Biology 1107 Exam 2 Kennesaw State University

Light Microscope

-visible light is passed through a specimen

Magnification

-ratio of image to real size

Resolution

-image clarity

Contrast

-difference in brightness

Cell fractionation

-Takes cells apart
-separate organelle
-Determine function of organelles

Prokaryotic Cell

-NO nucleus
-DNA is unbound region (nucleoid)

Eukaryotic cells

-DNA is in nucleus
-membrane bound organelles
-larger then prokaryotic cells

The Nucleus

-Cell's genes
-DNA in chromosomes

Nucleolus

-Site of RNA synthesis

Ribosomes: Protein Factories

-Ribosomes carry out protein synthesis in two locations
-ER and nuclear envelope

Endomembrane System Consists of:

o Nuclear envelope
o Endoplasmic reticulum
o Golgi apparatus
o Lysosomes
o Vacuoles
o Plasma membrane

Smooth ER

-Lacks ribosomes
-Synthesizes and Detoxifies

Rough ER

-Contains ribosomes
-Glycoproteins
-Transport Vesicles

Golgi Apparatus

o Modifies products of the ER
o Manufactures certain macromolecules
o Sorts and packages materials into transport vesicles

Lysosomes

-Digestive Compartment
-recycles cells own organelles

Phagocytosis

-Cell eating

Vacuoles

-Maintenance for cells
-Derived from ER and Golgi Apparatus

Mitochondria

-cell respiration uses ATP

Chloroplasts

-Found in plants
-photosynthesis

Mitochondria: Chemical Energy Conversion

-Mitochondria are in nearly all eukaryotic cells
-They have a smooth outer membrane and an inner membrane folded into cristae
-The inner membrane creates two compartments: intermembrane space and mitochondrial matrix

Chloroplasts: Capture of Light Energy

-Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis
-Chloroplasts are found in leaves and other green organs of plants and in algae

Peroxisomes: Oxidation

-Peroxisomes produce hydrogen peroxide and convert it to water

Cytoskeleton

-The cytoskeleton helps to support the cell and maintain its shape
-It interacts with motor proteins to produce motility
-Inside the cell, vesicles can travel along tracks provided by the cytoskeleton

Centrosome

-Microtubules near nucleus

Centrioles

-each with nine triplets of microtubules arranged in a ring

Cilia and flagella

o A core of microtubules sheathed by the plasma membrane
o A basal body that anchors the cilium or flagellum
o A motor protein called dynein, which drives the bending movements of a cilium or flagellum

Microfilaments

-Microfilaments are solid rods built as a twisted double chain of actin subunits
-Microfilaments that function in cellular motility contain the protein myosin in addition to actin

Chloroplast Movement

-Cytoplasmic streaming is a circular flow of cytoplasm within cells

Intermediate Filaments

-They support cell shape and fix organelles in place

Extracellular Matrix (ECM) of Animal Cells

-Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)
-The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin
-ECM proteins bind to receptor proteins in the plasma membrane called integrins

Cell Junctions

-Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact

Tight junctions

-membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes

-fasten cells together into strong sheets

Gap junctions

-(communicating junctions) provide cytoplasmic channels between adjacent cells

Cellular membranes

• Phospholipids are the most abundant lipid in the plasma membrane
• Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions
• A phospholipid bilayer can exist as a stable boundary between two aqueous compartments

Fluid Mosaic Model

-states that a membrane is a fluid structure with a "mosaic" of various proteins embedded in it

The Fluidity of Membranes

• Phospholipids in the plasma membrane can move within the bilayer
• Most of the lipids, and some proteins, drift laterally
• Rarely, a lipid may flip-flop transversely across
the membrane

Cholesterol

-has different effects on membrane fluidity at different temperatures

Membrane Proteins

• A membrane is a collage of different proteins, often grouped together, embedded in the fluid matrix of the lipid bilayer

Peripheral proteins

-are bound to the surface of the membrane

Integral proteins

-penetrate the hydrophobic core

Six major functions of membrane proteins

• Transport
• Enzymatic activity
• Signal transduction
• Cell-cell recognition
• Intercellular joining
• Attachment to the cytoskeleton and extracellular matrix (ECM)

Cell-Cell Recognition

• Cells recognize each other by binding to molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane

Synthesis and Sidedness of Membranes

• Membranes have distinct inside and outside faces
• The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and Golgi apparatus

Membrane structure results in selective permeability

• A cell must exchange materials with its surroundings, a process controlled by the plasma membrane
• Plasma membranes are selectively permeable, regulating the cell's molecular traffic
• The Permeability of the Lipid Bilayer

Hydrophobic

-(nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly

Hydrophilic

molecules including ions and polar molecules do not cross the membrane easily

Transport proteins

-allow passage of hydrophilic substances across the membrane

Channel proteins

-have a hydrophilic channel that certain molecules or ions can use as a tunnel

Aquaporins

-facilitate the passage of water

Diffusion

-is the tendency for molecules to spread out evenly into the available space

Concentration gradient

-the region along which the density of a chemical substance increases or decreases
-Substances diffuse down

Osmosis

is the diffusion of water across a selectively permeable membrane
• Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides

Isotonic

-Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Hypertonic

-solution: Solute concentration is greater than that inside the cell; cell loses water

