unit 2: the dynamic cell, part i reading: - ahs-biology3+biology+h...unit 2: the dynamic cell, part...
TRANSCRIPT
Daley Biology H 2013-2014 Name:____________________________________ Block:_____________ Date:________________________ PACKET #3
Unit 2: The Dynamic Cell, Part I Reading: Chapter 6, 9.8, 9.9, 2.1 !Objectives: Upon completion of this unit, you should be able to: !Topic 1: Microscopy 1. Explain how light microscopes are used to study cells (6.1). 2. Explain (and demonstrate) how scientists measure the length of objects using a microscope. (In class) 3. Demonstrate the use of a microscope to study cells. (In class) 4. Compare electron (transmission, scanning) and scanning tunneling microscopes with the compound light
microscopes and other types of microscopy. !Topic 2: Cell Theory, Structure, and Function 5. State the two ideas that make up the cell theory (6.1). 6. Compare and contrast the following: prokaryotic vs. eukaryotic cells, plant vs. animal cells. Using either !
pictures or descriptions, be able to identify a cell as prokaryotic, plant, or animal. Identify cells as plant or animal, using pictures and slides. (In class, 6.2, 6.3)
7. Identify all cell organelles on a picture of a cell (6.4) 8. Describe the structure and function of each cell organelle (6.4). 9. Describe how the cytosol (cytoplasm) differs in prokaryotes and eukaryotes, and how the cytoskeleton helps organize the cell’s structure and activities. 10. Compare the structure and action of flagella and cilia in prokaryotes and eukaryotes. !Topic 3: Cellular Organization and Interactions 11. Describe and compare the different levels of organization and specialization that exist in unicellular,
colonial, and multicellular organisms. What are the advantages / disadvantages of each? type of organization?
12. Explain how a biofilm is different from a multicellular organism (6.5) 13. Explain how the extracellular matrix aids in interactions between cells (6.6). 14. Give three reasons why specialized systems are necessary in large multicellular organisms (6.7). 15. Explain why cells must be small by analyzing the relationship between surface area and volume in cells
(Lab). !Topic 4: Virology 16. Describe the structures that make up a viral particle (9.8). 17. Explain the relationship between viruses and host cells and describe the impact of viruses on living systems
(9.8 & 9.9) 18. Defend the statement: “Viruses are not alive” using the characteristics of life (2.1).
!1
Daley Biology H 2013-2014 !Key Terms
Microscope Light microscope Scanning electron microscope Transmission electron microscope Scanning tunneling microscope Magnification Resolution Field of view !Cell Theory Cell theory Surface to volume ratio !Cell structure and organelles and Cell types Cytoplasm Ribosome Eukaryote Nucleus Nucleolus Nuclear envelope Nuclear pore Chromatin Chromosome Organelle Vacuole Vesicle Golgi apparatus Lysosome Mitochondrion Endoplasmic reticulum (rough, smooth) Cell wall Chloroplast Central vacuole !!Cytoskeleton Microtubule Microfilament Cilia Flagellum Basal body Centriole Dyenin arms
Extracellular Matrix !!Virology Virus Host cell !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Cell junctions Plamodesmata Tight junction Anchoring junction Communicating junction
!2
Daley Biology H 2013-2014 !Activity A – Identify the pictures below and what kind of microscope took the picture.!!
� ! � !!What is it? _________________! ! What is it? _______________________!!What kind of microscope took it? ___ ! What kind of microscope took it? ______!!
� � "!What is it? _______________________! What is it? _________________________!!What kind of microscope took it? _____ ! What kind of microscope took it? ________!!
!3
Daley Biology H 2013-2014 Activity B – Identify the parts and functions of a typical bacterial (prokaryotic) cell.!!Objective 6: Using a picture of a prokaryotic cell, label each of the following: nucleoid, plasmid, cell wall, cell membrane, cytoplasm, free ribosomes, flagellum. Also, discuss the function of each part.!
!!
!
NAME FUNCTION
A
B
C
D
E
F
!4
AB
C
FIMBRIAE (like pili) are used to help bacteria attach itself to another cell – like a human cell (NOT used for movement)!
DCapsuleE
NO Nuclear membrane in a bacterial cell - no nucleus!
F
Daley Biology H 2013-2014
!5
8
Act
ivity
D:
How
do
prok
aryo
tic, a
nim
al, a
nd p
lant
cel
ls c
ompa
re?
