Ap Bio Unit 2 Daily Video
2.1
Subcellular components universal to all cells
-all living cells contain a genome and ribosomes, reflecting the common ancestry of all known life.
-ribosomes synthesize protein according to mRNA sequence and the instructions that are encoded in that mRNA sequence originate frm the genome of the cell.
Structure and Funtion: Ribosomes
-ribosomes consist of two subunits that are NOT membrane-enclosed
-ribosomes are made of ribosomal RNA (rRNA) and proteins
-ribosomes synthesis protein according to mRNA sequences
Structure and Function: Endoplasmic Reticulum (ER)
-the endoplasmic reticulum is a network of membrane tubes within the cytoplasm of eukaryotic cells
-Two fomrs of the ER:
Rough ER
has ribosomes attached to its membrane
compartmentalizes the cell
rough ER is associated with packaging the newely synthesized proteins made by attached ribosomes for possible export from the cell
Smooth ER
Does NOT have ribosomes attached
functions include detoxification and lipid synthesis
-structural differences between rough ER and smooth ER leads to functional differences
Structure and Function: Golgi Complex
-series of flattened membrane-bound sacs found in eukaryotic cells
-involved in the correct folding and chemical modifitcation of newly synthesized proteins and packaging of protein trafficking
Structure and Function: Mitochondria
-has a double membrane
-outer membrane is smooth and inner membrane is highly convoluted, forming folds call cristae
-functions in production of ATP energy that eukaryotic cells can use for cell work
Structure and Function: Lysosomes
-membrane-enclosed sacs found in some eukaryotic cells that contain hydrolytic enzymes
-hydrolytic enzymes can be used to digest a variety of materials such as damaged cell parts or macromolecules
Structure and Function: Vacuoles
-membrane-bound sacs found in eukaryotic cells
-play variety of roles ranging from storage of water and other macromolecules to the release of waste from a cell
Structure and Function: Chloroplasts
-found in eukaryotic cells such, as photosynthetic algae and plants
-double outer membrane
-specialized for capturing energy from the sun and producing sugar for the organism
2.2
Structure and Function: Chloroplasts
-specialized for photosynthesis and capturing energy from the sun to produce sugar
-within chloroplasts are distinct compartments:
Thylakoid
Highly folded membrane compartments that are organized in stacks called grana
membranes contain chlorophyll pigments that comprise the photosystems and electron transport proteins can be found between the photosystems, embedded in the thylakoid membrane
light-dependent reactions occur here
folding of these internal membranes increases the efficiency of these reactions
Stroma
Fluid between the inner chloroplast membrane and outside thylakoids
the carbon fixation (Calvin-Benson Cycle) reactions occur here
Structure and Function: Mitochondria
-double membrane provides compartments for different metabolic reactions
-mitochondira capture energy from macromolecules
-the krebs cycle (citric acid cycle) reactions occur in the matrix of the mitochondria
-electron transport and ATP synthesis occur in the inner mitochondrial membrane
-folding of the inner membrane increases the surface area, which allows for more ATP to be made
Structure and Function: Vacuoles
-vacuoles play a variety of roles, including storage and release of water, macromolecules, and cellular waste products
-in plants, vacuoles aid in retention of water for turgor pressure
-turgor pressure is an internal cellular force, usually caused by water pushing up against the plasma membrane and cell wall
Structure and Function: Lysosomes
-contain hydrolytic enzymes and can contribute to cell function in the following ways:
intracellular digestion
recycling of organic materials
programmed cell death (apoptosis)
Structure and Function: Endoplasmic Reticulum (ER)
-the ER performs the following functions for the cell:
provides mechanical support
plays a role in intracellular transport
rough ER carries out protein synthesis on ribosomes that are bound to its membrane
2.3
Cells are typically small
-moving materials (such as nutrients and waste) in and out of cells gets more difficult the larger a cell is
-formulas can be found on AP formula sheet
Ex:
surface area
s=0.5 cm
SA=6(0.5cm)²
SA=6(0.25cm²)
SA=1.5cm²
volume
V=s³
V=(0.5cm)³
V=0.125 cm³
SA/V=1.5/0.125=12/1
Effect of Surface Area-to-Volume Ratios on the Exchange of Materials
-smaller cells typically have a higher surface area-to-volume ratio and more efficient exchange of materials with the environment
