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Bio 2 - Summary General Biology 2
General Biology 2 (BIOL 1113)
Northeastern University
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Chapter 1: Characteristics of living organisms (Define “Life”)
- Different levels of organization
- Atoms → Molecules/Macromolecules (ex. nucleic acids, lipids, etc) → Cells → Tissues → Organs → Organisms → Population → Community → Ecosystems → Biosphere
- Cellular composition
- Unicellular (one cell organisms) (ex)
- Single-cell organisms have everything they need to be self-sufficient (one type of cell can carry out all functions)
- Multicellular (many cell organisms)(ex/animals)
- In multicellular organisms, specialization increases until some cells do only certain things (many different cells have only certain functions; but cells have same basic structure)
- Unicellular (one cell organisms) (ex)
- Homeostasis
- Regulates body functions (ex. human body temperature)
- The ability to maintain a constant internal environment in response to environmental changes (external or internal)
- Reproduction
- Asexual (Producing offspring without the use of gametes)
- Sexual (Producing offspring with gametes) (Sperm and egg)
- Sensitivity or response to the environment (stimuli)
- Living things will make changes in response to a stimulus in their environment (ex will lean towards the sun) (A behavior is a complex set of responses)
- Growth and development
- Each cell divides to make new cells (cell division)
- In multicellular organisms, this results in growth of the organism and some cells become specialized and perform different jobs than others (differentiation)
- Energy processing
- Autotrophs (get energy from the sun) (ex)
- Heterotroph (get energy from consuming other organisms) (ex)
- Adaptation
- Traits that give an organism advantages in a certain environment, for survival and reproduction (genetics are changed over time)
Scientific Method
Two types of reasoning are used in the course of scientific research.
- Inductive reasoning (when a general conclusion is drawn from specific observations)
- Deductive reasoning (when specific results are predicted from a general premise)
Way to go about research:
- Observation
- visual observations or measurements
- Question
- Hypothesis
- a tentative answer to the question set in step 1 that can be tested through experimentation
- Experiment
- a test for the validity of the hypothesis (controlled or natural)
- variable: any factor of interest that can change (take different values)
- control variable: what is being kept the same
- Observation
independent variable: (the variable that is controlled by the scientist/nature) (what is being tested for/against)
dependent variable: (the data collected in an experiment that depends on the independent
Results and data analysis
Statistical significance (p) refers to the probability that a given result is not due to random chance. Value of p <0 denotes significance
Conclusions
Do the results support or reject the initial hypothesis?
A HYPOTHESIS CAN NEVER BE PROVEN
Write a report
Bio-Chemistry
Oxygen, Carbon, Hydrogen, and Nitrogen make up about 95% of the atoms in living organisms
- Hydrogen and oxygen occur primarily in water
- Nitrogen is found in proteins
- Carbon is the building block of all living matter
Mineral elements are less than 1% and Trace elements are less than 0%
- Yet they are essential for normal growth and function
- If one of either is missing in the body, it will cause illness/disorders/death
The Structure of the Atom
- Orbitals with electrons
- Nucleus has proteins and neutrons
- Isotopes (atoms that have the same number of protons but different numbers of
neutrons)
- Interested in radioisotopes (help us with diagnosis and to detect illness,etc) (ex. tumors found in the body using isotopes)
Electron configurations
- Bohr diagrams indicate how many electrons fill each shell. A full valence shell is the most stable electron configuration
Chemical Reactions and Molecules
- All reactions in the body are chemical
- Since not all elements have enough electrons to fill their outermost shells, atoms form chemical bonds with other atoms thereby obtaining the electrons they need to attain a stable electron configuration
- Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart (hydrolysis and condensation reactions)
Chemical Bonds
- Covalent Bond
- Forms when two non-metals share electrons
- Non-metals tend to gain electrons to achieve a full valence shell
- Covalent bonds are not rigid and rotation around single covalent bonds allows molecules to change shape
- Polar covalent and non-polar covalent
- Polar bond forms when two non-metals have different electronegativity (share unequally)
- Non-polar bond forms when two non-metals have similar electronegativity (share equally)
- Covalent Bond
