the study thread

[RandomGuy]

im gonna put all my notes on IA so we can all read together lol and also so i dont have to flip between .doc files. thank you for your patronage


Cell Structure and Function
Historical Overview
• Robert Hooke
– 1600s
– First to view plant cells

Historical Overview
• Matthias Schleiden and Theodor Schwann
– Mid 1800s
– All living things composed of cells

Historical Overview
• Rudolf Virchow
– Cells arise only from other cells
– Theory of spontaneous generation challenged
Cell Theory
• Every organism is composed of one or more cells

• The cell is the smallest unit having the properties of life

• The continuity of life arises directly from the growth and division of cells
Cell Size
Cell Shape
Prokaryotic Organisms
• Single cells
• No nucleus or organelles
• Smaller, less complex




Surface to Volume
Volume increases faster than surface area





Basic Features of All Cells
• Plasma membrane
• Nucleus (or nucleoid)
• Cytoplasm

Plasma Membrane
• Cell membrane

• Encloses the cell

• Mediates interactions between the cell and its environment
Nucleus (nucleoid)
• Nucle = pit or kernel

• Control center of the cell

• Houses DNA
Cytoplasm
• Cyto = cell
• Plasm = shaped, molded

• Between cell membrane and nucleus

• Major functional area

• Site where most cellular activities occur
Nucleus
• Control center
– Computer
– Design department
– Construction boss
– Board of directors
• Nuclear envelope
• Nucleoli
• DNA + Nucleoplasm
• Nucleolus is the site of ribosome assembly
Nuclear Envelope
• Double membrane barrier

• Each membrane is a phospholipid bilayer

• Fluid-filled space between each membrane (perinuclear cisterna)

• Fuse – nuclear pores
– Allows transport of large molecules

• The nuclear envelope allows selective exchange of materials

• Chromatin contains DNA, which codes for the synthesis of proteins





Cytoplasm
• Cytosol
• Organelles
• Inclusions
Cytosol
• Viscous (thick fluid)
– Mostly water
• Semitransparent
• Suspension
– Organelles
– Inclusions
– Soluble proteins
– Salts
– Sugars

Organelles
• Metabolic machinery

• Specific functions
Inclusions
• Chemical substances

• Varies between types of cells
Organelles
• Endoplasmic reticulum
– Smooth
– Rough
• Golgi Body
• Ribosomes
• Mitochondria
• Lysosomes
• Vacuoles

• Central Vacuole
• Chloroplasts
• Plastids









Cytoskeleton
• Unique to eukaryotic cells

• This structure acts as both muscle and skeleton, for movement and stability

• The long fibers of the cytoskeleton are polymers of subunits

Cytoskeletal Elements
Microtubules
• Largest elements
• Composed of tubulin
• Arise from microtubule organizing centers (MTOCs)
• Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to move on
• Microtubules also form the spindle fibers for separating chromosomes during mitosis
• When arranged in geometric patterns inside flagella and cilia, they are used for locomotion

Microfilaments
• Composed of actin
– Most abundant cell protein
• Microfilaments' association with the protein myosin is responsible for muscle contraction
• Microfilaments can also carry out cellular movements including gliding, contraction, and cytokinesis.

Intermediate Filaments
• Only in animal cells of certain tissues
• Most stable cytoskeletal elements
• Provide tensile strength for the cell

Motor Proteins
• Kinesin and Dynein move along microtubules
• Myosin move along microfilaments


Motor Proteins
• Kinesin and Dynein move along microtubules

• Myosin move along microfilaments

• http://www.sciencemag.org/feature/data/1049155.shl

Flagella and Cilia
• Structures for cell motility
• 9 + 2 internal structure


Pseudopods (False Feet)
• Temporary
• Irregular lobes
• Project from body
• Locomotion
• Catch prey
• Amoebas
• Macrophages





Cell Membrane Structure and Function
Plasma Membrane
• The plasma membrane isolates the cell while allowing communication with its surroundings

• Membranes are “fluid mosaics” in which proteins move within layers of lipids

• The phospholipid bilayer is the fluid portion of the membrane

Lipid Bilayer
• Main component of cell membranes
• Gives membrane its fluid properties
• Fatty acid tails sandwiched between hydrophilic heads

