Module 6.1- The cell is the fundamental unit of life

• the cell is the smallest most basic unit of living organisms

  • the simplest structure that exists as an independent unit of life

• all living organisms are either unicellular or multicellular

  • Unicellular- single cell

  • Multicellular- more than one cell

• bacteria, yeasts, and algae are mostly unicellular

• plants and animals are multicellular, specialized for certain functions

• a cell can be of many different sizes

• Cell theory- similarity in the microscopic organization of all living organisms, all organisms are made up of cells, the cell is the fundamental unit of life, cells come from preexisting cells

  • unites all forms of life

• the fundamental unit of life=simplest entity we can define as living

  • reproduce

  • respond to environment

  • harness energy

  • evolve

• helps transfer understandings to larger forms

Module 6.2- All cells maintain homeostasis, store and transmit energy, and transfer energy

• all cells have a discrete boundary that separates the interior of the cell from its external boundary and maintains the inside in life compatible way

• all cells contain an information molecule that they can use and pass on

• all cells harness energy and material from the environment

The cell membrane and homeostasis

• Cell membrane- the boundary between the interior of the cell and the nonliving exterior

• all cells must continually acquire and exchange ions and building blocks to make macromolecules

• cells must also release waste out of their membrane

• inside of the cell doesn’t change much, the specific pH and salt concentration

  • needed for reactions, protein folding, and other functions

• Homeostasis- the active maintenance of stable internal conditions, maintained by the cell membrane

  • important for cells and organisms

  • temperature, heart rate, blood pressure, blood pH, and water content

  • active energy-using process

Information

• cells store, use, and transmit info which encodes and determines features

  • archived like a blueprint

• this DNA must quickly and accurately be copied to daughter cells in reproduction

• nucleotides are the core-directs protein form

• proteins make the cell's internal architecture, shape, ability to move, and chemical reactions

• DNA guides RNA synthesis and RNA directs protein synthesis

• Ribosomes- complex structure, the site where a protein is assembled, translates RNA, a small unit and a large unit, 3 types of ribosomal RNAs and 20-50 types of ribosomal proteins

• central dogma- the path from DNA to RNA to protein, the basic flow of info on all cells, a key concept of biology

• DNA is easily copied/ replicated which makes passing between cells and cells or organisms to offspring easier

Metabolism

• essential cell feature or transfer from the environment-from sum and chemical compounds

• Metabolism- the entire set of chemical reactions by which cells transfer energy from one form to another and build and breakdown molecules

• Adenosine triphosphate (ATP)- a chemical form that stores energy, enables cells to carry out functions

  • used for growing, division, and transfer of substances in and out of cells

• Catabolism- a set of chemical reactions that break molecules into smaller pieces

• Anabolism- a set of chemical reactions that build molecules from smaller units, require energy

• many metabolic reactions have been used for 1000s of years

Modules 6.3- The structure and function of cells are closely related

• there is a connection between structure and function on all biological levels

• all cells have specialized shapes for specialized functions

Modules 6.4- Prokaryotes and eukaryotes differ in their internal organization

• Nucleus- membrane-bound space that contains the genetic material of the cell

  • nuclear membrane- controls substance moving in and out of the nucleus

• Cytoplasm- the space outside of the nucleus

• Prokaryotic- cells without a nucleus

• Eukaryotic- cells within a nucleus

Prokaryotes

• the first cells

• most live as a single-celled organism

• Domain- groups of organisms. bacteria, eukarya, and archaea

• 2 prokaryote domains- small size, reproduce rapidly, obtain energy and nutrients

  • bacteria- can be good and bad

  • archaea- can tolerate environmental extremes

• usually, 1-2 macromolecules in diameter, help them absorb nutrients

• DNA held in the nucleoid

  • one circular DNA molecule arranged in loops

• plasma membrane surrounding the cell wall- helps keep its shape

• the bacteria cell wall is thick peptidoglycan or thin lipid layer

• some archeae and bacteria have flagella- structures of their surface to help them move

• Plasmids- small circular molecules of DNA, few genes, transformed through pili

  • extend from one cell to another when exchanging plasmids

  • hold info about environmental advantages because it can spread quickly

• more prokaryotes than eukaryotes

• bacteria and archaea differ in the cell wall, DNA RNA synthesis, and different eukaryote’s evolution