Water is an excellent solvent (versatility as solvent)
- Hydrophobic: repels water (oils and fats)
- Hydrophilic: attracts water (carbohydrates)
- Water molecules create a hydration shell around polar molecules
Water moderates temperatures (high specific heat)
- Water has a high specific heat, meaning a given mass of water must gain a lot of
heat to increase temperature. Likewise, water gives up a lot of heat as it cools
- Requires lots of energy to increase its temperature (good for the body because it retains its temperature very easily
- Water has a high specific heat, meaning a given mass of water must gain a lot of
heat to increase temperature. Likewise, water gives up a lot of heat as it cools
Acids, Bases, pH
- Positively charged hydronium ion (H3O+) and a negatively charged hydroxide ion (OH-)
- Acids 1-
- An acid is a substance that increases the concentration of H3O+ in a solution
- Have more H+
- 7 is neutral
- 8-14 Base
- A base is a substance that decreases the concentration of H3O+ in a solution
- Have more OH-
- Acids 1-
- Pure water has an equal concentration of H3O+ and OH- (neutral pH of 7)
- Buffers are substances (weak acids and weak bases) that minimize changes in concentrations of H+ and OH– in a solution and organisms employ them to regulate their intracellular pH
- pH affects organisms
- Many enzymes are exquisitely sensitive to pH; many metabolic processes happen depending on the pH (enzymes all have different optimal pH’s where they work best)
- pH gradients across intracellular compartments are necessary for many cellular functions like causing movements between gradients
- pH affects ecosystems
- Acid precipitation and carbon dioxide levels in ocean water are increasing due to the
burning of fossil fuels
- Carbon dioxide reacts with water to form carbonic acid, which acidifies ocean water in a process called ocean acidification. Calcium carbonate, which forms the shells and skeletons of many marine organisms, dissolves in acidic conditions
- Acid precipitation and carbon dioxide levels in ocean water are increasing due to the
burning of fossil fuels
Chapter 2: Biological Macromolecules
Cells are made of many complex molecules called macromolecules
- proteins, nucleic acids (RNA and DNA), carbohydrates, and lipids
Macromolecules are large molecules composed of thousands of covalently connected atoms
The fundamental component for all of these macromolecules is carbon (organic compounds)
- The carbon atom forms covalent bonds with as many as four different atoms
- Can form both polar and non-polar covalent bonds
- C=O and C-O are polar (O is more electronegative)
- C-C and C-H are electrically neutral and non-polar
Functional Groups
- Groups of atoms that occur within molecules and confer specific chemical properties to those molecules (participate in specific chemical reactions)
Found along the “carbon backbone” of macromolecules
Polymers and Monomers
- Polymer is a long molecule consisting of many monomers
- Three of the four major types of life’s organic molecules are polymers:
- Carbohydrates, Proteins, and Nucleic acids (Lipids are not polymers)
- Biological macromolecules come from food and digestion
Hydrolysis vs Condensation reactions
- Hydrolysis Reaction: adds water to break bonds (split polymer into monomers)
- Condensation (dehydration) Reaction: lose water to form bonds (link monomers to make polymers)
Carbohydrates
- Store short term energy for organisms and provide structural support
- Monosaccharides: one sugar monomer (are known as isomers) (when broken down
provides parts for others) (In solution, monosaccharides exist in both linear and ring forms)
- Glucose: plants synthesize glucose from carbon dioxide and water
- During cellular respiration the energy stored in glucose is converted into the stored energy of ATP
- Galastose: part of lactose (sugar found in milk)
- Fructose: part of sucrose (sugar found in fruit)
- Glucose: plants synthesize glucose from carbon dioxide and water
- Disaccharides: composed of two monomers (formed when two monosaccharides are joined
in a dehydration reaction to form a glycosidic linkage)
- Lactose: composed of the monomers glucose and galactose
- Maltose: composed of two monomers of glucose
- Sucrose: (table sugar) composed of the monomers glucose and fructose
- Oligosaccharides: composed of three to ten monomers
- Polysaccharides: composed of many repeating monomers (a long chain of monosaccharides linked by glycosidic bonds is known as a polysaccharide) 1. Starch: (primary energy storage polysaccharide in plants) 2. Glycogen: (primary energy storage polysaccharide in animals e. liver & muscles) 3. Cellulose 4. Chitin (all three provide structural support in body to various organisms) 5. Peptidoglycan
Lipids
Non‐polar, hydrophobic, insoluble in water
Main categories of lipids:
- Fats, oils, phospholipids, steroids
