Transcript Unit 2: Cytology - Union Academy Charter School

UNIT 3: CELL PROCESSES
Union Academy Charter School
Cells must maintain homeostasis

Cells maintain homeostasis by letting specific
things in or out of the cell.
 The
cell membrane is selectively permeable!
O2, CO2, non-polar
(fat soluble) molecules
Glucose, water, ions (Na+),
polar (water soluble) molecules
Outside the cell
Transport protein
Inside the cell
Why aren’t cells big?

Surface area to volume ratio!
 The
higher the better!
 More
membrane per unit of
cytoplasm allows molecules
to move throughout the cell
much faster.
Diffusion of molecules

Diffusion – when molecules move from high to low
concentration without using energy.
Other examples?
Cells use diffusion

Diffusion – when molecules move from high to low
concentration without using energy.
High concentration
Low concentration
Cells use diffusion

Since diffusion uses no energy we call it passive transport.
 Some
diffusion is facilitated (helped) by proteins.
Osmosis - diffusion of water

Osmosis – when water moves from high to low
concentration without using energy.
 Sometimes
other molecules are too big so water has to move!
water
sugar
What would this
do to a cell??
The volume
increases on
the right!
Osmosis in the cell

Cells can be exposed to 3 types of solutions:
 Isotonic
– same amount of solute on both sides.
 Hypotonic – less solute outside the cell.
 Hypertonic – more solute outside the cell.
Osmosis in the cell
Red blood cells
This is
why we
use saline!
This is why
we can’t drink
salt water!
normal cells
cells swell, burst
shriveled cells
Isotonic
solution
Hypotonic
solution
Hypertonic
solution
normal cell
normal turgid cell
cytoplasm shrinks
from cell wall
Plant cells
Diffusion/osmosis problem setup

Some problems will use a U-tube.
 This
could be used for diffusion or osmosis.
 There is a semipermeable membrane.
 Sometimes
molecules can fit through, sometimes only water.
Diffusion
red dye
H2O
membrane
Time
Osmosis
Diffusion/osmosis problem setup

If osmosis occurs, what will move, and in which direction?
Diffusion/osmosis problem setup

If diffusion occurs, what will move, and in which direction?
Diffusion/osmosis problem setup

If osmosis occurs, what will move, and in which direction?
Diffusion/osmosis problem setup

If osmosis occurs, what will move, and in which direction?
10% salt 90% water
50% salt 50% water
40% water
60% salt
60% water
40% salt
What if the cell wants to move something
from low to high concentration?

Active transport – cells use energy (ATP) to move
molecules from low to high concentration.
 Ex.
Stomach acid.
Active transport in action!

Bulk transport:
 Endocytosis:



Using energy to bring something into the cell.
Phagocytosis: Cell eating
Pinocytosis: Cell drinking
Receptor-mediated endocytosis: Cell surface receptors bind to something and
pull it in.
 Exocytosis:
Using energy to push something out of the cell.
plasma membrane
Inside
Exocytosis
Active transport in action!

A paramecium lives in fresh water but likes to be salty
inside!
 Uses
a contractile vacuole to pump water out.
Passive vs. active transport
Passive



No energy used
High to low
Ex: O2 into blood cells.
Active



Energy used
Low to high
Ex. Stomach acid.
Photosynthesis – in the chloroplast

Light + 6H2O + 6CO2  C6H12O6 + 6O2
Reactants
Products
Cellular respiration – in the mitochondria
Notice that this is the photosynthesis equation flipped!

C6H12O6 + 6O2  6H2O + 6CO2 + 36ATP
Reactants
Products
outer membrane
inner membrane
double
membrane
water
glucose
matrix
carbon dioxide
oxygen
cristae
energy (ATP)
Aerobic respiration – use of oxygen to make energy.
WARM UP




2/23/15
Write the photosynthesis equation using words.
Write the photosynthesis equation using chemical
formulas (ex: 6CO2 instead of carbon dioxide).
Write the cellular respiration equation using words.
Write the cellular respiration equation using
chemical formulas.
How do we use ATP?

ATP (adenosine triphosphate): our energy currency.
 We
use it by breaking one phosphate from the end.
 This
leaves ADP and Pi (inorganic phosphate).
These pieces are recycled!
Photosynthesis and respiration work together!
Energy Conversions
heat
solar
energy
chloroplast
O2
Chemical energy
(carbohydrate)
CO2 and H2O
mitochondrion
heat
ATP
Chemical work
Transport work
Mechanical work
What if there isn’t any oxygen?

Even without oxygen, organisms can break down
glucose and make energy – anaerobic respiration.
glucose
Lactic acid fermentation
2Lactic acid + 2ATP
Alcoholic fermentation
2Ethanol + CO2 + 2ATP
Aerobic vs. Anaerobic recap

Aerobic respiration – uses oxygen.
 Carried
out by most eukaryotes when they have sufficient
oxygen.
 Aerobic

respiration: C6H12O6 + 6O2  6H2O + 6CO2 + 36ATP
Anaerobic respiration – does not use oxygen.
 Carried
out by prokaryotes and some eukaryotes like yeast.
acid fermentation: C6H12O6  2Lactic acid + 2ATP
 Alcoholic fermentation: C6H12O6  2Ethanol + 2CO2 + 2ATP
 Lactic
WARM UP

a.
2/24/15
Which organism is most likely to use anaerobic
respiration?
Mouse b. bird c. tree
d. yeast
Which produces more ATP, aerobic or anaerobic
respiration?
If you have more CO2 in the air, how will that affect
the rate of photosynthesis?
We use fermentation to make products
yeast