Exam 2 Flashcards
Which statement is true?
A cell placed in a hypotonic solution will swell
A concentration gradient ceases to exist when
there is no net movement
The method of movement that requires the expenditure of ATP molecules is
active transport
Cell membranes show selective permeability, which means that
some substances can cross freely; others cannot
A red blood cell will lyse (burst) when placed in which of the following kinds of solution?
Hypotonic
A red blood cell will crenate (shrink) when placed in which of the following kinds of solution?
hypertonic
What type of membrane proteins bind extracellular substances (example: hormones) that can trigger changes in cell activities?
receptor proteins
What type of membrane proteins acts as channels for direct signaling between two adjacent cells?
communication proteins
What type of membrane proteins keep cells together (i.e., form spot welds between cells)?
adhesion proteins
Cell membranes are primarily composed of phospholipids.
True
Lipid Bilayer
- main compontent of cell membranes
- gives membranes its fluid properties
Lipid Bilayer
fatty acid tails (hydrophobic) sandwhiched between hydrophilic heads
Hydrophilic parts
dissolves in water
Hydrophobic parts
repels water
Membrane is a mosaic (mixture) of:
- Phospholipids
- Glycolipids (lipids w/ sugar mono attrached
Membrane is a mosaic (mixture) of:
- Sterols (cholesterol; phytosterols
- Proteins
What can drift through membrane?
most phospholipids and some proteins
Nature of phospholipids (spinning an presence of unsaturated fats in tail)
contribute to membrane’s fluid nature
Postions of proteins in the membrane
- Integral membrane proteins
- Peripheral membrane proteins
Integral membrane proteins
span the lipid bilayer, with their hydrophilic regions extending past the surface of the membrane.
Peripheral membrane proteins
positioned at the surface of the membrane (do not span the bilayer)
Functions of Membrane proteins
-Adhesion protein, Communication protein, Receptor proteins, Recognition proteins, Transport proteins
Adhesion proteins
glycoproteins that helps cells stay connected to one another in a tissue
Communication proteins
form channels that match up across the plasma membranes of two cells (signals flow between their cytoplasms).
Receptor proteins
presence of binding sites for hormones (other signals) that can trigger changes in cell action
Recognition proteins
identify the cell as a certain type (tissue or individual). Identified as self or nonself (foreign).
Transport proteins
allow water-soluble substances to move through the membrane. open to both sides of the bilayer (passive and active)
WHat must rely on passage through transport proteins?
glucose and other large, polar molecules
Membrane crossinf mechanisms
Diffusion across lipid bilayer, passive transoport, active transport, endocytosis, exocytosis
Diffusion
the net movement of “like” molecules or ions down a concentration gradient
Factors affecting diffusion rate
-steepness of concentration gradient(steeper gradient, faster diffusion)
Factors affecting diffusion rate
-molecular size smaller=faster (smaller molecules, faster diffusion
Factors affecting diffusion rate
-Temperaturehigher=faster (higher tem, faster diffusion
Factors affecting diffusion rate
-Electrical difference in charge or pressure gradients
Exocytosis
A cytoplasmic vesicle fuses with the plasma membrane and contents are released outside the cell
Endocytosis
A small patch of plasma membrane sinks inward and seals back on itself, forming a vesicle inside the cytoplasm–membrane receptors often mediate this process
Hydrostatic pressure (fluid pressure)
pressure exerted by fluid on the walls that contain it (in plants, turgor pressure)
Osmotic pressure (fluid pressure)
amount of pressure necessary to prevent further increase of a solution’s volume
Tonicity
refers to relative solute concentrations of two fluids (hypotonic- fewer solutes, hypertonic- more solutes, isotonic- same amount)
Passive Transport
-doesn’t require energy inputs, solutes diffuse through channel inside the protein’s interior, net movement is down concentration gradient
Active Transport
requires ATP, protein is an ATPase pump, pumps solute against its concentration gradient
In _______ pathways, small molecules are assembled into large molecules.
biosynthetic
In _______ pathways, large molecules are broken down into smaller molecules.
catabolic
Essentially, the first law of thermodynamics says that:
energy can be neither created nor destroyed
ATP contains:
adenine
The addition of electrons is known as:
reduction
The removal of electrons is known as:
oxidation
The concept that concentration differences in H+ and electric gradients across a membrane are responsible for ATP formation is known as:
the chemiosmotic model
No energy conversion is ever 100% efficient. Further, each conversion produces energy (heat) that is unavailable for cellular work.
