Pennsylvania State University: Biology 110 study Guide 2 Latest
• Cells
o Make up all living things
o Smallest unit of life
o At least one cell to
... [Show More] be a living organism
• Prokaryote cell
o Small, has no nucleus, has no organelles
• Eukaryote cell
o Has a nucleus, larger, contains organelles
o Many shapes and sizes
• All cells have plasma membrane that surround the cells
• Chromosomes, that are structures that have DNA
• Cytosol, that is a jelly-like substance within a cell
• Eukaryotic cell
o Plasma Membrane (PM)
▪ Surrounds and encloses the cell
▪ Two layers of phospholipids, which is called the phospholipid bilayer
▪ It is a selective bilayer between the inside and outside of a cell
▪ There are specialized structures on the plasma membrane
• Cilia move substances through hollow organs
o Found in respiratory tract and in uterine tubes
o Made of microtubules (hollow rods)
▪ Are of globular proteins called tubulins, which form into dimers
o flagellum
▪ A single tail-like structure that propels a cell forward
• It has the same pattern as cilia
• It provides motility
• The only human cells with flagellum are sperm
• Microvilli
o Folds in the PM to increase its surface area
o This allows for rapid diffusions
▪ Large amounts of substance can be moved across them
o Cytoplasm
▪ Material within cell
• Cytosol: jelly-like fluid
• Cytoskeleton: protein fiber
• Organelles: structures with specific functions
o Organelles
▪ Nucleus
• Contains DNA in chromosomes
o Human DNA in 46 chromosomes
▪ Discrete structures contain DNA
▪ 23 from the father, 23 from the mother
▪ DNA is wrapped around proteins called histones to form long stands of chromatin
• Chromatin condenses, and becomes tightly packed to form chromosomes
• Most cells have only one nucleus
• Enclosed in a nuclear envelope
o Two membranes that enclose and surround it
▪ Nuclear pore complexes for small molecules moving in or out of the nucleus
▪ Nucleolus
• Mass of densely packed fibers: RNA and rRNA are made here, and ribosomes are produced here
▪ Endoplasmic Reticulum (ER)
• Usually found near nucleus
• Network of membranes form a channel
o Molecules move through the channel
▪ Rough ER
• Ribosomes on its surface
o Made of proteins and rRNA
o Large unit and small unit joined together
o Make secretory proteins
▪ Exit the cell
▪ They enter the rough ER through holes in the membranes
▪ Inside, they become tertiary and add molecules
▪ Smooth ER
• No ribosomes
• Lipid and steroid synthesis
• Stores calcium in muscle cells
• Helps detoxify drug and poisons
o Makes them more water soluble and easier to flush out of the body
▪ Golgi apparatus
• Stacks of flattened membrane, which forms sacs called cisternae
• Located near the rough ER
• Refine proteins to final form
o Modified into final form and packaged for secretion
o Packaged into vesicles and bud off to fuse with plasma membrane for exocytosis
▪ Mitochondria
• Only in animal cells
• Produces energy
• Energy (ATP) fuels all the reactions in the cell
• Outer membrane and inner membrane
o Inner membrane folded into cristae
o The inner space is a matrix
▪ Chloroplasts
• Plant and algae cells contain these
• Energy (ATP) for plant cells
• Contains green pigment, or chlorophyll, that absorbs sunlight, and through photosynthesis produces energy (ATP)
▪ Lysosomes
• Membrane vesicles filled with digestive enzymes
o Digest and break down foreign, and worn-out material, and debris
o Brought into the cell through phagocytosis
▪ Cell engulfs and ingests particles
▪ Aptosis
• Programmed cell death
o Lysosome spills contents, killing cell
▪ The cell digests itself
▪ Peroxisomes
• Contain enzymes that trigger breaking-down reactions
• They remove the hydrogen atom from molecules, add them to oxygen (oxidation), and convert them to water by another enzyme
o In most cells, but found most in the liver
o They break down fatty acids, and toxic or harmful molecules
o Lysosomes and Peroxisomes
▪ Waste and recycling center
▪ Foreign cells, dead broken-down cells, waste products, and toxic materials
o Centrosomes
