Download Bio Homeostasis, Cells, Transport 2009 Yingxin

Biology
term one
Tables
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Title
Independent variable in left column
Control values at beginning of table
Headings include units
Values to same level of significance
Summarize raw data, show any data transformations, descriptive statistics, results of statistical tests
Provide access to an accurate record of the data values
Graphs
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Title inclusive of units
Plot points accurately
Different things = different lines/symbols to distinguish
Label both axes with units
Independent: what you CHANGE (x axis)
Dependent: what you MEASURE (y axis)
Appropriate scale
Take up ¾ of graph paper
2cm indent (don’t start at edge!)
Present information in a way that makes trends/relationships in data apparent
Variables
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Independent: what you CHANGE (x axis)
Dependent: what you MEASURE (y axis)
Controlled: kept the same
Scale
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Magnification = Length of drawing = 10.0cm = x2
Length of actual
5.0cm
Homeostasis
Process of maintaining equilibrium in living organisms
Maintain conditions within the body, such as
o Constant body temperature
o Oxygen supply
o For body functions to occur, so that chemical processes can occur
 Breaking down
 Transportation
 Repairing
o Constant water balance
o Nutrient supply
o Control types of cells that move into our bodies
o Remove waste through kidneys, balance our blood concentration
o Hormones (growth, adrenaline, insulin, testosterone)
Boundaries; external,
internal environment
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Living organisms have boundaries to distinguish between the internal and external environments
External environments can cause changes in the internal environment of living organisms
Different organisms have different strategies for coping with external changes
Case studies
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Lungfish
o Bladder modified to a breathing chamber (lung) which has many folds to increase surface
area, take in as much oxygen from air as possible
o Burrows in the ground for shelter against external environment
o Less exposed to sun – less heat, less evaporation, more humidity
o Less fluctuation of heat
o Coats itself with a layer of mucus as an additional barrier (protection against dehydration)
o Swallows mud, which passes across gills, absorbing water
o Dormant state: reduces metabolic rate
Desert frog
o Burrows in the ground for protection against external environment
o Sheds many layers of skin
o Waterproof skin barrier
Thorny Devil
o Eats black ants for water
o Rough ridges on its skin
o Appear fierce and intimidating to ward off predators
o Capillary action
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Through blood vessels in skin
Channels water up to its mouth
Only water has necessary qualities for capillary action to take place
Regulation processes
Thermoregulation
o Process of temperature regulation within living systems
o So that enzyme activity can be at its optimum
Osmoregulation
o Process of keeping a constant amount of water and salts in the blood
o Need to replace water lost (through respiration, perspiration, excretion) because cells cannot function
without water
o Too much water though = water moves into cell by osmosis, cells may swell and burst
o Balance must be maintained
Temperature regulation
Endothermic
o Organisms whose body temperatures are kept relatively constant despite wide fluctuations in
environmental temperatures (warm-blooded)
o Consists of birds and mammals
o Constant body temp: can remain active in varying environment temp= greater range of habitats on
earth
o To maintain constant body temp, they must eat a lot to obtain energy required
Ectothermic
o Organisms whose body temperatures vary with environment temp
o Activities of ectoderms affected by environmental temp
o Enviro temp increase, more active. Enviro temp decrease, more sluggish and lethargic
o Restricted in habitat they can occupy
cells
Eukaryotic cells (plant and animal)
10 – 100 micrometers diameter
Prokaryotic cells
2 – 10 micrometers length, 0.2 – 2 micrometers diameter
Viruses
0.02 – 0.25 micrometers
Unit
1 meter (m)
1 millimeter (mm)
1 micrometer ( m)
1 nanometer (nm)
Equivalent
1000 mm
1000 m
1000 nm
1000 pedometers
Cell organelles
Cell membrane
o Contains cytoplasm and all the organelles
o Regulates passage of molecules in and out of cell
o Maintains homeostasis
o Barrier between internal and external environments of cell
Nucleus
o Processes information
o Stores DNA
o Coordinates and controls cell’s activities (eg growth, intermediary metabolism, protein synthesis, cell
