Download cell: the basic unit of structure in living things

CELLS
cell:
the basic unit of structure in
living things
A IM I Wh at are ce lls?
The G reat Pyramids
Buildings are put together with bricks. Birds buil
d their nests
with grass and twigs. l verything is made
up of smaller
Parts. ... EVEN YOU
Livia; things are made up of small parts called cells
. The
cell is the basic unit of structure in all living thing
s. Because all
living things are made up of cells, cells are ofte
n called the
building blocks of life."
Some organisms, like bacteria, are made up of
only one
cell. Larger organisms have many more cells. A
person, for example, is made up of trillions of cells. Can you
imagine how
many cells a whale must have?
Cells come in many sizes. Most are microscopic
)my kruh
SKOP ikj. Some cells, however, can be seen easil
y. For example,
a chicken's egg is a single cell. Do you need a micr
oscope to see
a chicken's egg?
Cells also come in many shapes. For example,
a muscle
cell has a different shape than a nerve cell. Skin
cells have a
different shape than fat cells.
As you see, there are many differences amo
ng cells. But
cells also have many things in common. For
example, all cells
are made up of a living material called prot
oplasm (PRO tub
plaz urn). Protoplasm is mostly water. But prot
oplasm also contains dissolved salts and many organic (car
bon) compounds.
The term organic means "life.,,
A cell is a living thing. It carries out all the life
functions.
For example, a c ell takes in nutrients and
oxygen. It gives off
w,wros(e products. Cells use and relea
se energy.
takes
place inside a + Ol?. il nd, cells d1 s o
reproduce.
Culls are ra2aat"h' 1.11:8 of m any parts. UaCI
'l cel l part has a
special job to dJu. 111415s:' part : ork
together to keep the cell
Inoctioning
propi.-rly,
im, ycui will learn about sore of these
cell parts.
You w6'11 also learn how aniral al cells are
different from plant (oils.
show s seven cell part s . These parts are found
name of each cell part is listed below,
F igu
ell membrane
brand l
tai (S
(ELL %MF
tulr pl : r.tx'r:r
• rttu"Ieos (NEW klee trs)
in
almos t
every
K€xk.irr rxl cell. The
m t.cr .hckrt ;tia (rny tub KON dreg
rah)
n ribosomes (.Y )till soarnkr
endoplasm c reticulum (EN deli
plaz ra ik rill TIK yoo lu n)
• nuclear (NEW klee ar) membrane
Each cell part is described below the diagram. As you read each description,
n identify the cell part in the diagram, then
Figure A A typical animal cell.
CE I, IF:MBB RANF
A thin covering that surrounds the cell. The cell.
membrane a) protects the cell,
b) helps give the cell its shape,
c) allows materials to enter and
leave the cell, and
d) helps keep the cell material to gether.
NUCLEAR MFMBR A 1E
A thin covering that surrounds the nucleus. The nuclear
membrane controls the passage of materials into and out of
the nucleus. It also gives the nucleus its shape.
MI " ONDI UA
Mitr::hondria are rod- shaped. They are the "power houses"
of the cell. Mitochondria store and release the ener;yT the
cell needs to carry out the life functions.
ENDOPL%SM IC
I lgTICULi..;It
A network of channels. The endoplasmic reticulum is like a
series of "roadways." They are used for moving materials
within the cell.
RIBOSOMIES
Tiny grainlike structures. The ribosomes make and store
protein. Most ribosomes are found on the endoplasmic reticulum. Some, however, move freely within the cytoplasm.
Answer the following questions about cells.
8.
The parts of the cell that you have labeled are all made
up of
"living" material,
What is the living material of the cell called?
9.
Where do most of the life functions take place within a cell?
10. a)
b)
Does each part of the cell work alone?
Explain you answer.
WORD ABOUT PLANT CELLS
Plant cells and animal cells are similar. But they are not
exactly
the same.
Plant cells have two parts that animal cells do not have. These parts
are: a cell wall
and chloroplasts.
The d: eli w all surrou nds the cell membrane
of the pla:
c::c 11 wail i s ma de of ;an on iv .i ng Yraat erial
gives a plant
called ^.iAlulose. The cell
its
g
^+
f
stiffne ss.
It
helps
a
plant
to st.,ind
>C
erect.
-;laloroplasts are sprea d throughout the cytopl asr
ri of plant cells. The
cc,hloropfasts contain a green substance called chloro
phyll. G reen
plants need chlorophyll (along with carbon dioxide
and light energy) to make the ir own food. Ghloa•otahy
-il is found mostly in leaf
ells.