Phospholipids


Fluid Mosaic Model
• Membrane is a mosaic of
– Phospholipids
– Glycolipids
– Sterols
– Proteins
• Most phospholipids and some proteins can drift through membrane

Adhesion Proteins
• Help cells adhere (stick) to one another or to proteins

Communication Proteins
• Match up with identical proteins of an neighbor cell and form a channel

• Connects the cytoplasm of the two cells

• Chemical and electrical signals pass through these channels
Receptor Proteins
• Docking station for hormones or other signals

• The docking of hormones (or others) cause the cell to change its activities
Recognition Proteins
• Cell ID

• Identifies the cell as belonging to a body or tissue

• Or identifies the cell as foreign

• Movement across membranes occurs by both passive and active transport

• Molecules in fluids move in response to gradients


Passive Transporters

• Passive transport includes simple diffusion, facilitated diffusion, and osmosis
– Plasma membranes are selectively permeable to diffusion of molecules
– Some molecules move across membranes by simple diffusion

• Channels that allow specific solutes to move through without an energy cost

• Diffusion

• Concentration or electric gradients
Concentration Gradient
• Means the number of molecules or ions in one region is different than the number in another region

• In the absence of other forces, a substance moves from a region where it is more concentrated to one where it’s less concentrated - “down” gradient
Selective Permeability
Diffusion
• The net movement of like molecules or ions down a concentration gradient

• Although molecules collide randomly, the net movement is away from the place with the most collisions (down gradient)
Factors Affecting
Diffusion Rate
• Steepness of concentration gradient
– Steeper gradient, faster diffusion
• Molecular size
– Smaller molecules, faster diffusion
• Temperature
– Higher temperature, faster diffusion
• Electrical or pressure gradients











Osmosis
• Across a membrane
• Water molecules tend to diffuse down water concentration gradient
• Total number of molecules or ions dictates concentration of water
• Tonicity - relative solute concentrations
Tonicity


Fluid Pressure
• Hydrostatic pressure
– Fluids exert pressure to any contact surface
– When at rest (static) it acts with equal magnitude in all directions.
• Osmotic pressure
– Hydrostatic pressure produced by osmosis
• Turgor pressure
– Turgidity
– Positive internal pressure in a cell resulting from osmotic pressure

Active Transporters
• Pumps specific solutes across the membrane

• Works against a concentration gradient
• Uses energy
Transport Proteins
• Span the lipid bilayer
• Interior is able to open to both sides
• Change shape when they interact with solute
• Move water-soluble substances across a membrane




Membrane Cycling
Exocytosis and endocytosis continually replace and withdraw patches of plasma membrane
Passive and Active Transport
• Doesn’t require energy inputs
• Solutes diffuse through a channel inside the protein’s interior
• Net movement is down concentration gradient
Cell Junctions
• Communication centers
• Send and receive signals
• Send and receive materials
• Recognition of same cell type
• Join cell of same type

[RandomGuy]

theres the easy part, lets move to the hard(er) part

[RandomGuy]

The Continuity of Life: Cellular Reproduction

– In sexual reproduction
• Fertilization of sperm and egg produces offspring

– In asexual reproduction
• Offspring are produced by a single parent, without the participation of sperm and egg
Like begets like, more or less
• Some organisms reproduce asexually
• And their offspring are genetic copies of the parent and of each other

Other organisms reproduce sexually
• Creating a variety of offspring

Cells arise only from preexisting cells

– Cell division is at the heart of the reproduction of cells and organisms

• Because cells come only from preexisting cells
Division Mechanisms
Prokaryotic organisms
– Binary fission

Eukaryotic organisms
– Mitosis
– Meiosis

• Prokaryotes reproduce by binary fission
– Prokaryotic cells
• Reproduce asexually by cell division

– As the cell
replicates its
single chromosome,
the copies move apart
• And the growing
membrane then
divides the cells

The large, complex chromosomes of eukaryotes duplicate with each cell division

– A eukaryotic cell has many more genes than a prokaryotic cell

• And they are grouped into multiple chromosomes in the nucleus

– Individual chromosomes contain a very long DNA molecule associated with proteins
• And are visible only when the cell is in the
process of dividing
– If a cell is not undergoing division
• Chromosomes
occur in the
form of thin,
loosely packed
chromatin fibers