True
Cells spend ATP in exergonic reactions
False
Enzymes are catalytic molecules (alter rates) for biological reactions.
True
What is energy?
capacity to do work (forms: potential-capacity to make things happen, kinetic-motion(includes heat), and chemical energy-potential energy of molecules)
What do cells use energy for?
chemical work-build, stockpile, and break apart substances; mechanical work-movement (flagella); electrochemical work-movement charged molecules across membranes
First Law of Thermodynamics
the total amount of energy in the universe is constant; energy can undergo conversions from one form to another, but it cannot be created or destroyed.
How much energy is available?
energy cannot be produced by a cell; it can only be borrowed from someplace else
Producers do what to energy?
Producers trap energy from the sun and convert it into chemical bond energy
Second Law of Thermodynamics
no energy conversion is ever 100% efficient; each conversion produces energy (heat) that is unavailable for cellular work; the total amount of energy is flowing from high-energy forms to form lower energy; as systems lose energy they become more disorganized (entropy)
Entropy
measure of degree of disorder in a system
Energy changes
energy changes in cells tend to run spontaneously in the direction that results in a decrease in usable energy
Cells & Energy Hills
Endergonic reactions (energy in)-prodects with more energy in than the reactants; Exergonic eaction (energy out)- products with less energy that the reactants
Adenosine trisphosphate (ATP)
composed of: adenine (nitrogen base), ribose (sugar), three phosphate groups
Phosphorylation
energy inputs links a phosphate group to ADP to produce ATP
Transferring Energy
ATP can donate a phosphate group to another molecule
Role of ATP
cells “earn” ATP in exergonic reactions; cells “spend” ATP in endergonic reactions
Electron transfer
transfered in nearly every reaction that harnesses energy (for ATP production); Electron transfer used in aerobic respiration to produce ATP
Electron Transfers
Oxidation-lose an electron; Reduction- gain an electron; central to the formation of ATP during photosynthesis and aerobic respiration
Reactants
-substances that enter the reaction
Intermediates
compounds formed btw the start and finish of the reaction
Products
substances present at the conclusion of a pathway
Enzymes
proteins that speed up (catalyze) reactions
Energy Carriers
activate enzymes and other molecules by phosphorylation group transfer (mainly ATP)
Cofactors
small molecules and metal ions that help enzymes by carrying atoms or electrons
Transport proteins
membrane-bound proteins that participate in adjusting concentration gradients (influence metabolic reactions)
Metabolic Pathways
series of reactions that regulate the concentration of substances within cells
Biosynthetic pathways
small molecules are assembled into large milecules
Degradative pathways
large molecules are broken down to form products of lower energy.
Which way will a reaction Run?
nearly all chemical reactions are reversible; direction reaction depends on 1)energy content of participants 2)reactant/product ratio
Four Features of Enzymes
1) Enzymes speed up reactions
2) Reactions do not alter or use up enzyme molecules
3) The same enzyme usually works for both the forward and reverse reactions
4) Each type of enzyme recognizes and binds to only certain substrates
Alcohol, Enzymes and the Liver
Body absorbs alcohol via the stomach (20%) and small intestine (80%)
The proton (H+) concentration gradients generated as a result of the light-dependent reactions of photosynthesis are use to produce _______.
ATP
The electrons generated as a result of the light-dependent reactions of photosynthesis are use to produce _______.
..NOT FADH2
The conversion of solar energy to chemical energy occurs during
photosynthesis
During the Calvin-Benson cycle (light-independent reactions), how many PGAL (3 carbon molecule) molecules must join together to form one molecule of glucose?
2
The light-dependent reactions occur in/at the _______.
thylakoid membrane
The light-independent reactions occur in/at the _______.
stroma
Chlorophyll b reflects (does not absorb) which wavelength of light?
orange (?)
