BM108

Second Law of Thermodynamics

Entropy is a measure of disorder. Disorder must always increase. Physical systems decay

What gets released between energy moving from the sun through the biosphere into the universe causing energy loss?

Hot photons get released between the sun and biosphere and cold photons get released between the biosphere and universe

How long ago did the big bang take place?

13.82 billion years ago

When did earth form?

4.6 billion years ago

When did the theia impact occur?

4.5 billion years ago

How long ago did the beginnings of complex life begin?

3.5 billion years ago in Australia

After what stopping did life start evolving?

Constant meteorite bombardment about 3.75 billion years ago

What element is life on earth based on?

Carbon, specifically the isotope C12

When did photosynthesis as a concept arise?

3 billion years ago

What is one of the first complex forms of life formed 3.5 billion years ago?

Blue-green cyanobacteria

How far away does the moon move from earth every year?

5cm

Deep sea vents (black smokers)

Contact point of sea water and magma. Hydrothermal vent. Steam jets shoot up. Potential theory for where life could have started due to its thermal environment. Not photosynthetic as too deep in the water so chemosynthetic

Chemosynthetic

Having the ability to use the energy from chemical reactions to construct organic food molecules

Describe a black smoker

The sea water is hot alkaline coming up from magma. Cool acidic water comes up from the surrounding sea. Rock wall inbetween these 2 becomes a 'battery'. In this environment, the temperatures are right for organic chemistry. Metal sulphides are used as catalysts. CO2 is captured on the rock

Hot springs

Another theory of where life could have started. 'Primordial soup', perfect environment of chemical and geological parts for life to grow

Describe some bacteria 'living off of just air'

In the antarctic, some bacterial species can survive by scavenging trace atmospheric gases, including H and CO, and create energy from this

Why do some believe that clay could have been an important home for early chemical life?

Clay provides an ordered microenvironment for complex molecules to assemble without immediate decomposition by hydrolysis. Clay acts as a catalyst for life

Describe what occurred in Oparin and Haldane's experiment

They attempted to mimic the 'primordial soup'; trying to form organic molecules in an oxygenless environment, triggered by UV light

Define Protists

The simplest, single-celled eukaryotes, but they still carry out life functions and show division of labour among the various cell structures

Metazoans

Multicellular animals that have cells specialised for particular functions

Why is bilateral symmetry important?

Better for moving in a direction

What is Cephalisation?

The differentiation of a head

What is an advantage of an organism moving head first?

Directional movement as nervous tissue, sense organs and often the mouth are located in the head

What are the 3 germ layers that contribute to different tissues and parts of the body?

Endoderm, Mesoderm, Ectoderm

Endoderm

Internal Layers. Lung cells, Thyroid cells, Digestive cells

Mesoderm

Middle Layer. Cardiac muscle cells, skeletal muscle cells, tubule cells of the kidney, red blood cells, smooth muscle cells

Ectoderm

External layer. Skin cells of epidermis, Neuron on brain, pigment cells

Coelomates

Have a body cavity entirely within the mesoderm called the Coelom

Step 1 of Embryonic Development

Fertilisation restores the diploid genome.

Cleavage in embryonic development

The division of cells in the early embryo. It undergoes rapid cell division with no significant growth. Produce a cluster of cells the same size as the original zygote

Blastocyst

A structure consisting of 128 cells. An inner cell mast/embryoblast. This goes on to form the embryo proper. An outer cell mass/trophoblast goes on to form placenta

What forms embryonic stem cells?

The inner cell mass

Pluripotent stem cells

Can give rise to every cell type in the animal body. Proliferate indefinitely. Firstly recognised in teratocarcinomas

How does the blastocyst 'hatch'?

By shedding outer layer

What does hatching do?

Exposes the bare trophoblast cells to the uterine wall (day 7)

When is an embryo fully embedded?

After 10 days

What begins to thicken as it begins to implant and form placenta?

The trophoblast

Epiblast

Dorsal, next to amniotic cavity

Hypoblast

Ventral, facing the yolk sac

What undergoes a complex rearrangement to form the germ cell layers?

The epiblast

Gastrulation movement

Some epiblast cells begin to migrate inwards toward the primitive streak. They then move through the layer towards the hypoblast. The first cells through become the definitive endoderm. The next cells through form the mesoderm. This movement progresses tail to head (caudal to cranial)

What type of tissue are ectoderm and endoderm?

Epithelial tissue meaning they form sheets of tissue

What type of tissue is Mesoderm?

