Basics of Biology


While exploring the intricate workings of the cell, it’s vital to remember that every action requires energy. This lecture delves into cellular metabolism, answering the question: How does the cell generate the energy needed for its countless reactions?
Key topics in this lecture:
All energy on Earth originates from the sun. While animals rely on consuming plants or other animals, plants harness solar energy to create the carbon bonds that sustain life.
Metabolism is the sum of all reactions in the body and can be categorized into two complementary processes:
Catabolism releases energy stored in molecules like carbohydrates, fats, and proteins. This energy fuels cellular functions, primarily through the production of ATP (adenosine triphosphate).
Anabolism synthesizes key biomolecules:
The term burning energy is metaphorical—no flames exist within the body. However, like a fire burning wood, catabolism:
The breakdown of glucose (glycolysis) and fats (lipolysis) provides energy precursors:
Fun Fact: Humans can produce glucose without dietary carbohydrates via gluconeogenesis.
The CO₂ produced is exhaled, completing a cycle where plants use CO₂ for photosynthesis and release oxygen for animals.
Plants reverse cellular respiration:
The Glucose-Ketone Index: A tool for managing glucose and ketone levels to suppress cancer growth.
Understanding cellular metabolism reveals the intricate balance between catabolism and anabolism, the pivotal role of ATP, and the interconnectedness of life processes. From the energy derived from the sun to the recycling of CO₂, metabolism is a testament to the beauty and complexity of life on Earth.
“You are now modest masters of biology, equipped with a deeper appreciation for the mechanisms of life.”

At this point in our journey through the cell, we’ve explored the structure and function of the cell itself and discussed the central dogma, the flow of genetic information that shapes how genes determine the structure and function of living organisms. Today, we turn to the life of the cell cycle—the series of events a cell undergoes to divide and reproduce. Along the way, we’ll uncover the intricacies of cell division, including its common forms, mitosis and meiosis, and the miraculous balance of processes that ensure its success.
Before delving into the cell cycle, let’s clarify a fundamental concept: chromosomes. These tightly packed structures of DNA hold the genetic instructions essential for life. Humans have 46 chromosomes arranged in 23 matched pairs, one set inherited from each parent. These are divided into:
The cell cycle encompasses several key stages, remembered using the acronym IPMAT:
Finally, cytokinesis completes the process, physically splitting one cell into two identical daughter cells.
Mitosis ensures the production of two genetically identical daughter cells, critical for tissue growth and repair. Key phases include:
This equational division maintains the same chromosome number, supporting organismal growth.
Meiosis, in contrast, occurs only in germ cells and involves two rounds of division, resulting in four haploid cells. This process introduces genetic diversity through:
Occasionally, errors during the cell cycle can lead to chromosomal abnormalities, such as:
These abnormalities highlight the delicate precision required for successful cell division.
The cell cycle not only ensures growth and repair but also underpins evolution by generating diversity. The interplay of genetic material through meiosis has been instrumental in shaping life as we know it.
At the conclusion of this exploration, you should be well-acquainted with the steps, purposes, and nuances of the cell cycle, along with the fundamental differences between mitosis and meiosis. By understanding these processes, we gain a deeper appreciation for the intricate machinery of life and the cellular miracles occurring within us every day.

The concept of the central dogma of biology is foundational to understanding the flow of genetic information and its significance in shaping life. This principle, proposed by Francis Crick in 1958, describes the process by which genetic information encoded in DNA is transcribed into RNA and subsequently translated into proteins. These proteins ultimately determine the structure, function, and appearance of living organisms.
At its core, the central dogma explains the flow of genetic information:
This sequence illustrates how genes direct the production of proteins, which, in turn, define the traits and functions of an organism. Proteins play a critical role in every biological process, from determining physical characteristics like height and eye color to regulating cellular functions.
Francis Crick, renowned for co-discovering the double-helix structure of DNA, introduced the central dogma as a means of connecting DNA’s structure to its function. His work laid the foundation for understanding how genetic information influences the composition and operation of living organisms.
The relationship between genotype (genetic code) and phenotype (observable traits) can be likened to blueprints and the structures they create:
Proteins synthesized through this process define everything from skin color to cellular function.
To ensure proper cellular function:
Introns, non-coding regions within genes, remain a topic of scientific intrigue. While they do not directly encode proteins, some hypothesize they serve as buffers against damage or play roles in evolutionary adaptability. Further research is needed to fully understand their purpose.
Epigenetics explores how environmental factors, diet, and lifestyle influence gene expression without altering the underlying genetic code. For example:
Understanding the central dogma provides insight into the intricate processes that define life. It bridges the gap between genetic information and the proteins that shape organisms, emphasizing the importance of maintaining cellular health to support life’s delicate balance.