O
bjec
tive
8: Com
pare
and
contrast t
he fo
llow
ing:
pro
kary
otic
vs.
euka
ryot
ic c
ells
, pla
nt v
s. an
imal
cel
ls.
Usi
ng e
ither
pic
ture
s or d
escr
iptio
ns,
be a
ble
to id
entif
y a
cell
as p
roka
ryot
ic, p
lant
, or a
nim
al (4
.3- 4
.15)
. Pl
ace
each
of t
he fo
llow
ing
into
the
Venn
Dia
gram
: cel
l mem
bran
e, c
ell w
all,
cellu
lose
cel
l wal
l, fla
gellu
m, s
moo
th E
R, r
ough
ER,
free
ri
boso
mes
, gol
gi a
ppar
atus
, lys
osom
e, v
acuo
le, l
arge
cen
tral
vac
uole
, pla
smid
, nuc
leoi
d, n
ucle
us, D
NA,
cyt
opla
sm, c
entr
iole
, chl
orop
last
, m
itoch
ondr
ia, s
tarc
h gr
anul
es, n
ucel
oid,
pili
, euk
aryo
tic, 1
0-10
0 µm
, 1-1
0 µm
.
Prok
aryo
tic c
ells
Ani
mal
cel
ls Pl
ant c
ells
Daley Biology H 2013-2014
!6
5
Act
ivity
C –
Iden
tify
the
parts
and
func
tions
of t
ypic
al e
ukar
yotic
cel
ls.
Obj
ectiv
e 7:
Usi
ng a
pic
ture
of a
euk
aryo
tic c
ell (
plan
t and
/or a
nim
al), label e
ach
of th
e fo
llow
ing:
nuc
leus
, fre
e rib
osom
es, r
ough
ER
, soo
oth
ER, g
olgi
app
arat
us, c
ell m
embr
ane,
cel
lulo
se c
ell w
all,
mito
chon
dria
, chl
orop
last
, vac
uole
, lar
ge c
entra
l vac
uole
, lys
osom
e. A
lso,
discuss t
he
func
tion
of e
ach
part
(4.4
– 4
.15)
.
A =
____
____
____
G
= __
____
____
__
A
= __
____
____
__
G =
____
____
____
B
= __
____
____
__
H =
____
____
____
B =
____
____
____
H
= __
____
____
__
C =
____
____
____
I
= __
____
____
__
C
= __
____
____
__
I =
____
____
____
D
= __
____
____
__
J =
____
____
____
D =
____
____
____
J
= __
____
____
__
E =
____
____
____
K
= __
____
____
__
E
= __
____
____
__
K =
____
____
____
F
= __
____
____
__
L =
____
____
____
F =
____
____
____
L
= __
____
____
__
M =
____
____
____
A B C
D E (d
ot)
F G H J I K
L St
arch
gr
anul
es
stor
ed w
ithi
n am
ylop
last
s
A
B C D E F
G H
I J K L
M
Daley Biology H 2013-2014
!7 6
Objec
tive 7
, Con
t: CE
LLUL
AR F
EATU
RES
OR O
RGAN
ELLE
S (A
ctivit
y C, c
ont.)
Nam
e of
Orga
nelle
or
Cellu
lar F
eatu
re
Desc
riptio
n of
Fu
nctio
n De
scrip
tion
of
Stru
cture
Diag
ram
In al
l Euk
aryo
tic
cells
? If
not,
in
which
spec
ific
type
s?
In
Prok
aryo
tic
cells
? Ot
her
info
rmati
on
Analo
gy
Cell
Mem
bran
e To
allo
w m
olec
ules
into
an
d ou
t of t
he ce
ll
Phos
phol
ipid
bila
yer
with
pro
tein
“tunn
els” e
mbe
dded
in
the b
ilaye
r
yes
yes
Chol
ester
ol
in th
e m
embr
ane
and
carb
s are
on
out
side
Custo
ms
offic
er fo
r a
coun
try; g
ate
keep
er
Nucle
us
Ribo
som
es
(free
)
Mito
chon
dria
Roug
h En
dopl
asm
ic Re
ticul
um
Smoo
th
Endo
plas
mic
Retic
ulum
!http
://learn.gene
tics.u
tah.ed
u/conten
t/be
gin/cells/insid
eacell/!an
d!http://
www.ce
llsalive.co
m/cells/cell_mod
el.htm
!:!look!at
!both!plant!a
nd!
anim
al!cells.!**Every!organelle!is!lis
ted!for!b
oth!plant!a
nd!an
imal!cells…!you!won
’t!know
!if!it’s!actually!in!that!ce
ll!until!y
ou!click
!on!it!!**!