Consist of long chains of carbon and hydrogen (non polar H-C)
Main functions:
- Gives cell membranes fluidity
- Cells store energy for long‐term use in the form of fats
- Lipids provide insulation from the environment for plants and animals (layer of fat around vital organs for shock absorbency)
Phospholipid
- Hydrophobic tails composed of long hydrocarbon chains
- Hydrophilic head interacts with water
20 amino acids in proteins (they differ by the type of attached side chain/R‐group)
- R‐groups are categorized according to their chemical properties (positive, negative, polar (has O or S), non-polar (has H or C))
Peptide bond: the covalent bond between carbon and nitrogen that forms after a dehydration/condensation reaction between two amino acids (between a carboxyl C of one group and the amino N of the other) (links amino acids)
Four Levels of Protein Structure
- Primary structure
- Unique sequence of amino acids
- Secondary structure
- Consists of coils or folds in the polypeptide chain by hydrogen bonds
- A helix and beta sheet are created due to these hydrogen bonds
- Tertiary structure
- Interactions/bonds among various side chains (R groups)
- Single polypeptides stop here; quaternary requires two or more to wrap around each other
- Quaternary structure
- When a protein consists of multiple polypeptide chains (subunits bonded together)
- Is fully functional at this state
- Primary structure
Denaturation
- Changes in temperature
- Changes in pH
- Exposure to chemicals
- The primary structure is not affected by denaturation (will return to this state if denatured)
- A denatured protein is biologically inactive (unfolded)
Factors that promote protein folding and stability
- Hydrogen bonds
- Ionic bonds and other polar interactions
- Hydrophobic effects
- Van der Waals forces
- Disulfide bridges
Enzymes
Enzymes speed up chemical reactions (catalysts) by lowering the activation energy needed to start a reaction
The enzymes are not used up in a reaction but they are re‐used over and over again
Enzymes exhibit remarkable substrate specificity
- Each enzyme can have more than one substrate
- Lock and Key theory was wrong; Induced fit is correct
- Enzyme binds to active site on substrate
- Each enzyme can have more than one substrate
Enzymes have optimal working temperatures and pHs
- Past optimal it becomes denatured
Substrate concentration
- With an enzyme the reaction time will be shorter, until a certain point when all substrates have been blinded by enzymes and there are none left to bind (it will plateau)
Factors that affect enzyme activity:
- pH, Temperature, Substrate concentration
Enzyme regulation
- Competitive inhibition
- Has the same structure as the substrate, binds to and blocks the active site so that the substrate cannot bind
- Allosteric inhibition
- Bind to allosteric sites separate from the active site and change the shape of the enzyme so that the active site can no longer bind the substrate
- Allosteric activators
- Bind to allosteric sites of inactive enzymes and change the shape of the enzyme to expose the active site to allow binding to the substrate
- Competitive inhibition
Cells
- Biological cell theory
- Cells are the basic unit of life
- The smallest living unit of structure and function of all organisms is the cell
- All living organisms are composed of cells
- The chemical reactions needed for life (such as cellular respiration) happen inside these cells
- All cells come from pre-existing cells
- New cells are made when one cell copies its DNA and divides, distributing an identical copy of the DNA to each new cell
- Cells are the basic unit of life
- Why giant cells don't exist
- Large cells have less surface area per unit volume
- Purpose is to have things go in and out of the cell, and the distance has to be short in order for this to happen more efficiently
- Bigger the cell the smaller the surface area to volume ratio, which is worse for cell (the cell will split if it becomes to big to avoid getting too large for function)
- Large cells are less capable of transporting materials across plasma membrane
- Large cells have less surface area per unit volume
- Ways to see cells
- Light microscopy (shining a light on sample)
- Transmission electron microscopy (electron beam goes through sample)
- Scanning electron microscopy (sample is sliced)
- Fluorescence microscopy (dye certain parts of the cell)
- Basic features of all cells
- Cells separate their internal environment from the external environment in order to maintain homeostasis (this is the function of the plasma membrane)
- Cells must store information and pass it on to the next generation (this is the function of DNA)
- Cells must be able to build proteins (this function is achieved by ribosomes)
- Cells must conduct the chemical processes of life (many of these chemical reactions occur in the cytoplasm)