-as cells increase in volume, the relative surface area decreases making it difficult for larger cells to meet the demand for internal resources and remove waste sufficiently
-these limitations can restrict cell size and shape
-the surface area of the plasma membrane must be large enough to adequately exchange materials
-smaller cells typically have a higher surface area-to-volume ratio and more efficient exchange of materials with the environment
-as cells increase in volume, the relative surface area decreases and the demand for internal resources increases
-more complex structures are necessary to adequately exchange materials with the environment
Use of Specialized Structures and Strategies
-membrane folding increases surface area
-root hairs on the surface of plant roots increase the surface area of the root allowing for increased absorption of water and nutrients
-the outer lining of the small intestine is highly folding containting finger-like projections called villi
-the surface of each villi has additional microscopic projections called microvilli which further increase the surface area available for absorption of nutrients
-if conditions arise that lead to the loss of this folding, these cells would not be as efficient in absorbing nutrients for the organism
-as organisms increase in size, their surface area-to-volume ratio decreases, affecting properties like rate of heat exchange with the environment
-in figure 1: elephant, flattened shape of ear allows the elephant to dissipate more thermal energy as blood flows closer to the surface
-organisms have evolved highly efficient strategies to obtain nutrients and eliminate wastes
-cells and organisms use specialized exchange surfaces, such as stomatal openings of leaves, to obtain molecules from and release molecules into the surrounding environment
-when stomata are open, CO2 can enter the leaf and O2 and H2O can be released into the atmosphere
2.4
Cells have membranes that allow them to establish an internal environment
-cell membranes provide a boundary between the interior of the cell and the outside environment
-cell membranes control the transport of materials in and out of the cell
Phospholipids have both hydrophilic and hydrophobic regions
- phospholipids are amphipathic
hydropilic phosphate head is polar
hydrophobic fatty acid tail is non polar
-phospholipids spontaneously form a bi-layer in an aqueous environment
tails are located inside the bilayer
heads are exposed to the aqueous outside and aqueous inside environments
Embedded proteins can be hydrophilic or hydrophobic
-peripheral proteins
loosely bound to the surface of the membrane
hydrophilic with charged and polar side groups
-integral proteins
span the membrane
hydrophilic with charged and polar side groups
hydrophobic with nonpolar side groups penetrate hydrophobic interior of bilayer
Embedded proteins play various roles in maintaining the internal environment of the cell
-membrane protein functions
transport
cell-cell recognition
enzymatic activity
signal transduction
intercellular joining
attachment for extracellular matrix or cytoskeleton
The framework of the cell membranes is decribed as the fluid mosaic model
-structured as a mosaic of protein molecules in a fluid bilayer of phospholipids
-the structure is not static and is held together primarily by hydrophobic interactions which are weaker than covalent bonds
-most lipids and some proteins can shift and flow along the surface of the membrane or across the bilayer
Fluid Mosaic Model components include steroids
-cholesterol, a type of steriod, is randomly distributed and wedged between phospholipids in the cell membrane of eukaryotic cells
-cholesterol regulates bilayer fluidity under different environmental conditions
Fluid Mosaic Model components include carbohydrates
-diversity and location of the (molecules) carbohydrates and lipids enable them to function as markers
glycoproteins - one or more carbohydrate attached to a membrane protein
glycolipids - lipid with one or more carbohydrate attached
2.5
The structures of the cell membrane
-Phospholipids are amphipathic
hydrophilic phosphate head is polar
hydrophobic fatty acid tail is nonpolar
-phospholipids spontaneously form a bi-layer in an aqueous environment
-fluid mosaic model - a moving phospholipid bilayer composed of varying types of molecules (proteins, steriods, carbohydrates)
-selective permeability is a direct consequence of membrane structure
The cell membrane is selectively permeable
-small nonpolar molecules pass
N2
O2
CO2
-hydrophilic substances such as large polar molecules and ions can NOT freely move across the membrane
-hydrophilic substances move through transport proteins
channel proteins - a hydrophilic tunnel spanning the membrane that allow specific target molecules to pass through