Daley Biology H 2013-2014
!8
7
Nam
e of
Org
anel
le o
r Ce
llula
r Fea
ture
Des
crip
tion
of
Func
tion
Des
crip
tion
of
Stru
ctur
e D
iagr
am
In al
l Euk
aryo
tic
cells
? If
not,
in
whi
ch sp
ecifi
c ty
pes?
In
Prok
aryo
tic
cells
? O
ther
in
form
atio
n A
nalo
gy
Gol
gi
App
arat
us
Lyso
som
e
Chlo
ropl
ast
Cent
ral V
acuo
le
Cellu
lose
Cel
l W
all
Cyto
skel
eton
Daley Biology H 2013-2014 Activity E
Lab: Using a Compound Light Microscope Background: Microscopes are very important tools in biology. The term microscope can be translated as “to view the tiny,” because microscopes are used to study things that are too small to be easily observed by other methods. The type of microscope that we will be using in this lab is a compound light microscope. Light microscopes magnify the image of the specimen using light and lenses. The term compound means that this microscope passes light through the specimen and then through two different lenses. The lens closest to the specimen is called the objective lens, while the lens nearest to the user’s eye is called the ocular lens or eyepiece. When you use a compound light microscope, the specimen being studied is placed on a glass slide. The slide may be either a prepared slide that is permanent and was purchased from a science supply company, or it may be a wet mount that is made for temporary use and is made in the lab room. !Objectives: In this lab you will: 1. Learn the parts of a compound light microscope and their functions. 2. Learn how to calculate the magnification of a compound light microscope. 3. Learn how to make a wet mount slide. 4. Understand how the orientation and movement of the specimen’s image changes when viewed though a compound light microscope. 5. Learn the proper use of the low and high power objective lenses. 6. Learn the proper use of the coarse and fine adjustments for focusing. 7. Learn how to estimate the size of a specimen (cell) using a microscope. !Materials: microscopeslides cover slips lens paper paper towels sheets of newspaper/phonebook waterpipettescissors !
!9
Daley Biology H 2013-2014 Procedure: Part I. Learning about the microscope 1. One member of your lab group should go and get a microscope. Always carry the microscope in an upright position (not tilted) using two hands. One hand should hold the microscope’s arm and the other hand should support the base, as shown in Figure 1. Set it down away from the edge of the table. Always remember that a microscope is an expensive, precision instrument that should be handled carefully. 2. Plug the microscope in at your lab desk. Turn it on and make sure that the light comes on (it may take a second or two to warm up). If the microscope light does not turn on, check with your teacher. 3. Compare your microscope with Figure 2 on the next page. Identify the parts on your microscope and determine the function of each part. Use the words from the word bank below to fill in the parts names in Table 1 below. !Word Bank (use for next page): Arm BaseCoarse adjustment DiaphragmFine adjustment Objective lenses Ocular lens LightStageStage clips !!!!!!!!!!!!!!!!!!!!!
!10
Daley Biology H 2013-2014 4. Fill in Table 1 with the names and functions of each microscope part in Figure 2. !!! !! ! ! !! !!!!!! !!! !!!!!TABLE 1:
Part Name Function
A
B
C
D
E
F
G
H
I
J !11
B
C
D
E
F
G
H
J
Daley Biology H 2013-2014 5. The ocular lens is marked with its magnification power. (This is how much larger the lens makes objects appear.) a. What is the magnification power of the ocular lens of your microscope? !!!6. The three objective lenses are marked with their magnification power. The first number marked on each lens is the magnification power of that lens. b. What is the magnification of the lowest power lens of your microscope? !!!c. What is the magnification of the high power lens? !!!7. To find the total magnification of your microscope as you are using it, multiply the ocular lens power times the power of the objective lens that you are using. For example, if the ocular lens of a microscope has a power of 5x and you use an objective that is 10x, then the total magnification of the microscope at that time is 50x (5x10=50). d. What is the total magnification of your microscope when using low power? !!!e. What is the total magnification of your microscope when using high power? !!!Part II. Preparing and using a Wet Mount 8. Using a piece of newspaper or phone book, find a small, lowercase letter “e.” Cut a 1 cm square with
that letter “e” near the middle of the square. (Do not just cut out the letter e, or it will be too hard to work with. The piece of paper that you cut out should be about the size of a fingernail.) !
