Differentiation

What is the genome?

The genetic code of an organism.

What are housekeeping genes?

Genes that are expressed in all types of cells.

How many genes are in the human body?

~20,000

How many housekeeping genes are in the human body?

4,000

What are housekeeping genes involved with?

Basic cellular functions (DNA replication, cell cycle regulation, metabolism)

How does differentiation occur?

Cells express different genes.

What stops genes from being expressed?

Regulatory proteins

What are stem cells?

Cells that can differentiate into many different types of cells.

The majority of differentiation occurs in which stage of a human life?

During embryonic development

Besides differentiation, what can influence gene regulation?

External conditions/environment

What is a tissue?

A group of cells that have differentiated the same way to perform the same function.

What are the benefits of cell differentiation?

1. Cells can work more efficiently, focusing only on the task that has been given to them.

2. They can have specialized structures for their functions.

3. As they do one specific task, they evolve faster at that task.

Which organisms does multicellularity exist in?

Plants, animals, most fungi, most algae

Did all multicellular beings evolve from the first multicellular being?

No, it evolved independently multiple times.

What are the three steps in the formation of multicellularity?

1. Indepent cells come together

2. Undifferentiated multicellularity

3. Differentiated multicellularity

Can bacteria come together in the first step for multicellularity?

Yes

What is the evolutionary pressure that encourages multicellularity?

Predation

Cells can increase their surface area to volume ratio by:

Forming long, thin extensions, having a thin, flat shape, or forming invaginations

What are the two types of cells that make up alveoli?

Type I and Type II Pneumocytes

Type 1 Pneumocytes are:

Thin and flat

Type II Pneumocytes have which adaptation to increase SA:V ratio?

Microvilli

Type II Pneumocytes have what role?

They release a surfactant to prevent an alveolus from sticking to itself

What is the basement membrane?

The ECM around alveoli, which is protein dense, and separates capilaries from alveoli.

What does it mean if muscle cells are striated?

Thin filaments of myosin and actin are organized into repeating sarcomeres

What is a sarcomere?

An organization of myosin and actin that powers muscle cell contraction

Which muscle type(s) have sarcomere?

Cardiac and skeletal

Which muscle type does not have striations?

Smooth

Which muslce type is voluntarily controlled?

Skeletal

What is skeletal muscle responsible for?

Movement

How are skeletal muscles attached?

In antagonistic pairs

What is smooth muscle for?

Contractions and movements of organs

Which muscle cells have atypical cell structure? How?

Skeletal muscles, their cells fuse together into multinucleated structures.

What are the levels of organization of muscle cells from big to small?

Muscle, Fascile, Muscle fiber (cell), Sarcomere, Myofibril

Muscle fibers are formed by the fusion of:

Myoblasts

Cardiac muscle cells are connected by:

Intercalated discs

Cardiac muscle cells are shaped like which letter of the alphabet?

Y

Intercalated discs allow for the passage of what?

Electrical signals

What are gamete?

Cells involved in reproduction

What are the parts of a sperm cell from top to bottom?

Acrosome, nucleus, centriole, Mitochondria, terminal disc, tail

What is the acrosome for?

Digesting the zona pellucida during fertilization

What are the structures of the egg from the outside in?

Corona Radiata, Zona Pellucida, Cortical Granule, Nucleus, Yolk

What is the Corona Radiata?

A group of follicle cells that formed with the egg

What is the zona pellucida?

A layer of glycoproteins that surround the egg and are digested by the acrosome of sperm cells

What are cortical granules?

Vesicles full of enzyme on the inner edge that prevents multiple sperm from fertilizing the egg.

What is the yolk?

The cytoplasm of the egg, which contains all the proteins required for early development.

Humans have how many distinct cell types?

220

What are the benefits of a sperm’s shape?

It reduces resistance

What are the benefits of the egg cell’s shape?

They are the largest cell in the human body, and store all the nutrition required for early development

What is the shape of an erythrocyte?

Biconcave disk

What are erythrocytes also known as?

Red blood cells (RBC)

What is the benefit of the biconcavity of erythrocytes?

They are small and flexible allowing them to fit in small capilaries, and their shape maximizes gas exchange

What are the benefits of the shape of B-lymphocytes?

They increase in size during infections allowing them to produce more antibodies

What are the benefits of the shape of cerebellum neurons?

They are small and narrow allowing them to pack densely

What is the function of cerebellum neurons?

They control sensory data and motor activity (Senses & Movement)

What are the benefits of the shape of motor neurons?

Their long size allows messages to pass rapidly

What is a formula for surface area, volume, and the SA:V ratio based on side length?

SA: 6a²

V: a³

SA:V: 6/a

Why does the SA:V ratio limit cell size?

Cells need a large SA:V ratio to excrete waste and intake nutrients fast enough to maintain their metabolism

What happens to cells when they start growing too large?

They divide via mitosis or binary fission (Meiosis is only for making gametes)

What are the benefits to using cubes to model SA:V ratios?

The formulas are easy to work with, and they can be modeled easily with agar for an intuitive grasp.

What are the downsides to using cubes to model SA:V ratios?

Most cells are not cubic in nature, and are often irregular, meaning that cubes cannot be used to even estimate the SA:V ratio.

What causes cells to differentiate?

Morphogens, which are released by cells and depending on the strength of the signal, differences in expression occur

What is an important morphogen in human development

Retinoic acid

Where are adult stem cell found?

Epidermis, brain, liver, heart, bone marrow, adipose tissue, skeletal muscle

Where are hematopoietic cells found?

Bone marrow

Hematopoietic cells differentiate into what?

Blood cells!

Stem cells are also found in a _______ of hair follicles

bulge region

Why are stem cells in a hair follicle in a bulge?

To protect them, while still having them close engouh to the skin to differentiate.

What are the three kinds of stem cells?

totipotent, pluipotent, multipotent

How many times can STEM cells differentiate?

As many times as they want (no limit)

During what stages of development are cells totipotent?

Zygote, Morula

During what stages of development are cells multipotent?

Inner cell mass of a bloastocyst

During what stages of development are cells pluripotent?

After the embryo starts differentiating to death

The morula becomes what?

A blastocyst, with and outer trophoblas which becomes the placenta, and an inner mass which becomes the embryo

What happens to the inner cell mass of a blastocyst?

It differentiates into the germ layers.

What are the germ layers? (List them)

Ectoderm, Endoderm, and Mesoderm

What does the ectoderm become?

Nerve, pigment, skin cells

What does the Endoderm become?

The digestive tract and respiratory system

What does the mesoderm become?

Muscles, bones, and connective tissue