1. Cell Unit – Chapters 4 and 5
Growing ORGANS video TED TALK
Inner Life of a Cell video
Cell Unit – Chapters 4 and 5
Cells create and maintain internal environments that are different from their external environment
2017

2. Prokaryote bacteria cells Eukaryote animal cells
Types of cells
Prokaryote bacteria cells
Eukaryote animal cells
Eukaryote plant cells

3. I. Why organelles? Organisms must exchange matter with
mitochondria
I. Why organelles?
Organisms must exchange matter with
the environment to grow/communicate
Cell membranes, golgi, vesicles
Exchange energy
unique combinations of lipids & proteins
embedded enzymes & reaction centers
chloroplasts & mitochondria
Maintain organization/homeostasis
partition cell into compartments
create different local environments
separate pH, or concentration of materials
distinct & incompatible functions
lysosome & its digestive enzymes, vacuoles
chloroplast
Golgi
Why organelles?
There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions.
Organelles as specialized structures
An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move.
Organelles as Containers
Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it.
Organelle membranes as sites for chemical reactions
An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast. ER

4. II. Cell FUNCTION What jobs do cells have to do? communication
proteins control every cell function
make energy
for daily life
for growth
homeostasis
growth
reproduction
repair

5. Why study protein production? - communication/cell signaling
proteins
DNA
cells
organism
Repeat after me…
DNA gets the glory, but
Proteins do all the work!

6. Protein Synthesis Organelles are cooperative nucleus ribosomes
endoplasmic reticulum (ER)
Golgi apparatus
vesicles
The Protein Assembly Line
Golgi apparatus
nucleus
ribosome ER
vesicles

7. endoplasmic reticulum
TO:
nucleus
protein on its way!
TO:
DNA
RNA
vesicle
TO:
TO:
vesicle
ribosomes
TO:
protein
finished protein
Golgi apparatus
Making Proteins

8. Transcription/Translation
Putting it together…
Transcription/Translation
proteins
transport
vesicle
Golgi
apparatus
smooth ER
rough ER
nuclear pore
nucleus
ribosome
cell
membrane
protein secreted
cytoplasm

9. Cell Junctions Plant Cells Plasmodesmata Animal Cells Tight junctions
Desmosomes
Gap Junctions
Refer to the Campbell website
Chapter 6 Activity Cell Junctions

10. ATP Cells FUNCTION What jobs do cells have to do? communication
proteins control every cell function
make energy
for daily life
for growth
homeostasis
growth
reproduction
repair
ATP

11. Cells need power! “Cell Respiration
Making energy
take in nutrients & digest it
take in oxygen (O2)
make ATP
remove waste
ATP

12. From food to making Energy
Cells must convert incoming energy to forms that they can use for work
mitochondria: What is this? from glucose to ATP
chloroplasts: What is this? from sunlight to ATP & carbohydrates
ATP = immediate energy
carbohydrates = stored energy
ATP
ATP +

13. Mitochondria & Chloroplasts
Important to see the similarities
transform energy
generate ATP
double membranes = 2 membranes
semi-autonomous organelles
move, change shape, divide
internal ribosomes, DNA & enzymes

14. Membrane-bound Enzymes
Specialized areas
glucose + oxygen  carbon + water + energy
dioxide
C6H12O6
6O2
6CO2
6H2O
ATP  +

15. Membrane-bound Enzymes
More membranes working together and efficiently
+ water + energy  glucose + oxygen
carbon
dioxide
6CO2
6H2O
C6H12O6
6O2
light
energy  +

16. Mitochondria are everywhere!!
animal cells
plant cells

17. Cells FUNCTION What jobs do cells have to do? communication
proteins control every cell function
make energy
for daily life
for growth
homeostasis
growth
reproduction
repair

18. Where old organelles go to die!
Lysosomes
Function
little “stomach” of the cell
digests macromolecules
“clean up crew” of the cell
cleans up broken down organelles
Structure
vesicles of digestive enzymes
Where old organelles go to die!
only in animal cells