9. Place the square of paper in the middle of a clean glass slide. Position the square so that the words are in normal reading position (in other words, don’t have the “e” turned sideways or upside-down). With a pipette, put 1 drop of water on the paper square. Drop the water from about 1 cm above the slide; do not touch the pipette to the paper square or the paper will stick to the pipette.
Figure 3 10. Now, cover the water drop with a clean cover slip. The best way
to do this is shown in Figure 3. Hold the cover slip at a 45° angle to the slide and move it over the drop. As the water touches the cover slip, it will start to spread. Gently lower the angle of the cover slip to allow the water to evenly coat the under surface, then let the slip drop into place. You should not just drop the cover slip onto the slide or air bubbles will get trapped. This makes the slidevery difficult to study. If you do
!12
Daley Biology H 2013-2014 trap several air bubbles, remove the slip and try again. Never press on the cover slip to try to remove air bubbles. This will break the cover slip and/or damage your specimen. !
11. On your microscope, move the low-power objective into place. You should always begin studying a slide on low power, because this makes it easiest to find objects on the slide. Position the diaphragm so that the largest opening is used. This will allow the maximum amount of light to be used. Check your wet mount slide to be sure that the bottom of the slide is dry. (A wet slide will stick on the stage of the microscope.) Sit so that the arm of the microscope is closest to you, and place the slide on the stage with the “e” in a normal reading position for you. !
12. You may use the stage clips to hold the slide in place if you like. If so, make sure that the clips do not bump into the cover slip or touch the water. Look at the microscope from the side and use the coarse adjustment knob to get the stage as close to the low-power objective as possible. !
13. Look through the ocular lens, keeping both eyes open. (It may seem difficult to keep both eyes open, but learning to do so helps to prevent eyestrain or headaches.) Slowly adjust the focus of the microscope using the coarse adjustment knob until the letters become clear. Then, use the fine adjustment to sharpen the focus. Move the slide left or right, forward or backward, until the letter “e” is in the center of the field of view. Do not turn the slide or pivot it. In the circle to the right, draw the letter “e” in the same size and position as you see it in the microscope. !
f. Describe the position of the image of the letter “e” through the microscope compared to the position that it is placed on the slide. Draw it as well. !!!!!!
14. Move the slide to the left. g. Which direction did the image move? !!!
15. Move the slide away from you. h. Which way did the image move? !!
16. Look through the microscope as you change the adjustment of the diaphragm. i. What does the diaphragm control? !!!!
!13
Daley Biology H 2013-2014 Important Note: Before switching to high power, you should always position the specimen in the center of the field of view and use the fine adjust to sharpen the focus of the image. Never use the coarse adjustment when using high power. Doing so could break the slide or the microscope! !17. Watching from the side, switch to the high-power objective lens. Make sure that the lens does not hit
the slide, but expect it to be very close. !18. Looking through the ocular, use a slight turn of the fine adjustment knob to focus the image of the
letter “e”. In the circle to the right, draw the letter “e” in the same size and position as you see it in the microscope. !!
j. Describe the appearance of the image that you see. Are you seeing more or less of the letter “e” than you did at low-power? !!!!
k. Is the field of view (the area that you are observing) larger or smaller when you use high power? !!!
19. Look through the microscope (on high power) with the diaphragm at its largest setting. While looking through the ocular, switch the microscope to low-power. !
l. Compare the brightness of the field under high power and low power. Which setting is brighter? Why? !!
!14
Daley Biology H 2013-2014 Part III. Plant and Animal Cells. 1. Elodea Select a small sprig of Elodea from the plant. The leaf should be as thin as possible. Prepare a wet mount slide of the Elodea. !
1. Examine the Elodea under LOW power and sketch and label your observations below. !2. Now examine the Elodea under HIGH power. Draw and label your observations below. Can you
see any organelles? Be sure to include them. !Your field of view (area you are viewing) is 1.4 mm under high power. Count the cells and calculate their average size. Show your work. !