Prokaryotic cells 1. No nucleus 2. DNA in an unbound region called the nucleoid 3. No membrane-bound organelles 4. Structure: 1. Plasma membrane 1. Components are in constant motion
Has nuclear pores (mRNA goes out, tRNA comes in)
Cytoplasm (is a viscous fluid; contains cell organelles, cytoskeleton, and substances like enzymes, minerals, organic molecules)
Ribosomes (found in all types of cells)
Ribosomes are the smallest organelles of the cell and are membrane free
Composed of rRNA (ribosomal RNA)
Free ribosomes float in cell: produce proteins for cell itself
Rough endoplasmic reticulum ribosomes: produce proteins for outside cell
Endoplasmic reticulum
Smooth endoplasmic reticulum: lipid synthesis, carbohydrate metabolism, calcium storage, and breaking down toxins
Rough endoplasmic reticulum: contains ribosomes, which synthesize membrane- embedded and secretory proteins
Golgi Apparatus and Vesicles
Golgi apparatus: modifies membrane-embedded and secretory proteins
Add different things (lipids, carbohydrates,etc) to modify proteins
Vesicles: transport synthesized proteins
Lysosomes (only in animal cells)
Membrane-bound vesicles containing digestive enzymes (not present in plants)
Peroxisomes (only in animal cells)
Membrane-bound vesicles containing enzymes for detoxification of cells
Vacuoles: Vesicles used for storage, transportation, and specialized functions 10
Mitochondria carry out cellular respiration (the process by which energy in the form of ATP is produced from the breakdown of carbohydrates and lipids)
Possess their own genome (mtDNA)
Outer membrane and inner membrane with foldings to maximize surface area
Believed to have come from endosymbiosis: was its own organism until it was engulfed by a bacteria (procaryote) 11 (complex protein network that organizes the cellular components and facilitates cellular activities)
Gives structural support
Ability for motion
Anchors organelles in place
Involved in cell division
Based on three major cytoskeletal structures:
Microfilaments
Thinnest cytoskeletal elements (rodlike)
Composed of the globular protein actin and enables cell to change shape and move
Intermediate filaments
Present only in animal cells
Fibrous proteins (ex. Keratin)
Provide internal structure (anchor organelles in place)
Microtubules
Long hollow tubes made of tubulin proteins
Anchor organelles and act as tracks for organelle movement
Move chromosomes around during cell division
Used to make cilia and flagella
Structure of Plant Cells:
- Chloroplasts (function deals with photosynthesis; the process by which light energy is used to make organic molecules from CO2)
- Central vacuole (large vesicles used for storage and specialized functions)
- Other plastids/vacuoles (chromoplast, amyloplast)
- Cell wall
- Provides structure and protection (prevents water loss)
- Wraps around the plasma membrane
- Made of cellulose
- Connect by plasmodesmata (channels through the walls so things can move between them)
Main differences between Animal Eukaryotic and Plant Eukaryotic
- Plants have central vacuole (nutrients and waste held inside)
- Plants have cell walls
- Plants have chloroplasts/chlorophyll
- Plants only have a thin lining of cytoplasm
Chapter 3 Membrane Transport
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
Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly
Polar molecules, such as sugars, do not cross the membrane easily (Proteins regulate transport across the membrane)
Types of membrane transport:
- Passive transport (no energy required)
- Diffusion: the tendency for molecules to spread out evenly into the available
space (high concentration to low concentration)
- Substances diffuse down their concentration gradient (small, non polar)
- Osmosis: 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
- Tonicity: To gain or lose water
- Isotonic solution: solute concentration is the same as that inside the cell; no net water movement
- Hypertonic solution: solute concentration is greater outside the cell; cell loses water (cell will shrivel up, dehydrated)
- Hypotonic solution: solute concentration is less outside the cell; cell gains water (cell will eventually burst)
- Osmoregulation: the control of solute concentrations and water balance
- Facilitated diffusion: polar molecules and ions unable to cross the membrane on
their own can diffuse with the help of transport proteins (large, polar)
- Facilitated diffusion is still passive because the solute moves down its concentration gradient, and the transport requires no energy
- Channel proteins provide corridors that allow a specific molecule or ion to cross the membrane
- Diffusion: the tendency for molecules to spread out evenly into the available
space (high concentration to low concentration)
- Passive transport (no energy required)
Many organisms, including humans and other animals, take in chemical energy in the form of food (heterotrophs)
