Cell Biology Basics

• Cells must replicate to create new cells
• They are responsible for forming all the body's structures

Two Types of Cells

• Somatic cells make up all cells except sex cells

• Diploid cells contain two copies of chromosomes, totaling 46 in humans, with one copy from each parent

• Sex cells are haploid cells, possessing only one set of chromosomes

• Haploid cells contain 23 chromosomes

• An egg cell contains 23 chromosomes

• A sperm cell contains 23 chromosomes

• When combined, they form a diploid cell with 46 chromosomes

• Somatic cells divide through mitosis

• Gametes are sex cells

• Somatic cells are diploid and possess two copies of chromosomes from each parent

• Sex cells are haploid

• Egg cells contain 23 chromosomes from the mother

• Sperm cells contain 23 chromosomes from the father, combining to form 46 chromosomes

• Fat pushes against the cytoplasm, causing the nucleus to be pushed to the side

• Sperm cells contain a tail

• Females have ovums, not males

• Cells area covered by a membrane that holds the cell together and separates the inside and outside environments

• Cytosol is a jelly-like fluid containing substances and cytoplasmic elements, also known as intracellular fluid (ICF)

• Organelles, which are subunits of the cell, carry out the functions of cells inside the cytoplasm

• Fluid outside the cell is known as extracellular fluid (ECF)

• The cell membrane separates the fluid inside the cell from the fluid outside

Cellular Anatomy - Organelles

• Key organelles include:
• Mitochondria
• Endoplasmic reticulum
• Lysosomes
• Nucleus
• Golgi apparatus
• Ribosomes
• Cytoskeleton
• Cytoplasm occupies all space within the cell
• Organelles are located within the cytoplasm
• The core of the nucleus is the nucleolus
• Cell membranes are composed of phospholipids
• Phospholipids arrange themselves in two layers
• The fatty acid tails of phospholipids do not like water
• Hydrophobic means fearing water
• Fatty tails gravitate towards the other phospholipid layer
• Phosphate heads of phospholipids face the extracellular fluid because they like water
• Cholesterol provides stability to the membrane
• Glycolipids contribute to membrane stability and facilitate communication between cells
• Gated channels must be open for them to function

Membrane Permeability

• Passive processes across the cell membrane do not require ATP or cellular energy

• Diffusion is a spontaneous movement of solutes

• Solutes can be amino acids, glucose, or ions

• Solutes move around, bumping until hitting the membrane

• They then cross over to the other side from high to low concentration

• Having more on one side is a gradient

• Osmosis is diffusion, involving the movement of water through a membrane

• When solutes cannot move but water is present, water moves toward the higher solute concentration

• Water is polar

• Facilitated diffusion is diffusion that occurs down a concentration gradient, from high to low concentration

• Some molecules are too thick to pass through the cell membrane directly.

• Fatty substances can pass through the membrane because it is made of fat

• Active processes require energy to move things across the cell membrane

• Phagocytosis is "cell eating"

• Pinocytosis is "cell drinking," where fluid is brought into the cell

• Receptor-mediated endocytosis involves substances binding to receptors on the cell membrane, causing invagination

• Represent Endocytosis

• Both are active processes and they use ATP

• Exocytosis

• Ribosomes are created in the nucleolus, not the nucleus

• They are made of RNA, mRNA, and tRNA

• Free ribosomes float in the cytoplasm

• Fixed ribosomes are attached to the reticulum

• Mitochondria are the powerhouse of cells

• Each possesses its own DNA and a double membrane

• They can replicate and make more of themselves

• Muscle cells require more mitochondria to make ATP

• The matrix inside mitochondria contains many enzymes

• The folded membrane is where the electron transport chain occurs

• Most ATP production occurs on the inner membrane

• Oxygen intake is destined for the cell, going from the outer to the inner membrane

• Oxygen is the final electron acceptor in the chain and cells cannot function without it

• The nucleolus is the largest organelle

Chromosome Structure

• DNA is 6 ft long

• Chromosomes contain and protect the DNA

• Smooth ER functions to produce lipids

• Protein synthesis supports the making of more proteins

• Smooth ER plays a vital role in both lipid synthesis and storing calcium

• Enzymes are digestive and break things down through hydrolysis

• Hydrolysis is the use of water to break the bonds bewteen molecules

• Autolysis is self destruction

• Anything that ends in "ase" is an enzyme

• Free radicals are unstable and snatch electrons to create stabillity for themselves

• Free Radicals degrade and breakdwon toxins

• Microfilaments help maintain the cell membrane's attachment to the cytoplasm.

• Microfilaments extend into microvilli to provide support

• Cilia and flagella are microtubules

• Microtubules extend into cilia

• Flagella allow cells to move

• Cilia move substances across the cell surface

• Flagella move the entire cell

• All cells in the heart need to respond to an electrical impulse to ensure coordinated muscle contraction

• Cells possess gap junctions allowing communcation

• Tight junctions are found in skin to provide structure

• They are similar to several layers of stitching

• Desmosomes are strong and stabilize cells on tissues

Cell Life Cycle

• The cell life cycle includes:
• Interphase (G1, S, G2)
• Mitosis (PMAT)
• The S phase is for synthesis (making or producing)
• Mitosis "PMAT"
• Prophase
• Metaphase
• Anaphase
• Telophase
• S phase duplicates
• Anaphase results in the chromosome being pulled apart
• Cleavage furrow leads to cytokinesis
• Some cells in the body never undergo mitosis

Terminology

• Tumor: also known as neoplasm and is a mass produced by abnormal cell growth and division
• Benign tumor: mass that remains within a connective tissue capsule
• Malignant tumor: mass that does not respoind to normal control
• Metastasis: when a mass is spreading through the blood
• Cancer: illness by malignant cells