Test 1 Flashcards
Theory
A widely accepted hypothesis to explain natural phenomena. It has yet to be disproved.
Fact
A piece of information provided objectively, presented as true.
Hypothesis
A proposed, scientifically testable explanation for an observed phenomenon.
Theory of evolution
Proposed by Charles Darwin:
All species have descended from a common ancestor.
Phylogenetics
The study of evolutionary relationships among biological entities – often species, individuals or genes (which may be referred to as taxa)
Natural Selection
A process in which individuals who have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Positive Control
A control group that is not exposed to the experimental treatment but that is exposed to some other treatment that is known to produce the expected effect.
Potential Energy
Energy stored due to an object’s position or arrangement
Valence Electrons
The electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds.
Octet Rule
States that atoms lose, gain, or share electrons to acquire a full set of eight valence electrons.
Covalent Bond
A chemical bond where electrons are shared/
Ionic Bond
Chemical bond between ions, 1 or more electrons have been transferred.
Chemical Bonds
The force of attraction holding atoms together to form molecules.
Hydrogen Bond
A chemical bond in which a hydrogen is shared between two electronegative atoms
(usually O and/or N).
Molecule
A substance made up of two or more atoms held together by covalent bonds.
Polar
Molecule with partial charges, mixes with water.
Non-polar
Equal sharing of electrons does not mix well with water. No partial charges.
Solvent
The liquid in which the molecule is dissolved.
Solute
A molecule dissolved in a liquid.
Specific Heat
The amount of energy required to raise the temperature of 1 gram of a substance 1* C.
Hydrophobic
Not mixing readily with water. Typically non-polar compounds that contain many
C-C and C-H bonds.
Hydrophilic
Mixing readily with water. Typically polar compounds
Amphipathic
Containing hydrophobic and hydrophilic elements.
Polymer
A long molecule consisting of many similar or identical monomers linked together.
Monomer
The subunit that serves as the building block of a polymer.
Dehydration Reaction
A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule.
Hydrolysis Reaction
A chemical reaction that breaks apart a larger molecule by adding a molecule of water.
Protein
A polpeptide chain formed of 20 different amino acids. Diverse size and shape, the shape or structure determines the function of the protein. The body’s building block. Provide structure, can act as enzymes, transport, gene expression, and immune response.
Amino Acid
The monomer of proteins. Bonded together amino acids are called polypeptides.
Enantiomer
Isomers that are mirror images of each other.
Kinetic Energy
Energy of motion.
1st Law of Thermodynamics
Energy cannot be created or destroyed.
2nd Law of Thermodynamics
Every energy transfer or transformation increases the entropy of the universe.
Exergonic Reactions
Chemical reactions that release energy.
Endergonic Reactions
A chemical reaction that requires energy imput.
Equilibrium
A state of balance.
Catalysis
Acceleration of the rate of a chemical reaction due to a decrease in the free energy of the transition state, called the activation energy.
Enzymes
Catalysts for chemical reactions in living things.
Activation Energy
The minimum amount of energy required to start a chemical reaction.
Theory of Chemical Evolution
Simple molecules became more complex becoming cells, became able to make a copy of oneself and surrounded by cell membrane.
Nucleotide
A building block of DNA, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.
Cytosine
A base of nucleic acids. Pairs with Guanine
Uracil
A base of nucleic acids found in RNA. Pairs with Adenine.
Thymine
A base of nucleic acids in DNA. Pairs with Adenine.
Guanine
Base of nucleic acids. Pais with cytosine.
Adenine
Base of nucleic acids. In DNA pairs with Thymine. In RNA pairs with Uracil.
Gel electrophoresis
Procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel.
DNA
A complex molecule containing the genetic information that makes up the chromosomes.
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell’s proteins.
RNA
A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.
Carries genetic information that is translated by ribosomes into various proteins necessary for cellular processes.
Information from DNA to ribosomes.
5 Prime End (5’)
The starting point of the strand when you write it out from left to right. The 5’ end is important because it dictates the direction in which the DNA or RNA strand is synthesized and how it is read during processes like replication and transcription.
