BIO-NOTESS.docx

**PLANT AND ANIMAL CELL ORGANELLES** ***ANIMAL CELL*** - The **cell nucleus** is a membrane-bound organelle found in eukaryotic cells. - **eukaryotic cells** usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others in...

**PLANT AND ANIMAL CELL ORGANELLES** ***ANIMAL CELL*** - The **cell nucleus** is a membrane-bound organelle found in eukaryotic cells. - **eukaryotic cells** usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many. - The **nucleolus** is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of signal recognition particles and plays a role in the cell\'s response to stress. - **Ribosomes** are macromolecular machines, found within all cells, that perform biological protein synthesis. Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains. - **Rough endoplasmic reticulum** is so-called because its surface is studded with ribosomes, the molecules in charge of protein production. When a **ribosome** finds a specific RNA segment, that segment may tell the ribosome to travel to the rough endoplasmic reticulum and embed itself. - The protein created from this segment will find itself inside the lumen of the rough endoplasmic reticulum, where it folds and is tagged with a **(usually carbohydrate)** molecule in a process known as glycosylation that marks the protein for transport to the Golgi apparatus. The rough endoplasmic reticulum is continuous with the nuclear envelope, and looks like a series of canals near the nucleus. - Proteins made in the rough endoplasmic reticulum as destined to either be a part of a membrane, or to be secreted from the cell membrane out of the cell. - **Smooth endoplasmic reticulum** makes lipids and steroids, instead of being involved in protein synthesis. These are fat-based molecules that are important in energy storage, membrane structure, and communication **(steroids can act as hormones)**. The smooth endoplasmic reticulum is also responsible for detoxifying the cell. - It is more tubular than the rough endoplasmic reticulum, and is not necessarily continuous with the nuclear envelope. Every cell has a smooth endoplasmic reticulum, but the amount will vary with cell function. For example, the liver, which is responsible for most of the body's detoxification, has a larger amount of smooth endoplasmic reticulum. - **Golgi apparatus** is the mailroom that sends our protein/substances to organelles. it is responsible for packing proteins from the rough endoplasmic reticulum into membrane-bound vesicles **(tiny compartments of lipid bilayer that store molecules)** which then translocate to the cell membrane. At the cell membrane, the vesicles can fuse with the larger lipid bilayer, causing the vesicle contents to either become part of the cell membrane or be released to the outside. - Different molecules actually have different fates upon entering the **Golgi**. This determination is done by tagging the proteins with special sugar molecules that act as a shipping label for the protein. The shipping department identifies the molecule and sets it on one of 4 paths. - **Cytosol** the proteins that enter the golgi by mistake are sent back into the cytosol **(imagine the barcode scanning wrong and the item being returned).** - **Cell membrane** proteins destined for the cell membrane are processed continuously. Once the vesicle is made, it moves to the cell membrane and fuses with it. - **Molecules** in this pathway are often protein channels which allow molecules into or out of the cell, or cell identifiers which project into the extracellular space and act like a name tag for the cell. - **Secretion** some proteins are meant to be secreted from the cell to act on other parts of the body. Before these vesicles can fuse with the cell membrane, they must accumulate in number, and require a special chemical signal to be released. This way shipments only go out if they're worth the cost of sending them **(you generally wouldn't ship just one toy and expect to profit).** - **Lysosome** the final destination for **proteins** coming through the **Golgi is the lysosome.** - **Vesicles** sent to this acidic organelle contain enzymes that will hydrolyze the lysosome's content - The **lysosome** is the cell's recycling center. These organelles are spheres full of enzymes ready to hydrolyze **(chop up the chemical bonds of)** whatever substance crosses the membrane, so the cell can reuse the raw material. These disposal enzymes only function properly in environments with a ph of 5, two orders of magnitude more acidic than the cell's internal ph of 7. - **Lysosomal proteins** only being active in an acidic environment acts as safety mechanism for the rest of the cell - if the lysosome were to somehow leak or burst, the degradative enzymes would inactivate before they chopped up proteins the cell still needed. - Like the lysosome, the **peroxisome** is a spherical organelle responsible for destroying its contents. Unlike the lysosome, which mostly degrades proteins, the peroxisome is the site of fatty acid breakdown. - It also protects the cell from reactive oxygen species **(ROS)** molecules which could seriously damage the cell. - **Ross** are molecules like oxygen ions or peroxides that are created as a byproduct of normal cellular metabolism, but also by radiation, tobacco, and drugs. - A **cell** can't run without energy. **ATP (adenosine triphosphate)** is the energy currency of the cell, and is produced in a process known as **cellular respiration**. Though the process **begins in the cytoplasm**, the bulk of the energy produced comes from later steps that take place in the **mitochondria**. - There are actually **two lipid bilayers** that **separate the mitochondrial contents from the cytoplasm.** We refer to them as the inner and outer mitochondrial membranes. - If we cross both membranes we end up in the matrix, where **pyruvate** is sent after it is created from the breakdown of glucose **(this is step 1 of cellular respiration, known as glycolysis)**. The space between the two membranes is called the **intermembrane space**, and it has a **low ph (is acidic)** because the electron transport chain embedded in the inner membrane pumps **protons (H+)** into it. Energy to make ATP comes from protons moving back into the matrix down their gradient from the intermembrane space. - **Cytoplasm** describes all material within an eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the **nucleoplasm**. - Within the **cytoplasm** there is network of protein fibers known as the **cytoskeleton**. This structure is responsible for both cell movement and stability. **The major components** of the cytoskeleton are **microtubules, intermediate filaments, and microfilaments.