A pycnometer (see Exercise 78) weighs 25.60 g empty and 35.55 g when filled with water at 20 C. The density of water at 20 C is When 10.20 g lead is placed in the pycnometer and the pycnometer is again filled with water at 20 C, the total mass is 44.83 g. What is the density of the lead in grams per cubic centimeter?
Cell Hierarchy & Homeostasis Anatomy- Study of structures Physiology- study of function of structures Correlations between structure and function begin at the molecular level Similar relationship between structure and function at cellular level Cell Shape and function correlate Biological Hierarchy Tissues- Group of similar cells that function as a unit 4 major categories of human adult tissues 1. Connective 2. Nervous 3. Muscle 4. Epithelial 1. Connective Tissues- Consists of cells lossley arranged in liquid, jelly like or solid ECM 4 Types 1. Loose 2. Dense 3. Supporting 4. Fluid Loose- Contains an array or proteins in a soft matrix, function- padding material Dense- Dominated by collagen fibes in ECM, Function- Connect muscles organs and bones Supporting- Very firm ECM, Function- Support/protection Fluid- Consists of cells surrounded by a liquid ECM Function- Major function of transport 2. Nervous Tissue- Consists of neurons and several types of supporting cells Dendries- short branches that transmit electrical signals from other cells to the cell body Longer than dendrites is Axons- carries electrical signals from cell body to other cells 3. Muscle Tissues- Function in movement and make of contracting cells Skeletal Muscle- Attach bones and exerts force when it contracts (voluntary) Cardiac Muscle- Pumps blood throughout the body (involuntary) Smooth Muscle- Lines the walls of the digestive tract and blood vessels (involuntary) 4. Epithelial Tissue- Barrier tissue cover the outside of the body and lines surface of organs and can form glands Organ- Structure that serves a specialized function and consists of several tissues Gland- Group of cells that secrete specific molecules or solutions Forms interface between interior and exterior of organ/organism Has polarity Basolateral- Faces inside Apical- Faces outside Humans Small intestines is composed of all major tissue types Human digestive system is essentially one long tube divided into chambers where food is processed and nutrients are absorbed Salivary glands, liver, pancreas secrete specific enzymes into the tube Out to inside 1. Epithelial 2. Connective 3. Nervous 4. Muscle Bio Lecture Notes Cell Hierarchy 3-18-2016 Surface Area and Volume Change as a Function of Overall Size-The AS of an object increases as the square of the length, the volume increases as the cube o the length Volume increases much more rapidly than SA as a linear dimension increases Metabolic Rate- Overall rate of energy consumed by an individual Consumption of energy is measured as the basal metabolic rate BMR is the rate an animal consumes O2 while at rest with an empty stomach under normal conditions Measured in mL of O2 consumption per hour On per Gram basis, smaller animals have higher BMRs than larger animals A gram of elephant tissue consumes less energy than a gram of mouse tissue does As size increase the metabolic rate Smaller animals have a higher BMR than larger animals The function of a cell or tissue depends on diffusion, it usually has a shape that increases SA relative to its V Homeostasis- Stability in chemical and physical conditions within an animals cells tissues and organs, Most enzymes function best under very certain conditions Epithelium plays a key role in Homeostasis Helps form internal environment such that physical and chemical conditions inside an organism can be maintained at relative constant levels 2 Types of Homeostasis 1) Conformational- Occurs by conformation to the external environment 2) Regulatory- Based on Mechanisms that adjust the internal state to keep it within the tolerated limit no matter what happens in the outside world Regulation Feedback Conditions that need to be monitored- Temperature, Blood Pressure, Blood PH etc… If a variable is changed a homeostatic system acts quickly to fix it 3 Homeostasis Components- Sensor Integrator Effector 1) Sensor- Records parameter 2) Integrator- Compares sensory input with the set point then instructs the effector 3) Effector- Changes parameter to return to the set point Thermoregulation Heat exchange is very important in animal physiology Overheating can make proteins denature Low Temperatues can slow down enzyme function and energy production Types of Therms Endotherms- Produce adequate heat to warm own tissue Ectotherms- Rely on heat from environment Homeotherms- Keep their body temperature constant Heterotherms- Allow body temperatures to fluctuate with the external conditions Torpor and Hibernation To survive when temperatures are cold some species reduce Metabolic rate and allow body temperatures to drop a form of Heterothermy, this is Torpor Hibernation is Torpor but for longer periods of time Mammals regulate temperature through negative feedback Countercurrent Heat Exchangers Some animal structures conserve heat with this, in which arteries and veins lie next ot each other Bio Lecture Notes 3-14-2016 Cell to Cell Interaction Clicker Questions 1. 