The Cell and Systems
Throughout the last month of the Biobiography project, we learned about cells, the parts of a cell, organs, and systems found in the body. We learned about these through notes, annotations, and lessons. At the end of it, we each wrote a nine paragraph report talking about everything that we had learned.
In this unit I learned that organelles work together to allow a cell to function and cells are the building blocks for organisms. Each organelle, in a cell, works with all of the other organelles to maintain balance, or homeostasis. The organelles have specific functions such as the mitochondria, which create energy, and the ribosome, which translates RNA into proteins. The organelles inside of a eukaryotic animal cell include; the nucleus, the cytosol, the Golgi apparatus, lysosomes, the cell membrane, the mitochondrion, the smooth endoplasmic reticulum, the rough endoplasmic reticulum, the ribosomes, and the cytoskeleton. The cell membrane of a cell separates the insides of the cell from the outside environment, and regulates what enters and exits the cell, effectively controlling the transport of molecules needed for vital functions. A eukaryotic plant cell also includes a cell wall and chloroplasts. A prokaryotic cell does not include a membrane-bound nucleus and instead has the DNA, or RNA, floating around in the cytosol of the cell. Cells can exist as an independent unit, a single-celled organism, or a sub-unit that specializes in carrying out specific functions within multi-cellular plants and animals. In an organism, a tissue is composed of similar cells that work together and make important macromolecules, such as proteins. Because these cells work together, the body is able to maintain homeostasis. So, cells form together to make up tissues, which are then used to form organs. The organs, in our body, are grouped into organ systems that function and work together to keep our body running. When an organism is in a state of homeostasis, it is in a state of balance. In order to remain in homeostasis, the organism’s systems must work together to maintain the body. The many different organs and organ systems, found in the body, work together to keep an organism alive.
A cell is composed of many various organelles that have specific roles to keep the cell functioning. The nucleus of a cell is a membrane-bound structure found in the center of a cell where DNA is stored. The DNA inside the nucleus is responsible for providing the cell with genetic information that differentiates it from other cells found in the body. The nucleolus of a cell produces ribosomes and is found within the nucleus. Once created, the ribosomes move onto the rough endoplasmic reticulum where they are critical in protein synthesis for the cell. The nucleus works together with the ribosomes by supplying the genetic information, mRNA, which is used by the ribosomes to create proteins, or enzymes that facilitate reactions taking place in the body. The mitochondria uses molecules, brought into the cell by the cell membrane, to create energy, or ATP, that a cell then uses to move, divide, and function. In the mitochondria, food is combined with oxygen to produce the primary energy source for the cell. Every cell is enclosed in a membrane that facilitates the movement of molecules, ions, or objects into and out of the cell. The cell membrane is composed of a double layer of phospholipids, or a lipid bilayer. The exposed sides of the membrane are hydrophilic, meaning that they are compatible with water both within the cytosol and the outside of the cell. The hidden tails of the phospholipids are hydrophobic, so the cell membrane acts as a barrier to the flow of water. The membrane includes an abundance of proteins that are crucial to cell activity. These proteins include receptors and pores responsible for the controlling of the entry and exit of ions like sodium, potassium, calcium, and chloride. The cell membrane facilitates the transport of molecules in and out of the cell through the use of six different transports.
The three main types of transportation that occur at the cell membrane are, passive transport, active transport and vesicle transport. Passive transport is when substances cross the membrane without using any energy from the cell. The types of passive transport are simple diffusion, osmosis, and facilitated diffusion. Simple diffusion is where molecules, or substances, move from a higher concentration of particles to a lower concentration, until the concentration is the same on both sides of the membrane. Substances that can move through the lipid molecules, in the membrane through simple diffusion, are really small, such as oxygen or carbon dioxide molecules. Osmosis is a type of diffusion where, specifically, water molecules move into or out of the cell until the concentration is the same on both side of the cell membrane. Facilitated diffusion occurs when large molecules, like glucose, cannot simply pass through the membrane. These molecules then require the assistance of, specialized, transport proteins found in the membrane. Two types of transport proteins are carrier proteins and channel proteins. Channel proteins form holes or pores in the membrane that allow molecules to pass through while carrier proteins bind with specific ions, or molecules, change shape, and then carry the ions, or molecules, across the membrane. Molecules that are too large to cross the cell membrane, such as proteins, despite the concentrations, must use vesicle transport. There are two types of vesicle transport, endocytosis and exocytosis. Endocytosis is a type of vesicle transport, where part of the plasma membrane consumes the substance for transport, and separates from the membrane inside the cell. Exocytosis is the type of vesicle transport that moves something out of a cell. Vesicle transport requires energy so it is a form of active transport. Active transport takes place when a substance is moving from a lower concentration to a higher concentration, through the membrane, thus requiring energy from the cell. Much like, passive transport, transport sometimes uses transport proteins to move substances. The energy for active transport comes from a molecule called ATP, which is produced through a process called, cellular respiration.
The Cell Membrane is the outer layer of the cell. Molecules are transported across the cell membrane through active and passive transport.
Cytosol is the fluid that is around and inside the cell. It is where all of the cellular metabolism happens.