carrier proteins- spans the membrane and change shape to move a target molecule from one side of the membrane to the other
-small polar molecules, like H2O, can pass directly through the membrane in minimal amounts
The cell wall is a structureal boundary and permeable barrier
-as a structural boundary:
protects and maintains the shape of the cell
prevents against cellular rupture when internal water pressure is high
helps plants stand up against the force of gravity
-as a permable barrier:
plasmodesmata - small holes between plant cells that allows the transfer of nutrients, waste, and ions
Cell walls are composed of complex carbohydrates
-cell wall - comprised of complex carbohydrates
plants - cellulose
polysaccharide
fungi - chitin
polysaccharide
prokaryotes - peptidoglycan
polymer consisting of sugar and amino acids
2.6
Selectively permable membranes allow for the formation of concentration gradients
-concentration gradient
a concentration gradient is when a solute is more concentrated in one area than another
a membrane seperates two different concentrations of molecules
Passive transport is the net movemeny of molecules from high to low concentration
-net movement of molecules from high concentration to low without metabolic energy, such as, ATP needed
-plays a primary role in the import of materials and the export of wastes
-diffusion - movement of molecules from high concentration to low concentration
small nonpolar molecules pass freely (N2, O2, CO2)
-facilitated diffusion - movement of molecules from high concentration to low concentration through transport proteins
allows for hydrophilic molecules and ions to pass through membranes
Active transport requires energy
-active transport requires the direct input of energy (such as ATP) to move molecules from regions of low concentration to regions of high concentration
Endocytosis requires energy to move large molecules into the cell
-in endocytosis, the cell uses energy to take in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane
phagocytosis - cell takes in large particles
pinocytosis - cell takes in extracellular fluid containing dissolved substances
receptor-mediated endocytosis - receptor proteins on the cell membrane are used to capture specific target molecules
Exocytosis requires energy to move large molecules out of the cell
-in exocytosis, internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell
proteins such as signaling proteins
hormones
waste
2.7
Membrane proteins are necessary for facilitated diffusion
-facilitated diffusion - movement of molecules from high concentration to low concentration through transport molecules
large and small polar molecules
large quantities of water can pass through aquaporins
charged ions, including Na+ and K+, require channel proteins
Active transport establishes and maintains concentration gradients
-active transport moves molecules and/or ions against their concentration gradient from low to high concentration
carrier proteins called pumps
requires metabolic energy (such as ATP)
establishes and maintains concentration gradients
Membrane protiens are necessary for active transport
-cotransport - secondary active transport that uses the energy from an electrochemical gradient to transport two different ions across the membrane through a protein
symport - two different ions are transported in the same direction
antiport - two different ions are transported in opposite directions
Membranes may become polarized by movement of ions
-the cell membrane allows for the formation of gradients
electrochemical gradient
type of concentration gradient
membrane potential - electrical potential difference (voltage) across a membrane
-membranes may become polarized by movement of ions across the membrane
The Na+/K+ ATPase contributes to membrane potential
-Na+/K+ ATPase (Na+/K+ pump) contributes to the maintenance of the membrane potential
3 Na+ pumped
2 K+ pumped
2.8
Water moves by osmosis
-osmosis is the diffusion of free water across a selectively permeable membrane
large quantities of water move via aquaporins
-osmolarity is the total solute concentration in a solution
water has high solvency abilities
solute is the substance being dissolved
solvent is a substance that dissolved a solute
solution is a uniformed mixture of one or more solutes dissolved in a solvent
(solvent + solute = solution)
Tonicity effects a cell's physiology
-tonicity is the measurement of the relative concentrations of solute between two solutions (inside and outside of the cell)
-internal cellular environments can be hypotonic, hypertonic, or isotonic to external environments
hypertonic
more solute and less solvent
isotonic