Substances must be able to get into and out of a cell
in order for the cell to do its
job. The passage of these materials takes place thruu
11 boss," controls the passage of these mater
membrane has tiny holes. Liquids carrying dissolved
substances pass
through these holes in it process called osmosis jahs
:' IOH sisJ. Osmosis i
"chaosr." It allows univ certain substances to move
into the ce ll. And only,
stances a stay move out of the cell. For example, dissolved
nutrients and oxygen can move
only into the cell. Dissolved wastes, such as carbon dioxi
de, can move only )tit of the
cell.
What might happen if the amounts of substances entering and leaving the cell were
not controlled? It depends.... The cell
might a) swell or
I.
shrink, or
c)
become poisoned.
Think about each of the following possibilities. Write
your
answer in the space provided.
What might happen if:
1.
too much liquid moved into a cell?
2.
too much liquid moved out of a cell?
3.
too little liquid moves into a cell?
too
4.
much liquid moves out of a cell?
5,
b)
too little waste moves out of a cell?
he letter of he correct Baas
What kin
liter
a)
llat
a ceii
cell needs
kinds
tit
i)Iat +-'r)+ils
E k(1d; tii
'...!'.ail
if
ai, O :!
F)ee(.ls
,v,as>te :m
i.ell,,
h)
.LS
C t
sidts
erect
sizeOsmosis
eater
cells
shape
nucleus
f(X)'d-IIIakijI8
chloroplasts
cell wall
life function
organn compoun d
protoplasm
. \
.ir o r
1. The "building blocks" of living things are
2.
Cells vary in
3.
A cell carries out every
4.
The living material of a cell is called
Pro
and
Moser,
and
Two cell parts that are found only i n plant cells are a
7. Chloroplasts are needed for
and
in plants.
8. The cell wall helps a plant stand
9. Substances move into and out of a cell through a proce
ss called
10. The passage of substances into and out of
a cell takes place through the
On a separate piece of paper, draw a plc
`rc>m rmemory. Be sure to include
an d labe
iY iYA,r
A C.n
• mitochondr
f
ear
is reticulun
rnembrai
WHAT 1S A CELL
cell:
the basic unit of structure in
living things
cell membrane: the thin outer
covering of a cell
nucleus: the part of a cell that controls the cell
nuclear membra ne: the thin outer
covering of the nucleus
cytoplasm :
the
jelly-like
sub-
stance inside a cell between the
nucleus f. rid the cell membrane
protoplasm:
a cell
the living material of
The invention of the microscope made many impo
rtant
scoveries possible. One of these discoveries was mad
e by the
ish scientist Robert Hooke in 1665. Hooke disc
overed that
iving things are made up of even smaller livin
g parts. He
called these living parts cells.
lying things are made up of cells. Some organism
s,
like large plants and animals, are made up of billions
of cells.
Others, like bacteria, are made up of only one cell.
Cells are living things. All of the life functions are carri
ed
out by every cell.
The cell itself is made up of smaller parts. These
parts
include the cell membrane [YMEM btane], the nucl
eus [Ni81V
klee us[, the nuclear [NEW flee ar] membrane, and
the cytoplasm [SY toh plat urn]. All of these parts are mad
e up of a
living substance called protoplasm [PRO tuh plat urn[
.
Plant and animal cells are not exactl alike. Plant
cells
have some parts that animal cells do not have. The
se parts are
the cell wall and the chloroplasts [KLOR uh plasts].
CELL MEMBRANE The cell membrane is like a thin
skin that
covers the cell. It protects the cell and gives it its
shape.
The cell membrane has tiny holes in it. Material
s enter
and leave the cell through these tiny holes.
NUCLEUS The nucleus is inside the cell. It cont
rols everything that happens in the cell. The nucleus is like
the
"boss" of the cell. The nucleus is usually near the cent
er
of a cell.
NUCLEAR MEMBRANE The nuclear membran
e surrounds
the nucleus. It controls the passage of materials
into and
out of the nucleus.
CYTOPLASM The cytoplasm is a jelly-like subs
tance located
between the nucleus and the cell membrane. It fills
most
of the inside of the cell. Like the cell membrane, the
cytoplasrn helps give a cell its shape. Most of the life
f lrnc-
tcjns take Place in the cytoplasm.
44
"D THE PARTS
The illustration on the right shows
an animal cell. Four parts of this animal
cell are shown . `rl ey are: the nucleus, the
cell membrane, the nuclear membrane,
and the cytoplasm.
Find each part of the cell in the picture. Write the nave of each part on the
correct line.
Are these parts also found in plant
cells?
PARTS OF AN ANIMAL CELL
WHAT Do Look at each picture. T hen answer the questions.
THE
PICTURES
SHOW?
The cell membrane has tiny holes in it.
Materials needed for the life functions enter
the cell through these holes; waste
materials leave.
1.
0 , .
oxygen and
digested food
What needed materials enter the cell
carbon
diox de
and
other
wastes
OUT
through the cell membrane?
t
2.
What waste materials leave the cell
o
cell membrane
through the cell membrane?