Eukaryotes

• evolved later than prokaryotes

• Eukarya- animals, plants, fungi, protists (single-celled microorganisms)

• defined by the presence of a nucleus, which houses most of the DNA

• DNA is a linear molecule rather than circular

• Nuclear membrane- allows for more complex regulation of gene expression

• can regulate DNA RNA and RNA protein synthesis

• Organelles- membrane-defined compartments, that divide cell contents

• Cytosol- jelly-like material outside of the nucleus and organelles

• eukaryotic ribosomes are longer than prokaryotes

• different of lipids in cell membranes between prokaryotic and eukaryotic

• eukaryotic have cilia

  • Cilia- a rodlike structure that extends from the cells

    • Nonmotile cilia- cilia that don’t move, sensor function

    • Motile cilia- cilia that move

Module 7- Subcellular compartments of Eukaryotes

Module 7.1- The endomembrane system compartmentalized the eukaryotic cell

• all cells…

  • have a membrane

  • use DNA and RNA

  • carry out metabolic reactions

• Eukaryotes have a nucleus and many membranes

  • the inside surface area is tenfold greater than a cell membrane

• Surface area- the total amount of area of the outer surface of an area

• internal membranes define the subcellular compartments/ organelles, each with a specific function and organization

The endomembrane system

• membranes are usually connected one way or another by membrane bridges or vesicles

• Vesicles- small membrane-enclosed sacs that transport substances within a cell or from the interior to the exterior of the cell, form a budding from an organelle

  • take a piece of the membrane and the internal contents of the organelle they derive from

  • fuse with another organelle or the cell membrane to reform a continuous membrane and unload their contents

• Endomembrane system- made up of interconnected membranes of the cell or connected by vesicles

  • cell membrane, nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles

• in plants, the endomembrane system is actually continuous between cells through intercellular connections

• most prokaryotic cells don't have extensive internal membranes, but some photosynthetic bacteria do

• the endomembrane system divides the cell interior into 2 parts- one inside the compartments defined by these membranes and one outside these compartments

  • separated inside of the membrane and cytosol

• Cytoskeleton- protects and gives structure to the cell

Nucleus

• the innermost organelle of the endomembrane

• protects the DNA

• Nuclear envelope- defines the boundary of the nucleus, 2 lipid bilayer membranes

• Nucleolus- makes mRNA and also holds ERNA and rRNA

• Nuclear pores- perforate the inner and outer nuclear envelope membranes

  • large protein complexes with an inner passageway that regulates which molecules move into and out of the nucleus

  • essential for communication between the nucleus and the rest of the cell

    • ex. proteins that decide gene expression

    • ex. info transfer in DNA depends on RNA movement through these pores

• Chromatin- DNA or cell information that is ready for use

• Chromosomes- DNA or information ready for transport around the cell

Endoplasmic reticulum

• Endoplasmic reticulum (ER)- an organelle that is involved in the production of proteins and lipids, bound with 1 membrane which is continuous with the nuclear membrane

  • produces many of the proteins and lipids used inside and outside the cell

    • transported by vesicles to the cell membrane, other organelles of the endomembrane system, or the cell exterior

• makes up much of the lipids for the membranes, also quite large in size

• made up of interconnected tubules and flattened sacs- the interior is called the lumen

• Lumen- the interior of the organelle or cell

• it has an extremely convoluted membrane

• Rough endoplasmic reticulum- studied with ribosomes, the site of RNA protein synthesis

• larger and more extensive ERs have larger amounts of proteins

• Enzymes- proteins that speed up rates of chemical reactions

• all cells have some ER to make transmembrane and organelle proteins

• Smooth endoplasmic reticulum- the site of fatty acid and phospholipid synthesis

  • predominates in cells specialized for the production of lipids- many synthesize steroid hormones

• SER contains enzymes that can help detoxify certain drugs and harmful products of metabolism

Golgi apparatus

• Golgi apparatus- modifies and sorts proteins and lipids produced by the ER, usually where vesicles go after the ER