Elodea: !!!!!!!!!!!!! Magnification: _____________ Magnification: _____________ !!!!
!15
Daley Biology H 2013-2014 2. Cheek Cell Using a toothpick, gently scrape the inside of your cheek to collect the cells and then rub the sample on the glass slide. IMMEDIATELY place the toothpick in the trash. Add a drop of methylene blue stain to the sample and cover it with a cover slip. After making your observations, place the entire glass slide and cover slip in the marked container. DO NOT TAKE A PEICE OF CHEEK OR HURT YOURSELF! !
1. Examine the cells under LOW power and sketch and label your observations below. Are you seeing cells or tissues or both? !
2. Now examine the cells under HIGH power. Draw and label your observations below. Cheek: !!!!!!!!!!!!! Magnification: _____________ Magnification: _____________ !!
!16
Daley Biology H 2013-2014 Final Analysis: 1. Why should you always begin to use a microscope with the low-power objective? !!!!!2. Why should you only use the fine adjust when the high-power objective is in position? !!!!!3. Why must the specimen be centered before switching to high power? !!!!4. If you placed a letter “g” under the microscope, how would the image look in the field of view? !!!!5. If a microscope has an ocular with a 5x power, and has objectives with powers of 10x and 50x, what is the total magnification of: (Show your math for full credit!) a. low power? !!!b. high power? !!!!6. If you are looking through a microscope at a freshly prepared wet mount and you see several perfect circles that are completely clear surrounding you specimen, what is the most likely explanation? !!!!7. Why does the specimen placed under the microscope have to be thin? !!!!!
!17
Daley Biology H 2013-2014 !8. Are the cells that you observed eukaryotic or prokaryotic? Explain how you know. !!!!!9. What structures do all cells have? !!!!10.What are three structures that plant and animal cells have in common? !!!!!11.What are two differences between plant and animal cells? !!!!!12. What structure was only seen in the elodea? !!!!!13. Rank the cells in order of increasing size. Which seemed the biggest? What about the nuclei? !!!!!!
!18
Ebola outbreak: mission instructions and resources – student guide Your Mission: to become an expert on the deadly Ebola virus and design a strategy to contain the rapidly growing outbreak in Western Africa. Background: The current outbreak of Ebola in Western Africa has already claimed the lives of over 2,000 people and leading international health organizations predict the number may reach ten times that amount before the virus has run its course. There is currently no cure or vaccine for Ebola and it is doubtful that one will be discovered during the outbreak. Local and international health workers are being pushed beyond their limits as they attempt to save as many lives as possible by identifying the sick (who are often reluctant to leave their homes), treating the infected patients with limited resources, and attempting to prevent the further spread of the virus through on-the-ground public health education campaigns. Tasks: Review the Ebola materials assembled for you by a team of experts and then use what you've learned to create a strategy to stop the outbreak.
1. Read about the Epidemiologic Triangle. It will help you to understand the method public health scientists use to stop an outbreak and will come in handy when you are creating your own strategy to halt the spread of Ebola.
2. Explore as many of the resources as you can. Keep in mind that the more materials you are able to watch, read and explore, the better chance you will have at creating a successful plan. The information is organized into three categories:
x Agent - the microbe that causes the disease x Host - the organism harboring the disease x Environment - the external factors that cause or allow the disease transmission
3. After you have finished your research, use what you have learned to complete the Ebola
outbreak: strategic plan - assessment which includes an Epidemiological Triangle, a graphic organizer for key facts and prompts to help you create your evidence-based recommended strategy to contain the Ebola outbreak.
Get started: You can find your Ebola outbreak: mission instructions and resources - digital student guide at the URL below. Good luck!
http://ec2-54-204-18-44.compute-1.amazonaws.com/newshour/extra/?p=7730
Ebola outbreak: the Epidemiologic Triangle – informational text What is Epidemiology? Epidemiology is the study of the distribution and determinants of health problems in specified populations and the application of that information to control health problems. In other words, epidemiology is the study of health problems—specifically who they affect, what factors play a role in getting a disease and how to contain it. It is the scientific method of problem-solving used by "disease detectives," which includes epidemiologists, laboratory scientists, statisticians, physicians and other health care providers, and public health professionals. These professionals work to get to the root of health problems in a community, solving issues that range from a measles outbreak on a small college campus to a global influenza pandemic, an increase in homicide in a single community to a national surge in violence, or a localized to widespread rise in cancer. Like investigators at the scene of a crime, disease detectives begin by looking for clues. They systematically gather information about what happened, asking questions like: who is sick? What are their symptoms? When did they get sick? Where could they have been exposed to the illness? Using statistical analysis, investigators study the answers to these questions to find out how a particular health problem entered a community. The Epidemiologic Triangle The Epidemiologic Triangle is a model that scientists have developed for studying health problems, specifically to understand infectious diseases and how they spread.