19. Lysosomal enzymes Lysosomal enzymes work best at pH 5
organelle creates custom pH
how?
proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome
why?
enzymes are very sensitive to pH
enzymes are proteins — pH affects structure
why is this an adaptation: digestive enzymes which function at pH different from cytosol?
digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself!
lysosomes create a space where cell can digest macromolecules safely
rupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cell
why evolve digestive enzymes which function at pH so different from cytosol?
digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself!
low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis

20. But sometimes cells need to die…
Lysosomes can be used to kill cells when they are supposed to be destroyed
some cells have to die for proper development in an organism
apoptosis – during development
“auto-destruct” process
lysosomes break open & kill cell
ex: tadpole tail gets re-absorbed when it turns into a frog
ex: loss of webbing between your fingers during fetal development
ex: self-destruct of cancerous cell
Feedback mechanism
There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes.
Brown spots on leaves too.
Virus infected plant cell auto-destructs and even cells around it to wall off virus.

21. syndactyly
Fetal development
6 weeks
15 weeks

22. When things go wrong… Diseases of lysosomes are often fatal
digestive enzyme not working in lysosome
picks up biomolecules, but can’t digest one
lysosomes fill up with undigested material
grow larger & larger until disrupts cell & organ function
lysosomal storage diseases
more than 40 known diseases
example: Tay-Sachs disease build up undigested fat in brain cells

23. Cytoskeleton Function structural support motility regulation
maintains shape of cell
provides anchorage for organelles
protein fibers
microfilaments, intermediate filaments, microtubules
motility
cell locomotion
cilia, flagella, etc.
regulation
organizes structures & activities of cell

24. Cytoskeleton
actin
microtubule
nuclei

25. Centrioles Cell division
in animal cells, pair of centrioles organize microtubules
guide chromosomes in mitosis

26. Effects of Cell Size

27. Limits to cell size Lower limit Upper limit smallest bacteria
mycoplasmas
0.1 to 1.0 micron (µm = micrometer)
most bacteria
1-10 microns
Upper limit
eukaryotic cells
microns
micron = micrometer = 1/1,000,000 meter
diameter of human hair = ~20 microns

28. Why is a huge single-celled creature not possible?
What limits cell size?
Surface to volume ratio
as cell gets bigger its volume increases faster than its surface area
smaller objects have greater ratio of surface area to volume
Why is a huge single-celled creature not possible?
square - cube law
As cell gets larger, volume increases cubically, but surface area only increases by the square.
The volume of the cell is demanding… it needs exchange. The surface area is the exchange system… as cell gets larger, the surface area cannot keep up with demand.
Instead of getting bigger, cell divides -- mitosis.
s:v
6:1
~1:1
6:1

29. Why is cell size an issue?
Metabolic requirements set upper limit
in large cell, cannot move material in & out of cell fast enough to support life O2 aa
CHO CH
What process is this?
CO2
NH3 aa O2 CH
CHO
CO2
What process is this?
diffusion
What’s the solution?
cell divides
make a multi-celled creature = lots of little cell, rather than one BIG cell aa
NH3
CHO CH O2 aa
What’s the solution?

30. How to get bigger? Become multicellular (cell divides) aa O2 aa aa aa
But what challenges do you have to solve now? aa
CO2
NH3 O2 CH
CHO aa O2 CH
CHO
CO2
Larger organisms do not generally have larger cells than smaller organisms — simply more cells
What’s challenges do you have to solve now?
how to bathe all cells in fluid that brings nutrients to each & removes wastes from each aa
NH3
CHO CH O2 aa

31. Cell membrane Exchange structure
plasma membrane functions as selective barrier
allows passage of O2 & nutrients IN
allows passage of products & wastes OUT
Phospholipid
Cholesterol
Membrane
proteins

32. Any Questions??