The Cytoskeleton helps to maintain the cell shape. It also plays a part in the returned movement of all organelles, cell locomotion, and muscle contraction.
The Centriole is a ring of nine groups of fused microtubles. Microtubles and centrioles are part of the Cytoskeleton.
The Centrosome is an area in the cell where microtubles are produced. it is a pair of small centrioles.
The Nucleus holds the DNA and who are are. It is essentially the “hub” of the cell. It is the most obvious organelle in the cell.
The Nucleolus is the center of the nucleus, and it creates ribosomes.
Lysosomes contain hydrolytic enzymes necessary for intracellular digestion in white blood ells that eat bacteria. The enzyme surrounds the bacteria and kills it. An uncontrolled release of it into the cytoplasm is a component of necrotic cell death.
Peroxisomes are responsible for protecting the cell from its own production of hydrogen peroxide. White blood cells produce hydrogen peroxide to kill bacteria. Peroxisomes then breat it down to water and Oxygen.
Secretory Vesicles are cell secretions (hormones, neurotransmitters) packaged in secretory vesicles at the Golgi Apparatus. The Secretory Vesicles are then transported to the cell surface for release.
The Golgi Apparatus is a stack of membrane bound vesicles that are important for transporting larger vesicles that are surrounded by smaller vesicles containing packages. The contents of Lysosomes, Peroxisomes, and Secretory Vesicles are packaged in vesicles at the periphery.
The Mitochondria provides energy for the cell. It has a double membrane. The outer one is smooth, and the inner is coarse. It is where Oxygen is combined with sugar to create ATP (the cell’s energy source). The DNA inside is shorter and irrelevant to nucleus DNA. The DNA in the Mitochondria is passed down by your mother.
The Ribosomes help the cell function by translating genetic messages into proteins by the production of peptide sequences.
The Endoplasmic Reticulum helps the synthesize lipids and proteins.
Systems – Structure and Function
The organ systems found in the body (shown above) include, the respiratory system, the cardiovascular (circulatory) system, the reproductive system, the digestive system, the excretory (urinary) system, the skeletal system, the nervous system, the lymphatic (immune) system, the endocrine system, the muscular system, and the integumentary system.
The respiratory system consists of the nose, trachea, bronchi, bronchioles, diaphragm, and alveoli. The respiratory system exchanges gases, mainly carbon dioxide and oxygen, between the body’s cells, tissues, or organs and the external environment. Oxygen is inhaled from the environment and is passed down into the lungs through the trachea, which branches off into bronchi, and then bronchioles, which carry oxygen deeper into the lungs which eventually end up in small air sacs, called alveoli. Oxygen diffuses through the wall of the alveoli into the blood, where it is exchanged for carbon dioxide that passes from the blood to the lungs and is exhaled.
The cardiovascular, or circulatory, system transports blood cells, immune cells, waste, and nutrients to and from cells.
The reproductive system produces sex cells used to pass on traits to offspring and replicate DNA.
The digestive system breaks food down in the mouth and stomach, extracts nutrients in the small intestines, and eliminates waste through the small intestines or colon (large intestine) to provide our cells, tissues, and organs with the means to make energy.
The excretory, or urinary, system consists of filtering blood through our kidneys, and storing urine in our bladder.
The skeletal system supports and protects our body. It plays a key role in movement, by working with the muscular system, and it makes blood cells and stores calcium.
The nervous system
The lymphatic, or immune, system defends the body against microorganisms and other foreign bodies, and is composed of the lymph, lymph nodes, lymph vessels, thymus, spleen, and tonsils.
The endocrine system, regulates and controls processes of the body by sending out hormones into the blood. The organs of the endocrine system, glands that release hormones, include: the pituitary gland, pineal gland, hypothalamus, thyroid gland, thymus, adrenal glands, pancreas, ovaries, and the testes.
The muscular system provides the human body with the ability to move, as well as movement of materials through organs and organ systems. The muscular system functions to maintain the position of a person’s body when standing or sitting, and produce heat. The muscular system consists of skeletal muscle, smooth muscle (your intestines), and cardiac muscle (which is what your heart is composed of).
The integumentary system acts as a protective layer for the human body against organisms, dehydration, and injuries found. The integumentary system also regulates body temperature. The integumentary system includes our hair, nails, and the largest organ of the body, the skin.
Towards the end of learning about the systems found in our body, we had a guest speaker from Palomar Community College come in and talk about the cardiovascular system, as well as show us one of the human body’s physiological responses, the mammalian dive reflex. The guest speaker, Richard Albistegui-Dubois, hooked himself up to a heart rate monitor, and then stuck his face into a bowl of ice water. His body reacted by slowing down his heart rate in order to preserve oxygen. The following week, we went on a field trip to the physiology lab at Palomar, and in groups, we were able to conduct our own experiments. My group decided to use and ECG sensor, to monitor heart rate, and then to observe what would happen when meditating. When getting a baseline of a person’s heart beat, we noticed the you could see the rate move up and down with a person’s breathing. Once we had the test subject start to meditate, over time, his heart rate continued to lower until he stopped. (See graphs below.)