The Triangle has three corners (called vertices):
1. Agent, or microbe that causes the disease (the “what” of the Triangle) 2. Host, or organism harboring the disease (the “who” of the Triangle) 3. Environment, or those external factors that cause or allow disease transmission (the “where”
of the Triangle)
An outbreak or an epidemic exists when there are more cases of a particular disease than expected in a given area, or among a specific group of people, over a particular period of time. Another other term you might come across is endemic, meaning that a population has a high level of the disease all the time. The mission of an epidemiologist is to break at least one of the sides of the Triangle, disrupting the connection between the environment, the host, and the agent, and stopping the continuation of disease. Here are more details on the parts of the Epidemiologic Triangle: Vertex 1. The Agent—“What” The agent is the cause of the disease. When studying the epidemiology of most infectious diseases, the agent is a microbe (an organism too small to be seen with the naked eye). Disease-causing microbes are bacteria, virus, fungi, and protozoa (a type of parasite). They are what most people call “germs.” Virus: A virus may have a spiny outside layer called the “envelope.” Viruses have a core of genetic material, but no way to reproduce it on their own. Viruses infect cells and take over their reproductive machinery to reproduce. Vertex 2. The Host—“Who” Hosts are organisms, usually humans or animals, which are exposed to and harbor a disease. The host can be the organism that gets sick as well as any animal carrier (including insects and worms) that may or may not get sick. Although the host may or may not know it has the disease or have any outward signs of illness, the disease lodges inside the host. The “host” heading also includes symptoms of the disease. Different people may have different reactions to the same agent. For example, adults infected with the virus varicella (chickenpox) are more likely than children to develop serious complications. Vertex 3. The Environment—“Where” The environment is the favorable surroundings and conditions external to the host that cause or allow the disease to be transmitted. Some diseases live best in dirty water. Others survive in human blood. Still others, like E. coli, thrive in warm temperatures but are killed by high heat. Other environmental factors include the season of the year (e.g. in the U.S., the peak of the flu season is between November and March). Questions Can you think of examples for each of the sides of the triangle? List them in the space below Agent Host Environment Source: The Center for Disease Control and Prevention
Ebola outbreak: strategic plan – assessment The mission of an epidemiologist is to break at least one of the sides of the Triangle, disrupting the connection between the environment, the host, and the agent, and stopping the continuation of disease. Epidemiologic Triangle Fill out the blank Epidemiological Triangle below by identifying the agent, host and environment for this Ebola outbreak.
Host
Environment
Agent
Key facts In the space below organize key facts you learned from your review of the critical information. Agent Host Environment
Ebola outbreak strategic plan Answer the questions in the space below in complete sentences. Make sure to use evidence from the critical information materials to support your plan. Make a brief assessment of the situation by describing the Ebola crisis (is it getting better or worse?) Which side of the Epidemiologic Triangle do you recommend be broken and why? Explain your answer in detail and include your thought process that led you to your decision. How would you carry out your strategic plan? What resources would you need? What do you believe will be the biggest challenges you would face carrying out your strategy and how will you overcome them?
What is the goal of your strategic plan? How will you know when you have reached it?
Daley Biology H 2013-2014 Activity F: “How Big is a…”!!URL: http://learn.genetics.utah.edu/content/begin/cells/scale/!!Navigating the site: There is a bar under the picture that allows you to zoom in and out.!!Here you will look at objects on a piece of paper. Your job is to find them and estimate the length of each (in picometers, nanometers, micrometers, or millimeters). Sketch each of the objects. (Note: 1 m = 1,000 mm = 1,000,000 micrometers = 1,000,000,000 nanometers)!!
*Note: Others may be N/A as well if it is not a cell.