2. 3. 4. 5. 6. Cell Surface Plasma membrane is not alone it is attached to cytoskeletal elements, attached to interior of face of the bilayer, complex array of extracellular structures interact with the membranes exterior surface The Extracellular Layer or Extracellular Matrix Fibers are like steel rods in concrete, a gel-forming mixtures of polysaccharides is like concrete Plant Primary Cell Walls Define the primary shape of the plant cell Fibrous Component in plants are cellulose micro fibrils Gelatinous Polysaccharides in plants is Pectin Plant cell walls are fiber composites in plants cell wall Plant Secondary Cell Walls occur between the plasma membrane and primary cell wall in some mature plant cells The structures vary from plant to plant and correlates with that cell’s function The Animal ECM Collagen are the steel like components in animal cells, this is a protein Proteoglycans is the Gelatinous Polysaccharides, has protein core and many polysaccharides connected Different tissues have different compositions of ECM, similar cells that function as a unit Intercellular Connections are the basis of multicellularity Indirect attachment Direct Attachment Tight Junctions seal cells together Desmosomes- Connect cytoskeletons of cells Gap Junctions- channels between cells Tight Junctions- Cell-Cell attachments composed of specialized proteins in the plasma membrane of adjacent animal cells Desmosomes- Gap Junctions- Form pipes between cells, allow for rapid communication by passing regulatory molecules Plasmodesmata- Are the Gap junctions that are in plant cells Long Distance Signaling- Cell-Cell signals allow the activities of cells in different parts of a multicellular organism to be coordinated Hormones- Secreted information carrying molecules that can act on distant target cells, one type of long distance signaling Steps to Cell to Cell Signaling 1. Signal Reception- Receptor must be present to receive the signal 2. Signal Processing- Something must happen to initiate cell’s response 3. Signal Response- Second messengers/proteins in target cell may be activated or deactivated, gene expression may also be altered 4. Signal Deactivation- Cells have built-in systems to turns signals off, if not will result in cancer Signal Reception- Cell need to know that it is being hit with chemicals, Receptor- a protein that changes its shape and activity after binding to a signaling molecule These are dynamic and can be blocked, so the cell will not receive signal Lipid Soluble vs. Lipid Insoluble Signals Ability of a signaling molecule to pass through lipid bilayers is crucial in determining how a target cell recognizes it Most Lipid Soluble Signaling Molecules can diffuse across the hydrophobic region of the plasma membrane, Insoluble cannot cross because it is hydrophilic Bio Lecture Notes Cell-Cell Signaling 3-16-2016 Signal Transduction Begins at plasma membrane amplification occurs inside the cell 2 Major Types 1. G Protein Coupled receptors, initiate production 2. Enzyme-linked receptors, trigger protein activation in the cell In response to ligant binding the receptor changes shapes and activates its G- Protein The active G protein interacts with another protein in the plasma membrane This produces a second messenger Second Messengers are small non-protein signaling molecules that elicit and intracellular response to the first messenger They are not restricted to a single role or cell type More than one second messenger may be triggered by the same extracellular signaling molecule Enzyme Linked Receptors 1. Signal reception causes receptors to dimerize 2. The activated receptor complex phosphorylates itself at tyrosine residues 3. Binding proteins bind to the receptor and one activates Ras by exchanging GDP for GTP 4. Activated Ras activates a protein kinase 5. A phosphorylation cascade results, and causes some effect in the cell Second messengers/kinase cascades will alter gene expression or activate/deactivate proteins in the target cell Crosstalk Signal transduction pathways form network so cells may respond to many signals in an integrated manner Signal Transduction pathways interact with each other not independent Signal Deactivation Cells have built in systems to turn signals off G proteins coupled receptors Once activated G proteins turn downstream enzymes, GTP is hydrolyzed into GDP and P, this returns the G protein to an inactive state When second messengers are cleared from cytosol, the response stops Enzyme linked receptors ‘ Phosphates- enzymes that remove phosphate group from cascade proteins