3 Prime End (3’)
In other words, it’s the end of the strand opposite the 5’ end. The 3’ end is crucial because it plays a significant role in the processes of DNA replication and RNA transcription, as nucleotides are added to this end during synthesis.
How can one use the Standard Error of the Mean to estimate whether the difference between two means is significant?
SD/√n
SD: Standard Deviation
——————————–
√n: Sample Size
Standard Deviation
A computed measure of how much scores vary around the mean score.
What are the two underlying theories of biology? What common concept(s) do they share?
The 2 underlying theories of biology are Cell Theory and the Theory of Evolution. Both share the opinion that life is very interconnected and diverse, that cells and species can replicate and evolve, and both are supported by scientific evidence.
Why might one accept cell theory when we cannot prove that all organisms are made of cells?
There is a lot of evidence and the theory has been validated across many different organisms. Has failed to be disproved.
How are theory, fact, and hypothesis related? How does the scientific view of these concepts differ from the typical response?
Hypothesis: A testable prediction
Fact: Observation that can be verified
Theory: Well-sustained explanation that hase been failed to disprove.
Theories are not just opinions but continuously tested frameworks.
What is the value of the phylogenetic classification of organisms?
Phylogenetics provide information into common ancestry and evolution.
What is the difference between the theory of evolution and the hypothesis of natural selection?
Natural selection is one of the key processes that drives evolution while the theory of evolution encompasses mechanisms like genetic drift, mutations, and gene flow.
Why is carbon such an ideal molecule for the basis of life?
It is a sharing element. It can form stable covalent bonds with many other atoms. Can bond to itself to create long carbon chains and rings, and they’re very stable yet reactive enough to create biochemical reactions. CARBON: AKA BACKBONE OF LIFE
Why might it be interesting to find water on another planet?
It suggests the potential for life.
What are the unique properties of water, and how do they support life?
Water is polar, solutes dissolve in water, its ability to participate in hydrogen bonds gives it a high heat capacity, and it can spontaneously dissassociates into hydrogen ions (H+) and hydroxide ions (OH-).
Living things share the same common set of molecules…why?
Because living things are all carbon based.
What monomers are used to create proteins?
Amino Acids.
What monomers are used to create nucleic acids?
Nucleotides. Nucleotides consist of a nitrogenous base, a 5-carbon sugar, and a phosphate group.
How are polymers made?
Polymerization: the bonding together of monomers, usually water is the byproduct.
How are polymers broken?
Enzymes that unzip the bonds or Hydrolysis, where water is added.
What functions do proteins have?
Enzyme Activity
Transport
Structure
Immune REsponse
Signaling
Movement
Storage
What determines protein function?
The shape.
What are the levels of protein structure and the bonds that maintain them?
Primary Structure: Peptide Bonds
Secondary Structure: Hydrogen bonding and Peptide Bonds
Tertiary Structure: Peptide Bonds, Hydrogen Bonds, Covalent, and Ionic bonds
Quaternary Structure: Bonds and Interactions iwth the R Group
How do enzymes facilitate chemical reactions energetically?
Lowering Activation Energy
How do enzymes facilitate chemical reactions mechanically?
Substrate orientation. Facilitate collisions and therefore bond formation.
What are the 2 ways that enzyme function can be regulated?
Competitive Inhibition and Allosteric Regulation.
How does temperature, pH, and substrate concentration affect the rate of an enzyme-catalyzed reaction
Depending on optimal pH, tmeperature, and substrate concentrations the enzymes can function at different levels of productivity.
What is the structure of DNA?
2 antiparalell strands
Nucleotides
Base Pairing
Sugar Phosphate Background
Major and Minor Grooves
What are anti-parallel strands?
One strand runs in the 5’ to 3’ direction, meaning it starts with a phosphate group at the 5’ end and ends with a hydroxyl group at the 3’ end.
The other strand runs in the 3’ to 5’ direction, starting with a hydroxyl group at the 3’ end and ending with a phosphate group at the 5’ end.