  • part of the pathway of modification of proteins and lipids

• function- modifies proteins and lipids, sorting, adds carbohydrates to proteins and lipids

• Glycoproteins and glycolipids- sacs that make up the majority of the Golgi apparatus

• Antigens/ recognition factors- carbohydrates added to proteins and lipids, like a badge

• made up of cisternae sacs that are flattened, many vesicles

• vesicles move from the ER to the Golgi through cisternae then to the cell membrane or other organelles

• enzymes chemically modify proteins and lipids as they go through the Golgi

• predominantly glycosylation, sugars, linked to proteins and lipids, occurs first

  • sugar links completely change the protein and its function

• Golgi to ER transport happens when proteins are accidentally moved forward and need to move back

Lysosomes

• Lysosomes- specialized vesicles derived from the Golgi apparatus, degrade damaged and unneeded macromolecules

  • have a key role in intracellular digestion and recycling of organic compounds

  • involved in programmed cell death

• lysosomes contain a variety of enzymes that break down macromolecules like nucleic acids, lipids, and complete carbs

  • packaged in the Golgi apparatus

• Golgi sends macromolecules for dehydration to lysosomes via vesicles

• lysosome interior has a pH of 5 (acidic)

  • protects the outside proteins and organelles because they can’t act in that pH

• enzymes in lysosomes are synthesized by rough ER, sorted in the Golgi, and then packed into lysosomes

• proteins embedded in the protein membrane come from the Golgi

  • keep homeostasis and transport

Module 7.2- Mitochondria and chloroplasts harness energy for use by the cell

• mitochondria and chloroplasts aren’t part of the endomembrane system

  • harness energy for the rest of the cell

• mitochondria and chloroplasts can grow and multiply independently of the other organelles

  • have their own DNA separate from that of the rest of the cell

• scientists believe they came from bacteria

Mitochondria

• Mitochondria- organelles that harness energy from organic molecules like carbohydrates

• use chemical reactions to break down molecules like other organisms

  • energy is stored as adenosine triphosphate (ATP)

    • drives many chemical reactions- the universal energy currency of the cell

    • growth, division, and moving substances

• provide eukaryotic cells with most of their usable energy

• Cellular respiration- a series of chemical reactions in which organic molecules are broken down and the energy is stored as ATP

  • takes place in the mitochondria

• in cellular respiration, oxygen is consumed and carbon dioxide is released

• mitochondria are rodshaped with 2 membranes, outer and highly convoluted inner membrane

• Intermembrane space- space between the inner and outer membranes

• Mitochondria matrix- space enclosed by the inner membrane

• cellular respiration happens in steps rather than all at once, energy is therefore not all released at once

  • some steps occur in the cytosol, the mitochondrial matrix, and some along the inner mitochondrial membrane

    • the mitochondrial membrane step makes or releases the most ATP

    • increases surface area for the chemical matching that synthesizes

Chloroplasts

• mitochondria are present in almost all plant and animal cells

• plant cells and green algae also have chloroplasts

• Chloroplasts- organelles that capture sunlight energy to synthesize simple sugars

• Photosynthesis- the capture of sunlight to synthesize simple sugars

  • carbon dioxide is consumed and oxygen is released

• chloroplasts are enclosed by a double membrane consisting of an outer and inner membrane

• Thylakoid- inside of chloroplasts, look like flattened sacs, grouped into structures called grana

• Grana- in the thylakoid, connected to one another by membrane bridges so they enclose a single, interconnected, compartment

• photosynthesis has many steps in different locations

• in the thylakoid, the light from the sun is turned into chemical energy which occurs along the thylakoid membrane

• Chlorophyll- light-collecting pigment molecule in the thylakoid membrane, green in color

• the folds of the thylakoid add surface area which increases its function

Module 7.3- The cytoskeleton and cell wall help to maintain cell shape

• Cytoskeleton- a system of protein filaments, that provides internal support for cells and tracks within the cell for transport of vesicles and other organelles, determines the cell’s shape

  • allow some cells to change shape, move about, and transport substances within the cell

• some cells have a cell wall outside the cell membrane, which provides structure and support

