Cell Membrane Transport Quiz

Chemical Fundamentals

• Molecules like lipids, nucleic acids, proteins, and carbohydrates are crucial to living things.
• Biochemistry studies the chemistry of biologically important molecules.
• Isotopes are atoms with the same number of protons and electrons but different numbers of neutrons. Their atomic masses differ.
• Radioisotopes spontaneously decay and have a half-life, the time it takes for half the nuclei to decay. They are used in radiometric dating and as radioactive tracers.
• A polar molecule contains polar covalent bonds and has an asymmetrical arrangement of bonds.
• Water is a polar molecule with unique properties vital for life on Earth. Its polarity allows it to dissolve many ionic and polar compounds.
• Electrons move around the atomic nucleus in energy levels, with those further from the nucleus having greater potential energy. Outermost energy levels contain valence electrons, determining an atom's chemical behavior.
• Chemical bonding includes intramolecular forces (between atoms), such as ionic and covalent bonds, and intermolecular forces (between molecules), including hydrogen bonds and hydrophobic interactions.
• Covalent bonds form when atoms share one or more pairs of valence electrons. Ionic bonds form from attraction between positive and negative charges.
• Polar molecules are water-soluble (hydrophilic). Non-polar molecules are insoluble (hydrophobic).

Molecular Polarity and Solubility

• Polar covalent bonds have unequal sharing of electrons resulting in partial positive and negative charges on atoms.
• Polarity affects how molecules behave in water.
• Water acts as a universal solvent due to its polarity.

Biochemical Reactions

• Acid-base reactions form water and a salt, and help maintain optimal pH.
• Buffers counteract changes in pH.
• Condensation reactions (dehydration synthesis) combine monomers to create polymers, absorbing energy.
• Hydrolysis reactions break down polymers with the addition of water, releasing energy.
• Organic molecules are composed primarily of carbon atoms because carbon can form strong, stable covalent bonds with other carbon atoms and other elements.

Functional Groups of Organic Molecules

• Functional groups are groups of atoms within molecules that give rise to particular chemical properties.
• Hydroxyl, carboxyl, amino, sulfhydryl, phosphate, and carbonyl are examples of functional groups that determine the chemical nature of specific organic molecules.

Common Biological Linkages and Functional Groups

• Hydroxyl + Hydroxyl -> Ether
• Hydroxyl + Carboxyl -> Ester
• Amino + Carboxyl -> Amide (peptide)
• Phosphate + Hydroxyl -> Phosphate Ester

Food and Nutrients

• Food provides energy for cellular work.
• Five main types of nutrients
• Carbohydrates, fats(lipids), proteins, vitamins, minerals, and water.
• Macronutrients are crucial for bodily function and growth.
• Vitamins and minerals are necessary in smaller quantities.

Carbohydrates

• Carbohydrates are used for energy and structural support.
• They contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.
• Classified into monosaccharides, oligosaccharides, and polysaccharides.
• Monosaccharides (e.g., glucose, fructose) are the simplest carbohydrates
• Disaccharides (e.g., sucrose, lactose) are formed by combining two monosaccharides
• Polysaccharides (e.g., starch, glycogen, cellulose) are complex carbohydrates formed by joining multiple monosaccharides.
• Starch and glycogen serve as energy storage in plants and animals
• Cellulose is a structural carbohydrate in plant cell walls.
• Chitin is a structural polysaccharide found in exoskeletons of insects and crustaceans.

Lipids

• Lipids are hydrophobic molecules that include fats, phospholipids, steroids, and waxes.
• Fats (triacylglycerols) are used for energy storage, insulation, cushioning and protection.
• Phospholipids are a component of cell membranes, creating a bilayer. Waxes act as waterproof coverings.
• Steroids have four fused hydrocarbon rings; including cholesterol, estrogen, and testosterone.

Nucleic Acids

• Nucleic acids (DNA and RNA) store and transmit genetic information.
• Nucleotides are the monomers of nucleic acids. Each contains a nitrogenous base, a five-carbon sugar, and a phosphate group.
• DNA is a double helix with bases paired in a specific way (A to T, and G to C) to maintain a constant helix width.
• RNA is a single-stranded molecule; it transmits genetic information from DNA to ribosomes.