This is important for base pairing, replication, and stability.
How do you determine the direction of a single strand of DNA?
he 5’ end has a phosphate group attached to the fifth carbon of the sugar (deoxyribose).
The 3’ end has a hydroxyl group attached to the third carbon of the sugar.
REad the sequence and see if it starts with 5’ or 3’.
What purpose(s) are served by the ability of DNA to bend?
PMore efficent binding, replication, and repair.
Can DNA store information? Does it have catalytic properties? Why or why not?
Yes it can store information. No it does nnot have catalytic properties, it can interact with catalytic orotein but not independently catalyze reactions.
Can RNA store information? Does it have catalytic properties? Why or why not?
Yes, not as much information as DNA though. Yes, some RNA, known as ribozymes can catalyze reactions. This id due to RNA less structured shape and many forms which can form into many different shapes, so amnt different functions,
What are the common structures of RNA?
Single Stranded RNA
Secondary Structures (hairpins, loops)
Tertiary Structures
rRNA
tRNA
Discuss the differences and similarities between DNA and RNA
BOTH
-Nucleotide Base Pairing
-Contain Genetic Info
-Involved in Protein Synthesis
DNA
-Deoxyribose
-Double Stranded, helix structure
-Has Base Thymine
-Long term genetic infostorage
-Super stable
RNA
-Ribose
-Single Stranded
-Uracil Base
-Messenger, Transger, and ribosomal roles
-Less stable due to extra hydroxyl group
Carbohydrate
Formed by linking monosaccharides to form polysaccharides
Monosaccharide
Sugar monomers that make up polysaccharide chains
Polysaccharide
Chains of monosaccharides that form proteins.
Glycoprotein
A protein with one or more carbohydrates covalently attached to it.
ATP
Adenine TriPhosphate primary energy carrier in cells. For energy transfer within cells.
Lipid
Polymers of fatty acids. Store energy in C–C and C–H bonds. Structural role. Fat in animals serves as insulation.
Steroid
A type of lipid characterized by a carbon skeleton consisting of four rings with various functional groups attached. Muscle growth.
Phospholipid
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
Fat
Lipid type that is solid at room temp. MAd eof triglycerides, store energy, provide insulation, and protection.
Diffusion
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration, resulting in a net movement until equilibrium is reached.
Facilitated Diffusion
Facilitated diffusion utilizes transport proteins to assist the movement of larger or polar molecules (like glucose or ions) across the membrane. This process does not require energy, as it relies on the concentration gradient, moving substances from areas of higher concentration to areas of lower concentration until equilibrium is reached.
Passive Transport
Passive transport is the movement of molecules across a cell membrane without the expenditure of energy. This process occurs along the concentration gradient, meaning substances move from areas of higher concentration to areas of lower concentration.
Active Transport
Active transport is the movement of molecules across a cell membrane against their concentration gradient, from areas of lower concentration to areas of higher concentration. Unlike passive transport, active transport requires energy, usually in the form of ATP, to drive the process.
Osmosis
The diffusion of water across a selectively permeable membrane.
Isotonic
Isotonic refers to a solution that has the same concentration of solutes as another solution, typically compared to the inside of a cell. In an isotonic environment, there is no net movement of water into or out of the cell, meaning the cell maintains its normal shape and function.
Hypertonic
Hypertonic refers to a solution that has a higher concentration of solutes compared to another solution, typically in relation to the inside of a cell. Cell shrivels becuase the higher concentration leaves. Same in animal and plants.
Hypotonic
Hypotonic refers to a solution that has a lower concentration of solutes compared to another solution, typically in relation to the inside of a cell. Cel swells and bursts in animals, in plants it is more resitant to bursting due to the need for water and long term hydration storage in plants (the cell wall).
Prokaryote
Prokaryotes are single-celled organisms that lack a membrane-bound nucleus and other membrane-bound organelles.
Small, simple, and asexual cells.