equal concentrations of solute and solvent
Hypotonic
less solute and more solvent
-water moves by osmosis into the area with higher solute concentration
water concentrations and solute concentrations are inversely related
water would diffuse out of a hypotonic environment to a hypertonic environment
solutes diffuse along their own concentration gradients, from the hypertonic environment into the hypotonic environment
-when a cell is in an isotonic environment, a dynamic equilibrium exists with equal amounts of water moving in and out of the cell at equal rates
no net movement of water takes place
Osmoregulatory mechanisms contribute to survival
-in plant cells, osmoregulation maintains water balance and allows control of internal solute composition/water potential
environmental hypertonicty
less cellular solute and more cellular water
plasmolysis
isotonic solution
equal solute and water
flaccid
environmental hypotonicity
more cellulaar solute and less cellular water
turgid
-the cell wall helps maintain homeostasis for the plant in environmental hypotonicity
osmotic pressure is high outside of the plant cell due to environmental hypotonicity
water flows into the plant vacuoles via osmosis causing the vacuoles to expand and press against the cell wall
the cell wall expands until it begins to exert pressure back on the cell, this presure is called turgor pressure
turgidity is the optimum state for plant cells
-in animal cells, osmoregulation maintains water balance and allows control of internal solute composition/water potential
environmental hypertonicity
less cellular solute and more cellular water
shriveled
isotonic solution
equal solute and water
normal
environmental hypotonicity
more cellular solute and less cellular water
lysed
A variety of processes allow for the movement of ion and other molecules across membranes
-a fresh water paramecium is a single celled organism
the environment is hypotonic to the paramecium
more cellular solute and less cellular water
water enters the cell via osmosis
the paramecium is in danger of cell lysis
excess water collects in the contractile vacuole and is pumped out
What would happen if the freshwater paramecium was placed in salt water?
Water would begin to diffuse out of the paramecium because the cell is now hypotonic to the saltwater environment and the contracile vacuole would not fill. The cell is at risk of shriveling.
The components of an effective graphs
Title
experiment details and what is being measured
labeled axes
independent variable
x-axis (horizontala axis)
dependent variable
y-axis (verticle axis)
Scaling- uniform intervals
scale is large enough to analyze data
scale numbers on the grid lines
identifiable lines or bars
legend or label each line or bar
trend line
line of best fit that shows the general pattern or overall direction of the data
Types of graphs
-Line graph
reveals trends or progress over time for multiple groups or treatments
tracks changes over time, concentrations, etc.
-X Y graph
scatterplot
to determine relationshipis between two different things
compare two variables that may or may not have a linear relationship
-Histogram
show how values in a data set are distributed across evenly spaced or equal intervals
explore the relationship between two or more variables
-Bar graph
compare multiple groups or treatments to each other
-Box and Whisker Plots
show the variability in a sample
ideal for comparing distributions in relation to the mean
-Dual Y
illustrate the relationship between two dependent variables
Water moves by osmosis
-water potential measures the tendency of water to move by osmosis
calculated from pressure potential and solute potential
-water moves from an area of high water potential to an area of low water potential
-the values of water potential can be positive, zero, or negative
-the more negative the water potential, the more likely water will move into the area
-water potential of pure water has value of zero (0) in an open container
Osmoregulation allows organisms to control their internal solute composition and water potential
-increasing the amount of solute in water will cause
an increase in solute potential
a decrease in water potential
-increasing water potential will cause
an increase in pressure potential
-decreasing pressure potential will cause
a dcrease in water potential
Solute potential of a solution
-in an open system, the pressure potential is zero, so water potential is equal to the solute potential
- -iCRT
i = ionization constant
sucrose = 1 and NaCl = 2
C = molar concentration
molarity (M) = moles of solute/volume of a solution
R = pressure constant
0.0831 L Bars/mol K
T = temperature in Kelvin
temperature in Celsius + 271 = kelvin