Protein Structure and Function

• Proteins are composed of amino acids. There are 20 different types of amino acids.
• The primary structure of a protein is the linear sequence of amino acids.
• Secondary structure involves folding of polypeptide chain into a-helices and β-sheets.
• Tertiary structure is the overall 3D shape of a polypeptide due to interactions between amino acid side chains (e.g., hydrogen bonding).
• Quaternary structure is the arrangement of multiple polypeptide chains in a protein.
• Proteins have diverse functions, including catalysis (enzymes), transport, structure, defense, and regulation.
• Denaturation is the alteration of a protein's shape, rendering it nonfunctional due to changes in temperature and pH. Enzymes are sensitive to these factors.

Enzymes

• Enzymes are proteins that act as catalysts for biochemical reactions.
• Enzymes speed up reactions by lowering the activation energy.
• The active site of an enzyme binds to the substrate, creating an enzyme-substrate complex, causing bonds to break and encourage bonds to form.
• Factors that affect enzyme activity include temperature, pH, substrate concentration, and enzyme concentration.

Membrane Transport

• Membranes are semipermeable, controlling what enters and leaves cells.
• Passive transport includes diffusion, osmosis, and facilitated diffusion. No energy required
• Active transport moves substances against the concentration gradient, requiring energy (ATP)
• Types of membrane transport proteins that assist with transport include -Channel proteins -Carrier proteins Other membrane Assisted Transport Processes
• Endocytosis and exocytosis
• Phagocytosis engulfs a solid particle
• Pinocytosis engulfs a liquid particle
• Receptor-mediated endocytosis

Cell Theory

• All living things are made of cells.
• Cells are the basic structural and functional units of life.
• All cells come from pre-existing cells.

Cell Structural Support

• Cell walls provide structural support to plant, fungi, and protists.
• Cytoskeleton provides structural support to cells with a dynamic framework.

Metabolic Processes

• Catabolism breaks down complex molecules into simpler ones, releasing energy. Many catabolic reactions are exergonic and contribute to the overall free energy released in the breakdown of complex molecules to simpler forms.
• Anabolism builds complex molecules from simpler ones, requiring energy. Many anabolic reactions are endergonic, requiring input of energy to form new molecules.
• Redox reactions involve the transfer of electrons between molecules; a molecule is oxidized when it loses electrons and reduced when it gains electrons.
• Gibbs free energy (G) considers the energy changes in a chemical reaction in terms of energy to do work- can be exergonic or endergonic.
• ATP is an energy carrier. Energy input to form ATP is used to drive many cellular reactions. Hydrolysis of ATP releases energy.

Cellular Respiration

• Cellular respiration is a series of exergonic metabolic reactions that derive energy from glucose, capturing that energy in bonds of ATP.
• Aerobic respiration requires oxygen. Anaerobic respiration does not require oxygen.
• Steps in aerobic respiration include glycolysis, pyruvate oxidation, the Krebs cycle, and electron transport chain.
• The electron transport chain uses an electron transport chain along a series of electron carriers in the inner mitochondrial membrane, ultimately using oxygen as the electron acceptor resulting in the production of water.
• Oxidative phosphorylation generates ATP through chemiosmosis, using the proton gradient established by the electron transport chain.
• ATP theoretical/actual yield depends on which shuttle used for NADH.
• ATP is the primary source of free energy in cells.