Bacteria and Archaea
Plasmid
A plasmid is a small, circular piece of DNA that exists independently of the chromosomal DNA within a cell. Plasmids are primarily found in prokaryotic organisms, such as bacteria, but can also be present in some eukaryotic cells.
functions:
resitance to antibiotics
enabling bacteria, caarry genes that enhance the pathogenicity of bacteria
Eukaryote
A eukaryote is an organism whose cells contain a nucleus and other membrane-bound organelles.
Visible, multicellular organisms.
Cell Membrane
The cell membrane, also known as the plasma membrane, is a biological barrier that surrounds and protects the cell, controlling the movement of substances in and out.
Composed of the phospolipid bilayer, contains protein (receptors, enzymes, and transport).
Enables selective permeability, communication, structure, and transport.
Nucleus
Membrane bound oranelle found in eukaryotic cells that is the control center of the cell. Houses genetic material.
Ribosome
A ribosome is a complex molecular machine found in all living cells that is essential for protein synthesis (translation). Ribosomes can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum (in eukaryotic cells), forming what is known as the rough ER.
Smooth Endoplasmic Reticulum
The smooth endoplasmic reticulum (smooth ER) is a type of endoplasmic reticulum (ER) that lacks ribosomes on its surface, giving it a smooth appearance. It plays several important roles within the cell.
Lipid Synthesis
Detoxification
Calcium storage
Metabolism of carbs
Rough Endoplasmic Reticulum
The rough endoplasmic reticulum (rough ER) is a type of endoplasmic reticulum characterized by the presence of ribosomes on its surface, giving it a “rough” appearance. It plays a crucial role in the synthesis and processing of proteins.
Protein synthese
Protein folding
Quality control
Golgi Apparatus
The Golgi apparatus, also known as the Golgi complex or Golgi body, is a vital organelle in eukaryotic cells responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to various cellular destinations.
UPS
Lysosome
A lysosome is a membrane-bound organelle found in eukaryotic cells that contains digestive enzymes. These enzymes are responsible for breaking down waste materials, cellular debris, and foreign substances.
Peroxisome
A peroxisome is a small, membrane-bound organelle found in eukaryotic cells that plays a crucial role in lipid metabolism and the detoxification of harmful substances.
Vacuole
A vacuole is a membrane-bound organelle found in the cells of plants, fungi, and some protists.
Animals don’t have.
Play a role in storage, structure, regulation, and degradation
Mitochondrion
Mitochondria are membrane-bound organelles found in eukaryotic cells, often referred to as the “powerhouses” of the cell. They generate adenosine triphosphate (ATP) through cellular respiration, providing energy for various cellular processes. Mitochondria also play roles in regulating metabolism, apoptosis, and maintaining cellular homeostasis.
Chloroplast
Chloroplasts are membrane-bound organelles found in the cells of plants and some algae, responsible for photosynthesis. They contain chlorophyll, the pigment that captures light energy, allowing the conversion of carbon dioxide and water into glucose and oxygen. In addition to energy production, chloroplasts play a role in synthesizing certain nutrients and regulating plant metabolism.
Extracellular Matrix
The extracellular matrix (ECM) is a complex network of proteins and carbohydrates that provides structural and biochemical support to surrounding cells in tissues. It plays a crucial role in cell adhesion, migration, and communication, influencing processes such as tissue development and repair. The ECM also helps maintain tissue integrity and regulates cellular functions through various signaling pathways.
Cytoskeleton
The cytoskeleton is a dynamic network of protein filaments and tubules that provides structural support, shape, and organization to eukaryotic cells. It is composed of three main components: microfilaments, intermediate filaments, and microtubules, each serving different functions in cell movement, division, and intracellular transport. Additionally, the cytoskeleton plays a critical role in maintaining cell integrity and facilitating communication between cells.
Actin
Actin is a globular protein that polymerizes to form long, thin filaments known as microfilaments, which are a key component of the cytoskeleton in eukaryotic cells. It plays crucial roles in various cellular processes, including muscle contraction, cell shape maintenance, and cell motility. Actin filaments also participate in intracellular transport and are involved in signaling pathways that regulate cell division and other functions.