division)
o Contains nucleoplasm, surrounded by nuclear envelope
Nuclear Pore
o Hole in nuclear membrance, allows communication between nucleus and rest of cell
Nucleolus
o Ribosome synthesis
Nuclear Membrane
o Double-layered structure penetrated by nuclear pores
Mitochondria
o Respiration
o Breaks down carbohydrates and sugar molecules to provide energy
o Chemical energy to ATP
o Particularly when light isn’t available for chloroplasts to produce energy
o Double-membrane bounded
o Number in cell dependent on metabolic activity
Cilia
o Extensions to the external wall, on outside of cell
o Help bacterial cells to move
o Plant and animal cells: increase surface area without increasing size
Endoplasmic Reticulum
o Manufactures, processes and transports chemical compounds for use inside and outside of cell
o Connected to double-layered nuclear envelope, providing pipeline between nucleus and cytoplasm
o Smooth ER
o Lipid synthesis
o Carbohydrate metabolism
o Hormone synthesis
o Generates new layers of Golgi bodies
o Rough ER
o Ribosomes embedded in surface
o Protein synthesis
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Polypeptide chain grows from a bound ribosome, threaded through the ER membrane
into the cisternal space
Proteins destined for secretion leave ER wrapped in transport vesicles which bud off end
of ER
Vesicles received by GA
Golgi Apparatus
o Distributes and ships cell’s chemical products
o Stores, modifies and packages proteins and fats built in the ER
o Tags proteins so they go to correct destinations
o Produces secretory vesicles
o Connected with ER
o Exported through exocytosis
o Eg Nerve cells export neurotransmitters, endocrine glands export hormones, digestive glands export
enzymes
Ribosome
o 60% RNA, 40% Protein
o Protein synthesis
o May be free in cytoplasm or bound to ER
Protoplasm
o Everything except cell wall
Cytoplasm
o Watery solution in which organelles are suspended
o Containing dissolved substances, enzymes
Cytoskeleton
o Provides structure and shape to cell
o Responsible for cell movement (eg muscle contraction)
o Provides intracellular transport of organelles and other structures
Cell junctions
o At cell membrane surface, connecting adjacent cells
o Desmosomes fasten cells together
o Gap junctions act as communication channels between cells
o Tight junctions prevent leakage of extra-cellular fluid from layers of epithelial cells
Plant cells
Cell wall
o Prokaryotic cells (eg plant cells)
o Maintains firm shape of plant cell
o Protects and supports organelles
o Made of cellulose
o Limits volume, prevents excessive water uptake
Chloroplasts
o Converts light energy to chemical energy for photosynthesis
o Mainly occur in leaves
Vacuole (large, central)
o Stores compounds (food, water, waste)
o Contains cell sap, which contains dissolved substances such as sugars, mineral salts and amino acids
o Enclosed by tonoplast
o Helps in plant growth
o Plays an important structural role for plant, providing turgidity and firmness for plant
Starch granule
o Carbohydrates stored in amyloplasts
Peroxisome
o Single-membrane-bounded, most common microbody
Animal cells
Vacuoles (small, numerous)
o Storage of water, wastes, and soluble pigments
o *Contractile vacuole
Lysosome
o Sac bounded by a single membrane
o Pinched off from Golgi Apparatus
o Contain and transport enzymes that break down food and foreign matter (autolysis)
Centrioles
o Control movement of chromosomes during cell division
o Composed of microtubules
Bacterial cells prokaryotic
Bacilli: rod-shaped
Cocci: ball-shaped
Spirilla: spiral-shaped
Plasmids
o Small, circular DNA molecules
o Can move between cells by conjugation, explaining the transmission of antibiotic resistance between
bacteria
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Used as vectors in recombinant DNA technology
Fimbrae
o Hairlike structures that are shorter, straighter and thinner than flagella
o Used for attachment, not movement
o Involved in bacterial conjugation and as phage receptors
Flagellum
o Locomotion
Single, circular main chromosome
o Makes them haploid for most genes
Cell wall
o Gives cell shape
o Prevents rupture
o Anchorage point for flagella
o Contributes to virulence (disease-causing ability)
Cell membrane
o Similar to eukaryotic membranes, though less rigid
Glycocalyx
o Viscous, gelatinous layer outside cell wall
o Capsule / slime layer
o Contribute to virulence in pathogenic species (eg by protecting bacteria from host’s immune attack)
o Can allow attachment to substrates
Plant
Animal
Have nucleus containing DNA
Have vacuoles (large and small respectively)
Do not have fimbrae and flagellum
Have cell wall
No cell wall
No glycocalyx
Have chloroplasts
