Download Cycling of Matter in Living Systems

Cycling of Matter in Living Systems
Life from Life
- Spontaneous generation or abiogenesis –Aristotle living organisms arose spontaneously from nonliving
matter was believed for 2000 years.
- Francesco Redi (1626-1697) tested this theory with
experiments – disproved abiogenesis.
- With the discovery of microorganisms abiogenesis
was once again accepted.
- Louis Pasteur (1822-1895) developed a swan-neck
flask and through experiments disproved abiogenesis
once and for all (p.259)
- Biogenesis – the theory that living organisms could
only come from other living organisms - Rudolf
Virchow (1821-1902)
Abiotic – non-living
Biotic - living
Developing the Cell Theory
- Robert Hooke (1635-1703) looking at cork cells under
a microscope coined the term ‘cells’
- Antony van Leeuwenhoek (1632-1723) first person to
describe single celled organisms
- Theodor Schwann (1810-1882) studying animal cells
and Matthias Schleiden (1804-1881) studying plant
cells observed a nucleus in all cells
The Cell Theory
1. All organisms are composed of one or more cells
2. The cell is the smallest functional unit of life
3. All cells are produced from other cells
Assignment - Page 265 #1-6
(copy question or complete sentences)
Cells and Technology
- Simple microscopes used only one lens and were used
early in science
- Compound Light microscopes first designed by
Janssen (1580-1638) had two lens and can magnify to
2000x
- Electron Microscopes use a beam of electrons instead
of light and can magnify up to 1.2 million times
- Transmission Electron Microscope (TEM) gives a
two dimensional image
- Scanning Electron Microscope (SEM) sweeps a
beam of electrons over the surface to create a three
dimensional image
- Confocal Laser Scanning Microscope (CLSM) is
used on thicker specimens, a laser beam is used to
collect images on different planes and a computer puts
the images together
- Scanning Tunnelling Microscope (STM) has greater
magnifying power and is used to view things like
DNA
Assignment: Label the parts of a microscope (p. 508)
Lab – take 2 different slides and sketch the
samples on low, medium and high power.
A Molecular World
- the genetic information in a cell is contained in the
DNA molecules
- DNA subunits consist of 4 bases
o Adenine – A
o Cytosine – C
o Guanine – G
o Thymine – T
- The order of these bases are different in every gene
- Gene sequencing involves mapping the order of the
gene’s bases
- Human Genome Project (HGP) was an international
project to sequence all 30 000 to 40 000 human genes
- One of the ways researchers learn more about cancer
causing genes is to determine their sequences
Culturing Cells
- Cell culturing is a valuable technique in cancer and
cell research
- Isolated cells are placed in test tubes or petri dishes
and supplied with all the nutrients they need for
growth
- The generations of cells that result are called cell lines
- Stem cells are cells that can divide to produce all other
types of specialized cells.
- Most of the cells in a one-week-old embryo are stem
cells. Most adult stem cells are in bone marrow, where
new blood cells are produced
Assignment - Page 276 #1-5 (copy question or complete
sentences)
Finish p. 286 key terms and hand in.
Read pages 277 –281
*In your notes sketch the cell and label the parts of
the cell**
“BOTH ANIMAL and PLANT”
do:
p. 286 – key terms
p. 284 #1- 6
p. 285 (b, e, i, k)
Cell Structure
The 3 main parts of a cell are:
1. Cell membrane
2. Cytoplasm
3. Nucleus
Cell Membrane
- composed of a double layer of phospholipids –
bilayer (p. 293)
- proteins and other molecules are embedded between
and attached to the phospholipids
- the phospholipid has a head and a tail (p. 291)
- the top end is hydrophilic – ‘water-loving’
- the tail end is hydrophobic – ‘water-fearing’ (do not
dissolve readily in water)
- the two tail ends point to the middle – shielded from
the water
- the heads point toward the water
- the embedded proteins move substances across the
membrane and carry out chemical reactions
- some proteins may act as attachment sites for
messenger molecules like hormones.