Understanding the cell’s intricate machinery brings us to a crucial concept known as the central dogma—the flow of genetic information that defines our individuality. Before diving into this cornerstone of biology, it’s essential to grasp the four fundamental biomolecules that underpin cellular function:
These biomolecules form the foundation of life, each playing unique roles in cellular processes.
All biomolecules share a common component: carbon. Due to its chemical versatility, carbon can form strong bonds with other elements—including itself—resulting in diverse structures like chains and rings. This versatility allows carbon to serve as the backbone of:
Carbon’s ability to form stable and varied molecular frameworks makes it essential to the chemistry of life.
Carbohydrates exist in three forms:
Lipids play critical roles in both energy storage and cellular structure.
Proteins are versatile and essential for nearly all cellular functions.
DNA and RNA are vital for storing and transmitting genetic information.
Enzymes, specialized proteins, drive the chemical reactions essential to life by:
Key features of enzymes:
Example: Glucokinase initiates glycolysis by adding a phosphate group to glucose, committing it to energy production.
The biomolecules—carbohydrates, lipids, proteins, and nucleic acids—are the essential building blocks of life. Together, they enable cells to perform complex functions, sustain energy, and express genetic information. Enzymes further enhance these processes, ensuring life thrives efficiently and dynamically.

Understanding how molecules move across or through gradients is key to cell biology. This subtopic delves into diffusion, concentration gradients, and the different types of molecular movement.
This lecture explored:
Understanding these processes provides the foundation for appreciating cellular function and the principles of molecular movement. The next lecture will focus on the central dogma of molecular biology.

By studying these notes, you’ll have a solid understanding of the cell’s structure, its role in life, and its importance in the broader study of biology.
Dante Sisofo emphasizes the significance of repetition in street photography as a means to enhance one’s skills and deepen understanding of urban environments. Key aspects of his perspective include:
- Daily Practice: Sisofo advocates for consistent daily practice, suggesting that photographers follow the same routes during their commutes. This repetition allows photographers to become attuned to the nuances of their surroundings, increasing the likelihood of capturing compelling images. Dante Sisofo
- Pattern Recognition: By repeatedly traversing the same areas, photographers can identify patterns in light, movement, and human behavior. This familiarity enables anticipation of moments before they occur, leading to more intuitive and impactful photography. Dante Sisofo
- Embracing the Mundane: Sisofo believes that beauty often resides in everyday scenes. Through repetition, photographers can uncover extraordinary elements within ordinary settings, fostering a deeper appreciation for the subtleties of daily life. Dante Sisofo
- Discipline and Growth: He likens street photography to disciplines like weightlifting, where consistent repetition and practice lead to gradual improvement. By focusing on the process rather than immediate results, photographers can achieve meaningful progress over time. Dante Sisofo
In summary, Dante Sisofo views repetition as a fundamental component of street photography, essential for honing skills, recognizing patterns, and discovering beauty in the everyday.
Looking through reflections is like looking through a portal to another world. Currently, I’m positioning my Ricoh GR3X up against the glass, duplicating City Hall, with the building in the background.
This location is bustling with pigeons, which I’ve photographed countless times in countless ways. But that’s the fun of it—challenging yourself to photograph the same thing in new ways. How many vantage points can you discover? How many angles can you explore? City Hall, as an icon of the city, offers endless possibilities.
Nearby, someone is feeding the birds. It’s always fascinating to watch them fly, and I managed to capture a great moment: five pigeons perfectly aligned, with City Hall split into light and shadow. The triangle formed by their position was striking. It’s moments like this that make photography rewarding—finding perfection in spontaneity.


