Download cells - Githens Jaguars

th
7
Grade Science
Unit 2NCFE Review
Cells
• The basic units of a
living system or
organism
2 Types of Cells:
•  Prokaryotic - Cells that don’t
have a membrane-covered nucleus
for example: bacteria
•  Eukaryotic – Cells with a nucleus
covered by a membrane for
example: plant and animal cells
How do we know cells exist?
•  Invention of the microscope made it
possible for people to discover and learn
about cells
•  Robert Hooke looked at cork cells
• 
Anton van Leuenhock used a simple
microscope and was the first person to
see microorganisms.
Anton van Leeuwenhoek
• First
compound
light
microscope
Cell Theory –
•  developed by 3 German
scientists:
•  Matthias Schleiden,
•  Theodor Schwann,
•  and Rudolf Virchow
These scientists discoveries led to
the cell theory…
What is the CELL THEORY???
Theory that states…
1.  All organisms are made of one or
more cells.
2.  The cell is the basic unit of life
which can perform life processes.
3.  All cells come from other living
cells.
Cells
•  Smallest living unit
•  Most are microscopic
Characteristics of All Cells
• 
• 
• 
• 
A surrounding membrane
Protoplasm – cell contents in thick fluid
Organelles – structures for cell function
Control center with DNA
Organelles
• -Tiny cell structures that are
specialized parts of a cell
that have specific
functions – a cell “organ.”
Representative Animal Cell
Animal Cell
Representative Plant Cell
Plant Cell
CELL MEMBRANE
•  – “gate keeper”
•  outer boundary (or layer) of
the cell
•  controls the movement of
materials into and out of the
cell
CELL WALL
•  found in plant cells
•  tough rigid boundary – made
of cellulose
•  gives cells their shape (it also
provides protection, as well
as support)
CYTOPLASM
•  – “cell fluid”
•  a gel-like material inside the
cell
•  Many cellular activities occur
here and where the organelles
are contained
NUCLEUS
– “brain
of the cell”
•  controls cell processes
•  Contains DNA or chromosomes
- the heredity material or
genetic blueprint of the cell
NUCLEAR MEMBRANE
•  – materials pass in and out
through tiny holes called
porins
NUCLEOLUS
•  – ribosomes are made here
Cell Structures and Functions
Chloroplast
Traps suns energy
and Makes food
Location: in plant
cells
Cell Parts and Functions
Mitochondria
Makes energy/
powerhouse
Location: in
cytoplasm
RIBOSOMES
•  – “protein factories”
•  place where protein is made in
the cells
•  some are attached –
some float in the
cytoplasm
ENDOPLASMIC RETICULUM
•  – “conveyer belt”
•  transports synthesized proteins
throughout the cell
GOLGI BODIES (Also called the
Golgi Apparatus)
•  sort, modify, process, and ship
the proteins through the cell
•  (Also known
As GOLGI
Apparatus)
VACUOLES
“storage”
•  store water, sugar, salts,
nutrients, & wastes in cells
•  maintains the proper pressure
to provide structure
and support in
plant cells
•  –
LYSOSOMES
•  contain chemicals that break
down waste materials.
What is cellular respiration?
ð The process by which cells break
down simple food molecules (glucose)
to release energy.
Glucose
What is selectively permeable?
¤ A property of cell membranes to
allow some substances through,
while other cannot
A spaghetti strainer
allows water to pass
through but does
not allow spaghetti
to pass
What two ways do materials enter
the cell?
¤ Passive Transport
¤ Active Transport
Entering through the Cell Membrane
Passive
Transport
Diffusion/
Osmosis
Active
Transport
What is passive transport?
¤ The movement of materials through
the cell membrane without using
energy
¤ Diffusion and Osmosis
What is diffusion? NO ENERGY!
¤ The process by which molecules tend
to move from an area of high
concentration to an area of low
concentration.
diffusion
What is active transport?
¤ The movement of materials through a
cell membrane using energy
¤ Uses energy to move molecules from
an area of low concentration to an
area of high concentration.
ENERGY!
Unicellular organisms
•  Some organisms only consist of a single
cell
•  But these do usually have the components
of cells (nucleus, membrane etc)
Image Credit Paramecium
Euglena
•  Environment: Ponds or puddles with rich
organic matter.
•  Movement: By flagella
– Flagellum: helps to move
– Chloroplast: helps with photosynthesis
•  Food: They make their own food or absorb
food from their environment.
Euglena
Amoeba
•  Environment: Mud at the bottom of
freshwater ponds.