** - **Microtubules** are small tubes made from the **protein tubulin**. These tubules are found in **cilia and flagella**, structures involved in cell movement. They also help provide pathways for secretory vesicles to move through the cell, and are even involved in cell division as they are a part of the mitotic spindle, which pulls homologous chromosomes apart. - **Intermediate filaments** are smaller than the microtubules, but larger than the microfilaments, the intermediate filaments are made of a variety of proteins such as keratin and/or neurofilament. They are very stable, and help provide structure to the nuclear envelope and anchor organelles. - **Microfilaments** are the thinnest part of the cytoskeleton, and are made of actin \[a highly-conserved protein that is actually the most abundant protein in most eukaryotic cells\]. Actin is both flexible and strong, making it a useful protein in cell movement. In the heart, contraction is mediated through an actin-myosin system. - **Centrioles** are self-replicating organelles made up of nine bundles of microtubules and are found only in animal cells. They appear to help in organizing cell division, but aren\'t essential to the process. **ORGANELLES PRESENT IN PLANTS BUT NOT IN ANIMAL CELLS** ***PLANT CELLS*** - The **cell wall** is the outer covering of a cell, present adjacent to the cell membrane, which is also called the plasma membrane. As mentioned earlier, the cell wall is present in all plant cells, fungi, bacteria, algae, and some archaea. - **Chloroplasts **produce energy through photosynthesis and oxygen-release processes, which sustain plant growth and crop yield. As such, chloroplasts are responsible for the biosynthesis of active compounds such as **amino acids, phytohormones, nucleotides, vitamins, lipids, and secondary metabolites.** - **Vacuole** is a membrane-bound cell organelle. In animal cells, vacuoles are generally small and help sequester waste products. In plant cells, vacuoles help maintain water balance. Sometimes a single vacuole can take up most of the interior space of the plant cell. ***CELL THEORY*** - **What is a cell?** - In biology, the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body. - The **cell theory** describes the basic properties of all cells. The **three scientists** that contributed to the development of cell theory are **Matthias Schleiden, Theodor Schwann, and Rudolf Virchow**. A component of the cell theory is that all living things are composed of **one or more cells.** **Matthias Schleiden** - He studied microscopic **structures of plants**, he observed that plant cells are composed of different derivatives. - cells. Specifically, he observed that "the lower plants all consist of one cell, while the higher ones are composed of (many) individual cells." In **1839 Theodor** Schwann extended Schleiden\'s cell theory to **[animals](https://www.britannica.com/animal/animal).** **Theodor Schwann** - focused on studying the structure and function of **[nerves](https://en.wikipedia.org/wiki/Nerves), [muscles](https://en.wikipedia.org/wiki/Muscles) and [blood vessels](https://en.wikipedia.org/wiki/Blood_vessels)**. - **Muscle tissue -** developed and described an experimental method to calculate the contraction force of the muscle, by controlling and measuring the other variables involved. - **Pepsin -** He conceptualized digestion as the action of a physiological agent, which, though not immediately visible or measurable, could be characterized experimentally as a \"peculiar specific substance\" - **Yeast, fermentation, and spontaneous generation -** Powerful microscopes made it possible for him to observe yeast cells in detail and recognize that they were tiny organisms whose structures resembled those of plants **Rudolf Virchow** - Pathologist, he emphasized that diseases arose, not in organs or tissues in general, but primarily in their individual cells. ***Organelles in the Animals cells*** ***Organelles in the Plant cells***  ***[Codominance]*** - Refers to both alleles copies being expressed Neither allele is **RECESSIVE** or **DOMINANT** ***Variable expression*** - Refers to a situation where people have the same disease genotype but different symptoms ***Incomplete penetrance*** - Refers to situation where somebody has the disease allele but not the expressed trait.  ***Animal Cells*** **Nucleus** - which controls all the activities of the cell, also contains the instructions for making new cells or new organisms. **Cytoplasm** - a liquid gel in which most of the chemical reactions needed for life takes place. One of the most important of these is respiration, where oxygen and sugar react to release energy the cell needs. **Cell membrane** - controls the passage of substances in and out of the cell. **Mitochondria** - are structures in the cytoplasm where most of the energy is released during respiration. **Ribosomes** - are where protein synthesis takes place. All the proteins needed in the cell are made here. ***Plant Cells*** All plant cells have the structures in an animal cell and: **Cell wall** - made of cellulose which strengthens the cell and gives it support. Many, but not all, plant cells also have: **Chloroplasts** - found in all the green parts of the plant. They are green because they contain chlorophyll. They absorb light energy to make food by photosynthesis. **Permanent vacuole** - is a space in the cytoplasm filled with cell sap, which is important for keeping the cells rigid to support the plant. Chemical reactions that take place in cells are controlled by enzymes. Each enzyme, which are proteins, typically control one specific reaction. **Enzymes** - that control different functions are found in different structures of a cell. **Mitochondria** - formed enzymes control respiration. **Chloroplasts** - form enzymes which control photosynthesis. **Protein synthesis enzymes** - are found on the surface of ribosomes