Bacteria
No defined nucleus
No vacuoles
Have fimbrae and flagellum
Have cell wall
Have glycocalyx
No chloroplasts
Cell membrane functions
Barrier between external and internal environments of cell
o Separates (protects) cells from outside environment
Separate reaction and chemical activities of the cell
Divide organelles into compartments (eg vesicles)
Entry/export of substances
o Selectively permeable, allowing only certain molecules and ions to enter/leave cell
o Essential for homeostasis
Transport processes
o Channel and carrier proteins involved in selective transport
Energy transfer
o Mitochondria
o Enzymes involved in cellular respiration arranged in different parts of mitochondria
o Various reactions are localized and separated
o Outer: Entry and exit of materials involved in aerobic respiration
o Inner: Attachment sites for enzyme activity
Isolation of enzymes
o Membrane-bound lysosomes contain enzymes for destruction of wastes and foreign material
Cell communication and recognition
o Proteins embedded in membrane act as receptor molecules for hormones and neurotransmitters
Containment of DNA
o Surrounds nucleus (nuclear membrane)
o Controls passage of genetic information to cytoplasm
o Protect DNA
Compartmentalizes
o Golgi Apparatus: stacks of membrane-bound sacs
o Compartmentalizes the modification, packaging and secretion of substances such as hormones
and proteins
Cell membrane fluid mosaic
model
Phospholipid bilayer
o Polar hydrophilic (attract water) head
o Two non-polar hydrophobic (repel water) tails – one saturated, one unsaturated
o One is a straight chain fatty acid (saturated)
o One has a kink in the tail because of a double bond (unsaturated)
 Influences packing and movement in the lateral plane of the membrane
 Allows for fluidity of membrane, so that lipids can move
 Prevents tight packing, makes bilayer difficult to freeze
o Stable arrangement (tails repel heads)
o Water is present on inside and outside of cell
o Non-polar regions face interior, where they are shielded from water
o Polar regions face outward, interact with water inside and outside of cell
o Individual molecules are free to move laterally
Cholesterol
o Same direction as phospholipid molecules
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Stabilize animal cell membranes
Prevent close packing
Flexible tail of cholesterol molecule allows more movement, making central part of bilayer most fluid
More cholesterol, more fluidity
Important role in MEMBRANE FLUIDITY AND STABILITY
Glycoprotein
o Proteins with attached carbohydrates
o Proteins produced by ribosome, then pass into interior of RER, carbohydrates added, forming
glycoproteins
o Type of integral protein
o Carbohydrates: different kinds of sugar linked together
o Carbohydrates act as markers that determine destination of glycoprotein within the cell/for export
o Carbohydrates position/orientate glycoproteins, prevent them from rotating in membrane
o Carbohydrates are important for intercellular recognition (to form tissues and detection of foreign
cells by immune system)
o CELLULAR RECOGNITION, IMMUNE RESPONSE, RECEPTORS for hormones and
neurotransmitters
o Together with glycolipids, stabilize membrane structure
Integral protein
o Completely/partially penetrate lipid bilayer
o Play a role in the selective transport of certain substances across phospholipid bilayer
(channels/active transport molecules)
o Receptors: bind information-providing molecules (eg hormones) and transmit corresponding signals
to interior
o Membrane proteins may also have enzymatic activity, catalyzing reactions
o Gateway proteins
o Cellular recognition
Peripheral protein
o Stuck to surface of membrane
o Via attachment to portions of integral membrane proteins jutting out of membrane interior
Lipoproteins
o Modified proteins
o Transport lipids in the plasma between various organs in body
Cell membrane fluidity
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Lipids in membrane are not fixed
Lipids can move in the membrane (semi-fluid nature)
Interior of membranes attached to cytoskeleton to give cell membrane FIRMNESS and SHAPE
Why must it be fluid?
o Frozen membrane cannot:
o Move
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o Carry out cytosis
o Heal small punctures
Allow interactions to take place easily among membrane components
o Enzymes: pass on series of reactions1
Allow newly synthesized protein to reach destination quickly
o Go out of cell through exocytosis
Membrane fusion and subsequent mixing of components allowed
o Lysosome (vesicle containing enzyme) + food vacuole – membranes fuse, enzymes can digest food
Enzyme distribution of components at cell division
o Splitting of cells
What allows it to be fluid?
