Biology Review PDF

- Biology is the study of life All living things (organisms) are: Made of cells Responds to stimuli Able to grow and reproduce Use energy (have a metabolism) The sum of all the biochemical processes in the body Contain DNA or RNA as genetic material - Cells are the most basic structural and func...

- Biology is the study of life All living things (organisms) are: Made of cells Responds to stimuli Able to grow and reproduce Use energy (have a metabolism) The sum of all the biochemical processes in the body Contain DNA or RNA as genetic material - Cells are the most basic structural and functional unit of life. - It is the smallest part of an organism that is still capable of all of life’s processes - Cells are very diverse. - There are prokaryotic and eukaryotic cells. - Eukaryotic cells differ between plants, animals, fungi, and protista. - Even within humans there are believed to be more than 200 types of specialized cells! - Cells are made up of organelles. - Specialized structures within the cell that work together to help the cell function. - Structure - Jelly-like fluid inside of cells - Mainly made up of water - Function - Holds everything in place - Structure - A selectively permeable barrier (known as the phospholipid bilayer) - 2 layers of phospholipids with hydrophilic (likes water) heads and hydrophobic (dislikes water) tails - Carbohydrates are embedded throughout to provide structures - Proteins are embedded to aid in transporting nutrients and signals - Made up of phospholipids - Phosphate “head” - 2 fatty acid chain “tails” - Arranged in a bilayer (2 layers) - Polar heads = hydrophilic, meaning they “like water” - Nonpolar tails = hydrophobic, meaning they are “afraid of water” - Function - Controls what goes in and out of the cell - The arrangement of the phospholipids allows some molecules to easily pass through and others to require more effort. • CAN PASS EASILY = Small, non-polar, hydrophobic, neutral molecules and water (even though H2O is polar it is reallyyyy tiny!) • CANNOT PASS EASILY = Polar molecules (must go through protein channels) and large molecules (must use vesicles) - Critical for communication and maintaining a stable internal environment (homeostasis) - Structure - Threadlike fibers - Made of proteins - 3 Types: microtubules, intermediate filaments, and microfilaments - Function - Support, maintain shape, motility, and regulate biochemical activities An organelle associated with the cytoskeleton - Structure - Made of microtubules - Microtubules “grow” out of - 2 centrioles are referred together as a centrosome - Function - Appear during cell division - Help cell divide by pulling chromosomes apart during Anaphase An organelle associated with the cytoskeleton - Structure - Cilia: shorter, more numerous, like tiny oars - Similar projections that are short and numerous but don’t move are called microvilli - Flagella: longer, fewer (1-3) - Function - Cilia: move fluid across cell’s surface - Flagella: move entire cell through extracellular fluid - Structure - Contains genetic material (DNA) - When it appears threadlike, it is considered to be chromatin - Chromatin condenses into 46 chromosomes (which appear rodlike) in body cells - Remember sex cells, like egg and sperm, only have 23 chromosomes - Genes are sections of chromosomes that code for proteins (which then do most of the work in the cell) - Surrounded by a nuclear envelope/membrane with pores that control what goes in and out - Nucleolus is in the center - Function - Protects the DNA that controls the activities of the cell - Nucleolus is where ribosomes are formed - Structure - Made of proteins and rRNA - Located on Rough ER and floating in cytoplasm - Function - Make proteins!! - Ribosomes on the Rough ER make proteins to export from the cell - Ribosomes floating in the cytoplasm produce proteins to use within the cell - Structure - Has ribosomes on surface - Hugs the nucleus - Network of membranes and sacs - Function - Make proteins! - Package them for secretion - Send transport vesicles to the Golgi apparatus - Vesicles: like mini-carts that transport proteins around and out of the cell - Structure - No ribosomes on surface - Attached to the Rough ER - Network of membranes and sacs - Function - Makes lipids (membrane) - Chemically modifies small molecules - Site of glycogen degradation - Stores Ca+2 (a trigger for many cell responses) - Structure - Folded/flattened membrane sacs - Function - Gets vesicles of protein from the Rough ER and further processes, modifies, packages and sorts them for transport - Vesicles: like mini-carts that transport proteins around and out of the cell - Processes, sorts, and ships proteins where needed - Structure - Contain hydrolytic enzymes for breaking stuff down - Function - Breakdown dead stuff (food, bacteria, old parts of cell, etc.) - Can do programmed cell death (apoptosis) - Structure - Smaller and (can be) more numerous in animal cells - Function - Storage (water, nutrients, waste, etc.) - Structure - Two parts: folded inner membrane (cristae) and enzyme-packed fluid (matrix) - Function - Where cellular respiration happens - Break down chemical energy in food to release it as usable energy in the form of ATP Mitochondria Cytoplasm Cell Membrane Golgi apparatus Rough ER Ribosomes Smooth ER Vacuole Nucleolus Nucleus Centriole/Centrosome Lysosome - Cells are organized into tissues, which work together for a common function. - About 70% of our living