A bird's egg is made up of only one cell. A
bird's egg has a hard shell that covers the
cell membrane.
3.
Do you need a microscope to gee this
cell?
4,
What extra part does a bird's egg
hat most other cells do not
have?
PECtAL KIND
OF C
EIJ,
4S
ARE PLANT CELLS DII~ F EREN
N IMAL C
Plant cells and animal cells are not exactly alike. Plant c
ells have certain parts that
animal culls do not have. These parts include a cell wall
and c hioroplasts.
• The cell
the entire plant cell.
outside the cell riser
plant cell. It surrounds
The cell w all is made of a nonliving material called cellul
ose [S E LL yuh loasj. The
is more rigid (stiff) than the cell membrane. It gives a plant
cell its stiffness, It
-es
it its shape.
n Chloroplasts are found in the cytop
lasm of a plant cell. Chloroplasts contain a
green substance called chlorophyll {KLOR uh fillJ.
Chlorophyll is needed by green plants for food- making,
The food-making process
of green plants is called photosynthesis [fo tuh SIN
thuh sis . Most chlorophyll is found
in the leaf cells of green plants.
Plants can make their own food. Animals cannot. Anim
al cells do not contain
chlorophyll.
1.
Does photosynthesis take place in animals?
2.
Why?
MORE ABOUT PLANT CELLS
The picture on the right shows a plant
cell. The parts of the plant cell that are
shown in the picture are listed below.
cell membrane
nucleus
chloroplasts
x:ytoplasruu
f
1.
Find each part of the plant cell in the
picture. Write the name of the part on
the correct line in the picture. One of
the parts has been labeled for you.
'taw, answer the questions about plant cells
.
1. What is found inside of the chioroplasts?
2. '}Vhdt is this
al used for?
Answer the following c
and animal culls.
ahoc
1.
s I
.
2.
animt7aI
c cal
ls
do
not
have?
_ and
Wheat is the cell ",all mad
protoplasm, cellulose
3.
Is cellulose living material?
ties, 110
4.
What is the cell membrane made of?
5.
Is protoplasm living materi al?
6.
Where are the chloroplasts located?
protoplasm, c lluInse
yes, no
in the nucleus, in the cytoplasm
7.
Wha t substance is found inside the chloropl
asts?
protoplasm, chlorophyll
S.
What is the substance inside the chloroplasts
used
for?
food-making, excretion
9.
Can animals make their own food?
yes, no
10.
Match
W hy can' t animals make their own food?
the
two lists. Write the correct letter
on the line next to
each number.
chlcaroplasts and c ell
"v,all
i hoto.;v
ott(;leus, maclear mein
no, ('61 r^i ntnlrrane,
^
f
.l^^lli,.ltiflt
i'It I, 4(t'i t'.
a)
parts of all cells
h)
food-making process of plants
c)
found only in plant cells
d)
nnnlivin ,g material of the coil sill
e)
any living m aterial of the cell
:)1PLE TING Complete the sentences with the words below. Three words will
SENTENCES be used twice.
chlorophyll
living
chloroplasts
rnocleus
1.
cell membrane
cellulose
cytoplasm
waste products
The parts that all plant and animal cells have are the
the
2.
life functions
cell wall
nuclear membrane
the
, and the
A plant cell has two parts that animal cells do not have. They are the
and the
3.
Cells are
every cell.
4.
The
5.
Materials
things. All of the
are carried out in
is the control center of the cell.
needed
for
the
life
functions
enter
the
cell
throu
the
6.
leave the cell through the cell membrane.
7.
The cell wall of a plant cell is made of a nonliving substance called
8.
The special cell parts needed for food-making in plants are the
9.
Chloroplasts contain a green substance called
WORD Unscramble each of the following to forma word or term that you
SCRAMBLE have read in this aim. Write your word in the spaces below.
t,CoT`\lYc
_SA',fPLOTRO'
Look at each picture. Answer the questions next to each pictu
What holds up a person?
2.
3.
4.
What holds up a plant? --
What is taking place in this picture?
In what part of a plant is food made?
l'
1 'E' (? ( Write T on the line next to the number if the sentence is true.
Write F if the sentence is false.
ck has cells.
,Most of a cell is the nucleus.
ly the ruckus of it cell is protoplasm.
The cell membrane has holes,
Most cells sire microscopic in size.
t'huit
^_ il "3 , â t;!
c2
,3u mn it t Ods ir(.'
t
(:
it)
RE
ACC
IN(.
without looking back, try to draw a picture of an animal cell. Label the nucleus, the
nuclear membrane, the cell membrane, and the c°toplasm.
2.
Now try to draw a picture of a plant cell. Label the nucleus, the nuclear membrane,
the cell membrane, the cell wall, the cytoplasm, and the chloroplasts.
s.L'hat do you think would happen i f c vaste products could not leave a cell?
t:t