▪ Made of centrioles
• Made of microtubules
o Vacuoles
▪ Follow membranous sacs
▪ Secretory: carry to PM
▪ Storage: store reserves of materials
▪ Contractile: pump out excess air
o Cytoskeleton
▪ Network that extends throughout either the cell or the cytoplasm
▪ microtubules
• Hollow tublike structures
• Made of globular proteins
▪ Microfilaments
• Made of two intertwined strands
• Each strand is made of actin proteins
▪ Intermediate fibers
• Small keratin fibers coiled together to form rope structures
▪ Cytoskeleton provides support
▪ Cytoskeleton provides movement for the cell
▪ Cytoskeleton serves as a railway system for material in a cell to move along
▪ Motor proteins can move along fibers
• Animal cells versus plant cells
o Plants have an outside cell wall
o Cellulose is the main component of the cell wall
o Cell walls are thicker and more rigid compared to the plasma membrane
o Cellulose protects plant cell, maintains the cell’s shape, and hold plants upright against gravity
• Cells are organized into tissue in living organisms
o Tissues are multiple cells grouped together to form a similar structure or function
▪ Sometimes joined together with no open spaces
▪ Sometimes loosely organized
• Space between is the extracellular matrix (ECM)
o Consists usually of glycogen fibers, and other carbohydrate molecules
▪ One main fiber, collagen
• Tight cells are held together by complexes of proteins called cell junctions
o Three types
▪ Tight junctions have a tight seal between two cells
• This causes a barrier that prevents leakage between two cells
▪ Gap junctions
• Proteins from a channel or pore between two cells
o Connects cytoplasm
o Allows small molecules to pass from cell to cell
• Plasma Membrane (PM)
▪ Desmosomes
• Attached at spots between two cells
o Anchors the cells, but also allows them to move
o Surrounds and encloses
o Separates intracellular environment from extracellular environment
▪ Intracellular is inside the cell
• Cytoplasm, organelles
▪ Extracellular is outside the cell
o Hydrophobic portions go inward to stay away from water
o Hydrophilic portions go outwards
▪ Not rigid
o Phospholipid contains membrane proteins
o Fluid mosaic model means that proteins can move across the surface
▪ Movement is temperature dependent
• Cooling slows it down
• When temperature is low enough, the molecules is locked into place, and the substance becomes solid
o PM contains cholesterol
▪ Restrains the movements of phospholipids and causes them to be more rigid
o Protein type based on location
▪ Integral protein penetrates into phospholipid bilayer and is permanent.
▪ Peripheral proteins are loosely attached to the surface and can move
• Membrane proteins and functions
o Structural support
▪ Attach cells together or to ECM
o Cell signaling
▪ Receptors for hormones and other molecules
▪ Allow cells to bind together and recognize one another
o Enzymatic activity
▪ Trigger chemical reaction within cell
o Transport
▪ Move material from one side of a membrane to another
• PM is a selective barrier
o d permeability
▪ Some substances pass more easily than others
▪ Nutrients, oxygen, water, and waste products must cross in and out of the cell
• There are two ways for this to happen
o Nonpolar hydrophobic molecules directly cross membrane
o Charged ions, polar, and hydrophilic cannot directly cross the PM
▪ Channel proteins in the PM transport material through
the PM
• Contain a hollow core or channel
• Selective transport: only specific molecules and ions can cross
• There are different mechanisms to move molecules through the PM
o Net Diffusion
o Passive transport: no energy
▪ Osmosis: movement of water: involves molecules movement in a solution
▪ Diffusion: molecules in a solution are in a constant state
of motion
▪ Net movement of solute across the membrane
• Many molecules are moving from side to side
• No energy required
• Requirements
o Membrane is permeable
▪ The solute must be able to cross the membrane
o Concentration gradient: concentration is different on each side of the membrane.