Hypotonic

-Solute concentration is less than that inside the cell; cell gains water

If a plant cell and its surroundings are isotonic:

-there is no net movement of water into the cell;
the cell becomes flaccid (limp)

facilitated diffusion

-transport proteins speed the passive movement of molecules across the plasma membrane

Active transport

-moves substances against their concentration gradients
• Active transport requires energy, usually in the form of ATP
• Active transport is performed by specific proteins embedded in the membranes

• Active transport allows cells to maintain concentration gradients that differ from their surroundings

Membrane potential

-is the voltage difference across a membrane
• Voltage is created by differences in the distribution of positive and negative ions across a membrane

Cotransport

-occurs when active transport of a solute indirectly drives transport of other substances

Exocytosis

• In exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell
• Many secretory cells use exocytosis to export their products

Endocytosis

• In endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane
• Endocytosis is a reversal of exocytosis, involving different proteins

Three types of endocytosis

• Phagocytosis ("cellular eating")
• Pinocytosis ("cellular drinking")
• Receptor-mediated endocytosis

Metabolism

-is the totality of an organism's chemical reactions
• Metabolism is an emergent property of life that arises from orderly interactions between molecules

Metabolic pathway

-begins with a specific molecule and ends with a product
• Each step is catalyzed by a specific enzyme

Catabolic pathways

-release energy by breaking down complex molecules into simpler compounds
• Cellular respiration, the breakdown of glucose
in the presence of oxygen, is an example of a pathway of catabolism

Anabolic pathways

consume energy to build complex molecules from simpler ones
• The synthesis of protein from amino acids is an example of anabolism

Thermodynamics

is the study of energy transformations
• An isolated system, such as that approximated by liquid in a thermos, is unable to exchange energy or matter with its surroundings
• In an open system, energy and matter can be transferred between the system and its surroundings
• Organisms are open systems

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed

The Second Law of Thermodynamics

• Every energy transfer or transformation increases the entropy (disorder) of the universe

Free energy

• The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin units (T)
o ∆G = ∆H - T∆S

exergonic reaction

proceeds with a net release of free energy and is spontaneous

endergonic reaction

absorbs free energy from its surroundings and is nonspontaneous

A cell does three main kinds of work

o Chemical
o Transport
o Mechanical

ATP Hydrolysis

• The bonds between the phosphate groups of ATP's tail can be broken by hydrolysis
• Energy is released from ATP when the terminal phosphate bond is broken
• This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves

catalyst

is a chemical agent that speeds up a reaction without being consumed by the reaction

enzyme

is a catalytic protein

Activation energy

• The initial energy needed to start a chemical reaction is called the free energy of activation

The active site can lower an EA barrier by:

o Orienting substrates correctly
o Straining substrate bonds
o Providing a favorable microenvironment
o Covalently bonding to the substrate

Cofactors

are nonprotein enzyme helpers

Competitive inhibitors

bind to the active site of an enzyme, competing with the substrate

Noncompetitive inhibitors

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

Allosteric regulation

• Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and
affects the protein's function at another site

Cooperativity

is a form of allosteric regulation that can amplify enzyme activity

Feedback inhibition

the end product of a metabolic pathway shuts down the pathway

The Principle of Redox

• Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions
• In oxidation, a substance loses electrons, or is oxidized
• In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced)

NAD+

functions as an oxidizing agent during cellular respiration

NADH

represents stored energy that is tapped to synthesize ATP

Glycolysis

• Glycolysis occurs in the cytoplasm and has two major phases
-Energy investment phase
-Energy payoff phase
-Glycolysis occurs whether or not O2 is present

Gylcolysis and the Citric Acid Cycle Yield

• For each molecule of glucose
o 6 CO2: citric acid cycle (CAC) only
o 10 NADH: 2 from Glycolysis and 8 from CAC
o 10 H+: 2 from Glycolysis and 8 from CAC
o 2 FADH2 : CAC only
o 4 ATP: 2 net from Glycolysis and 2 from CAC

The Pathway of Electron Transport

• The electron transport chain is in the inner membrane (cristae) of the mitochondrion
• Most of the chain's components are proteins, which exist in multiprotein complexes

Chemiosmosis

• Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space
• H+ then moves back across the membrane, passing through the protein complex, ATP synthase
• ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP

Cellular Respiration

o glucose → NADH → electron transport chain → proton-motive force → ATP

Fermentation

• Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP
• Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis
• Two common types are alcohol fermentation and lactic acid fermentation

Alcohol Fermentation

• In alcohol fermentation, pyruvate is converted to ethanol in two steps
• The first step releases CO2
• The second step produces ethanol
• Alcohol fermentation by yeast is used in brewing, winemaking, and baking

Lactic Acid Fermentation

• In lactic acid fermentation, pyruvate is reduced by NADH, forming lactate as an end product, with no release of CO2
• Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt
• Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce

Photosynthesis

-is the process that converts solar energy into chemical energy
• Directly or indirectly, photosynthesis nourishes almost the entire living world

Autotrophs

-sustain themselves without eating anything derived from other organisms
• Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules

Heterotrophs

-obtain their organic material from other organisms
• Heterotrophs are the consumers of the biosphere
• Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2