Object Sketch Eukaryotic or Prokaryotic
Size in picometers (pm), nanometers (nm),
micrometers (µm), or millimeters (mm)
Grain of rice N/A*
Amoeba proteus
Skin Cell
Red Blood Cells
Baker’s Yeast
Mitochondrion N/A*
E. coli
HIV
Rhinovirus
Hemoglobin (protein) N/A*
!19
Daley Biology H 2013-2014 !Objective 9 &13: Identify the three types of cell junctions and explain how, with the extracellular matrix, they aid in interactions between cells. (worksheet below) Extracellular Matrix and Junctions: A Review BSCS sect. 6.6
1. What is a junction?
!2. What class(es) of biomolecule is the primary component of junctions?
________________________________
3. Describe each type of junction:
4. What class of biomolecule is the primary component of the cytoskeleton?__________________
5. Why does the cell have the consistency of a gel?
6. State 3 functions of the cytoskeleton.
1.
2.
3.
Name the 3 structures that form the cytoskeleton. State the diameter of each.
1.
2.
3.
***Fun fact: Cytoskeleton structures are composed of two proteins with repeating primary sequences that from fibers: tubulin forms microtubules and actin forms intermediate filaments and microfilaments.
Tight&Junc+on&!Desmosome&!Gap&Junc+on&!Pits/plasmodesmata&!
!20
Daley Biology H 2013-2014 Activity G: Why Are Cells So Small? (Objective 16) An Investigation of the Relationship between Diffusion and Cell Size (Revised from Kim B. Foglia, www.ExploreBiology.com, 2010) !Background Information: Most cells are between 2 micrometers and 200 micrometers – too small to be seen with the naked eye. Remember, a micrometer is 1 millionth of a meter! Why can’t cells ever become larger than that? Why don’t we regularly find one-celled organisms the size of small multicellular animals, like frogs or even flies? In other words, why can’t there ever be an organism which is visible to the naked eye and that is one giant cell? When cells grow to a certain size, their rate of growth slows down until they stop growing entirely. They have reached their limit. When one of these larger cells divides into two smaller cells, the rate of growth increases again.
In order for cells to survive, they must constantly exchange ions, gases, nutrients, and wastes with their environment. These exchanges take place at the cell’s surface – across the cell membrane. The movement of these materials is accomplished mostly by diffusion (flow of solutes from high to low concentration) across the cell membrane. Surface area is the amount of cell membrane available for diffusion. So for a cell, surface area actually represents how much diffusion can happen at one time. It would seem reasonable, then, that a cell would want plenty of surface area (meaning membrane area).
Volume is the amount of cytoplasm contained within the cell membrane. So for a cell, volume represents how long it takes to get from the membrane to the center of the cell by diffusion. Therefore, a large cell would need more materials (more metabolic need) and those materials would take longer to reach the center of the cell. What, then, is the relationship between the surface area and the volume of a cell? How does this affect the rate of diffusion of materials that pass in and out? In this lab, we will investigate this relationship and how it affects diffusion time. !Part I Procedure In this lab activity, you will use agar cubes as cell models. You will investigate how increasing a cell’s size affects the time for diffusion to move material across the cell. The agar for the cubes has been dyed with bromothymol blue – a pH indicator that turns from blue to yellow in the presence of acid. When the agar cubes are placed in vinegar (a source of acid), they will begin to turn yellow as the vinegar diffuses into the agar. You will time this diffusion process for 3 different sized cells and compare them. Diffusion will be considered complete when the blue color completely disappears from the center of the cell. We will complete Part I as a class demonstration. !Materials: A metric ruler, vinegar, beaker, spoons, knife, paper towels, 3 cubes of 3% agar-bromothymol blue: 1x1x1 cm, 2x2x2 cm, and 1x1x8 cm !Procedure:
1. Cut three cubes of agar – one with 1 cm on each side, another with 2 cm on a side, and third that is 1 cm x 1 cm x 8 cm. Be exact in your measurements. Be very careful not to cut into or puncture the blocks.