Before a cell starts dividing, the chromosomes
replicate
• Producing sister chromatids joined together at the centromere

– Cell division involves the separation of sister chromatids
• And results in two
daughter cells,
each containing
a complete and
identical set of
chromosomes

The cell cycle multiplies cells
– The cell cycle consists of two major phases

During interphase
• Chromosomes duplicate and cell parts are made

During the mitotic phase
• Duplicated chromosomes are evenly distributed into two daughter nuclei

The cell cycle multiplies cells
– The cell cycle consists of two major phases
Interphase – G1
• Interval (“Gap”) of cell growth


The cell cycle multiplies cells
– The cell cycle consists of two major phases
Interphase - S
• DNA replication (“Synthesis”)
• Chromosomes duplicated

The cell cycle multiplies cells
– The cell cycle consists of two major phases
Interphase – G2
• Second interval (“Gap”)
• Preparation for division
Control of the Cycle
• Once S begins, the cycle automatically runs through G2 and mitosis
• The cycle has a built-in molecular brake in G1
• Cancer involves a loss of control over the cycle, malfunction of the “brakes”
Stopping the Cycle
• Some cells normally stop in interphase
– Neurons in human brain
– Arrested cells do not divide
• Adverse conditions can stop cycle
– Nutrient-deprived amoebas get stuck in interphase

During interphase
• Chromosomes duplicate and cell parts are made

During the mitotic phase
• Duplicated chromosomes are evenly distributed into two daughter nuclei

The cell cycle multiplies cells
– The cell cycle consists of two major phases
Mitosis
• Period of nuclear division
• Usually followed by cytoplasmic division
– cytokinesis
• Four stages
Stages of Mitosis
Prophase
Metaphase
Anaphase
Telophase

PMAT
Early Prophase -
Mitosis Begins
Duplicated chromosomes begin to condense
Late Prophase
• New microtubules are assembled
• One centriole pair is moved toward opposite pole of spindle
• Nuclear envelope starts to break up
Transition to Metaphase
Metaphase
• All chromosomes are lined up at the spindle equator

• Chromosomes are maximally condensed
Anaphase
• Sister chromatids of each chromosome are pulled apart

• Once separated, each chromatid is a chromosome
The Spindle Apparatus
• Consists of two distinct sets of microtubules
– Each set extends from one of the cell poles
– Two sets overlap at spindle equator
• Moves chromosomes during mitosis
Spindle Apparatus

Telophase
• Chromosomes decondense

• Two nuclear membranes form, one around each set of unduplicated chromosomes
Cytoplasmic Division
• Usually occurs between late anaphase and end of telophase
• Two mechanisms
– Cell plate formation (plants)
– Cleavage (animals)

Cytokinesis differs for plant and animal cells
– In animals
• Cytokinesis occurs
by a constriction of
the cell (cleavage)
Animal Cell Division

– In plants
• A membranous cell
plate splits the cell
in two
Cell Plate Formation
Results of Mitosis
• Two daughter nuclei
• Each with same chromosome number as parent cell
• Chromosomes in unduplicated form



w00t w00t mitosis in the hizzouse

[bigdare23]

Fuck that shit {runs out of thread}

[Rican219]

Kill yourself that's the easy part

[RandomGuy]

The Continuity of Life: Cellular Reproduction


Review
• Binary fission
• Mitosis



– When the cell cycle operates normally, mitotic cell division functions in
• Growth

– Replacement of damaged or lost cells

– Asexual reproduction




MEIOSIS AND CROSSING OVER
• Chromosomes are matched in homologous pairs

– The somatic (body) cells of each species
• Contain a specific number of chromosomes
– For example human cells have 46
• Making up 23 pairs of homologous chromosomes


– The chromosomes of a homologous pair
• Carry genes for the same characteristics at the same place, or locus

• Gametes have a single set of chromosomes

– Cells with two sets of chromosomes
• Are said to be diploid
– Gametes, eggs and sperm, are haploid
• With a single set of chromosomes