Microtubules
Microtubules are cylindrical structures made of tubulin protein subunits that form part of the cytoskeleton in eukaryotic cells. They provide structural support, shape the cell, and are essential for cell division by forming the mitotic spindle that segregates chromosomes. Additionally, microtubules serve as tracks for the movement of organelles and vesicles within the cell, facilitating intracellular transport.
Centrioles
Centrioles are cylindrical organelles found in animal cells, typically occurring in pairs, and play a key role in cell division. They are involved in organizing microtubules to form the mitotic spindle, which helps segregate chromosomes during mitosis and meiosis. Centrioles also contribute to the formation of cilia and flagella, which are important for cell movement and fluid movement across cell surfaces.
Cilia/Flagella
Cilia and flagella are hair-like structures that extend from the surface of eukaryotic cells, aiding in movement and sensory functions. Cilia are short and numerous, beating in a coordinated fashion to move fluids or propel the cell, while flagella are longer and usually occur singly or in pairs, providing propulsion through a whip-like motion. Both structures share a common “9+2” arrangement of microtubules, which is essential for their movement.
Cell Wall
The cell wall is a rigid outer layer that provides structural support and protection to the cells of plants, fungi, bacteria, and some protists. Composed primarily of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria, the cell wall helps maintain cell shape and prevents excessive water uptake. Additionally, it plays a role in regulating interactions with the environment and neighboring cells.
Plasmodesmata
Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, allowing for direct communication and transport of materials between neighboring cells. These structures facilitate the exchange of ions, nutrients, and signaling molecules, enabling coordinated responses and metabolic activities within plant tissues. By connecting the cytoplasm of adjacent cells, plasmodesmata play a crucial role in maintaining tissue integrity and function.
Tight Junction
Tight junctions are specialized connections between adjacent epithelial cells that create a barrier to prevent the passage of substances between the cells. They seal the space between cells, ensuring that materials must pass through the cells rather than between them, which helps maintain distinct environments on either side of the epithelium. Tight junctions play a critical role in regulating permeability, protecting tissues, and contributing to the overall function of epithelial barriers in organs like the intestines and the blood-brain barrier.
Gap Junction
Tight junctions are specialized connections between adjacent epithelial cells that create a barrier to prevent the passage of substances between the cells. They seal the space between cells, ensuring that materials must pass through the cells rather than between them, which helps maintain distinct environments on either side of the epithelium. Tight junctions play a critical role in regulating permeability, protecting tissues, and contributing to the overall function of epithelial barriers in organs like the intestines and the blood-brain barrier.
Desosome
Desmosomes are specialized cell junctions that provide strong adhesion between adjacent cells, particularly in tissues subjected to mechanical stress, such as skin and cardiac muscle. They consist of protein structures that anchor the cytoskeleton of one cell to that of another, creating a resilient network that helps maintain tissue integrity. Desmosomes play a crucial role in resisting stretching and tearing, ensuring that cells remain connected under physical strain.
Pulse-Chase experiment
The pulse-chase experiment is a technique used in molecular biology to study cellular processes, particularly protein synthesis and transport. In this experiment, cells are first exposed to a “pulse” of labeled precursors (such as amino acids or nucleotides) for a short period, allowing researchers to track newly synthesized molecules. After the pulse, a “chase” phase begins where the labeled precursors are replaced with non-labeled ones, allowing scientists to observe how the labeled molecules move through the cell over time and how long they persist in various cellular compartments. This method provides insights into cellular dynamics, protein localization, and turnover rates.
Motor Protein
Motor proteins are specialized proteins that convert chemical energy from ATP hydrolysis into mechanical work, facilitating movement within cells. They play essential roles in various cellular processes, such as muscle contraction, intracellular transport of organelles and vesicles, and cell division. Key types of motor proteins include myosin, which interacts with actin filaments for muscle movement; kinesin and dynein, which move along microtubules to transport cellular cargo; and they are crucial for maintaining cellular organization and function.