- the molecules that make up membranes are thought to
be in constant motion – fluid-mosaic model
- Carbohydrates – sugars attached to the membrane’s
outer surface are involved with cell-to-cell
communication
- are thin flexible and semi-permeable
Assignment: p. 286 #1-12
(copy questions)
Transport Across Cell Membranes
Brownian motion
– particles are in constant motion
– the motion is random, in a straight line
Passive Transport
- Molecules move without using energy
- 3 types:
1. Diffusion – net movement of molecules from an
area of high concentration to an area of lower
concentration
o diffusion may occur across cell membranes
o ends when equilibrium occurs.
o occurs faster the higher the temperature
o always moves with the concentration gradient
(from high to low concentration), faster the greater
the difference in concentration
o oxygen and carbon dioxide easily diffuse through
cell membranes
2. Osmosis
- is the diffusion of water from a higher concentration to
a lower concentration through a cell membrane
o Hypotonic solutions lose water- they have more
water and less solute than surrounding solution
o Hyper tonic solutions gain water – they have less
water and more solute than the surrounding
solution
o Isotonic solutions are at equilibrium with their
surroundings
3. Facilitated Diffusion
o glucose, ions and other substances too big to
diffuse through the cell membrane must have a
way to get into the cells
o transport proteins are membrane proteins that
help move molecules across the membrane
o are highly specific – only recognize certain
molecules
o always occurs with the diffusion gradient
Active Transport
- requires energy
- may move molecules against the concentration
gradient
- moves larger molecules
Endocytosis (p. 304)
- process that moves substances into a cell that cannot
be moved by other methods
- the cell membrane folds in forming a pocket enclosing
the molecule
- this pinches off as a vacuole or vesicle
- phagocytosis – when cell ‘eat’ large particles, eg
amoeba eating or white blood cells engulfing bacteria
- pinocytosis –when cells ‘drink’ taking in droplets of
fluid
- membrane proteins assist in this process – receptormediated endocytosis – eg cholesterol
Exocytosis (p. 305)
- allows the materials stored in vesicles to exit the cell
- opposite to endocytosis
- very important to cells that specialize in the secretion
of cell products – hormones and enzymes
Assignment: p. 316 – key terms
Read pages 306 – 307
Questions pg 307 #1- 4 (copy question)
p. 316 – key terms
Plant Cells
- cells in the leaves of plants are designed to carry out
different functions
- The main purpose is photosynthesis –during which
energy from sunlight, carbon dioxide from the air and
water from the soil are combined to make glucose
- Glucose is important energy source for both plants and
animals
Cellular Organization
- Multicellular organisms have:
1. A larger size
2. A variety of specialized cells
3. An ability to thrive in a broader range of
environments
- all of these demand organization
- within a cell different functions are preformed by
organelles
- groups of specialized cells are called tissues
- groups of tissues that work together for one purpose
are called organs
- organs working together form organ systems and
many organ systems create an organism
Gas Exchange in Plants
- the stomata in surface cells of the leaves allow gas
exchange to occur
- carbon dioxide, oxygen and water move in and out by
diffusion
- these gases then circulate to other cells through the
spaces in the spongy layer
- in woody plants lens shaped openings perforate the
bark allowing direct gas exchange between the
environment and the living cells just under the bark
- during cellular respiration plant cells consume oxygen
and produce carbon dioxide and water
- during photosynthesis plants consume carbon dioxide
and water and produce oxygen as waste
Water Loss by Plants
- transpiration is the evaporation of water from the
leaves of plants
- water diffuses out of the stomata
- guard cells can change their shape to stop the loss of
water on hot days thus preventing the plants from
dying due to dehydration
- water moves in and out of the guard cells by osmosis
- when water moves in the cells swell due to increased
pressure – turgor pressure
- the swollen guard cells change shape opening the
stomata
- when water decreases in the guard cells the cells
deflate and the stomata closes
- stomata open during the day and close at night
- in desert plants the stomata only open at night
Water Transport in Plants
-
Vascular plants have a system of vessels that
transport water, minerals and sugars throughout the
plant.