o Phospholipid bilayer gives plasma membrane its fluidity
o Individual molecules are free to move laterally due to their one unsaturated tail, allowing lipids to
move and increasing fluidity
o Cholesterol helps stabilize animal cell membranes at different temperatures
o Depending on a number of factors (eg composition of bilayer, temperature), plasma membranes can
undergo phase transitions which render molecules less dynamic and more gel-like/nearly solid
o Cells can regulate the fluidity of their plasma membranes to meet their particular needs by
synthesizing more of certain types of molecules, such as those with specific kinds of bonds that keep
them fluid at lower temps
Active and Passive
transport
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Plasma membranes = selectively permeable
Boundaries for cell
Allow water, oxygen, food, minerals IN and carbon dioxide, nitrogenous wastes OUT
Active
Needs energy (ATP)
Against/up concentration gradient
Region of low conc to high conc
1. Ion pumps
2. Exocytosis
3. Endocytosis
Pinocytosis
Phagocytosis
Attributes/Comparisons
Energy expenditure
Direction
Types
Passive
No need energy (spontaneous)
Across/down concentration gradient
Region of high conc to low conc
1. Diffusion
2. Osmosis
3. Facilitated diffusion
Diffusion
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Spontaneous net movement of ions or molecules
From high conc to low conc (down concentration gradient)
Continue until both regions are of equal concentrations: equilibrium has been reached
May involve membrane or not
Examples
o Carbon dioxide in lungs diffuses through alveoli into bloodstream
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Gaseous exchange in gills
Movement of carbon dioxide during photosynthesis
Rate of diffusion
o Steeper conc gradient, faster
o Shorter distance, faster
o Larger area, faster
o Thinner barrier (or presence of pores), faster
o Higher temperature, faster
Surface Area: Volume Ratio
o Increase in size: Volume increases faster than area, hence SA: V ratio decreases
o Limited range of SA: V ratios which cells can survive at because nutrients cannot enter quickly enough
to support reactions needed for life
o Large cells can become very flat, or have irregular shaped protrusions
o Greater SA:V ratio, faster rate of diffusion
o Eg Small Intestines
With folds, SA: V ratio increases, so rate of absorption increases, increasing the efficiency of the
intestines as this is where nutrients and water from the food diffuses into the bloodstream
Facilitated Diffusion
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Facilitated by transport proteins (one-way)
Polar molecules and charged ions are dissolved in water
But cannot diffuse freely across membrane due to hydrophobic lipids
Water is repelled by the hydrophobic phosphate tails
Only small non-polar molecules like oxygen can easily diffuse across
Specialized integral proteins serve as transmembrane channels
Protein channels create pathway so that hydrophilic molecules and ions can pass through
Channel proteins
o Always “open” for simple diffusion across membrane
Ion channels
o Do not bind the solute
o Hydrophilic pores through membrane that open and allow certain types of molecules to pass through
o Specific for type of molecule they will transport
o Faster than carrier proteins
Carrier proteins
o Changes shape naturally when molecules come near
o Binds specific type of molecule, induced to undergo a series of conformational changes that has the
effect of carrying molecule to other side of membrane
o Carrier then discharges molecule, then reorients in membrane to original state
Osmosis
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Net movement of water molecules from a solution of higher water potential to that of lower water
potential through a selectively permeable membrane
Occur when they have different water potentials
Until both have even distribution of water molecules and equilibrium has been reached
Dilute
Low solute concentration
High water potential
High osmotic concentration
HYPOTONIC
Concentrated
High solute concentration
Low water potential
Low osmotic concentration
HYPERTONIC
isotonic
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Concentration of solutes outside cell = concentration of solutes inside
Isotonic drinks: Gatorade, H2O, 100 Plus
o Replenish salts we lose when we sweat
 Magnesium
 Sodium
 Potassium
 Chloride
Plant and Animal Cells
o Will still be movement of water
o Equal amounts of water moving in and out
o ZERO NET MOVEMENT of water molecules
Hypertonic
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Concentration of solutes outside cell > concentration of solutes inside
Water leaves cell – shrink
Eg concentrated salt solution
Plant cells
o Water moves out of plant cell
o Loses water, causing vacuole to decrease in size
o Becomes FLACCID (limp and soft)
o Cytoplasm shrinks away from cell wall (PLASMOLYSIS)
o Plant cell is plasmolysed
o Examples
 Young non-woody plants rely on turgor for support; without enough water they wilt. Plants take up
water through their root hair cells, by osmosis, and must actively pump ions into their cells to keep
them hypertonic compared to the soil. This is particularly difficult for plants rooted in saltwater.
 Cells in marine environments are surrounded by a hypertonic solution, and must actively pump ions
into their cells to reduce their water potential and so reduce water loss by osmosis.