Cytoskeleton

• all eukaryotic cells have at least 2 cytoskeletal elements- microtubules and microfilaments

  • long chains of polymers made up of protein subunits

  • allow cells to change shape, move about, and transport substances

• Microfilaments- present in various locations of cytoplasm, extensively branched just beneath the cell membrane

  • play an important role in maintaining cell shape

  • log bundles form a band that extends around the circumference of epithelial cells

• Microtubules- hollow tube-like structures, that help maintain cell shape and internal structure

  • in animal cells, they radiate outward from a microtubule organizing center to the cell periphery

  • helps cells withstand compression

  • many organelles tether to these to be guided to organelle arrangements

• some eukaryotic cells may have cytoskeletal proteins, in cytoplasts and mitochondria

Cell wall

• present in plants, algae, fungi, and bacteria

• maintains the cell shape and size, protection, and structure

• outside the cell membrane

• rigid and resists expansion

• Turgor pressure- the force exerted by water pressing against an object, a result of water moving into cells surrounded by a cell wall

  • provides structural support and protection for cells

• Vacuole- in plants and fungi cells, absorbs water and contributes to turgor pressure

  • why plants wilt

  • can store nutrients, ions, and water

  • why plant cells are usually larger

• the cell wall is made up of carbohydrates and proteins but its main component is polysaccharide cellulose

• much algae and plants have cellulose cell walls but some are silicon or calcium carbonate

• must fungi cell walls are chitin

• the bacteria cell wall is mostly peptidoglycan

• animal and plant cells have a cell membrane, mitochondria, an endomembrane system, and a cytoskeleton

• plant cells have chloroplasts, a cell wall, and vacuoles while animal cells don’t

Module 8- Cell and Organism Size

Module 8.1- Surface area increases more slowly than volume as an object gets larger

• Volume- the total amount of space an object occupies

• volume increases more quickly than the surface area

• Microplasma- a bacteria, the smallest free-living organism

• prokaryotic cells are usually smaller than eukaryotic

Surface area and volume

• volume and surface area can be found of any 3D object

• the surface area describes a flat 2D structure

• to find volume and surface area one must think of an organism as a geometric shape

• cube: volume- S^3, surface area- 6S^2

• Sphere: volume-4/3Pir^3, surface area- 4Pir^2

Surface area to volume ratio

• a later object has a larger volume-to-surface area ratio than a smaller object

Scaling

• the volume: the surface area is the reason things are a certain size

• Isometry- increase in size but shape overall kept

• Allometry- increase in size and change in shape, what happens in the bio world

• as 3D objects get bigger the shape does too, balancing the v:as ratio

• Ex. the increased folds in mitochondria can support a larger volume organism because it increases the surface area without increasing volume

Module 8.2- Diffusion limits the size of prokaryotes

• most bacteria are tiny, 20-300 nanometers in diameter

• bacteria are sphere, rod, or spiral-shaped

• have a larger surface area compared to the volume

  • allows them to take in nutrients and other things through their membranes

• Diffusion- the movement of molecules from areas of high to low concentration

• bacteria rely on diffusion to take in molecules and remove waste

• diffusion is fast over short distances yet incredibly slow and ineffective over long distances

  • why things with larger surface areas compared to volume can use rely on diffusion

• the biggest bacteria is 100,000,000x larger than the average bacteria and only works because its large vacuole takes up a large amount of space

Module 8.3- Cells and organisms have evolved in ways to circumvent the limits of diffusion

• eukaryotes are larger meaning they have a larger volume:surface area than prokaryotes

• internal membranes can be used by larger cells to combat higher v:as ratios

  • highly folded ER, Golgi, mitochondria, and thylakoid

Diffusion in multicellular organisms

• diffusion supplies key molecules for metabolism

  • constrains the size, shape, and function of cells and organisms

• humans and other animals have organs that provide a large amount of surface area for oxygen absorption

  • the human lungs have 600 million alreali which have a combined surface area of a tennis court

• a large surface area and thin walls allow diffusion in large cells

Bulk flow in multicellular organisms

• Bulk flow- the movement of a fluid driven by pressure differences

  • how oxygen flows to other parts of the body

• hemoglobin in red blood cells binds to oxygen, then are pumped around by the heart