2. Put the three cubes in a beaker and pour vinegar over them until the blocks are submerged. Record the time.
3. Record the amount of time it takes for the blue color to completely disappear from each cell. !!!21
Daley Biology H 2013-2014 Part 2 Procedure Now that you have been able to explore the relationship between cell dimensions and diffusion time, let’s see if you can put your new-found understanding to good use. Cells come in many shapes and sizes in organisms. Natural selection favors cell shapes that enable the cell to perform its function efficiently. For example, neurons (nerve cell) and cells that line the small intestine have different jobs, so each has its own unique shape that allows it to do its job better. You will find that the relationship between structure and function is a recurrent theme throughout biology. !In this activity, each group will compete by creating cell shapes that they think will be most efficient at getting nutrients. We will then simulate natural selection by have a race to see which shape is best at its desired function. Each group will get an equal size block of bromothymol blue agar and will have the opportunity to design a cell to maximize mass but minimize diffusion time. The cell with the greatest mass and the shortest diffusion time will be judged the winner. !
!Analysis: Answer the following in complete sentences. Please write neatly on a separate sheet of paper or type them. Make the question clear in the answer or you will get points off (for example, "yes, because…" is not a good answer). !1. What evidence suggests the vinegar diffused into the 3% agar-bromothymol blue cubes? (0.5 point)!2. Copy the following chart onto your answer sheet. Complete the chart to investigate the relationship
between surface area and volume as a cube increases in size. !
As the cube increases in size, what happens to the surface area to volume ratio? Explain.!
3. Based upon what you know about cells, explain how cells “feed” themselves. How do the nutrients get into the cell? (Don’t over-think this.) (1 point)!
4. According to your data from Part 1, which cell was most efficient at receiving the needed “nutrient” (vinegar)? Use data from your table to back up your conclusion. (1 point)!
!
The Cell Diffusion Race Rules:
1. No donut-like holes through the agar cell – this is biologically impossible because it is unstable.
2. Once the agar cell is in the beaker of vinegar, no poking, prodding, touching the beaker.
3. Teacher determines when 100% diffusion takes place. Diffusion will be considered complete when the blue color completely disappears from the center of the cell.
4. Students mass agar at the end of the race and the cell must not break when handled! If the cell breaks upon massing, then the entry is disqualified.
5. WINNER = highest ratio of mass divided by time.
Cube (cm) Surface Area Volume SA : V ratio
1 x 1 x 1
2 x 2 x 2
3 x 3 x 3
!22
Daley Biology H 2013-2014 5. The 2x2x2 cell and the 1x1x8 cell have the same volume. Were their diffusion times the same?
Explain why or why not.!6. In general, what is the relationship between the SA:V ratio and diffusion time?!7. Most cells measure less than 0.01 cm on a side. !
a. Calculate the surface area to volume ratio for a cube that measures 0.01 cm on each side. Show your work. (1 point)!
b. If we were able to create a 0.01 cm cube out of agar, do you think it would be more or less successful than the 1 cm cube at receiving the vinegar “nutrient?” (1 point)!
8. In real life, provide two examples of molecules that must move into human cells? (1 point)!9. In real life, provide two examples of molecules that must move out of human cells? (1 point)!
10. Describe your cell design. Explain why you chose that design – on what principles were you basing your design on to decrease diffusion time?
11. If all of the student-designed cells from Part 2 happened to arise randomly, which cell would have the best chance of survival? Explain how you know and what characteristics of that cell might have allowed it to survive better.
12. Give an example of a type of cell in a living organism (animal or plant) that is shaped very differently than the classical round or boxy shape that you see drawn in introductory textbook chapters on cells. You could pick muscle cells, cells of the small intestine, nerve cells, red blood cells, leaf pore guard cells, or some other cell. Explain how that unique shape is tied to the function that those cells can perform.
13. Write a well-organized paragraph in which you explain why smaller cells have an advantage over bigger cells, both in terms of movement into cells AND movement out of cells. (In other words, what would happen if your cells failed to divide and instead just grew bigger and bigger?) In your paragraph, include data from this lab, to support your statements. (4 points)
!!!!!!!!!!!!!!!!!!23
Daley Biology H 2013-2014 Table 1. (3 pt)
!Table 2. Cell Mass and Time for Diffusion (Part 2) !Circle the letter of YOUR OWN group!
Cell Size (cm)
Surface Area (units!)
Volume (units!) SA: Volume Ratio Time for Complete Diffusion
1 x 1 x 1!!
2 x 2 x 2!!
3 x 3 x 3!!
Group Sketch Cell Mass (g) Time for Complete Diffusion (minutes) Mass (g) / Time (min)
A
B
C
D
E
F
G
H
!24