+
Area of Study 2:
Detecting and responding
Unit
3
Biology:
signatures
of
life
+
conceptual framework
Chemical nature
of the cell
The nature of
molecules
Interactions between
molecules determine
shape of
biomacromolecules
and produces
binding sites for:
•enzymes and
substrates
•Signals and
receptors
•Antibodies and
antigens
Explains how:
•various materials
enter and leave a
cell
•Cells receive
and respond to
signals
•How the immune
system works
•How vaccines
work
•How we design
drugs
+
HOMEOSTASIS
EXPECTED LEARNING
 To
revise what we already know about
homeostasis
+
Big questions
 Complete
the ‘Big Questions’ worksheet
and hand it in
+
Activity
Think, pair, share:
 Why
do cells and organisms need to detect
& respond?
 What
do cells need?
 What
is homeostasis? Draw a simple model
to explain how it works.
 What
are some factors that are maintained
in homeostasis?
+
Why do cells and organisms need
to detect & respond?
Responding to signals for cells and organisms is
essential for three main reasons:
1.
Major developmental processes including growth
and reproduction.
2.
Surviving challenges in the external environment.
3.
Homeostasis.
+
What do cells need?
 An
environment in which their requirements
are met and conditions remain stable.
 In
the external environment, factors that
change include:






Temperature
Light intensity
Gases
Nutrients
Water
Other organisms
 Despite
this, the internal
environment remains fairly
constant
+
Homeostasis
The maintenance of a constant internal
environment.
NB. Internal environment = The medium in which the
body cells of multicellular organisms are bathed (i.e.
extracellular fluid, interstitial fluid, plasma, lymph)
+
+
Homeostasis & Controls
+
Internal environment
 Complex
organisms control internal
environment within narrow range,
including:
Body temperature
 Levels of chemicals in the blood and tissues (eg
glucose, oxygen, carbon dioxide, water and ions)
 Blood volume
 Blood pressure

+
Detecting signals from external
environment
Mechanoreceptors respond to
mechanicalenergy (e.g. ear drum)
Thermoreceptors respond to heat or
cold (e.g. nerve endings in skin)
Electromagnetic receptors respond to
electromagnetic energy (e.g. ampullae of
Lorenzini in sharks)
Photoreceptors respond to visible light
and UV radiation (e.g. eyes).
Chemoreceptors respond to chemical
stimuli (e.g. olfactory)
+
Stimulus-response model
Stimulus
Receptor
Transmission nerves
Control
centre
Response
Effector
Transmission –
nerves or hormones
+
Stimulus-response model example
Negative Feedback
Increase in
blood CO2
Receptor in
arteries
and veins
Transmission nerves
Respiratory
centre in
brain
Negative feedback –
response counteracts the
stimulus
More CO2
exhaled
Respiratory
muscles in
lungs
Transmission nerves
+
Two Types of Feedback