• many invertebrate animals lack cell-defined blood vessels so they just pump into the body cavity

• bulk flow moves nutrients and hormones as well

• the diaphragm uses bulk flow to move air into the lungs

• vascular channels powered by evaporation allow bulk flow to move water and nutrients in large plants

• bulk flow allows plants and animals to have different shapes, sizes, and functions

Module 9- Cell Membranes

Module 9.1- cell membranes are composed of 2 layers of lipids

• cell membranes separate cells from their external environment and define compartments within eukaryotic cells

• lipids form a barrier in an aqueous or watery environment

• the cell membrane is a mix of components- lipids, proteins, and carbohydrates

  • keep the internal environment stable

  • movement of components in and out of the cell

• phospholipids are made up of a glycerol backbone attached to a phosphate group and 2 fatty acids

  • the head is hydrophilic and the tail is hydrophobic

  • nonpolar and don’t form hydrogen bonds with water

  • called amphipathic- having hydrophilic and hydrophobic regions

• phospholipids arrange themselves in structures for the heads and tails

  • caused by waters polarity

• phospholipid tails interact with other fatty acids

  • also caused by waters polarity

• different head shapes create different sized shapes

• lipid bilayer- formed by a less bulky head and 2 lipid-tailed phospholipids, chains come together with heads on the outside, form all cell membranes

• when phospholipids are put in water (pH 7) they form bilayers in a liposome shape

  • spherical structures with an inner and outer space, have a bet input of energy

    • self-healing

    • interacts with watery inside and outside

    • acts as a barrier to polar molecules

Module 9.2- Cell membranes are dynamic

• membranes are dynamic- lateral movement of lipids and other membrane components

  • help vesicles break off and are absorbed

  • allows shape change, movement, and engulfment of particles

• Van der Waals forces allow phospholipid tails to associate

  • weak, allowing for movement, can spin and move fat

• fatty acid tails are flexible and move, form, and reform

• the membrane is fluid, tail length influences fluidity

  • a longer tail makes the membrane less fluid

  • also influenced by the number of carbon-carbon bonds

    • more double bonds make it unsaturated making it less stable and more fluid

• cholesterol is amphipathic and participates in the membrane bilayer

  • at higher temperatures, the cholesterol membranes become more stable and less fluid

  • helps temperature not drastically change membrane fluidity (homeostasis)

• lipid rafts- lipids formed into defined patches

  • bilayers aren’t uniform and rather made up of different rafts

• lipid flip-flop- spontaneous transfer of lipid between bilayer layers, very rare

  • hydrophilic head would have to pass through the hydrophobic area

  • why different layers have different components

Module 9.3- Proteins and carbohydrates associate with cell membranes

• Membranes- phospholipids, cholesterol, proteins, and carbohydrates

• proteins make up to 50% of the mass of red blood cell membranes

• membrane protein functions: transport molecules, and pass electrons along the membrane in the process of harnessing energy for use by the cell

• transport proteins-more ions and molecules across the membrane

• receptor proteins- allowed the cell to receive signals from the environment

  • some act as enzymes and others help maintain structure and shape

• Integral membrane proteins- permanently associated with the cell membrane and can’t be removed without destroying the membrane

• Peripheral membrane proteins- temporarily associated with the membrane or integral membrane proteins through weak noncovalent bonds, easily separated

• Transmembrane proteins- the main type of integral membrane proteins, span the entire bilayer, have 2 hydrophilic regions on either end and a hydrophobic piece in the middle

  • the hydrophobic piece holds the proteins in place

  • act for the outer hydrophilic end to receive signals and send them through the hydrophobic piece

• peripheral membrane proteins can be associated with internal or external end

  • interact with polar heads of lipids or weak noncovalent interactions with integral membrane proteins

• peripheral membrane proteins are only transiently associated with the membranes and transmit signals from the environment

• peripheral membrane proteins help proteins cluster in lipid rafts

• proteins can freely move in the cell membrane

• carbohydrates are in the membrane too

• carbohydrates in the cell membrane are attached to other membrane components via covalent bonds