Photosynthetic organisms produce their own food by converting light energy into chemical energy (autotrophs)
Metabolism is the sum of all chemical reactions that transform energy and matter within a living organism
A metabolic pathway is a series of defined steps along which a molecule is converted to another molecule (specific enzymes catalyze the steps that occur in metabolic pathways)
The bonds between the atoms of a molecule contain potential energy that can be released if the bonds are broken in a chemical reaction
During every energy transfer or transformation, some energy is unusable, and is often lost as heat
Catabolic reactions
Metabolic pathways that break down complex molecules into simpler ones, releasing some potential energy in the process (ex. cellular respiration)
Anabolic reactions
Metabolic pathways that build more complex organic molecules from simpler ones, consuming some energy in the process (ex. photosynthesis)
Gibbs free energy is the energy that can be used by a system to perform work when temperature and pressure are uniform (ΔG = G final state ‐ G initial state)
When a reactant with greater free energy is converted to a product with lower free energy, ∆G has a negative value
When a reactant has a lower free energy than the product, ∆G has a positive value
Exergonic reactions
Net change in Gibbs free energy is negative, and energy is released from system 10 reactions
Net change in Gibbs free energy is positive, and energy must be added to system
ATP
Adenosine triphosphate (ATP) is the most widely used energy storage molecule among organisms
ATP components:
- nitrogenous base (adenine)
- sugar (ribose)
- three phosphate groups
7 kcal of energy is released for each mole of ATP hydrolyzed with water
When a cell "pays" more for a reaction than the reaction requires, any leftover energy is released as heat
Most reactions require less energy than the hydrolysis of ATP releases
- The hydrolysis of ATP would simply result in organisms overheating
- Energy coupling (the transfer of energy from one chemical reaction to another) solves this issue
Main Points:
- ATP must be regenerated continuously
- ATP is synthesized by using energy from photosynthesis or cellular respiration
- ATP is hydrolyzed to release energy needed for cellular work
ATP is not the only "energy molecule“; others include creatine phosphate and phosphoenolpyruvate, which release more energy than ATP
The advantages of ATP are:
Its utility
Ease of use
Rapidity of regeneration
Energy flow in living systems
- Photosynthesis (only in animals)
- Cellular respiration (In both plants and animals)
- In cellular respiration, a series of chemical reactions moves electrons between molecules. As electrons move from higher energy states to lower energy states, energy is released that can be used to form ATP
- Aerobic
- Anaerobic
- Autotrophic producers:
- Autotrophs are the producers of the biosphere
- Use light energy, carbon, and water to produce organic molecules (and associated energy) through photosynthesis (ex plants)
- Heterotrophic consumers:
- Acquire organic molecules (and associated energy) from other organisms (ex. animals)
- Redox reactions: (they move electrons between molecules, releasing energy) (OILRIG)
- Oxidation: A reactant that donates electrons is oxidized, which results in a positive charge.
- Reduction: A reactant that accepts the electrons is reduced, which results in a negative charge
Cellular respiration overview
Cells need energy for their functions; this energy comes from eating carbohydrates, proteins, etc (body digests food and breaks it down) (the energy is not recycles by living organisms)
Cellular respiration converts some of the chemical energy in organic molecules to usable energy‐currency molecules, primarily ATP
- Glucose + Oxygen —> CO2 (diffuses out of body) + H2O (body uses) + Heat + ATP
(energy)
- Glucose and CO2 become oxidized (lose electron); O2 and H2O become reduced (gain electron)
- Whenever there is an oxidation, there has to be a reduction
- The cell oxidizes glucose in many small steps, each step releasing a relatively small
amount of energy
- If the free energy from the complete combustion of glucose were liberated all at once, the massive release of heat would destroy the cell
- Glucose + Oxygen —> CO2 (diffuses out of body) + H2O (body uses) + Heat + ATP
(energy)
ATP is produced in two ways:
- Substrate level phosphorylation
- ATP is formed when a phosphate group is directly transferred to ADP from another molecule
- ADP + P(inorganic) —> ATP
- Creates 2 ATP
- Oxidative phosphorylation
- ATP production is coupled to the oxidation of the electron carriers NADH and FADH and the generation of a proton gradient
- NADH —> NAD+ (oxidized)
- Substrate level phosphorylation
Chemiosmosis: Chemical active transport of protons out of cell using the ATP synthase
