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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?
Cells can work more efficiently, focusing only on the task that has been given to them.
They can have specialized structures for their functions.
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?
Indepent cells come together
Undifferentiated multicellularity
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