2.9
Passive transport is the net movement of molecules down their concentration gradient
-diffusion - movement of molecules from high concentration to low concentration
small nonpolar molecules pass freely (N2, O2, CO2) across a ccell membrane
small amounts of very small polar molecules, like water, can diffuse across a cell membrane
-facilitated diffusion - movement of molecules from high concentration to low concentration through transport proteins
large and small polar molecules
charged ions, including Na+ and K+, require channel proteins
Osmosis is the diffusion of water across a selectively permeable membrane
-large quantities of water move via aquaporins
-difference in relative solute concentrations can facilitate osmosis
Active transport is the movement of molecules against their concentration gradient
-active transport moves molecules and/or ions against their concentration gradient, from low to high concentration
protein pumps care carrier proteins used in active transport
requires metabolic energy (such as ATP)
establishes and maintains concentration gradients
Movement of large molecules into and out of cells requires energy
-in endocytosis, the cell uses energy to take in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane
the types of endocytosis are phagocytosis, pinocytosis, and receptor-mediated endocytosis
-in exocytosis, internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell
2.10
Compartmentalization in Eukaryotic Cells
-cells have a plasma membrane that allow them to establish and maintain internal environment that are different from their external environments
-eukaryotic cells have additional internal membranes and membrane-bound organelles that compartmentalize the cell
-cellular compartments allow for various metabolic processes and specific enzymatic reactions to occur simultaneously, increasing the efficiency of the cell
Cellular Compartments: Lysosomes
-membrane minimizes ceompeting interactions
-the hydrolytic enzymes of the lysosome function at an acidic environment
-by having this compartmentalization, the inside of the lysosome can maintain a more acidic pH and allow for efficient hydrolysis to occur, while the rest of the cytoplasm can remain a more neutral environment
Cellular Compartments: Mitochondria
-membrane folding maximizes surface area for metabolic reactions to occur
-electron transport and ATP synthesis occur in the inner mitochondrial membrane
-folding of the inner membrane increases the surface area, which allows for more ATP to be made
Cellular Compartments: Chloroplasts
-membrane folding maximizes surface area for metabolic reactions to occur
-the thylakoids are highly folded membrane compartments that increase the efficiency of the light dependent reactions
2.11
Comparison of Compartmentalization in Prokaryotic and Eukaryotic Cells
-both cell types have a plasma membrane that seperates their internal environment from their surrounding environment
-prokaryotic cells have an internal region, nucleoid region, that contains genetic material
-eukaryotic cells have additional internal membranes and membrane-bound organelles that compartmentalize the cell
genetic material is contained within a membrane-bound nucleus
The evolution of membrane-bound organelles
-the nucleus and other internal membranes (e.g. ER) are theorized to have formed from the infoldings of plasma membrane
-mitochondria evolved from previously free-living prokaryotic cells via endosymbiosis
a free-living aerobic prokaryote was engulfed by an anaerobic cell through endocytosis
the engulfed prokaryotic cell did not get digested by engulfing cell; this arrangement became mutually beneficial
over time, the engulfed cell lost some of its independent functionality and became the mitochondria of the eukaryotic cell
-chloroplast evolved from previously free-living prokaryotic cells via endosymbiosis
a free-living photosynthetic prokaryote was engulfed by another cell through endocytosis
the engulfed prokaryotic cell did not get digested by the engulfing cell; but rather each benefitted from the arrangement
over time, the engulfed cell lost some of its independent functionality and became the chloroplast of the eukaryotic cell
Relationship between the functions of endosymbiotic organelles and their ancestors
-both mitochondria and chloroplasts have double membranes, which function to regulate the passage of materials into and out of the cell and to maintain a stable internal environment
-like prokaryotic cells; mitochondria and chloroplasts
both have their own circular DNA encoding genetic information and can reproduce by a similar process used by prokaryotes
both contain their own ribosomes that synthesis proteins