Hormone
Hormones are chemical messengers produced by glands in the endocrine system that regulate various physiological processes in the body. They are released into the bloodstream and travel to target organs or tissues, where they elicit specific responses, such as regulating metabolism, growth, mood, and reproductive functions. Hormones play crucial roles in maintaining homeostasis and coordinating complex bodily functions across different systems.
What are the functions of carbohydrates?
Carbohydrates serve several essential functions in living organisms:
- Energy Source: Carbohydrates are a primary source of energy for cells, providing quick fuel through simple sugars like glucose.
- Structural Support: They contribute to the structure of cells and tissues, such as cellulose in plant cell walls and chitin in fungal cell walls.
- Cell Signaling: Carbohydrates play a role in cell recognition and signaling, often found on the surface of cells as glycoproteins and glycolipids, aiding in immune responses and cell communication.
- Storage: Carbohydrates like glycogen in animals and starch in plants serve as energy reserves that can be mobilized when needed.
- Hydration: They help maintain hydration in the body, as carbohydrates can attract and hold water.
Overall, carbohydrates are vital for energy, structure, and cellular communication.
Why are carbohydrates and fats a good source of energy?
Carbohydrates and fats are excellent sources of energy for several reasons:
- High Energy Density: Both carbohydrates and fats contain a high number of calories per gram. Fats provide about 9 calories per gram, while carbohydrates provide about 4 calories per gram, making them efficient energy sources.
- Chemical Structure: Their chemical bonds store significant amounts of energy. When metabolized, the breakdown of these bonds releases energy that cells can use for various functions.
- Versatile Metabolism: Carbohydrates can be quickly converted into glucose, providing immediate energy, while fats are utilized for sustained energy during prolonged activities or fasting.
- Storage Efficiency: Both are stored in the body in forms that are easily accessible. Carbohydrates are stored as glycogen in the liver and muscles, while fats are stored in adipose tissue, allowing the body to tap into these reserves when needed.
Together, carbohydrates and fats play crucial roles in energy metabolism and support various bodily functions and activities.
What gives Cellulose and chitin their tough structural qualities?
Cellulose and chitin derive their tough structural qualities from their unique chemical structures and the way their molecules interact:
-
Molecular Structure:
- Cellulose is composed of long chains of glucose molecules linked by β-1,4-glycosidic bonds. This arrangement creates straight, rigid fibers that can pack closely together.
- Chitin is similar to cellulose but has N-acetylglucosamine units instead of glucose. This structural variation also leads to strong, long chains that provide rigidity.
- Hydrogen Bonding: Both cellulose and chitin molecules form extensive hydrogen bonds between adjacent chains, resulting in strong intermolecular interactions. This bonding enhances their strength and stability, contributing to their toughness.
- Crystalline Structure: In both materials, the arrangement of the chains leads to a crystalline structure, which increases resistance to mechanical stress. The organized structure makes it difficult for enzymes and other substances to break them down.
These features make cellulose and chitin effective at providing structural support in plants and fungi, respectively.
What is found in the membrane? What are the properties of each of these molecules?
Cell membranes are composed of several key molecules, each contributing to the membrane’s structure and function. The main components include:
-
Phospholipids:
- Structure: Composed of a hydrophilic (water-attracting) “head” and two hydrophobic (water-repelling) “tails.”
- Properties: They form a bilayer, with heads facing outward towards the aqueous environment and tails facing inward, creating a barrier that separates the cell from its surroundings. This amphipathic nature allows for membrane fluidity and flexibility.
-
Proteins:
- Types: Integral (or membrane) proteins that span the membrane and peripheral proteins that are attached to the surface.
- Properties: Integral proteins can function as channels or transporters for substances, while peripheral proteins are often involved in signaling or maintaining the cell’s shape. They contribute to selective permeability and communication.
-
Cholesterol:
- Structure: A sterol molecule embedded within the phospholipid bilayer.
- Properties: Cholesterol helps maintain membrane fluidity, providing stability in varying temperatures. It prevents the fatty acid chains from packing too closely, which can help keep the membrane flexible.
