the S phase of the cell cycle?

During the S phase, DNA is replicated, resulting in two sister chromatids for each chromosome.

What is apoptosis?

Apoptosis is programmed cell death, which may occur in response to cellular damage or during development.

What is the difference between mitosis and cytokinesis?

Mitosis is the division of the nucleus, while cytokinesis is the division of the cytoplasm.

How do CDKs and Cyclins regulate the cell cycle?

Cyclins activate CDKs, which phosphorylate target proteins to drive the cell cycle forward.

What is genetic linkage?

Genetic linkage refers to the tendency of genes located close together on a chromosome to be inherited together.

What is the expected phenotypic ratio for a monohybrid cross?

The expected phenotypic ratio for a monohybrid cross is 3:1.

What is the expected phenotypic ratio for a dihybrid cross?

The expected phenotypic ratio for a dihybrid cross is 9:3:3:1.

How can the environment affect phenotype?

The environment can influence phenotype by affecting gene expression and the interaction of genes with environmental factors.

What is aneuploidy and what causes it?

Aneuploidy is the presence of an abnormal number of chromosomes in a cell, caused by errors in cell division such as nondisjunction.

What is a karyotype and how can it be interpreted?

A karyotype is a visual representation of an individual's chromosomes, used to identify chromosomal abnormalities like aneuploidies.

What is the significance of being able to draw and interpret a pedigree?

Pedigrees help determine the mode of inheritance of a condition (sex-linked, autosomal, dominant, recessive) and infer possible genotypes.

How can probability be used in genetics?

Probability can analyze and predict the passage of genes from parents to offspring using the Laws of Probability.

What are the advantages of sexual reproduction?

Sexual reproduction increases genetic diversity, which can enhance survival and adaptability of a species.

What does it mean for DNA to be 'antiparallel'?

Antiparallel refers to the orientation of the two strands of DNA running in opposite directions, with one strand running 5' to 3' and the other 3' to 5'.

What are the differences in DNA structure between prokaryotes and eukaryotes?

Prokaryotic DNA is circular and not associated with histones, while eukaryotic DNA is linear and wrapped around histones.

What are the base pairing rules in DNA and how do they differ in RNA?

In DNA, adenine pairs with thymine and cytosine pairs with guanine; in RNA, adenine pairs with uracil instead of thymine.

What are the key enzymes involved in DNA replication?

Key enzymes include helicase (unwinds DNA), DNA polymerase (synthesizes new DNA strands), topoisomerase (relieves strain), and ligase (joins Okazaki fragments).

What does it mean for DNA replication to be semi-conservative?

Semi-conservative means that each new DNA molecule consists of one original strand and one newly synthesized strand.

What are the differences between the leading and lagging strands during DNA replication?

The leading strand is synthesized continuously in the same direction as the replication fork, while the lagging strand is synthesized in short segments (Okazaki fragments) in the opposite direction.

How does transcription differ between prokaryotes and eukaryotes?

In prokaryotes, transcription occurs in the cytoplasm and is coupled with translation; in eukaryotes, it occurs in the nucleus and requires RNA processing.

What is the function of RNA polymerase?

RNA polymerase synthesizes RNA from a DNA template during transcription.

What direction is mRNA synthesized?

mRNA is synthesized in the 5' to 3' direction.

What is the difference between the template and coding strands of DNA?

The template strand is used by RNA polymerase to synthesize mRNA, while the coding strand has the same sequence as the mRNA (except for thymine being replaced by uracil).

What happens during RNA processing in eukaryotes?

RNA processing includes adding a 5' cap and a poly-A tail, splicing out introns, and retaining exons.

What are spliceosomes?

Spliceosomes are complex molecular machines that remove introns from pre-mRNA and splice exons together.

What is alternative splicing?

Alternative splicing allows for the production of multiple mRNA variants from a single gene by including or excluding different exons.

What are codons and anticodons, and where are they found?

Codons are three-nucleotide sequences on mRNA that specify amino acids; anticodons are complementary three-nucleotide sequences on tRNA.

What are the three phases of translation?

The three phases are initiation (start codon), elongation (matching mRNA codons with tRNA anticodons), and termination (stop codon).

What are regulatory sequences in gene expression?

Regulatory sequences are sections of DNA that interact with regulatory proteins to control transcription.

What are epigenetic changes?

Epigenetic changes are reversible modifications of DNA or histones that affect gene expression without altering the DNA sequence.

How do specific transcription factors influence gene expression?

Specific transcription factors can activate or repress gene expression, leading to tissue-specific protein production and cell differentiation.

What allows related eukaryotic genes to be regulated even if they are far apart or on different chromosomes?

They can be regulated by the same activators or signals.

What role do repressors play in gene regulation?

Repressors inhibit transcription by stopping the process of gene expression.

What is a promoter in the context of gene transcription?

A promoter is a section of DNA located before a gene where RNA polymerase and transcription factors bind to initiate transcription.

What are negative regulatory molecules?

Negative regulatory molecules bind to DNA to block transcription and inhibit gene expression.

How does gene regulation influence cell function?

Gene regulation determines what a cell can produce and how it will function, leading to cell specialization.