Which wavelength of light has the most enegry?
blue
The oxygen released in photosynthesis comes from:
water
Plants need which of the following to carry out photosynthesis?
H2O and CO2
Photautotrophs
-carbon source is carbon dioxide, energy source is sunlight; captures sunlight energy and use it to carry out photosynthesis(plant, some bacteria, and many protists)
Heterotrophs
Get carbon and energy by eating auotrophs, one another, or waste
Photosynthesis
-energy-storing pathway, releases oxygen,requires carbon dioxide
Aerobic Respiration
-energy-releasing, requires oxygen, releases carbon dioxide
Two stages of photosynthesis occur in the chloroplast
light-dependent reactions: thylakoid membrane; light-independent reactions: stroma area that surrounds the grana
Properties of light
- Energy from the sun radiates in wavelengths (gamma rays to radio waves), electromagnetic spectrum.
- Photoautotrophs use only small range (400-750 nm) of wavelengths. Visible light range.
- Light energy is packaged as photons (energy varies as a function of wavelength)
Electromagnetic Spectrum(shortest to longest wavelength)
Gamma Rays, X-Rays, UV radiation, Visible light, Infrared radiation, Microwaves, Radiowaves
Visable Light
Wavelengths humans perceive as different colors
Violet (380 nm) to red (750 nm)
Longer wavelengths = lower energy; shorter wave lengths = higher energy
Photons
- Packets of light energy
- Each type of photon has fixed amount of energy
- Photons having most energy travel as shortest wavelength (blue-violet light)
Rainbow Catchers (Chemical Basis of Color)
- Electrons in pigments absorb photons of specific energy (specific wavelengths)
- If the quantity of energy of a photon matches energy required to boost an electron to higher energy level, wavelength will be absorbed.
- Photons that are not absorbed are transmitted (reflected).
Pigments
- Colors you see are the wavelengths not absorbed
- Light-catching part of molecule often has alternating single and double bonds
- These bonds contain electrons that are capable of being moved to higher energy levels by absorbing light
Variety of Pigments
- Chlorophylls - primary pigments in photoautotrophs (Chlorophyll a (green) main pigment in chloroplast; Chlorophyll b (bluish-green))
- Carotenoids - absorb blue-violet; reflect yellow, orange, and red.
- Anthocyanins – pigments found in many flowers
- Phycobilins – reflect red and blue pigments (red algae and cyanobacteria)
Pigments in Photosynthesis
- Bacteria (Pigments in plasma membranes)
- Plants (Pigments and proteins organized into photosystems that are embedded in thylakoid membrane system (200-300 pigment molecules))
3 events of Light-Dependent Reactions
1) Pigments absorb light energy; give up excited electrons
2) Electron and hydrogen transfers lead to ATP and NADPH formation
3) Pigments that give up electrons; get electron replacements (from water)
Electron Transfer Chain
- Adjacent to photosystem
- Acceptor molecule donates electrons from reaction center
- As electrons pass along chain, energy they release is used to produce ATP
Cyclic Electron Flow
Most likely the oldest means of ATP production (early bacteria):
- Excited electrons leave the P700 reaction center, pass through electron transport system, then return to photosystem I.
- Energy associated with the electron flow drives the formation of ATP.
Noncyclic Electron Flow
- Two-step pathway for light absorption and electron excitation
- Uses two photosystems: type I and type II
- Produces ATP and NADPH
- Involves photolysis - splitting of water via photon (light) energy.
Noncyclic Pathway
- Begins – chlorophyll (P680) in photosystem II abosrbs energy.
- Boosted electron move through ETS; energy released for ATP production.
- Electron moves to photosystem I
- Electron from water fills electron hole left in photosystem II
- Pathway continues when chlorophyll (P700) in photosystem I absorbs energy
- Boosted electron from photosystem I moves to ETS; finally joins with NADP to form NADPH
Chemiosmotic Model of ATP Formation
- Electrical and H+ concentration gradients are created between thylakoid compartment and stroma
- H+ flows down concentration gradient into stroma through ATP synthase (ATP synthase - enzyme that synthesizes ATP)
- Flow of ions drives formation of ATP
Light-Independent Reactions
- Synthesis part of photosynthesis (Building up sugars (glucose))
- Can proceed in the dark
- Take place in the stroma
- Also called the Calvin-Benson cycle
Calvin-Benson Cycle
- Overall reactants-Carbon dioxide, ATP, NADPH
- Overall products-Glucose, ADP, NADP+
- Reaction pathway is cyclic and RuBP (ribulose bisphosphate) is regenerated
Two ATP are produced during the preparatory reaction, just prior to Krebs cycle.