Photosynthesis

• Photosynthesis traps light energy and uses it to convert carbon dioxide and water into glucose.
• Photosynthesis occurs in chloroplasts.
• Two processes are involved in photosynthesis: light-dependent reactions and the Calvin cycle.
• The light-dependent reactions capture light energy to produce ATP and NADPH.
• The Calvin cycle uses ATP and NADPH to convert CO2 into carbohydrates.
• Photosynthetic organisms capture the sun's energy to produce glucose, along with other products required for their use in many metabolic pathways.
• Light is absorbed by pigments that function as antenna complexes that transfer from pigment to pigment within a photosystem until it is captured by the reaction centre.
• The reaction centre is made of chlorophyll a molecules where electron are excited as light photons are absorbed. Other electrons replace those used with electrons from splitting of two water molecules that are present in the photosystem II
• Energy is released, and used by protein complex to pump hydrogen ions from stroma across thylakoid membrane into thylakoid space
• Electrons continue to move through various electron carriers until oxygen acts as final acceptor
• Electrons combine with hydrogen atoms from splitting the water molecules
• As electrons passed through electron transport chain concentration gradient across thylakoid membrane is set up.
• Hydrogen ions move down gradient through ATP synthase, and energy of gradient is coupled to produce ATP molecules.

Feedback Systems

• Homeostasis is maintained by negative feedback loops. A negative feedback loop is a process in which a system's response to a stimulus has the effect of reducing the stimulus, bringing the system back to a set point.
• Positive feedback loops magnify a stimulus. Often result in large-scale change. E.g. blood clotting, childbirth
• The body's response to heat or cold also involves negative feedback control.

Excretory System

• The excretory system removes metabolic wastes and regulates water and salt balance.
• Kidneys are the primary organs for removing metabolic wastes from the blood and regulating water and solute balance in the body.
• Urine is filtered and modified by nephrons within the kidney.
• Stages in urine production include glomerular filtration, tubular reabsorption, tubular secretion, and water reabsorption.
• Processes involved in water-salt balance
• ADH influences water reabsorption
• Renin-angiotensin regulates blood pressure

DNA Replication

• DNA replication is the process by which a cell duplicates its DNA before cell division.
• Enzymes involved in replication (DNA polymerases, helicases, primase, DNA ligase)
• DNA replication follows a semiconservative model- one strand of original DNA and one new strand pair to produce new double stranded DNA
• DNA polymerase needs a 3' hydroxyl group to add bases
• Leading and lagging strands
• DNA polymerase III adds nucleotides to growing strand, which is built continuously on one strand of original DNA (called leading strand)
• DNA polymerase I removes RNA primers and replaces them with appropriate deoxyribonucleotides on fragments called Okazaki fragments in lagging strand
• DNA polymerase I also proofreads the new strand for accuracy
• Mismatch repair

DNA Structure and Function

• DNA and RNA are polymers of nucleotides.
• DNA is double helix with alternating sugar and phosphate groups forming the backbone and nitrogenous bases forming the rungs.
• DNA replication follows a semiconservative model.

Gene Regulation

• Gene expression involves turning genes on or off as needed in response to stimuli.
• Transcription factors are proteins that regulate gene expression by binding to DNA and affecting RNA polymerase binding and initiating transcription.
• Operons are clusters of genes in prokaryotes that are controlled by a single promoter.
• The Lac operon, and the Trp operon are example of operons.
• Eukaryotic genes regulated at more than one level: Pretranscriptional, transcriptional, posttranscriptional, and posttranslational.

DNA Sequencing

• Sequencing methods determine the order of nucleotides in DNA.

Genetic Engineering

• Genetic engineering alters an organism's genetic makeup by inserting or deleting genes.
• Transgenic organisms receive genes from another species.
• GMOs are commonly produced, used in pharmaceuticals, bioremediation and for improved crop traits.

Cell Signaling

• A cell binds to receptor on cell surface or internal to cell in order to initiate a response. Chemical messengers like hormones bind to receptors on target cell membranes, activating processes inside the cells such as enzyme action
• Cells communicate with each other using chemical signals called hormones.
• Hormones travel through the bloodstream to target cells, triggering specific responses.
• Examples of hormones include steroid and peptide/protein hormones.

Other

• Transgenic animals are engineered to express foreign genes.
• Various methods for gene introduction into plants and animals; including: gene gun methods, Ti plasmid method
• Cloning of mammals. Early work focused on mammals and has subsequently expanded and improved.
• Various disorders associated with homeostasis and how it affects the different body systems.
• Methods used to study human genetic material and understand the human genome.