“Repetition is critical. It’s about trying again and again, looking at the same thing with fresh eyes.”
I’ve photographed City Hall through a bus stop, from a simple street corner, vertically, and even with pigeons perched on top of newspaper stands. It’s a constant exercise in observation—lines, shapes, forms—and finding the puzzle pieces that fit together.
Reflections feel like portals into another world. Light and shadow transform the mundane into the magical. The clouds in the background are always shifting, adding new dimensions to familiar scenes.
“The power of photography lies in the fact that you cannot make the same photograph twice.”
City Hall remains a constant, standing tall. But the interplay of light, clouds, and pigeons ensures there’s always something new to discover. It’s a powerful exercise to revisit the same place and find new angles, new stories to tell.
Photographing pigeons is a thrilling challenge. Their spontaneity demands fast reactions and patience. Capturing them mid-flight, wings outstretched, or in unique formations is incredibly satisfying.
“It’s all about patience and pattern recognition.”
With time, the scene evolves. The pigeons take flight, and the patterns shift, offering endless opportunities to create. This process of observing, waiting, and recognizing patterns is what makes photography such a joyous and dynamic art form.
What’s poppin, people? It’s Dante. Just walking by Mr. Benjamin Franklin’s house. I believe his house was here. Right? Here’s the printing office and bindery, and to the left is Benjamin Franklin’s Post Office.
Here’s the tunnel. Yeah, pretty cool. Benjamin Franklin went to and from his house through this original passage. And now Dante is entering. Echo. I can hear Franklin in the echoes.
Yeah, it’s a really beautiful city, Philadelphia. So much rich history. The architecture is just incredible too. This kind of stuff stands the test of time.
There’s the keystone. The city is order, right? All of these alleyways, passages, sidewalks, roads, the grid, the traffic lights, the signals, the signs that give you information. All the paths, all the nooks and crannies of a city are what set things in order.
But the individual within the city is chaos. The unique individual is that ball of frenzy, that ball of chaos, the unknown. There’s something unpredictable about humanity—something spontaneous about the way people move through a city despite the order of the streets.
“When I walk on the streets, I’m walking on the intersection between order and chaos.”
As an artist and photographer, this is where I thrive: in the unknown. Observing humanity, observing life on the streets in all its spontaneity with a camera allows me to put order to the chaos. This is where I thrive. City life to me is superior—it’s where I love to be, where I love to walk and spend my time endlessly. I love humanity.
A couple of years ago, I stopped at a bar near the river to get water. I wound up coming back with a framed print, leaving it behind for them. If you visit that bar, maybe you’ll see it.
I love giving my photos away, just for no reason. My bus driver changes every month, and I try to chat with them, get to know them for that brief time. It’s always sad when they leave. Recently, I gave one of my prints to Adriana, the woman who was driving me. Shout out to Adriana, super cool woman.
Here’s a simple way to spread joy with photography:
It’s a cheap, easy way to make gifts. Photography as a gift is interesting—it brings me joy to spread joy with others.
Throughout my travels, I carried an Instax camera and gave photos to people in the moment. I did this in Hanoi, Vietnam, back in 2022. Those photos remind me that, as much as photography can feel like a selfish act of taking, it’s also a gift.
“Maybe photography is a love letter to life, a gift for humanity.”
Sharing these moments with others brings purpose to the act of making photographs.
Man is designed to be outside. Man is designed to move. Anytime I’m indoors, I feel trapped. I don’t know if that’s just me, but it’s hard to stay inside.
Recently, I upgraded my computer mouse to a Logitech vertical mouse with better ergonomics. It keeps your hand in a handshake position, much more natural. I rarely use the computer, but when I do, I want it to be better for my health. I’m starting to learn Adobe InDesign and maybe dabble with Lightroom to organize my archive.
While walking by the Delaware River, I noticed a beautiful strip of light cast on the water. The sky was mostly clouds, but there were little openings where light shone through. It looked unreal, like an angel might come down from the sky. Moments like this remind me how open the world is.
The tragedy of modern city life is how ordered it feels, like a cage. Skyscrapers, condos, and buildings make you forget you are free.
“I always try to get to the horizon or an elevated point—just to look out, to see what’s out there.”
Philadelphia’s beauty lies in its balance. Alongside its structured grid are the wide-open spaces by the rivers and trails. The parks, forests, and rivers represent chaos—always changing, always flowing, always growing. This dichotomy fuels me.
“Perhaps my photographs are ultimately just a love letter to Philadelphia.”
The Great Fire of London in 1666 had a profound influence on urban planning, architecture, and fire safety standards. These lessons significantly shaped the development of Philadelphia, particularly in its early layout and design under William Penn, who founded the city in 1682. Here’s how:
1. Grid System for Fire Prevention
• The Great Fire of London demonstrated the dangers of dense, unplanned urban development and narrow streets, which allowed the fire to spread rapidly.
• Learning from this, William Penn designed Philadelphia with a grid system of wide streets and open spaces to minimize fire risk.
• Penn included five public squares (now parks), which acted as firebreaks, ensuring no part of the city became overly congested.
2. Fireproof Building Materials
• The Great Fire highlighted the risks of wooden buildings, which were highly flammable.
• Philadelphia incorporated brick and stone as preferred building materials for its major structures, following London’s post-fire reconstruction strategy.
3. Focus on Cleanliness and Health
• The Great Fire exposed the hazards of overcrowded cities, leading to reforms in urban sanitation and housing.
• Philadelphia’s design emphasized open spaces, wide streets, and good ventilation to prevent fires and promote public health.
4. Firefighting Infrastructure
• After the Great Fire, London implemented organized firefighting efforts, including the establishment of the Insurance Fire Brigades and improved water access.
• Philadelphia adopted these ideas early, with Benjamin Franklin founding the Union Fire Company in 1736, one of the first volunteer firefighting organizations in America.
5. Quaker Ideals in City Planning
• William Penn, a Quaker, sought to build a city that was orderly, safe, and reflective of Quaker values of simplicity and practicality.
• The lessons from London’s destruction reinforced his vision of a “greene countrie towne”, where buildings were separated by gardens, reducing fire risks.
Legacy:
The lessons from the Great Fire of London ensured Philadelphia was one of the best-planned cities of its time, prioritizing fire safety, public health, and efficient urban design. These principles helped Philadelphia become a model for other cities and played a critical role in its rapid growth and importance during the colonial era.
It is very rare for me to do any computer work, but I would like to start learning Adobe InDesign and playing around with Lightroom on my desktop more so I decided to upgrade from my magic mouse to a Logitech MX Vertical Ergonomic Wireless Mouse
This is the perfect combo for a standing desk. If I am going to spend any time using a mouse I am going to use the one that is best for your health!
A fun idea: only do computer work while standing with a 40lb weighted vest on?

You don’t need a church, your body is the church.
The word church has an interesting etymology rooted in ancient languages and Christian tradition.
1. Greek Origins
The word derives from the Greek term κυριακόν (kuriakón), meaning “of the Lord” (from κύριος (kyrios), meaning “Lord”).