Xylem and phloem are the specialized tissues that
make up the transport system
Xylem tissue transports water and minerals from the
soil to the leaves.
In mature plants most xylem cells are dead
They form hollow tubes consisting only of cell walls
The cells are connected end to end – xylem vessels
Phloem cells transport the sugars produced during
photosynthesis from the leaves to all parts of the plant
Phloem vessels are living cells.
Assignment: p. 330 #1 p. 340 #1 p. 350 – key terms
Water
- cohesion is the tendency for water molecules to stick
together
- this helps explain water moving upward in xylem
vessels
- adhesion is the tendency of water molecules to stick to
other surfaces – the clinging of xylem sap to the xylem
walls helps to prevent the sap from falling back down
to the roots
- root pressure is the turgor pressure inside the root
xylem
- this pressure only accounts the movement of water a
few meters up a plant
- transpiration from the leaves pulls the water up
Sugar
- sugars produced by photosynthesis provide energy for
the whole plant
- Phloem vessels transport the sugars throughout the
plant
Plant Control Systems
1. Phototropism
- the growth of a plant towards light is called
phototropism
- this maximizes the amount of light absorbed by plants
- more light more photosynthesis
- the chemicals found to cause plants to grow toward the
light are auxins produced in the growing tips of some
plants
2. Gravitropism
- is a plant’s growth response to the force of gravity
- plant stems grow away from the pull of gravity called
negative gravitropism.
- roots show positive gravitropism
3. Nastic Response
- response by plants to touch
Assignment: p. 348 #1 - 3
p. 349 (b, c, e, h, i, o)
p. 350 #1-3, 6 - 8 (copy questions)
Cell Size and Function
As an efficient, open system, the cell must be able to carry out
all of the life processes. To ensure access to oxygen and
nutrients, cells must minimize the distance over which
substances diffuse.
There is an upper limit on cell size. The relative magnitude
(size) of a cell’s surface area to its volume is called its
surface area-to-volume ratio.
A very large cell with a very low surface area-to-volume
ratio could either starve to death or be poisoned from the
build up of its waste – such a cell would not survive.
Thus, the higher the surface area-to-volume ratio, the more
transport is possible across the cell membrane.
Multi-cellular organisms (such as humans) have millions
of cells. These organisms grow by adding more cells
instead of simply growing larger cells (small cells are
more efficient).
Cell Life
1. Cell Growth
 90% of a cell’s life is spent growing
 growth phase is called interphase
 during growth the cell produces organelles and
cytoplasm
 rate of cell growth varies depending upon type
of cell
 Metabolism is the changing of food into usable
energy
 cells are constantly adjusting to changing
conditions in order to maintain a balance. This
is called homeostasis.
 cells in higher level organisms specialize to
perform one specific task (e.g. muscle cells)
2. Division of Cells – Mitosis
 10% of life is spent dividing
 as cells get larger, the surface area to volume
ratio becomes too large and cells have difficulty
feeding themselves
 Mitosis = division of the DNA
 two daughter (identical) cells are formed from
the mother cell
Mitosis or Cell Division
 There are 5 stages of the life of a cell
1. Interphase – cell grows
2. Prophase
 nuclear membrane disappears
 chromosomes condense and become
visible
3. Metaphase
 duplicated chromosomes line up on both
sides of the cell
4. Anaphase
 individual chromosomes move to each
end
5. Telophase
 the cell begins to divide
 nuclear membranes reforms around
chromosomes
 two identical daughter cells are produced
Assignment:
p. 356 #1-7, 9, 11, 14, 15, 17, 19, 20
Complete sentences or Copy question first.