-
Carbohydrates:
- Structure: Often attached to proteins (glycoproteins) or lipids (glycolipids) on the extracellular surface.
- Properties: Carbohydrates play critical roles in cell recognition, signaling, and adhesion. They form protective layers and help in cell-to-cell communication.
Together, these molecules create a dynamic and versatile membrane that regulates the entry and exit of substances, facilitates communication, and maintains the integrity of the cell.
What functions do membrane proteins have?
Membrane proteins serve several essential functions, including transport of ions and nutrients across the membrane, and enzymatic activity that catalyzes biochemical reactions. They play a crucial role in signal transduction by binding to ligands and initiating cellular responses. Additionally, glycoproteins and glycolipids are involved in cell recognition and intercellular adhesion, maintaining tissue structure. Lastly, some membrane proteins anchor to the cytoskeleton, providing structural support and aiding in cell shape and movement.
Why is there a difference in the ability of hydrophobic and hydrophilic molecules to pass through the membrane?
The ability of hydrophobic and hydrophilic molecules to pass through the cell membrane differs due to the structure of the phospholipid bilayer. Hydrophobic molecules, such as lipids and nonpolar gases, can easily dissolve in the lipid environment and pass through without assistance. In contrast, hydrophilic molecules, like ions and polar substances, cannot cross the bilayer easily and often require specific transport proteins or channels. This selective permeability allows cells to regulate their internal environment effectively, facilitating the entry of essential nutrients while excluding harmful substances.
How can you passively transport a molecule that doesn’t pass through the membrane easily?
To passively transport a molecule that doesn’t easily cross the membrane, cells can utilize facilitated diffusion. This process involves specific transport proteins, such as channel proteins or carrier proteins, that assist in moving the molecule across the membrane without requiring energy.
- Channel Proteins: These create hydrophilic pathways through which ions or polar molecules can pass directly, allowing for selective movement based on size and charge.
- Carrier Proteins: These bind to the molecule on one side of the membrane, undergo a conformational change, and then release the molecule on the other side, enabling transport without the need for ATP.
Facilitated diffusion allows for the movement of substances along their concentration gradient, making it an efficient way to transport molecules that cannot freely diffuse through the lipid bilayer.
When is active transport required?
Active transport is required when molecules need to be moved against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This process is essential in several scenarios:
- Nutrient Uptake: Cells often need to absorb essential nutrients (like glucose or amino acids) from the surrounding environment where their concentration is lower.
- Ion Regulation: Maintaining ion gradients (such as sodium, potassium, and calcium) is crucial for processes like nerve impulse transmission and muscle contraction, which requires transporting ions against their gradients.
- Cell Volume Regulation: Active transport helps control the osmotic balance of the cell, preventing excessive swelling or shrinking by moving ions and solutes as needed.
- Removal of Waste: Cells may need to expel waste products or toxins that have accumulated inside, requiring energy to move these substances out against their concentration gradients.
In all these cases, active transport relies on the energy provided by ATP or other energy sources to drive the movement of molecules.
What are the major differences between prokaryotes and eukaryotes?
Prokaryotes and eukaryotes differ in several fundamental ways:
-
Cell Structure:
- Prokaryotes: Have a simple cell structure without a nucleus; their genetic material (DNA) is located in a nucleoid region. They lack membrane-bound organelles.
- Eukaryotes: Have a complex cell structure with a true nucleus that encloses their DNA and various membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum).
-
Size:
- Prokaryotes: Generally smaller (0.1 to 5 micrometers) and simpler in design.
- Eukaryotes: Typically larger (10 to 100 micrometers) with more complex structures.
-
Reproduction:
- Prokaryotes: Primarily reproduce asexually through binary fission, a simpler process.
- Eukaryotes: Can reproduce both asexually (e.g., mitosis) and sexually (e.g., meiosis), allowing for greater genetic diversity.
-
Genetic Material:
- Prokaryotes: Usually have a single, circular DNA molecule that is not associated with histones.
- Eukaryotes: Have multiple linear DNA molecules organized into chromosomes and associated with histones, which help in packaging and regulating gene expression.
