This document discusses the basic building blocks of matter. It explains that all matter is made up of tiny particles called atoms, which can combine to form molecules or elements. Atoms are the smallest particles that make up elements, which can further combine to form compounds or mixtures. The key difference between elements and compounds is that elements are made of only one type of atom, while compounds contain two or more different types of atoms bonded together.
For my students: this is a story of the beginning of the development of the atomic theory. Now, you are to first listen to the presentation. Your task will then to pick one of the four choices to complete:
1. Create a storybook complete with pictures that would compliment the presentation.
2. Create a diorama to tell a similar story
3. Make models of each stage of development.
4. Create a story for part 2 of the development of the atomic theory that will be coming up.
For my students: this is a story of the beginning of the development of the atomic theory. Now, you are to first listen to the presentation. Your task will then to pick one of the four choices to complete:
1. Create a storybook complete with pictures that would compliment the presentation.
2. Create a diorama to tell a similar story
3. Make models of each stage of development.
4. Create a story for part 2 of the development of the atomic theory that will be coming up.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
3. What is matter?
• Matter is everywhere in the
universe.
• Everything is made of matter.
• You are made out of matter.
• Matter is everything that
takes up space (volume) and
has mass.
• Matter has three states: solid,
liquid and gas.
• Organic matter are all solids,
liquids, and gases that
comprise of organisms, living
or dead.
• Inorganic matter are
comprised of materials in
non-living substances, such as
rocks.
4. OXYGEN FIRE SMOKE
A CELL A CLOUD A THUNDER
AIR BUBBLES A LIGHTING THE MOON
Which of the following items ARE NOT matter?
6. Breaking matter into the smallest parts.
• You can cut, break,
chop, smash anything
into tiny parts.
• You can break down any
living or nonliving thing
into small particles.
• Draw or represent the
smallest piece of
anything you might
imagine.
7. From tiny to a large piece of matter
• Isn’t it amazing to think
that everything is made
out of tiny particles.
• Let’s think this about
this size.
.
This size
is even
huge
compare
to an
atom. Dust grain under
a microscope
Electron microscope photograph
of clay - magnification 23,500
14. From an onion to a cell.
Nucleus of a cell
chromosomes
Atoms
15. You have watched and listened to some
facts related to the microscopic world
hidden in the huge universe.
Think about this:
What has been the most revealing idea
about this micro universe.
Write your insights.
16. We can see solids and liquids easily
because light reflects on their surface.
Watching gases is more difficult
because their particles are smaller and
are moving constantly.
17. When light reflects it bounces off.
Visible light is the light that
humans can see.
http://www.physics4kids.com/files/light_intro.html
Light cannot reflect on an atom
because it is so small.
Sunlight hits the Apple’s surface.
Light contains many wavelengths or colors.
All of the colors are absorbed except red which bounces.
Red is the visible light that gets to your eyes after bouncing from the tomato.
18. What are the parts of an atom?
Read the second
paragraph: parts of an
atom.
Think about it and draw a
picture to represent a
model illustrating its
parts.
An atom has two different regions –
the nucleus and the electron cloud.
The nucleus is located in the center
of the atom. It is composed of
protons and neutrons. A proton is a
particle that has positive charge. A
neutron is a particle that has no
charge.
The nucleus of an atom is
surrounded by the electron cloud.
This part of the atoms contains
electrons and a great deal of empty
space. Electrons are always moving
around the nucleus. An electron is a
particle that has a negative charge.
20. Watch these video clips to reinforce ideas.
Copy and paste in your browser
• https://www.youtube.com/wa
tch?v=lP57gEWcisY
• https://www.youtube.com/wa
tch?v=o-3I1JGW-Ck
• https://www.youtube.com/wa
tch?v=Nx90iE6wmig
• https://www.youtube.com/wa
tch?v=Vi91qyjuknM
Listening comprehension Exercise
Listen to the first video and
write three new facts or ideas.
21. Most things are made of more than
one kind of atom. For example, water
is made of two atoms of oxygen and
an atom of hydrogen.
H2O
22. Elements & compounds
Elements, are made up of
only one type of atom.
An element cannot be
separated into smaller
substances by chemical
means.
Elements are the purest
form matter.
23. Pure element
• A sample of an element
contains only one kind of
atom in the sample.
Suppose you had a lump
of copper in your hand.
The ONLY type of atom in
the lump is copper.
• In the lump there are
trillions and trillions and
trillions of copper atoms.
NOTHING else.
26. Pure compounds
• A compound is a substance
composed of two or more
different atoms chemically
bonded to one another.
• A compound can be broken
down by chemical means. It
might be broken down into
into its elements or a
combination of the two.
• The key distinction is that
compounds break down but
do not cause an element to
break down.
• Water is a typical example
of a compound. One
molecule of water is
composed of two hydrogen
atoms and one oxygen
atom, chemically bonded
together.
27. Pure substances
• Some people define a pure
substance to be a material
that consists of one type of
"building block" of matter. If
this definition is used, only
elements and compounds are
pure substances, while
mixtures are not considered to
be pure substances.
• Gold, silver and diamond are
examples of pure elements.
• Water, sugar, salt and baking
soda are pure substances
which are chemical
compounds.
28. Compounds
• Most elements can interact
with other elements to
form compounds.
• Compounds can have
different states of matter
like liquid, solid, gas.
• Most things in nature are
compounds.
• Hydrogen gas, for example,
burns in oxygen gas to form
water.
Sodium chloride NaCl
29. Listening comprehension exercise
• https://www.youtube.c
om/watch?v=AfXxZwNL
vPA
• https://www.youtube.c
om/watch?v=cV4jJZCIM
Po
• https://www.youtube.c
om/watch?v=vlSOESXQI
7o
• Listen to the first video
clip and write in your
science notebook three
new facts or ideas
about elements and
compounds.
33. Is it an element or a compound?
Look at the pictures and identify what are elements and
what are compounds.
Divide a page with a line in two sides.
On the left write elements and on the right write
compounds.
Then write each item in the corresponding side.
silver carbon dioxide aluminum sulfur
34. Elements in nature
• Less than 100 different
elements occurs
naturally on Earth.
• All matter found on
Earth and everything
that we have found in
the universe is made of
these elements.
35. Read the text again.
Look at the examples of a pure element (gold)
and a compound (propane)
What is the main difference between a pure
element and a compound?