o Nature wants to be in equilibrium: solute concentration should be the same on both sides
▪ Moves from high to concentration until there is an equal amount on both sides
▪ Diffusion can occur in living cells
• Lipid-soluble molecules pass easily
o Oxygen, carbon dioxide, and steroid hormones
o Passive diffusion
o Molecules flow down their concentration gradient
▪ No energy
▪ Passive net diffusion: direct
▪ Facilitated diffusion: cross by proteins
• Channel or carrier proteins
o Gated channels: can be open or closed
o Carrier proteins change shape
o Osmosis requirements
▪ Concentration gradient
▪ Membrane must be semi-permeable
• Water can cross, solute cannot
▪ Osmosis rule
• Water moves from low to high solute concentration
• Water continues moving until equilibrium occurs
o Tonicity
▪ Compares concentration of solute on one side to the other
▪ Tells us if and which direction osmosis will occur
• Isotonic ▪ Affects blood cells
o Equal
▪ Equal solute concentration (equilibrium)
▪ No osmosis
• Hypotonic
o Solution with lower concentration
o Relative
• Hypertonic
o Solution with higher concentration
o Water always moves here
o Relative
▪ Osmosis occurs in living cells
• Cell bursting is lysis
• Cell shrinking is crenation
• Active transport
o Requires energy
o Two types: pumps, bulk transport
▪ Pumps
• Molecules are moved up their concentration gradient
• Used to help maintain concentration gradient
• Living cells use them (Na+/K+ pumps)
o Sodium is Na+
o Potassium is K+
• Pumps 3Na+ out for every 2K+ pumped in
o Ion pumps help determine membrane plasma osmosis in cell
o Membrane potential differ in charge on each side of the PM
▪ Caused by the difference in ion concentration in and out of the cell
▪ How ions are distributed in a typical cell
• More anions inside
• More cations outside
• Not distributed evenly
• Different in charge in membrane potential
o 70 mv
• Bulk transport
o Moves material too large to fit through protein channels
▪ Move large numbers of molecules at once
▪ Requires energy
o Endocytosis
▪ Brings material into a cell
▪ Two main types
• Phagocytosis
o Cells ingest material
o Some cells, limb-like structures called pseudopods
▪ Engulf large things and bring them into a cell
• Pinocytosis
o Brings many molecules into the cell at once
o PM furrows inward, molecules enter space
o Membrane pinches off and molecules are brought into the cell
• Exocytosis
o Large cellular products (proteins) are brought out of the ell
o Products are packaged into vesicles, fuse to membrane, and contents spill out of the cell
• Chemical reactions must have a constant supply of energy and enzymes
o Chemical reactions equal metabolism equals life
o Chemical energy source or living cells is adenosine triphosphate or ATP
▪ Consists of a ribose sugar and an adenine nitrogen bases with three attached phosphates
• Stores energy in bonds
• Broken down to release energy
o Third phosphate is removed from the molecule
o Turns into a diphosphate, or ADR
▪ Animal cells make it by cellular respiration
• Breakdown, or catabolism, of glucose
▪ Animals must have steady glucose in the bloodstream to make ATP
• From food and from energy from lipids and glycogen
o Aerobic respiration: inhaling oxygen
o Anaerobic: no oxygen
• Glucose is broken down into CO2 and H2O
• As it is broken down, energy is released that is used to make ATP
o Specifically, energy is released with electrons, or e’s, and is removed form molecules
▪ Oxidation/reduction
• Electron gain: reduction
• Electron loss: oxidation
▪ Often called redox electrons
• Chapter 8:
• Metabolism
o Sum of all the biochemical reactions occurring in an organism
▪ Two categories
• Anabolism, or anabolic reactions
o Small molecules joining to from larger molecules
o “Building-up” reactions
• Catabolism, or catabolic reactions
o Larger molecules broken down into smaller molecules
▪ “Breaking-down” reactions
o Metabolic pathway
▪ Series of chemical reactions
• Chemical reaction
o Molecule is altered in series of chemical reaction
o Final product doesn’t happen with a single reaction
o Each step is triggered by specific enzymes
▪ Chemical reactions can release or require energy
• Exergonic is releasing energy
o Break-down causes energy release (usually catabolism)
o Less free energy is in the product
• Endergonic is requiring energy
o Build up reactions (anabolic)
o More free energy is in the product
• Coupled reactions
o Endergonic and exergonic together
▪ Energy released in the exergonic reaction fuel the endergonic reaction: free energy
▪ A system’s energy can be used to perform work
▪ In a cell, available energy is used to fuel reactions in the cell
o Energy is the capacity to cause change
▪ Kinetic: motion of objects
• Moving objects, perform work by making other things move
▪ Thermal energy: random movement of atoms and molecules
• Transferred from object to object
▪ Potential energy
• Net movement possessed by objects
• Stored for later
▪ Chemical energy
• Potential energy to be released during a reaction
• Found in living cells
• Bioenergetics
o Flow of energy in living systems
▪ Obeys laws of thermodynamics
• First Law of Thermodynamics
o Energy cannot be destroyed or created, only transformed
o Cells need energy to:
▪ Three different types of work
• Chemical work equals anabolic reaction equals synthesis of large molecules
• Transport work equals physical movement of cell equals cilia beating, muscle cells concentration, cell division