Mesenchymal tisse

Mesenchyme cells

Star shapes and do not attach to one another, therefore migrate freely

Notochord Maturation

A rod defining the body axis and is the future site of the vertebral column

Neurulation

How the brain and spine form. The notochord induces a fold in the overlying epiblast/ectoderm. Pinches off to form a neural tube

Notochrord signals

Converts the overlying ectoderm. Notochord signals overlying ectoderm to become the neural plate. Neural plate to neural groove to neural tube: pinched off into body

What is folic acid for?

It helps the neural tube be pinched off

When does the closure of the neural tube happen?

Begins at the end of week 3 and complete by the end of week 4.

How is the neural tube closed?

It is zipped cranially and caudally

What do neural crest cells form?

Sensory nerve cells and other structures

Spina Bifida

A condition caused by incomplete neural tube closure

What is the most effective way to prevent Spina Bifida?

To take folic acid supplements before and during pregnancy

Somites

Segmentation of body plan

What do somites derive into?

Dermatone, Myotome, Sclerotome

Segmented Myotome

Abs

Segmented Sclerotome

Spine

Differntiation

Start as pluripotent in the blastocyst until they reach their terminally differentiated form: heart muscle, neuron, liver cell

Cell differentiation forming blood cells is what process

Mesoderm

What do local cellular interactions do?

Organise tissue

What do long-range 'morphogen' signals do?

Determine the orientation of the embryo and its specific region

What do cellular responses to these 2 types of signals cause?

MIgration and specific differentiation processes to be irreversibly started

Cells organising themselves

Cell adhesion often drives this. Proteins expressed on the surface of cells that like to stick the same molecules on other cells: homophilic interactions

What is a Morphogen?

A secreted molecule that induces cell fate decisions in recipient cells in a concentration gradient-dependent long-range manner

What does this require?

-Production from a point source

-Long-range distribution

-Reception and interpretation by cell

What do cells do when they sense the quantity of morphogen?

Compare it to 2 programmed thresholds and respond to that level with specific differentiation/behaviour

What can an injection of Wnt or Nodal morphogens induce?

A secondary axis

Situs Inversus

Body organs are swapped over

Morphogen Receptors

i.e. Patched for Shh signal to the nucleus to initiate appropriate differentiation programs within the cell

How are HOX genes arranged on the chromosome?

In a co-linear fashion

In females, which degenerates: medullary cords or cortical cords?

Medullary cords

In males, which degenerates: medullary cords or cortical cords?

Cortical cords

What does SRY do?

Codes for a transcription factor that regulates many other genes. It promotes development of male reproductive anatomy and suppresses development of female reproductive anatomy

What cells form testes?

Sertoli Cells

What cells form ovaries?

Follicle Cells

Turner's Syndrome

A singular X chromosome (XO). Females who do not mature sexually. Short stature, often other congenital abnormalities e.g. web of skin on either side of neck

Klinefelter's Syndrome

XXY. Male, sterlile, testes small, may have breast growth. Tend to be tall. May have mild mental impairment

Name the 5 main parts of Neuroanatomy

-Spinal Cord

-Brain Stem

-Cerebellum

-Diencephalon

-Cerebral Cortex

What are the 3 parts of the Brain Stem?

Medulla, Pons and Midbrain

What are the 3 parts of the Diencephalon?

Thalamus, Basal Ganglia and Hypothalamus

What are the 4 parts of the Cerebral Cortex?

Frontal, Parietal, Temporal and Occipital Lobes

Anatomy of a Neuron

Cell Body, Dendrite, Axon, Synapse

3 Germ Cell Layers

ectoderm, mesoderm, endoderm

Where is the Ectoderm found?

Nervous System

What is the Neural Plate?

The precursor of the central and peripheral nervous systems

What does BMP stand for?

Bone Morphogenetic Protein

BMP Inhibitors

Chordin, Noggin and Follistantin

Where does BMP go?

Epidermis

Where do BMP inhibitors from the organiser go?

Neural Induction

What is the longitudinal axis of the brain called?

Rostrocaudal

What axis is at the top and bottom of the brain?

Dorsoventral

Different types of patterning of the nervous system

Rostrocaudal, Dorsoventral, Forebrain

What type of patterning is responsible for spinal cord development?

Dorsoventral

Which part of the brain is Otx2 found?

Forebrain and Midbrain

Where in the brain is Gbx2 found?

Hindbrain

Are Wnt inhibitors found at the rostral or caudal side of the neural plate?

Rostral

Are Wnt signals found at the rostral or caudal side of the neural plate?

Caudal

Where in the brain is the engrailed gene found?

MHB (midbrain-hindbrain boundary)

What is the ventral tube of dorsoventral patterned by?

Sonic Hedgehog protein secreted from the notochord and floor plate

What is the dorsal neural tube of dorsoventral patterned by?

Bone Morphogenetic proteins