tissue is made of water - Around 26% is composed of macromolecules - Key large biological molecules that make up all living things - The rest is ions and other small molecules - Macromolecules are larger molecules (polymers) made of smaller molecules (monomers) typically linked together through covalent bonds. - Each macromolecule plays a critical role in organisms with regards to running the body, containing information for how to run the body, and providing the energy needed to do so. Informational molecules Nucleotides Nucleic Acids A, T, C, G make up DNA and RNA A, U, C, G make up Blueprint for life Stores, transmits, and expresses our genetic information Energy storage molecules Lipids Fatty acids and glycerol Fats, oils, steroids, phospholipids Also used structurally in the cell membrane, for protection, and insulation Energy storage molecules Carbohydrates Proteins Monosaccharides Glucose, fructose, glycogen Amino Acids Enzymes, hormones, motor proteins, transport proteins, etc. Also used structurally, to transport stored energy, and for recognition in signaling pathways EVERYTHING ELSE molecules Enzymes, signaling, receptors, structural, regulatory, contractile, protection against disease, transport, storage, etc. - Your DNA, organized in 46 chromosomes and thousands of genes, provides the instructions for making proteins, which run the body. - 1 gene gets transcribed into a copy of mRNA, which leaves the nucleus and heads to a ribosome to be translated and then modified into a functioning protein. - This process is highly regulated!! - DNA is unzipped and a single stranded copy of mRNA is made form one side. - tRNA molecules transfer corresponding amino acids to the ribosome, which are bonded together to form the polypeptide chain. This chain with then undergo folding until it has all four levels of protein structure and is ready to be transported where it is needed to be used. - Enzymes are mostly proteins that are biological catalysts. - Catalysts speed up biochemical reactions by lowering the activation energy needed to get the reaction going. - They are highly specific, only binding to certain substrates (reactants) at their active sites. - If the shape of the active site gets changed, such as due to a change in the pH or temperature of the environment, then the enzyme can no longer function as it should. - Enzymes remain unchanged after the reaction and can be reused. - They are critical for regulation of life processes in all organ systems that make up an organism!! - - - All living things are organized. An organism is made of organ systems (ex. The digestive system) Each organ system is composed of organs (ex. Stomach) Each organ is made up of tissues (ex. Muscle tissue) Each tissue is made up of cells (ex. Smooth muscle cells) This hierarchy of organization comes about via cell division and differentiation. All cells come from other cells via cell division during the cell cycle. The cell cycle in somatic (body) cells consists of 3 main phases: Interphase: where the cell spends most of its “life” DNA is doubled à sister chromatids ( l à X) during the end of this phase in preparation for division Mitosis: where the cell begins to divide Consists of Prophase, Metaphase, Anaphase, and Telophase Cytokinesis: where the cytoplasm splits forming 2 identical daughter cells These cells are also identical to the parent cell unless a random mutation occurred. - - Differentiation is the process of stem cells, or undifferentiated cells, undergoing specialization to become specific types of cells with different functions. Gene expression determines what a cell becomes. The organelles that make up the cell’s structure give insight to the job that the cell specializes in Form (structure) dictates function!! - Homeostasis: stability of the internal environment and the mechanisms that maintain the stability - A dynamic equilibrium is maintained where the rate of loss balances out with the rate of gain - Organisms not only detect but respond to stimuli - Homeostasis is maintained through regulation at the organ system level all the way down to the cellular level - Feedback mechanisms evolved to help maintain homeostasis in organisms - These loops use the output of a system to signal a change in input so that a system response can be stabilized or amplified - Can be positive or negative - In a positive feedback loop, the output (or product) of a system intensifies the response - Examples: - Human child birth - Hormones à Contraction à Pressure à Release of more hormones à More contractions à More pressure…etc. - Fruit ripening - Fruit ripens à Releases ethylene à Signals surrounding fruit to ripen à Neighboring fruit ripen à Release more ethylene…etc. - In a negative feedback loop, the output (or product) of a system causes a counter response to return to a set point - Examples: - Human body temperature (thermoregulation) - Water concentration (osmoregulation) - Blood sugar regulation - All feedback loops have: - Receptor = sensory organ that receives the stimulus - Stimulus = an action that evokes a response - Effector = an organ that does the response - Response = the effect, caused by the stimulus - When a mistake happens in a feedback loop, homeostasis is thrown off. - Example: Type 1 Diabetes Too high Too low - Living systems depend on reactions that occur spontaneously, but at very slow rates. - Catalysts = substances that speed up the reactions without being permanently altered. - No catalyst makes a