  • attach to lipids

• glycolipids- a carbohydrate covalently attached to a lipid

• glycoproteins- a carbohydrate covalently linked to a proteins

• glycolipids and glycoproteins are free to move around the membrane

• fluid mosaic model- inspired by lipids, proteins, and carbohydrates freely moving in the membrane, the lipid bilayer is a structure within which molecules have laterally (fluid) and is a mixture (mosaic of various components)

• what can pass in and out of a cell independent of what molecules make up the membranes (maintains homeostasis)

• Liposomes- formed when phospholipids are placed in water with a natural pH, form a spherical shape that resembles a cell

• Micelle- large headed single tailed lipids packed tightly together into a spherical shape

Module 10- Membrane transport

Module 10.1- Passive transport involves diffusion

• the cell membrane is selectively permeable to maintain homeostasis

  • due to lipids and embedded proteins

• polar, charged, and large molecules are generally unable to pass through the membrane on their own

• nonpolar, uncharged, and small molecules can pass through the membrane on their own

  • because of the nonpolar bilayer interior

• Proteins and many polysaccharides are too big to cross

• lipids and small gasses like oxygen and carbon dioxide can pass freely

• some small uncharged polar molecules can pass too, like water

• transport proteins move molecules like water, ions, and nutrients

Simple diffusion

• water at room temperature moves about 500m a second, with 5 trillion collisions per second

  • important for chemical reactions

• concentration gradient- areas of higher and lower concentrations of a substance

  • cause a net movement of molecules

• diffusion is the movement of a concentration gradient

• dynamic equilibrium- the movement of molecules in both directions when in an even concentration

• Passive transport- when molecules move across a membrane by diffusion

  • results in a difference in concentration

• simple diffusion- passive transport and moves directly through the membrane

• steroids, lipids, oxygen, carbon dioxide

• export waste and take in nutrients

Facilitated diffusion

• transport proteins are used in simple and passive transport to move molecules

• transport proteins span the cell membrane and provide a route for substances to enter and exit

• Facilitated diffusion- diffusion across a cell membrane through a transport protein

  • high to low concentration

• Channel proteins- a transport protein, provide an opening between the inside and outside of a cell through which certain molecules can pass through

  • depends on shape and charge

• some transport proteins are gated and respond to a chemical or electrical signal

• Carrier protein- binds to and then transports specific molecules across the cell membrane

  • either open to the inside or outside of the cell

• the shape of the carrier protein lets specific molecules through

• the number and type of transport proteins depend on the cell

• Aquaporins- allow water to enter or exit the cell by facilitated diffusion

• Gated channels

  • ligand-gated- open with signal proteins like hormones

  • Voltage-gated- open with an electrical charge like a nerve impulse

Module 10.2- Active transport requires energy

• Active transport- the movement of a substance against a concentration gradient, requires cellular energy

  • primarily active transport cells use ATP directly to move molecules

• Secondary active transport- cells use ATP indirectly to move molecules across the membrane

Primary active transport

• energy in primary active transport comes from the breakdown of adenosine triphosphate (ATP)

• transport proteins change their shapes and pump molecules against the concentration gradient

• Antiporters- move molecules against the gradient and across the membrane

• Symporters- move 2 molecules in our out of the cell

Secondary active transport

• the move of charged ions across the membrane, through transport proteins, builds a build-up of ions on one side of the membrane

  • causes a store of energy

  • can be used to move molecules from areas of low to high concentrations

• transport driven by built-up charges and not ATP is the main idea of secondary transport

• a pump generates a chemical gradient and the membrane acts as a dam to store energy

• an electrical gradient is caused by a more negative or positive molecule charge on one side

• Electrochemical gradient- a gradient with both chemical and charge components

• proteins move from areas of high to low concentrations causing a potential for other molecules to move against the gradient

Module 10.3- Endocytosis and exocytosis move large molecules into and out of a cell

• all transported molecules end up in the cytoplasm or outside of the cell

• some cells use vesicles to export or import molecules

  • usually come from the rough ER

• Vesicles- small spherical organelles that travel between the endomembrane system in eukaryotic cells

• vesicles bud off and fuse with other cells or organelles releasing their contents

• Exocytosis- vesicle fuses with the cell membrane and releases its contents into the extracellular space