Positive Feedback

Negative Feedback
Organ or Gland
Organ or Gland
Promotes or
encourages
more of the
original
substance
to be
released
Releases a
substance to act
on a system
Releases a secondary
substance which acts
on the gland or organ
System Acted
Upon
Inhibits
(stops)
further
release of
the
original
substance
Releases a
substance to act
on a system
System Acted
Upon
Releases a secondary
substance which acts
on the gland or organ
+
Feedback Loops
+
Stimulus-response model example
Negative Feedback
+
Stimulus-response model example
Positive Feedback
+
Homeostatic mechanisms
 Transmission
of information from the
receptors to the control centre and then to
the effector may involve the nervous
system, the endocrine system or both
e.g. Regulation of body temperature
involves both
+
Thermoregulation
+
Activity/homework
 Group
activity: Activity 5.3
 Quick
check questions 1-12
+
Reflection
 What
did you learn OR remember learning
previously about homeostasis today?
+
ENDOCRINE SYSTEM
EXPECTED LEARNING
 To
explore how the endocrine system is
involved on detecting and responding
+
Endocrine System
 Uses
chemical signals for cell to cell
communication
 Coordinates
 Response
the function of cells
to an endocrine signal occurs
within minutes to hours
+
Endocrine System
Endocrine glands
Release hormones into the
bloodstream.
Hormones
Chemicals released in one
part of the body that travel
through the bloodstream and
affect the activities of cells in
other parts. body.
Pituitary Gland
Function: secretes nine hormones
that directly regulate many body
functions and controls functions of
other glands.
Disorders: Too much growth
hormones (GH) in early childhood
can result in a condition called
gigantism. To little GH can result in
Pituitary Dwarfism.
Robert
Wadlow
Thyroid
Gland
+
 Function: plays
a major role in regulation
the body’s metabolism.
 Disorders: Too
much Thyroxin can cause
a condition known as Hyperthyroidism. If
to little thyroxin produces it is called
Hypothyroidism.
+Pancreas
 Function: The
insulin
and glycogen in the
pancreas help to keep
the level of glucose in
the blood stable.
 Disorders: When
the
pancreas fails to
produce or properly use
Insulin, it can cause a
condition known as
diabetes mellitus.
+ Adrenal Gland
 Functions:
-The adrenal glands
release adrenaline in the
body that helps prepare
for and deal with stress.
-also regulates kidney
function.
Testes
+
 Functions:
 Pair
of reproductive glands that
produces sperm.
 Also secrete testosterone to give the
body its masculine characteristics.
+Interaction of Glands
The hypothalamus is
located in the brain and
controls the release of
hormones from the
pituitary gland.
It is an important link
between the endocrine
and nervous systems.
+
Test your hormones
Complete the drag and drop at
http://www.zerobio.com/drag_oa/endo.htm
to test your memory
OR
Complete the worksheet match up
+
Hormones
 Cell
to cell communication molecules
–
Made in gland(s) or cells
–
Transported by blood
–
Distant or local target tissue receptors – can only
communicate message to cell with the corresponding
receptor (on cell membrane or within cytosol)
–
Activate physiological response
–
Negative feedback prevents hormone overproduction
+
Types of hormones
+ Long Distance Communication:
Endocrine Hormones
 Made
cells
in endocrine
 Transported
via
blood to act at a site
distant from the
secreting cell or
gland
 Receptors
cells
on target
+ Local communication:
Paracrine and Autocrine Hormones
 Act
locally, either on
the secreting cell or a
neighbouring cell
 Diffuse
to target

Autocrine – receptor on same
cell

Paracrine – neighbouring cells
 e.g. cytokines
in
immune system
+Neurocrine Hormones
+
Pheromones
 Chemicals
released by animals to
communicate with other members of their own
species
 Can be used for:
 Attracting mates

Inducing mating activity

Marking territory

Signalling alarm

Marking food trails
+
Controlling Glucose levels
 Your
cells need an exact level of glucose in
the blood.
 Excess
glucose gets turned into glycogen
in the liver
 This
is regulated by two hormones
produces by the pancreas: insulin and
glucagon
Glycogen
If there is too
much glucose in
the blood, insulin
converts some
of it to glycogen
Glucose in the blood
Glycogen
If there is not
enough glucose
in the blood,
glucagon
converts some
glycogen into
glucose.
Glucose in the blood
+
Diabetes
 Some
people do not produce enough insulin.
 When
they eat food, the glucose levels in their
blood cannot be reduced.
 This
condition is known as DIABETES.
 Diabetics
sometimes have to inject insulin into
their blood. They have to be careful of their
diet.
Glucose
Concentration
Glucose levels rise
after a meal.
Insulin is produced
and glucose levels
fall to normal
again.
Normal
Meal eaten
Time
Glucose
Concentration
Glucose levels rise
after a meal.
Diabetic
Insulin is not
produced so
glucose levels stay
high
Meal eaten
Time
The glucose in the
blood increases.
Glycogen
But there is no
insulin to convert
it into glycogen.
Glucose in the blood
Glycogen
Glucose
concentration rises
to dangerous
levels.
Glucose in the blood
+
Activity and homework
 Complete
 Quick
activity 5.4
check questions 13, 17 &18
 Chapter
review questions 2, 3 & 9
+
Reflection and homework
 What
have you learnt about the endocrine
system today?
+
SIGNAL TRANSDUCTION
EXPECTED LEARNING
 To
learn what signal transduction is and
how it works
+
Signal transduction pathway
A mechanism linking a mechanical or
chemical stimulus to a specific cellular
response.