False
The conversion of energy, stored in glucose, to the energy stored in the ATP produced as a result of aerobic respiration is 90% efficient.
False
NADPH is an electron carrier for the processes of aerobic respiration.
False
The electrons released during the proces.s of lactate fermentation are NOT used for ATP synthesis
True
How many carbon dioxide molecules are generated from the complete oxidation of glucose?
?
Anaerobic reactions require the presence of oxygen.
False
How many ATP (net gain) are produced as a result of glycolysis?
2
How many ATP (net gain) are produced as a result of Krebs cycle?
2
How many ATP (net gain) are produced as a result of electron transfer ATP
32
The glycolysis takes place in
cytoplasm
ATP is the universal energy source
- Photosynthetic organisms get energy from the sun
- Animals get energy second- or third-hand from plants and/or other organisms
- Regardless of the source, energy is converted to the chemical bond energy of ATP
Making ATP
- Plants make ATP during photosynthesis (Light-dependent reactions)
- Cells of all organisms (including plants) make ATP by breaking down organic molecules: Carbohydrates, Fats, Proteins
Anaerobic pathways
- Don’t require oxygen
- Start with glycolysis in cytoplasm
- Completed in cytoplasm
Aerobic pathways
- Require oxygen
- Start with glycolysis in cytoplasm
- Completed in mitochondria
Three Series of Reactions Required for Aerobic Respiration
1) Glycolysis 2) Krebs cycle 3) Electron transfer phosphorylation
Glycolysis Occurs in Two Stages (cytoplasm)
- Energy-requiring steps: ATP energy activates glucose and its six-carbon derivative (fructose-6-phosphate)
- Energy-releasing steps: The product of the first part are split into three-carbon pyruvate molecules; ATP and NADH form
Krebs cycle is found in
mitochondria
The Krebs Cycle
- Overall Reactants: Acetyl-CoA, 3 NAD+, FAD, ADP and Pi
- Overall Products: Coenzyme A, 2 CO2, 3 NADH, FADH2, ATP
Electron Transfer Phosphorylation
- Occurs in the mitochondria
- Coenzymes deliver electrons to electron transfer chains
- Electron transfer sets up H+ ion gradients
- Flow of H+ down gradients powers ATP formation
Importance of Oxygen
- Electron transport phosphorylation requires the presence of oxygen
- Oxygen withdraws spent electrons from the electron transfer chain, then combines with H+ to form water
Efficiency of Aerobic Respiration
- 686 kcal of energy are released
- 7.5 kcal are conserved in each ATP
- When 36 ATP form, 270 kcal (36 X 7.5) are captured in ATP
- Efficiency is 270 / 686 X 100 = 39 percent (Most energy is lost as heat)
Anaerobic Pathways
- Operate when oxygen is absent (limited); do not use oxygen
- Pyruvate from glycolysis is metabolized into molecules other than acetyl-CoA
- Produce less ATP than aerobic pathways
Alternative Energy Sources in the Human Body (Carbohydrates)
- Excess carbohydrates are stored as glycogen in liver and muscle tissue (for future use)
- Free glucose is used until it runs low, then glycogen reserves are tapped (glycogen glucose)
Alternative Energy Sources in the Human Body (Fats)
- Excess fats are stored in adipose tissue.
- Fats are digested into glycerol, which enters -glycolysis, and fatty acids, which enter the Krebs cycle
- Fatty acids have many more carbon and hydrogen atoms (compared to glucose); yield greater amounts of ATP
Alternative Energy Sources in the Human Body (Proteins)
- Amino acids are released by digestion and enter the blood.
- After the amino group is removed, the amino acid remnant enters the Krebs cycle