What are the advantages of compartmentalization of cells?
Compartmentalization in cells enhances efficiency by allowing multiple biochemical processes to occur simultaneously without interference. It enables specialization of organelles, creating unique environments optimal for specific functions, such as energy production in mitochondria. Additionally, it regulates metabolic pathways by controlling substrate and enzyme availability, preventing unwanted reactions. Lastly, compartmentalization protects sensitive cellular processes from potentially harmful substances in the cytoplasm, ensuring overall cellular integrity and function.
What dictates the ability of a protein to enter or exit the nucleus?
The ability of a protein to enter or exit the nucleus is primarily dictated by specific signals it contains, such as nuclear localization signals (NLS) for entry and nuclear export signals (NES) for exit. Nuclear transport receptors, like importins and exportins, recognize these signals and facilitate the transport of proteins through the nuclear pore complex. The nuclear pore complex itself acts as a selective barrier, regulating the passage of molecules based on size and the presence of these signals. Additionally, post-translational modifications can influence a protein’s localization by altering its interaction with transport receptors or its conformation.
What is the general process for the extracellular excretion of a protein?
The extracellular excretion of a protein begins with its synthesis in the endoplasmic reticulum (ER), where it is folded and modified. The protein is then transported to the Golgi apparatus for further processing and sorting. After processing, it is packaged into secretory vesicles that bud off from the Golgi. These vesicles travel to the plasma membrane, fuse with it, and release the protein into the extracellular space through exocytosis.
How does the Golgi apparatus deliver proteins to the appropriate location?
The Golgi apparatus delivers proteins to the appropriate location by using specific sorting signals present in the proteins. As proteins pass through the Golgi, they undergo modifications that help determine their final destination, such as glycosylation or phosphorylation. The Golgi then packages these proteins into vesicles that contain specific tags or markers for their intended location, whether for secretion, incorporation into the membrane, or delivery to lysosomes. These vesicles transport the proteins to their designated sites within the cell or outside of it, ensuring proper cellular function.
How do microtubules facilitate vesicle transport?
Microtubules facilitate vesicle transport through their role as tracks for motor proteins. Here’s how it works:
- Structural Framework: Microtubules form a network throughout the cell, providing a structural framework that supports the movement of vesicles.
- Motor Proteins: Motor proteins, such as kinesin and dynein, attach to the vesicles and move along the microtubules. Kinesin typically transports vesicles toward the plus end (cell periphery), while dynein moves them toward the minus end (cell center).
- Energy Dependency: The movement of motor proteins along microtubules is powered by ATP hydrolysis, allowing for active transport of vesicles.
- Directional Transport: This system ensures that vesicles are accurately and efficiently delivered to their target destinations within the cell, facilitating processes such as secretion, endocytosis, and organelle communication.
What are 3 purposes for cell-cell adhesion? How are they accomplished?
Cell-cell adhesion serves several important purposes:
- Tissue Integrity: Cell-cell adhesion helps maintain the structural integrity of tissues by holding cells together. This is accomplished through adhesion molecules, such as cadherins, that link the cytoskeletons of adjacent cells and form strong connections.
- Cell Communication: Adhesion facilitates communication between cells, allowing for the exchange of signals and molecules. This is achieved through gap junctions, which are specialized connections that permit direct transfer of ions and small signaling molecules between neighboring cells.
- Development and Morphogenesis: During development, cell-cell adhesion is crucial for guiding cells to their proper locations and forming organized structures. This is accomplished through various signaling pathways activated by adhesion molecules, such as integrins and selectins, that influence cell behavior, migration, and differentiation.
These mechanisms enable cells to work together effectively, ensuring proper function and organization within tissues.
Feedback Inhibition
Feedback inhibition is a regulatory mechanism in biological systems where the end product of a metabolic pathway inhibits an enzyme involved in its production. This process prevents the overproduction of the product, helping to maintain homeostasis within the cell. By modulating enzyme activity, feedback inhibition allows cells to respond efficiently to changes in their environment and resource availability.