Communicating cells may be close together or far
apart
+
Cell communication
1.
Production of extracellular signalling molecule
(called a ligand) by a cell
2.
Detection of this ligand by a receptor protein on or in
target cell
3.
Transduction of ligand through cell
4.
Cellular response
5.
Control or regulation of ligand or response
+
2. Detecting the signal
To stimulate a response, hormones bind to
specific receptor on OR in the target cell to
form hormone-receptor complex

The cell targeted by a particular signal has a receptor
molecule complementary to the signal molecule, or ligand.

Most amine and polypeptide-based hormones are not able
to move through cell membrane – receptor proteins are on
the cell membrane

Steroid hormones move through membrane and bind with
receptors in cytoplasm
+ Receptor locations
 Cytosolic
–
–
–
Lipophilic ligand enters
cell
Often activates gene
Slower response
 Cell
–
–
–
or Nuclear
membrane
Lipophobic ligand can't
enter cell
Outer surface receptor
Fast response
Figure 6-4: Target cell receptors
+
3. Transduction

Converts the change in the receptor to
a form that can bring about a cellular
response.

This might involve a series of steps - a
signal transduction pathway - that alters
and amplifies the change.

Small amounts of signalling molecule
can produce a significant response or
even multiple responses due to
amplification.
+
3. Transduction
 Once
a hormone-receptor complex is
formed, the way the signal is transferred
depends on the type of hormone:

Amine and polypeptide hormones: Second
messenger is produced that stimulates cell response.

Steroid hormones: hormone can enter the cell easily,
binding to receptor and initiating response. Tends to
be slower, but longer lasting than second messenger
response.
+
Non-steroidal, lipophobic hormones
 Usually
involves the binding of extracellular
signalling molecules, like hormones and
neurotransmitters, to receptors that face
outwards from the membrane and trigger
events inside the cell.
 The
binding of a hormone with a receptor
often stimulates the action of a second
protein (e.g. G protein), or an enzyme, within
the cytoplasm.
 This
enzyme can then stimulate the activity of
other enzymes to bring about a response.
+
+
+
Steroidal, lipophillic hormones

Lipid soluble hormone travels in bloodstream
via a carrier protein( insoluble in water) and
passes through the cell membrane.

Binds to receptor protein found only in target
cells.

Hormone-receptor complex then enters the
nucleus.

Binds to specific regulator site for the targeted
gene.

Stimulates the gene to produce mRNA.

mRNA is read by ribosomes to produce a
specific protein.
+
+
4. Response
 the
transduction process brings about a cellular
response.

can be one of many different cellular activities,
such as:
activation/inhibition of a certain enzyme
 rearrangement of the cytoskeleton
 regulate protein expression through activation of
specific genes.
 Open or close protein channels, etc

 Once
the cellular response is initiated, the ligand
is degraded by cell enzymes
+
Summary
+
Summary
+
Activity
 Split
into 2 groups (4 and 5)
 Group
of 5: amine/polypeptide hormone
signal transduction
 Group
of 4: lipid hormone signal
transduction
 10
mins prep time, 2-3 mins each group to
present to the class
+
Reflection and homework
 What
did you learn about signal
transduction today? What are you confused
about?
 Homework:
Quick check qu 14-16
 Biochallenge 1
 Chapter review qu 4

+
DETECTING AND RESPONDING IN
PLANTS
EXPECTED LEARNING
 To
learn how plants detect and respond to
their environment.
+
Plant tropisms
A
plant growth response to an external stimulus
Light = phototropism
 Gravity = geotropism
Thigmotropism = touch
http://www.youtube.com/watch?v=1ZuZ_1cQnv4&feature=related


 Growth
towards the stimulus is a positive tropism
 Growth
away from the stimulus is a negative tropism
 Responses
rely upon chemical signals that initiate a
signal transduction pathway in plant cells to produce
a growth response.
What type of tropism is shown in these pictures?
+ Plant communication
Plant cells will send signals to one another to tell them:
1.
When trees to drop their leaves.
2.
When to start new growth.
3.
When to cause fruit to ripen.
4.
When to cause flowers to bloom.
5.
When to cause seeds to sprout.
Tree
Budding
Fruit
Ripening
Leaf Drop
Cactus
Blooming
Sprouting
Corn Seeds
+
Hormoneproducing
cells
Plant hormones
 Plant
cells produce
hormones that travel
throughout the plant
causing target cells to
respond.

