Cell Basics
Most cells are composed of four elements, Which ones? Also how much water is in a cell?
Carbon, Hydrogen, Oxygen, Nitrogen
Cells are about 60% water
Ribisomes?
They are made in the nucleus of protein and RNA, They are then sent to the Rough Endoplasmic Reticulum, through fluid tunnels. They are there to synthesize proteins, then sent to the Golgi Via Vesicles.
Receptor Mediated Endocytosis
Method for taking up specific target molecules
Receptor proteins on the membrane surface bind only certain substances
(lock and key)
Highly selective process of taking in substances such as enzymes, some hormones, cholesterol, and iron
Solute Pumps
Amino acids, some sugars, and ions are transported by protein carriers known as solute pumps. ATP energizes solute pumps. In most cases, substances are moved against concentration (or electrical) gradients
Two major phases
Interphase (metabolic phase
Cell grows and carries on metabolic processes
Longer phase of the cell cycle
Cell division (Mitosis). Cell reproduces itself
What is Cell Theory?
A cell is the basic structural and functional unit of living organisms and the human body has 50 to 100 trillion cells.
The smooth ER?
This metabolizes lipids, and purifies drugs and pesticides.
Membrane transport
Passive processes: substances are transported across the membrane without any input from the cell (no energy needed)
Simple diffusion
Filtration
Osmosis
Facilitated diffusion
Active processes: the cell provides the metabolic energy (ATP) to drive the transport process
Pumps (Na+/K+ Pump)
Vesicular Transport
Vesicular Transport
Substances are moved across the membrane “in bulk” without actually crossing the plasma membrane
Types of vesicular transport
Exocytosis
Endocytosis
Phagocytosis – Cellular eating
Pinocytosis – Cellular drinking
Interphase
DNA Replication toward the end of interphase
Guanine (G) always bonds with cytosine (C)
Example, TACTGC bonds with new nucleotides in the order ATGACG
The three parts of the Nucleus are?
The nuclear envelope (porous membrane), Nucleolus, and Chromatin.
Golgi apparatus
Modifies and packages proteins arriving from the rough ER via transport vesicles, Produces and secretes different types of packages or vesicles.
Passive transport
Diffusion
Molecules move from high concentration to low concentration, down a concentration gradient (O2, CO2)
Size of the molecule and temperature affect the speed of diffusion
Simple diffusion
Unassisted process, solutes are lipid-soluble or small enough to pass through membrane pores (aquaporons)
Osmosis
simple diffusion of polar water molecules across a selectively permeable membrane pores (aquaporons) using a concentration gradient
Higher water concentration → Lower water concentration
Goal: WATER BALANCE
HOMEOSTASIS
Exocytosis & Endocytosis
Exocytosis
Cells use to actively secrete hormones, mucus, and other products
Vesicles migrate to and combine with the plasma membrane to empty contents to the outside
Endocytosis
Stages of Mitosis
Prophase
Chromatin coils into chromosomes; identical strands called chromatids are held together by a centromere (constricted section of chromosome held together by spindle fibers)
Centrioles direct the assembly of a mitotic spindle
Nuclear envelope and nucleoli have broken down
Metaphase
Chromosomes are aligned in the center of the cell (at center of the spindle midway between the centrioles)
Anaphase
Centromere splits; Chromatids move toward the opposite ends of the cell
Telophase
Reverse of prophase
Chromosomes uncoil to become chromatin
Spindles break down and disappear
Nuclear envelope re-forms around chromatin
Nucleoli appear in each of the daughter nuclei
Cytokinesis
Division of the cytoplasm
Begins during late anaphase and completes during telophase
A cleavage furrow (contractile ring of microfilaments) forms to pinch the cells into two parts
Two daughter cells form
Plasma membrane basics.
It is made of phospholipids, which have hormones, proteins, pumps, and Channels. Membrane sugars have glycoproteins and serve as chemical markers. They connect like zippers.
Lysosomes, and Peroxisomses?
Membranous contains digestive enzymes that can digest worn-out or waste cell structures. Use Phagocytosis, Peroxisomes sacs of oxidase enzymes that Detoxify harmful substances such as alcohol and formaldehyde.Break down free radicals (highly reactive chemicals) and convert them to hydrogen peroxide and then water
Filtration and Facilitated diffusion
1.Water and solutes are forced through a membrane by fluid, or hydrostatic pressure
2.
Facilitated diffusion
Transports lipid-insoluble and large substances
Glucose is transported via facilitated diffusion
Protein membrane channels or protein molecules that act as carriers are used
Phagocytosis
Cell engulfs large particles such as bacteria or dead body cells
Substances from the external environment (such as bacteria or dead body cells)
A protective mechanism, not a means of getting nutrients
Phagocytes (neutrophils and monocytes)
Protein Synthesis
DNA located in genes serve as a blueprint for making proteins
What are the main components of the cytoplasm?
Cytosol, Inclusions, and Organelles.
Cytoskeleton?
The cytoskeleton plays an important role in maintaining cell shape and structure, promoting cellular movement, and aiding cell division. The three Components of the Cytoskeleton.Microtubules (largest-compressional support), Intermediate filaments ,Microfilaments (smallest-tensional support)
Active transport
ATP is used to move substances across a membrane when Substances are too large to travel through membrane channels. The membrane may lack special protein carriers for the transport of certain substances. Substances may not be lipid-soluble. Substances may have to move against a concentration gradient.
Sodium-potassium pump
Necessary for nerve impulses
Electrical gradient across cell membrane as cell polarity changes (membrane potential)
3 Sodium molecules (Na+)is transported out of the cell
2 Potassium molecules (K+) is transported into the cell
The excess negative charges inside the cell are electrically attracted to the excess positive charges outside the cell, and vice versa
Pinocytosis
Cell “gulps” droplets of extracellular fluid containing dissolved proteins or fats
The plasma membrane forms a pit, and edges fuse around droplets of fluid
Protein Synthesis: RNA
Transfer RNA (tRNA): Transfers appropriate amino acids to the ribosome for building the protein
Ribosomal RNA (rRNA): Helps form the ribosomes where proteins are built (where?)
Messenger RNA (mRNA): Carries the instructions for building a protein from the nucleus to the ribosome
Transcription
Transfer of information from DNA’s base sequence to the complementary base sequence of mRNA
the ribosome moves along the mRNA, adding new amino acids to the growing protein chain (polypeptide)
detaching tRNA molecules returns to the cytoplasm, ready to be pick up a new amino acid