- Protons (H+) are pumped from the mitochondrial matrix to the intermembrane space
- H+ move back across the membrane, passing through the ATP synthase protein
- Oxygen is the final electron transporter (O2 and 2H+ become H2O in the end)
Cellular Respiration without Oxygen (Anaerobic or Fermentation)
The electron transport ceases to operate
Glycolysis couples with fermentation or anaerobic respiration to produce ATP
Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example sulfate (25% less ATP than aerobic respiration)
Fermentation uses substrate‐level phosphorylation instead of an electron transport chain to generate ATP (93% less ATP than aerobic respiration)
Lactic Acid
Ethanol + CO2 (Alcoholic Fermentation)
Photosynthesis (Anabolic, Endergonic) (> 0 energy)
Photosynthetic organisms: plants and algae
Takes place in Plant cells in chloroplasts
Photosynthesis is the process that converts solar energy into chemical energy (energy‐ storing carbohydrates)
- During photosynthesis light energy is converted into the potential energy of the chemical
- bonds in carbohydrate molecules
Directly or indirectly, photosynthesis nourishes almost the entire living world
Photosynthesis is a complex series of reactions that can be summarized as the following equation:
- Energy + CO2 + H2O —> Glucose + O
- CO2 and Glucose become reduced; H2O and O2 become oxidized
Light
- Visible spectrum:
- The colors of visible light do not carry the same amount of energy
- Violet has the shortest wavelength and therefore carries the most energy
- Red has the longest wavelength and carries the least amount of energy
- Plant pigments absorb different parts of the light spectrum to acquire energy
- Chlorophyll absorbs violet/red and blue/orange light but reflects green light
- After light is harvested by pigments, the next act of photosynthesis is the conversion of light energy to chemical energy (sugars)
- Visible spectrum:
Photosynthetic part of plants:
- Leaves are the major locations of photosynthesis
- Their green color is from chlorophyll, the green pigment within chloroplasts
- Each mesophyll (interior tissue of the leaf) cell contains 30–40 chloroplasts
Chloroplast:
- The organelle where photosynthesis is carried out
- The thylakoid membrane (folded into stacks called grana) of the chloroplasts contains the light‐harvesting machinery required for photosynthesis
- Stroma: where enzymes exist
- Granum: stacks of thylakoids
Photosystem:
- A photosystem consists of a light‐harvesting complex and a reaction center
The light‐harvesting complex is the photosystem's light collector
- Pigments (chlorophyll) transfer energy to other pigments in the light‐harvesting center (photosystem 1) (absorbs 700 nm light waves)
The reaction center complex is the actual site where the energy‐ conversion reactions of photosynthesis take place (photosystem 2) (absorbs 680 nm light waves) 10 of photosynthesis:
Light dependent reactions in the thylakoid membrane of the chloroplast
Use light energy to make ATP and NADPH
In the light‐dependent reactions, the excited electrons are used by various enzymes to produce ATP from ADP and NADPH from NADP+
ATP is generated by harnessing the proton gradient across the thylakoid membrane
NADPH is generated as part of the electron transport chain
ATP and NADPH are then used in the carbon reactions to combine carbon dioxide and water into carbohydrates
Light independent reactions (The Calvin cycle) take place in the stroma of the chloroplast
Calvin Cycle:
This is a cyclic flow of carbon fixation reactions in which the cell converts, or "fixes“, inorganic carbon from carbon dioxide into organic carbon
Electron transport and chemiosmosis from the light dependent reactions generate ATP and NADPH to help with the sugar assembly
The Calvin cycle has three phases:
Carbon fixation: the enzyme RuBisCO incorporates carbon dioxide into an organic molecule, ribulose bisphosphate (RuBP), and forms 3phosphate glycerate (3PGA)
Reduction: the 3PGA is reduced using electrons supplied by NADPH
Regeneration: RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue
Carbon uses energy derived from ATP and NADPH to make sugars from CO
The process of photosynthesis:
Photopigments, such as chlorophyll, absorb light
Electrons in the pigment molecules are excited into higher energy states
Light energy ultimately converts into the potential energy of the chemical bonds in carbohydrate molecules 11:
Electron transport chain is a series of electron transporters embedded in the thylakoid membrane that shuttles electrons from PSII to PSI and generates NADPH
The energy released by the electron transport chain drives the creation of a proton (H+) gradient across the thylakoid membrane
This creates a higher concentration of H+ in the thylakoid lumen than the stroma
H+ move back across the membrane (from the thylakoid lumen to the stroma), passing through the ATP synthase protein complex, which phosphorylates ADP to ATP