Animal cells
o Loses water
o Membrane of cell forms little spikes and cell shrinks (CRENATION)
o Becomes dehydrated and will eventually die
o Animal cell crenates
Hypotonic
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Concentration of solutes outside cell < concentration of solutes inside
Water enters cell – swell
Eg most hypotonic substance: pure water
Plant cells
o Vacuole increases in size as water enters cell and pushes cell contents against cell wall
o Cell wall prevents over-expansion of cell by exerting an opposing pressure (TURGOR) and hence
prevents entry of more water
o Plant cell becomes TURGID
o Cell does not burst because cell wall is strong and slightly elastic
o Turgor
o Plays an important role in maintaining the shape of soft tissues in plants (eg leaves)
o Helps plant remain firm and erect
o High rate of evaporation of water from cells – cells lose turgidity, plant wilts
Animal cells
o Vacuole increases in size as water enters cell and pushes cell contents against cell membrane
o Cell will swell
o Animal cell may BURST, killing the cell!
o Too much water
o Cells will swell preventing more entry of water, and be too dilute. The salt concentration will
be too low, which may be harmful as salts are necessary for bodily functions
o Contractile vacuole
o Paramecium and other single-celled freshwater organisms are usually hypertonic relative to
their outside environment, hence water tends to enter cell, swelling and bursting it.
o Contractile vacuole excretes water by pumping water out of the cell
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Requires energy cause it is moving against concentration gradient
Water is collected into the central ring of the vacuole and actively transported from the cell
Animal Cell
Plant Cell
Carrier proteins - ion
pumps
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Transport proteins harness energy of ATP
Pump molecules from a low to high concentration
Carrier protein first binds to molecule
When ATP transfers a phosphate group to the carrier protein, protein changes its shape in such a way
as to move the bound molecule across the membrane
Sodium-potassium pump
o Sodium is maintained at low concentrations inside cell, Potassium at higher concentration
o Reverse is the case on the outside of the cell
o When a nerve message is propagated, the ions pass across the membrane, thus sending the message
o After the message has passed, the ions must be actively transported back to their “starting positions”
across the membrane
o Unequal balance of Sodium and Potassium across membrane creates large concentration gradient
that can be used to drive other active transport mechanisms
Proton pump
o Use ATP to remove hydrogen ions, moving them from inside to outside of cell
o Creates large difference in proton concentration (inside becomes negatively charged)
o Can be used to drive transport of other molecules
Coupled transport
o Plant cells use gradient in PROTON PUMPS (hydrogen ions) to drive active transport into plant cell
o Specific transport protein couples return of hydrogen ion to transport sucrose into phloem cells
o Sucrose rides with hydrogen ions as it diffuses down the concentration gradient
o Doesn’t really need ATP, since the concentration gradient is maintained by either sodium-potassium
pump or proton pump
ATP: Adenosine TRiPHOSPHATE
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Product of respiration
Energy is released when 1 phosphate molecule is lost, become adenosine diphosphate (ADP)
Exocytosis and endocytosis
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Form of active transport involving the in/out folding of plasma membrane
Results in bulk transport in/out of cell
Achieved through localized activity of microfilaments and microtubules in cytoskeleton
Very large molecules (eg bacteria)
Endocytosis (IN)
o Engulfment of material
o Typically in protozoans and certain white blood cells of mammalian defense system
o Fluid membrane encases substances coming into cell, forming vesicles that contain the substance
o Molecule causes cell membrane to bulge inwards, forming a vesicle
o Removes portions of cell membrane and takes them inside cell
o Phagocytosis (eating)
o Engulfment of solid material
o Results in formation of vacuoles
o Eg Amoeba: Pseudopodia engulf food particle, food vacuole is formed where membrane
pinches off after particle is engulfed
o Eg Paramecium: food vacuole develops at end of oral groove, pinched off to circulate within
cell
o Eg Phagocyte (white blood cell)
o Pinocytosis (drinking)
o Engulfment of liquids or fine suspensions
o Results in formation of pinocytic vesicles
o Receptor-mediated endocytosis occurs when material to be transported binds to certain specific
molecules in membrane (eg transport of insulin and cholesterol into animal cells)
Exocytosis (OUT)
o Golgi Apparatus packages substances that are to be secreted out of cell into vesicles
o Vesicle moves within cytoplasm to the plasma membrane
o Vesicle membrane and plasma membrane fuse
o Vesicle contents are released to outside of cell
o Typically in secretory cells
o Eg pancreas, upper small intestines, salivary glands
o Eg stomach cells: gastric glands
Pepsin is an enzyme that digests protein into polypeptins, then leaves cell through exocytosis