Reading 3 - Human Physiology

Cells and Biomolecules (Part 2)

What is the primary responsibility of each cell?

To maintain and contribute to Homeostasis

What is Homeostasis?

What happens when a particular parameter moves too far out of homeostasis?

Dynamic state of balance within parameters that are that are compatible with life

Can lead to illness, disease, or even death

What two things do all living cells in multicellular organisms contain?

An internal cytoplasmic compartment and a nucleus within the cytoplasm

What is Cytosol?

What are Organelles?

Clear, semi-fluid medium of the cytoplasm, that is made up of mostly water and provides the fluid medium necessary for biochemical reactions

One of several different types of membrane-enclosed bodies in the cell, each performing a unique function

What two things compose the cell’s Cytoplasm?

What is the cell’s central organelle?

Cytosol and Organelles

The nucleus

What is the Endomembrane System?

What organelles make up the Endomembrane System?

Set of three major organelles that perform various cellular jobs, including the task of producing, packaging, and exporting certain cellular products

Endoplasmic Reticulum, Golgi Apparatus, and Vesicles

What is the Endoplasmic Reticulum?

What is the function of the ER?

How does its structure relate to its function?

System of channels continuous to the nuclear membrane that covers the nucleus and is composed of the same lipid bilayer material

Provides passages throughout the cell for transporting, synthesizing, and storing materials

Winding structure results in a large membranous surface area

What two forms can the ER exist as?

Rough and Smooth ER

Why is the Rough ER called rough?

What is a Ribosome? What is it composed of?

Contains ribosomes on its membranes, while the smooth ER does not

Organelle that serves as the site of protein synthesis; composed of two rRNA subunits that wrap around mRNA to start the process of Translation, followed by protein synthesis

What is the function of the Smooth ER?

Why is Calcium important?

1. Synthesis of Lipids - synthesizes phospholipids and steroid hormones (^ hormones = ^ # of smooth ER)

2. Sequesters and regulates concentration of Calcium

3. Metabolizes some Carbs. and performs a detoxification role on certain toxins

Trigger for neurotransmitter release in nervous system cells

What is the function of the Rough ER?

How do Ribosomes interact with the Rough ER?

Synthesis and modification of proteins destined for the membrane or export from the cell

During protein synthesis, the ribosomes attach to the Rough ER and synthesize proteins that are then released into the channel of the Rough ER

Sugars are then added to the proteins (Glycosylation) and packaged into a Vesicle to be sent to the Golgi Apparatus

What is Glycosylation?

Addition of sugars to the ribosome-synthesized proteins within the channels of the rough ER

What is the Golgi Apparatus?

What is the function of the Golgi Apparatus?

How does its structure relate to its function?

Organelle formed by a series of flattened, membrane-bound sacs that functions in protein modification, tagging, packaging, and transport

Responsible for sorting, modifying, and shipping off products that come from the Rough ER

Has two distinct sides:

• Cis face — receives products in vesicles that are then sorted and released on the opposite side, repackaged in new vesicles

• Trans face — releases the new vesicles containing the products

What is a Lysosome?

What is the function of a Lysosome?

Membrane-bound cellular organelle originating from the Golgi Apparatus and containing digestive enzymes

Contains enzymes that break down and digest unneeded cellular components

• Break down foreign material

• Can open up and release their enzymes into the cell to kill it in the event of damaged or unhealthy cells (Autolysis)

What is Autophagy?

What is Autolysis?

Lysosomal breakdown of a cell’s own components

Breakdown of cells by their own enzymatic action

What is the name of the cells in the liver that detoxify many of the toxins in the human body?

Hepatocytes

What are Mitochondrion?

What is the function of Mitochondrion?

One of the cellular organelles bound by a double lipid bilayer that functions primarily in the production of ATP

Uses biochemical reactions to convert stored energy in nutrient molecules into ATP

What are the different parts of the Mitochondria?

Outer lipid bilayer membrane

Inner lipid bilayer membrane (Cristae)

Space inside the Cristae (Matrix)

Space in between Cristae and the outer membrane (Intermembrane Space)

How does the number of mitochondrion in a cell relate to ATP usage?

What is an example of a high-ATP use organ system?

What is an example of a low-ATP use cell?

Cells that use more ATP tend to have more mitochondrion

Muscular system; muscle cells are packed filled with mitochondrion to generate ATP to sustain muscle contraction

Bone cells; not as metabolically active and might only have a couple hundred mitochondria

What are Peroxisomes?

What is the function of Peroxisomes?

Membrane-bound organelles that contain enzymes primarily responsible for detoxifying harmful substances

Lipid metabolism and chemical detoxification

What is the purpose of the enzymes located within Peroxisomes?

Serve to transfer hydrogen atoms from various molecules to oxygen in order to produce Hydrogen Peroxide (H2O2) and effectively neutralize poisons

What are Reactive Oxygen Species (ROS)?

What are some examples of these species?

Why are free radicals reactive?

Group of extremely reactive peroxides and oxygen-containing radicals that may contribute to cellular damage

Peroxides and Free Radicals

• Hydroxyl Radical OH

• H2O2

• Superoxide (O^-2)

They contain free unpaired electrons and can easily oxidize other molecules throughout the cell

How do Peroxisomes neutralize free radicals?

Contain enzymes that convert H2O2 into water and oxygen that are then safely released into the cytoplasm

Which organ is primarily responsible for detoxifying the blood before it travels through the body?

What is the relative number of Peroxisomes in this organs cells?

The liver

Liver cells contain an exceptionally high number of Peroxisomes

How do Antioxidants work?

Become oxidized themselves, which halts the destructive reaction cascades initiated by the free radicals

What is Oxidative Stress?

How do ROS cause this?

Term used to describe damage to cellular components caused by ROS

Set off chain reactions in which electrons are removed from other molecules, which are then oxidized and reactive— then doing the same to other molecules in a chain reaction

What are some other consequences of ROS?

What are some diseases that are triggered / exacerbated by ROS?

Permanent damage to cellular lipids, proteins, carbohydrates, and nucleic acids — leading to genetic mutations and sometimes even cancer

Alzheimer’s, Cardiovascular diseases, Diabetes, Parkinson’s, Arthritis, Huntington’s Disease, and Schizophrenia (all mainly age-related)

What is the Cytoskeleton?

What is the function of the Cytoskeleton?

“Skeleton” of a cell; formed by rod-like proteins that support the cell’s shape and provide, among other functions, locomotive abilities

Helps the cell to maintain its structural integrity and is crucial for maintaining cell motility, cell reproduction, and transportation of substances within the cell

What are the three kinds of protein-based filaments used by the cytoskeleton to form its network? Which one is the thickest

What are Microtubules?

What is the function of Microtubules?

Microfilaments, intermediate filaments, and Microtubules — microtubules are the thickest

Structural filament composed of tubulin subunits that function in cellular movement and structural support

Maintain cell shape and structure, help resist compression of the cell, and play a role in positioning the organelles within the cell

What two types of cellular appendages that are important for motion are made up of microtubules?

Cilia — small appendage on certain cells formed by microtubules and modified for movement of materials across the cellular surface

Flagellum — appendage on certain cells formed by microtubules and modified for movement

Where are the cilia and flagella located?

What is the relative size of cilia and flagella to each other?

Cilia — epithelial cells that line the airways of the respiratory system

Flagellum — only flagellated cells in humans, sperm cells that must propel itself towards female egg cells