In plants, hormones
control:
1.
Plant growth &
development
2.
Plant responses to
environment
Movement
of hormone
Target
cells
+
Plant hormones
 Are
very effective at low concentrations
 The
same hormone can produce different
responses in different parts of the plant (cf
animal hormones)
 Plants
don’t possess specialised secretory
organs or cells – most cells can produce and
secrete the hormones in the right conditions
+
Activity
 Read
over upcoming powerpoint slides on
plant hormones and/or read your text book
 At
the end of the class we will be playing a
game based on the different hormones and
what they do.
+
Plant hormones
+
What causes plants to grow toward
light?
+ Phototropism experiments with
coleoptiles
+ Auxin
 Indole
acetic acid and related molecules
 Photo-and
gravitropism
 Stimulates
cell elongation
 Made
in the shoot apex
 Travels
down the stem
+ Auxin promotes root growth
+
Other Effects of Auxin
 Apical
dominance
 Prevents
leaf abscission (ie leaf shedding)
 Enhances
fruit growth
+
Auxin
 http://www.youtube.com/watch?v=zctM_T
Wg5Ik
+
Cytokinin
Auxin 
 Cytokinins
delay and
even reverse senescence
 Release
buds from apical
dominance
 Stimulate
cell division
Cytokinins 
+
Gibberellins
 Essential
for stem elongation
 Found
as the toxin produced by some
fungi that caused rice to grow too tall
 Dwarf
plant varieties often
lack gibberellins
+
Gibberellins
 Gibberellins
are involved in bolting of rosette
plants
 Promote
cell division and elongation
 Gibberellins
are used to improve grapes
 Gibberellins
are involved in seed germination
–
gibberellins will induce genes to make enzymes that
break down starch
+
Ethylene gas
 The
smallest hormone
 Important
in seed germination, fruit ripening,
epinasty (i.e. downward bending of leaves),
abscission of leaves
 Sex
expression in cucurbits (i.e. pumpkins,
zuccini)
Ethylene causes Fruit to Ripen
1.
Causes fruits to ripen.
2.
Fruit tissues release a small amount of ethlyene
3.
As fruit become ripe, they produce more and more
ethylene, accelerating the ripening process.
Ethylene released by apples and
tomatoes causes fruit to age quickly.
+
Abscisic acid (ABA)
 Generally
acts as an inhibitor
 Important
in water stress and other stresses
 Causes
stomatal closure
 Prevents
premature germination of seeds
 Changes
gene expression patterns
+
Responding to light
 Plants
possess light-sensitive enzymes –
phytochromes
 Exist
in two forms that interchange
according
to the light they are exposed to.


active form (Pfr) at sunrise (i.e. red light)
inactive form (Pr) at sunset (ie far-red light)
 when
exposed to red light the enzyme is
able to catalyse a number of reactions
within the cell, leading to altered
transcription of genes in the nucleus, or
activation of proteins already in the cell
 influences
responses such as seed
germination, stem elongation, and
formation of leaves, flowers, fruits, and
seeds
+ Photoperiodism
 Photoperiodism
is a biological response to a
change in relative length of daylight and darkness
as it changes throughout the year.
 Phytochrome, and
other chemicals not yet
identified, probably influence flowering and other
growth processes.
 "Long-day
plants" flower in the spring as daylength
becomes longer (e.g. spinach).
 "Short-day
plants" flower in late summer or early
autumn when daylength becomes shorter (e.g.
broad beans).
 "Day-neutral
plants" flower when they are mature.
+
+
Activity & homework

Celebrity hormone
 Set
up activity 5.1 and 5.2 (FRIDAY START
OF LESSON). We will make observations at
the beginning of class for the next 2 weeks
 Quick
7 & 8.
check qu 19-22, Chapter review qu 5,
+
Reflection
 Write
a poem or anagram to remember
what plant each plant hormone does.