▪ All run off the energy created by adenosine triphosphate or ATP
• Enzymes
o Required for living cells, as well as energy
o Usually proteins
o Function as a catalyst
▪ Causes other molecules to change without changing itself
o Speed up reactions
o Don’t change reaction’s nature
• Mechanism of Enzyme Action
o Substrates
▪ Molecules that go into reactions and become altered
▪ Must physically bind to enzymes for reaction to occur
o End products
▪ Produced by reactions
o Active site
▪ Where substrate binds on enzymes
o Lock and Key Model
▪ Substrate must perfectly fit into active site for reaction to occur
o Enzymes work to decrease activation energy
▪ Activation energy is the energy required to drive a reaction and cause it to occur
• Much less energy is needed when the enzyme is present
▪ Work by physically holding and aligning substrates together
• Reaction requires less energy, occurs faster
• Most reactions are reversible
o Control of enzyme activity
▪ Activity measured by rate at which substrate is converted to product
▪ Influenced by different factors in the environment
• Temperature
o Increase of temperature will increase reaction until approximately 40 degrees C, at which point it will rapidly decline
o High temperature causes the enzymes to denature and lose their three-dimensional shape
o Enzymes lose active site, and the substrate cannot bind, so the reaction does not occur
• pH
o peak activity is within a narrow pH range
o changes in the pH equals changes to the active site equals no bond
o optimum pH reflects the environments the enzymes are found in
• substrate concentration
o increases of concentration makes increase in substrate activity until every substrate has an enzyme attached to it (saturation)
• Law of Mass Action
o Reaction is driven from high concentration to low concentration
• Coenzymes and cofactors
o Small molecules that help substrates fit into active sites
o Coenzymes are molecules derived from water-soluble vitamins
o Cofactors are metal ions
• Enzyme inhibitors
o Competitive inhibitor
▪ Competes with substrate for active site
▪ Prevents substrate from binding
▪ Competitive
• Prevents substrate from binding
▪ Non-competitive
• Binds to enzyme, though not on the active site, and the enzyme changes shape
• Substrate and end products of respiration
o Glucose + oxygen + ADP + P → CO2 + H2O + ATP
o Energy is released when electrons are moved from the molecules
• Oxidation/reduction
o Electron gain is reduction
o Electron loss is oxidation
o These are both known as redox reactions
• During cell respiration, glucose is oxidized, then electrons are removed, energy is released. Electrons are often with H+ ions. When H+ ions are removed, the electrons go with them.
• Aerobic respiration
o Metabolic pathway
o Glucose is not converted to ATP all at once
▪ Glycolysis
• Glucose is split into two molecules called pyruvate
o This occurs in the cytoplasm
o Two phases
▪ Energy investment phase
• ATP is burned (2 molecules)
▪ Energy payoff phase
• ATP is made (4 molecules
o Net gain of 2 ATP molecules
o Two places where the molecule is oxidized
o NAD+ is reduced to NADH and that acts as an electron carrier molecule
o For each glucose molecule, there are 2 molecules of NADH
• End products
o 2 molecules of pyruvic acid
o 2 molecules of ATP
o 2 molecules of NADH
▪ Pyruvic acid is the substrate for the next step
▪ Preparatory step
• Pyruvate is oxidized and converted into acetyl CoA
o Leaves cytoplasm and enter the inner matrix of the mitochondria
• CO2 and H with electrons are removed to form acetic acid
o Molecule is oxidized
• H with electrons in tow combine with NAD for more NADH
• The acetic acid combines with coenzyme A and acetyl CoA
• End products
o 2 acetyl CoA
o 2 carbon dioxide
o 2 NADH
▪ Krebs cycle (acetyl CoA), (cycle happens twice)
• Acetyl CoA enters cycle and is converted into six different acids
• Acetyl CoA combines with oxaloacetate to form citrate (6 carbons)
• End products
o 6 NACH
o 2 FADH2
o 2 ATP
o 4 CO2
▪ Electron transport chain
• Oxidation phosphorylation pathway
• Each glucose molecule yields 12 electron carriers
• These carriers and the new substrate
• Occurs in the cristae, or folds, of the mitochondria
• Electron transport molecules are embedded in the membrane
o Transport molecules in the cristae membrane
▪ FMN
▪ Coenzyme
▪ ?
o Takes from carrier molecules and pass the electrons along
▪ Each get reduced and oxidized
▪ Exergonic reaction, and energy released makes ATP
▪ Aerobic respiration
• Oxygen is the final electron acceptor
o Binds to and removes electrons at the end of the chain
o Without oxygen, the electrons would get stuck and stop
o Water is formed when reduced oxygen binds to hydrogen in the environment
o Phosphate added to ADP, and you get ATP
• Chemiosmotic Theory
o ATP Production
▪ Proton pumps pump H+ ions from the matrix into the space between the inner and outer membrane
• This causes a concentration gradient
o The leads to diffusion, and it flows down the concentration gradient, movement of the H+ causes ATP synthase to make ATP
o End products of and electron transport chain
▪ About 30 molecules of ATP
▪ 6 molecules of H2O
o About 36 ATP molecules for glucose molecule
• Anaerobic respiration (fermentation)
o Just glycolysis
▪ End products
• 2 ATP
• 2 NADH
• 2 pyruvic acid
o Two last are converted into an end product
▪ Acid
▪ Gas
▪ alcohol [Show Less]