  • depends on the fluidity and dynamic nature of a membrane

• exocytosis is used to remove cytoplasmic waste

  • the vesicle fuses with the cell membrane

• exocytosis is used to deliver proteins to the cell membrane

  • protein embedded in the membrane of the rough ER

  • carry any other of the membrane proteins and fuse with the next membrane

• Endocytosis- a vesicle buds off from the cell membrane toward the cell interior (invaginates) enclosing material from outside the cell and bringing it into the cell

• microorganisms and large particles can be ingested by other cells

  • can be transported to lysosomes for digestion

• endocytosis and exocytosis are ways to transport molecules without going through the membrane

  • only in eukaryotes

• Molecular motors- associated with the cytoskeleton and move vesicles in the cell

  • much faster than diffusion

• cytoskeleton helps move vesicles around the cell

Module 11- Water movement: osmosis, tonicity, and osmoregulation

Module 11.1- Osmosis governs the movement of water across the membranes

• Water balance- how much water is in a cell or organism, a form of homeostasis

• water levels determine concentrations of ions and solvents

• water determines the size and shape of a cell

• many biochemical processes need a specific water concentration

• water can move via diffusion

• water concentration often occurs because ions, amino acids, sugars, etc. are dissolved in water

• Solutes- dissolved in a substance

• Solvent- liquid a solvent is dissolved in

• Molarity- molar concentration, the concentration of a solute in a solution, MOL/L, M

• membranes sometimes split 2 liquids or solutions

• Permeable- freely allows water and solutes through

• Impermeable- blocks the diffusion of water and solutes

• Selectively permeable- lets some solutes and water molecules through but not all

• a high solute level means a low water concentration and a low solute concentration means a large water concentration

• Osmosis- the movement of water across areas of selectively permeable membranes in response to a difference in solute concentration

• if a membrane was permeable to the molecules then it would diffuse on its own, osmosis is needed when the membrane is impermeable to the solute

• when multiple solutes are present the direction depends on which side has a greater total number of solutes

Module 11.2- Water potential combines all of the factors that influence water movement

• the cell wall and gravity can exert pressure on water

• Water potential- all of the chemical and physical forces that affect the movement of water- osmosis, pressure, and gravity

  • helps us understand where water is moving

Osmotic pressures

• Osmotic pressure- the tendency of water to move from one solution to another with osmosis

• higher solute means a higher osmotic pressure

• osmotic pressure is the tendency for a solution to draw water in

• Hydrostatic pressure- the pressure gravity exerts on a solution

• when water stops moving the osmotic pressure and hydrostatic pressures are equal

• waters height and force are used to measure osmotic pressure

Tonicity

• Tonicity- describes osmotic pressure and direction of water movement

  • how strongly water is pulled into a solution compared to another

• higher tonicity has a higher solute concentration than another solution

• Hypotonic solution- a solution with a higher solute concentration than another solution

• Hypertonic solution- a solution with a lower solute concentration than another solution

• Isotonic solution- a solution was the same concentration as another solution

• animal cells try to keep intracellular and extracellular fluids isotonic

• some protists live in hypotonic environments and use contractile vacuoles to prevent exploding

• Contractile vacuoles- organelles that take up excess water from inside the cell and expel it into the external environment

Turgor pressure

• Turgor pressure- the force exerted by water pressing against an object, developed as a result of water moving by osmosis into cells with a cell wall

• the cell wall presses back on turgor pressure

• a high turgor pressure makes the cell expand and low turgor pressures make a cell wilt

Water potential

• water potential uses osmotic pressure, turgor pressure, and gravity to determine which way water will flow

• water moves from high water potential to low water potential

• Ψ- water potential symbol

• Ψp- pressure potential

• Ψs- solution potential, Ψs= -iCRT, becomes more negative with move solute, negative of the osmosis pressure

  • i- ionization constant, substances that don’t ionize in the water get a 1

  • C- solution concentration, molarity

  • R- pressure constant, 0.0831

  • T- the temperature in kelvin

• pure water at ground level has a Ψ of 0

• Ψ= Ψs+Ψp

• trees for example have lower water potential at the top and pull water up

Module 11.3- Osmoregulation is a form of homeostasis

• Osmoregulation- regulation of osmotic pressure inside cells and organisms

  • the regulation of water content, keeps the internal fluid in the right concentration