reaction occur that cannot otherwise occur. - Most biological catalysts are proteins (enzymes) - Every step in a metabolic pathway is catalyzed by a specific enzyme - Cells can regulate metabolism by controlling the amount of an enzyme. - They can turn synthesis of enzymes off or on - Feedback inhibition: output of a process is used as an input to control the behavior of the overall process itself, usually leading to inhibition of the process - The activity of an enzyme can also be regulated. - Chemical inhibitors can bind to enzymes and slow reaction rates. - Environmental conditions play a role in enzyme function too. - pH and temperature changes can lead to denaturation - Cells also maintain homeostasis with highly regulated signaling and transport mechanisms. - Remember, the cell membrane consists of a selectively permeable phospholipid bilayer to control what goes in and out. - Transport can be passive, requiring no extra energy as molecules move down the concentration gradient, or active, requiring extra energy to move molecules against the gradient. - The spreading out of molecules across the membrane until equilibrium is reached - A net movement from regions of greater concentration to regions of lesser concentration. - Ex. O2, CO2, and small, nonpolar, lipid-soluble molecules. - A transport protein acts to help (facilitate) the diffusion of molecules that normally couldn’t pass through the cell membrane (large molecules and polar molecules) - Transport proteins can act as a channel to allow specific molecules through (Ex. Ions like Ca+2) - Transport proteins can also act as carriers that bind to substances to carry them across the membrane (Ex. Glucose) - The simple diffusion of water across the cell membrane - Water moves from areas of high water concentration (meaning low solute [ ]) to areas of low water concentration (meaning high solute [ ]) until equilibrium is reached. - Hypertonic solutions: water [ ] is lower than the cell’s cytoplasm. - Net movement of water out of cell à Cell shrivels - Hypotonic solutions: water [ ] is higher than the cell’s cytoplasm. - Net movement of water into a cell à Cell swells - Isotonic solutions: identical water [ ] to cell’s cytoplasm à Cell stays the same Hypertonic Hypotonic Isotonic - When a cell uses energy to pump molecules across the membrane, against the gradient, through a protein channel. - Ex. 1 molecule of ATP is used to move two K+ and three Na+ in the Sodium-Potassium pump. - Endocytosis uses vesicles to move large particles into the cell. - Ex. When white blood cells engulf bacteria in order to fight infection - Exocytosis uses vesicles to export materials out of the cell. - Ex. When nerve cells secrete neurotransmitters to send signals throughout the body. - Complex multicellular organisms, like humans, must have methods for communication on a cellular level in order to maintain homeostasis. - Cell signaling allows cells to process information from their environment (stimuli) and communicate to other cells - Signals can be physical stimuli (like heat or light) or chemical stimuli - Ligands = molecules that bind to other molecules (receptor proteins) for signaling purposes - A sequence of events initiated by a signal that leads to a cellular response - Involves: - Signal - Receptor - Response Receptor Signal Transduction Signal Extracellular fluid Cytoplasm Response - Autocrine signals: “self”; affect the same cell that releases them - Paracrine signals: diffuse to nearby cells - Juxtacrine signals: require direct contact between the signaling cell and the receiving cell - Hormones: signal travels to distant cells - Known as endocrine signaling - Protein where the signal is received on the target cell - Can be: - Intracellular receptors: located inside a cell - Ligands for these signals are small and/or nonpolar so they can easily diffuse across the cell membrane to reach these receptors - Membrane receptors: located on surface of the cell - Ligands for these signals are large and/or polar that cannot diffuse through the cell membrane - Receptors are highly specific and 3-D - Only certain ligands bind certain receptors!! - When a ligand binds to the receptor protein, the bond is noncovalent (therefore not strong) and is reversible - This is so signal can be regulated more easily - Inhibitors can block the normal ligand to prevent communication - Ex. Caffeine - The passing along of the signal until the desired response is reached - Transduction can be short or long - Longer if a signal cascade of reactions is induced - The passing along of the message usually happens by changing the shape of different proteins - Phosphorylation (addition of phosphate groups) by kinases - Dephosphorylation (removal of phosphate groups) by phosphatases Sometimes a “second messenger” is involved to stimulate signal transduction - Second messenger = a small molecule that serves as an intermediate between the receptor and the cascade of responses after - Key for regulation - Either distribute and/or amplify the initial signal received at the receptor - Ex. cAMP is a second messenger in our fight-or-flight response - The transduction pathway eventually triggers a response - The same signal can cause many different responses, such as: - Opening of ion channels: by changing the balance of ion concentration inside and outside of the cell - Alteration in gene expression: genes may be switched on (upregulated) or switched off (downregulated). - Alteration of enzyme activities