– Sexual life cycles
• Involve the alternation of haploid and diploid stages

• Meiosis reduces the chromosome number from diploid to haploid

– Meiosis, like mitosis
• Is preceded by chromosome duplication
– But in meiosis
• The cell divides twice to form four daughter cells


– The first division, meiosis I
• Starts with synapsis, the pairing of homologous chromosomes
– In crossing over
• Homologous chromosomes exchange corresponding segments
– Meiosis I separates each homologous pair
• And produce two daughter cells, each with one set of chromosomes

– Meiosis II is essentially the same as mitosis
• The sister chromatids of each chromosome separate
• The result is a total of four haploid cells
Why Meiosis
• Conservation of chromosome number
• Random (independent) assortment
• Random selection (fertilization)
• Crossing over
– AKA Recombination
Conservation of Chromosomes
• Meiosis produces cells with half the parental number of chromosomes
• Humans = 46 chromosomes
• Egg or sperm = 23 chromosomes
Independent Assortment
• Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring

– Each chromosome of a homologous pair
• Differs at many points from the other member of the pair

– Random arrangements of chromosome pairs at metaphase I of meiosis
• Lead to many different combinations of chromosomes in eggs and sperm
Random (Independent) Assortment

– Random fertilization of eggs by sperm
• Greatly increases this variation
Crossing Over
• Increases genetic variability
– Genetic recombination
• Which results from
crossing over during
prophase I of meiosis,
increases variation
still further

– How crossing
over leads to
genetic variation
Crossing Over (Recombination)
Meiosis
Step by Step
Interphase
• Just like mitosis
• G1 – growth
• S – duplication of DNA
• G2 – Preparation for division
Meiosis
• Two-part process
– Meiosis I
– Meiosis II

Meiosis
• Two-part process
– Meiosis I
• Prophase I
• Metaphase I
• Anaphase I
• Telophase I

– Meiosis II
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II

Meiosis I – Prophase I
• Chromosomes condense
• Homologues pair up
• Crossing over (recombination)

Meiosis I – Metaphase I
• Homologous chromosomes at equator
• Spindle fibers attach to chromosomes

Meiosis I – Anaphase I
• The homologous chromosomes separate
Meiosis I – Telophase I
• Homologous chromosomes reach “poles”
• Nuclear envelope forms
Meiosis I - Result
• Two daughter cells
• Cells are haploid
• Chromosomes are duplicated
Meiosis II
• From here on out – phases are just like in mitosis
Meiosis II – Prophase II
Meiosis II – Metaphase II
Meiosis II – Anaphase II
Meiosis II – Telophase II
Meiosis II - Result
• Four daughter cells
• Cells are haploid
• Chromosomes are not duplicated
• Cells are all different

Animal Life Cycle

Plant Life Cycle
Fertilization
• Male and female gametes unite and nuclei fuse
• Fusion of two haploid nuclei produces diploid nucleus in the zygote
• Which two gametes unite is random
– Adds to variation among offspring
Factors Contributing to Variation among Offspring
• Crossing over during prophase I
• Random alignment of chromosomes at metaphase I
• Random combination of gametes at fertilization
Mitosis & Meiosis Compared
Mitosis
• Functions
– Asexual reproduction
– Growth, repair
• Occurs in somatic cells
• Produces clones


Meiosis
• Function
– Sexual reproduction

• Occurs in germ cells

• Produces variable offspring
Prophase vs. Prophase I
• Prophase (Mitosis)
– Homologous pairs do not interact with each other
• Prophase I (Meiosis)
– Homologous pairs become zippered together and crossing over occurs
Anaphase, Anaphase I, and Anaphase II
• Anaphase I (Meiosis)
– Homologous chromosomes separate from each other
• Anaphase/Anaphase II (Mitosis/Meiosis)
– Sister chromatids of a chromosome separate from each other
Results of Mitosis and Meiosis
• Mitosis
– Two diploid cells produced
– Each identical to parent
• Meiosis
– Four haploid cells produced
– Differ from parent and one another


sperm making time

[dodgekota]

[/thread failure]



-1 for you.

[RandomGuy]

[/thread failure]



-1 for you.

LoL LOOK AT MY REP AND LOOK AT YOURS

[bigdare23]

someone likes that print screen button LOL

[LiL PaKi]

BIOLOGY FTL! ...