  • a form of homeostasis

Osmoconformers

• Osmoconformers- keep their internal fluid at the same osmotic pressure as the surrounding environment

  • don’t use very much energy to do this

• must adapt to the solute concentration of their external environment

  • usually like to stay in places with stable solute concentrations like seawater

• use energy to regulate the concentration of ions like sodium, potassium, and chloride and molecules like amino acids and glucose

  • have to pump potassium in and sodium out

• many sea invertebrates are osmoconformers and have high sodium and chloride concentrations

  • need to match the external environment

• some have high levels of urea

• Urea- a waste product of many animals’ protein metabolism

Osmoregulation

• Osmoregulators- water and electrolyte homeostasis by maintaining internal solute concentration different than the environment

• use energy to pump ions across cell membranes

• adapt to many different environments

• marine osmoregulators have lower inner electrolyte concentrations than seawater

• freshwater osmoregulators have higher electrolyte concentrations than the environment

Module 12- Origin of compartmentalization and the eukaryotic cells

Module 12.1- The organization of the eukaryotic cell helps obtain eukaryotic diversity

• cell similarities- a cell membrane, DNA, can harness energy from its environment, regulate substances through the membrane

• prokaryotes- small, with no nucleus, and no internal membrane system, harness carbon, and energy in many ways

• eukaryotes- larger, have a nucleus, and internal membranes, harness carbon and energy in limited ways

• eukaryotes are successful because they can form diverse shapes and sizes and multicellular structures

  • engulf other cells, large trees, complex humans

Dynamic cytoskeleton and membranes

• the cytoskeleton can be remodeled quickly which allows cell shape to change quickly

• dynamic cytoskeleton requires dynamic membranes to function during remodeling

• the endomembrane system can quickly change shape as well

• dynamic continuity- membranes are interchangeable via vesicles

• mitochondria and chloroplasts have more stable membranes

  • have membrane-embedded proteins that require a stable membrane

• the cytoskeleton and membrane allow for endocytosis

• Phagocytosis- a form of endocytosis, eukaryotes surround food particles and package them in vesicles

Energy metabolism

• passive and active transport are the only ways for prokaryotic cells to take in molecules

  • can metabolize the molecules in many ways to obtain carbon and energy

• eukaryotes are limited to what the organelles can do

• some vesicles fuse with lysosomes with enzymes which break down the particles

  • some are processed by the mitochondria

• multicellularity allows eukaryotes to feed on bacteria, other cells, large food, plants, and animals

  • began predation- increased the complexity of interactions among organisms

• flexible photosynthetic eukaryotic cells can interact with their environments much more than photosynthetic bacteria

• many plants have evolved multicellular bodies with many different cells- working together

  • can have leaves high in the sky

Module 12.2- Chloroplasts and mitochondria originated by endosymbiosis

• chloroplasts are in certain algae and plants

  • use energy from sunlight to build energy-rich carbohydrates

• mitochondria are in most eukaryotic cells and every multicellular eukaryote

  • the site of cellular respiration, harness energy stored in the carbohydrate and other organic molecules and transfer it to the form ATP

Chloroplasts and mitochondrial origins

• Symbiosis- the close association between two species

• Endosymbiosis- when one partner becomes permanently incorporated into their host

• mitochondria and chloroplasts are double membraned- one membrane of the original bacteria and the second being the membrane from the vesicle from the endocytosis cell

Other symbioses

• much of the evolution of eukaryotic cells came from formerly free-living organisms

  • symbiosis between bacteria and eukaryotic cells

• eukaryotes can live in different environments by using bacteria to carry out reactions they couldn’t on their own

Eukaryotic cell origins

• some think archeal cells first evolved into eukaryotic cells

  • had a nucleus, cytoskeleton, and an endomembrane system but only had a limited way of deriving energy from organic molecules

  • later engulfed a proteobacterium to gain a mitochondria

• some think an archeal cell engulfed a proteobacterium to gain mitochondria first