This movement of protons is called chemiosmosis
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria:
Mitochondria:
Transfer chemical energy from food to ATP
Signal transduction pathways may involve intracellular signals called second messengers (when signal molecule is a protein and cannot enter the cell)
- Kinase: enzymes that favor phosphorylation of proteins
Cellular response
Different responses are possible
Change enzyme activity
Change function of structural proteins
Change gene expression
The response to a given signaling molecule depends on which cell is responding
Proteome: a set of proteins that each cell makes that determines the response of the cell
Ex. Epinephrine
Different effects throughout body
Airways of the lungs relax to provide more oxygen
More glycogen breakdown in skeletal muscle
Heart muscle cells beat faster
Surface Receptors vs Intracellular Receptors
- Surface Receptors:
- Enzyme‐linked receptors
- Extracellular enzyme binds substrate; Intracellular domain becomes functional
- G‐protein coupled receptors (GPCR)
- 7 transmembrane segments required
- Another pathway for signals that cannot directly enter the cell
- Ligand‐gated ion channels
- Ligand binding causes ion channels to open and ions to flow through the membrane (facilitated diffusion)
- Enzyme‐linked receptors
- Intracellular Receptors:
- ex. Estrogen
- Hormone passes through cell membrane and into the nucleus where it binds estrogen receptor
- ex. Estrogen
Extracellular Structures (support and communication)
Two main types:
- Extracellular Matrix (animal cells)
- Contains glycoproteins and glycolipids, integral proteins, collagen, etc
- The extracellular matrix is composed of collagen, proteoglycans and associated proteins that link cells and the extracellular matrix to one another
- Collagen constitutes almost 40% of the total amount of protein in the human body (Collagen forms fibers that integrate into a network of proteoglycans)
- Contains glycoproteins and glycolipids, integral proteins, collagen, etc
- Cell Wall (plant cells)
- The cell wall provides protection to the plant cell and maintains the cell's shape
- It also resists expansion and therefore prevents the excessive influx of water into plant cells
- The primary component of a plant cell wall is the polysaccharide cellulose (4 different
types in the primary cell wall)
- Cellulose gives structure so that the cell does not collapse on itself when pressure is applied
- Extracellular Matrix (animal cells)
Cell Junctions:
Anchoring junctions (animal cells)
- Attach cells to each other and to the ECM and rely on cell adhesion molecules
Plasmodesmata (plant cells)
- Cytoplasmic channels that allow transport of materials between cells
Tight junctions
- Cells are so close that there is no passing of material (seal off things)
Gap junctions
- Cells have gaps when connected so that material may pass through
Tissues
- Tissue: Group of cells having a similar structure or function
- Humans have over 200 different cell types that are grouped into a few general categories
- Organ: Collection of two or more tissues that perform a specific function or set of functions
- 6 cell processes that produce tissues and organs:
- Cell division
- Cell growth (grow in order to carry out functions)
- Differentiation (different types of cells do different things)
- Migration (cells move to different parts of the body for different things)
- Apoptosis (cell death)
- Cell connections
- 4 types of animal tissues:
- Epithelial tissue
- Cells joined together forming continuous sheets to cover or line body surfaces (protective linings)
- Connective tissue
- Support body or connect tissues
- Nervous tissue
- Receives, generates and conducts electrical signals
- Muscle tissue
- Generates force that facilitates movement (contracting and relaxing muscles)
- Epithelial tissue
- 3 types of plant tissue:
- Dermal tissue (outermost tissue)
- Covering on various plant parts
- Vascular tissue
- Most of plant’s body with variety of functions
- Parenchyma, collenchyma, sclerenchyma (depends on age of plant)
- Ground tissue (innermost tissue)
- Form interconnected conducting vessels for water and nutrients
- Dermal tissue (outermost tissue)
DNA
- Hereditary information is encoded in DNA and reproduced in all cells of the body
- DNA structure:
- DNA Nucleotides (monomers)
- Composed of:
- A nitrogenous base
- The four bases in DNA are adenine, thymine, cytosine, and guanine
- Adenine and guanine are purines, and cytosine and thymine are pyrimidines
- A base pairs to T (double bond), C base pairs to G (triple bond)
- A nitrogenous base
- Composed of:
- DNA Nucleotides (monomers)
Bio 2 - Summary General Biology 2
Course: General Biology 2 (BIOL 1113)
University: Northeastern University
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