•  Movement: They change shapes which
allows them to move (called shape
shifters).
Pseudopodium: what allows it to move
over mud (false foot)
•  Capturing Prey: They surround their prey
and engulf it.
Amoeba
Volvox
•  Environment: ponds, ditches, shallow
puddles
•  Movement: They beat cillia which allows it
to swim.
– Daughter colonies
– Cillia: helps to move
– Chloroplast: contains chlorophyll
•  Food: makes its own food by
photosynthesis.
Volvox
Paramecium
•  Environment: Fresh water or stagnant
water
•  Movement: Cilia bend and straighten
helping propel the paramecium through
water
– Cilia: hair-like projections that propel it
through water
•  Food: uses cilia to sweep the food into the
cell.
Paramecium
Where are my “genes”?
•  Your genes are inside all
•  the cells of your body.
•  Inside the nucleus of your
•  cells, are chromosomes.
•  Chromosomes are made
•  of tightly wound up DNA
•  (called chromatin).
•  The DNA code makes up
•  your genes.
Chromosomes?!?!
•  Chromosomes are tightly
wound-up “packages” of DNA.
•  Humans have 23 pairs of
chromosomes, 46 in all.
• (Sperm & Egg cells only
• have 23 single chromosomes!)
•  Each parent contributes one
chromosome to each pair, so you
get half your chromosomes from
your mom and half from your dad.
The Structure of DNA
• DNA looks like a long, twisted
ladder called a DOUBLE HELIX.
•  There are 2 long strands.
•  These are the sugarphosphate
•  “backbones” of DNA.
•  The “steps” of the ladder that
•  connect the strands are base•  pairs.
DNA
• DNA is located in the nucleus and controls all cell ac+vi+es including cell division
• Long and thread-­‐like DNA in a non-­‐dividing cell is called chroma+n
• Doubled, coiled, short DNA in a dividing cell is called chromosome Consists of 2 parts: chroma+d and centromere
Asexual vs. Sexual
Reproduction
47
Asexual Reproduction
•  Requires only one parent
•  Offspring have 100% the same
chromosomes as the parent.
–  In other words, the offspring are exact
“clones” of the parent.
–  Most unicellular organisms
reproduce this way.
–  Mitosis
48
Different Types of
Asexual Reproduction
•  Fission
•  Budding (Like when a plant has a new shoot that can
be cut off and planted, which becomes a new plant.)
•  Fragmentation (Like when an organism is cut in 2 and
becomes 2 different organisms)
•  Regeneration (Like when a starfish growing an arm
back)
Cell Division—Mitosis Notes
Cell Division — process by which a cell divides into 2 new cells • Why do cells need to divide? 1. Living things grow by producing more cells, NOT because each cell increases in size
2. Repair of damaged Hssue
3. If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell
• The original cell is called the parent cell; 2 new cells are called daughter cells
• Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of gene+c informa+on from parent cell
• Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell
2
Daughte
r Cells
Parent Cell
• Many organisms, especially unicellular organisms, reproduce by means of cell division – called asexual reproduc+on – Ex: bacteria
o 2 idenHcal “sister” chromaHds aVached at an area in the middle called a centromere o When cells divide, “sister” chroma+ds separate and 1 goes to each new cell
• ChromaHn to chromosomes illustraHon:
ChromaHn
Duplicates itself
Why does DNA need to change from chromaHn to chromosome?
Coils up into chromosomes
More efficient division
Cell Cycle -­‐-­‐ series of events cells go through as they grow and divide • Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again
• 4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT)
Prophase
Metaphase—(Middle)
Anaphase—(Apart)
Anaphase—(Apart)
Telophase—(Two)
Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) aZer the nucleus divides
In animal cells the cytoplasm
pinches in In plant cells a cell plate forms
• AZer mitosis and cytokinesis, the cell returns to Interphase to conHnue to grow and perform regular cell acHviHes
Phase
Interphase
Prophase
Chromosome Appearance & Loca+on
DNA copies itself;
chromatin
Chromosomes coil up
Important Events
DNA replication, cell
grows and replicates
organelles
Nuclear envelope
disappears, spindle
fibers form
Chromosomes line up in
the middle
Spindle fibers connect
to chromosomes
Anaphase
Chromosome copies
divide and move apart
Telophase
Chromosomes uncoil
back into chromatin
Cytokinesis
Chromati
n
Spindle fibers pull
chromosome copies
apart to opposite poles
Nuclear envelopes
reform, 2 new nuclei are
formed, spindle fibers
Division of the rest of
disappear
the cell: cytoplasm and
organelles
Metaphase