Cell Structure and Function

• Key components for all cells: plasma membrane, cytoplasm, DNA, and ribosomes.

Eukaryotic vs Prokaryotic Cells:

• Prokaryotes are smaller, simpler, and lack a nucleus.
• Eukaryotes are more complex, larger, and possess a nucleus.

Cell Membrane:

• The cell membrane is a phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward.
• The membrane selectively regulates the entry and exit of substances.

Cell Membrane Proteins:

• Integral proteins facilitate molecule movement in and out of the cell.
• Peripheral proteins aid in communication, cell shape, and speed up reactions.
• Channel proteins allow specific molecules to pass through without energy.
• Carrier proteins transport molecules in or out, sometimes using energy.
• Receptor proteins receive signals and trigger responses.
• Glycoproteins help cells recognize each other and participate in the immune system.

Cell Walls:

• Primary cell wall is the first layer in plant cells, enabling growth and flexibility.
• It has a primary cellulose composition.
• Secondary cell wall develops inside the primary wall in some plant cells.
• Lignin is an example of a component that increases rigidity.
• Middle lamella is a pectin layer that connects adjacent plant cells.
• Gram-positive bacteria have a thick peptidoglycan layer.
• Gram-negative bacteria have a thinner peptidoglycan layer plus an outer membrane.

Organelles & Functions:

• Organelles are specialized structures with specific functions within a cell.
• Nucleus stores DNA and coordinates cellular activities related to growth and reproduction.
• It is considered the "brain" of the cell.
• Mitochondria produces energy through cellular respiration.
• Ribosomes are responsible for protein synthesis.
• Endoplasmic Reticulum (ER) is a network of membranes involved in protein and lipid synthesis.
• Rough ER has ribosomes attached, while Smooth ER does not.
• Golgi Apparatus modifies, sorts, and packages proteins for secretion.
• Lysosomes contain digestive enzymes that break down waste and worn-out cell parts.
• Vacuoles store water, nutrients, and waste, and are prominent in plant cells.
• Cell Membrane separates the cell from its environment, controlling what enters and exits.
• Cytoplasm is the jelly-like substance where cellular processes occur.
• Centrioles organize microtubules during mitosis for cell division.
• Ribosomes are found in mitochondria and chloroplasts.

Cell Junctions:

• Tight junctions form a continuous seal to prevent leakage in tissues.
• Adherens junctions provide strong cell-to-cell adhesion, important for tissues under mechanical stress.
• Desmosomes are specialized adherens junctions for strong connections, especially in tissues with high tensile strength like the epidermis.
• Gap junctions create channels for direct exchange of ions and small molecules, crucial for rapid communication.

Cytoskeleton:

• Microfilaments (actin filaments) aid in cell movement, shape, and division.
• They are important for muscle contraction.
• Intermediate filaments provide strength and stability, helping cells resist stress.
• Microtubules act as tracks for moving things and are important for cell division, most notably chromosome separation.

Energy - Kinetic vs Potential:

• Potential energy is stored energy due to an object's position or condition.
• Kinetic energy is the energy an object has because it's moving.
• Potential energy is stored and kinetic energy is in motion.
• Electrons carry energy when they move, which is how electricity is transferred.
• Oxidation is losing electrons.
• Reduction is gaining electrons.
• ATP (adenosine triphosphate) is the main energy source for cells, storing energy in the bond between the second and third phosphate groups.
• When a cell needs energy, it breaks off the third phosphate group, converting ATP to ADP (adenosine diphosphate).
• ATP is like a charged battery that releases energy when it loses a phosphate.*
• The sun is a source of energy.

Photosynthesis and Cellular Respiration:

• Photosynthesis makes glucose and oxygen.
• Respiration uses glucose and oxygen to release energy.
• Carbon dioxide produced by respiration is used in photosynthesis.
• Materials for photosynthesis are carbon dioxide, water, and light energy.
• Materials for respiration are glucose and oxygen.

Enzymes

• Enzymes are proteins made of amino acids
• The active site is the part of the enzyme where the substrate binds.
• It is like a "lock" and the substrate is the "key".
• Enzymes speed up reactions by lowering the needed energy.
• The active site is where the enzyme works.
• Competitive inhibition blocks the active site.
• Non-competitive inhibition changes the enzyme shape.

Cell Transport:

• Diffusion involves molecules moving from high to low concentration without energy.
• Osmosis involves water moving through a membrane from low to high solute concentration without energy.
• Active transport involves molecules moving against the concentration gradient, requiring energy (ATP).
• Endocytosis is when the cell takes in large molecules by engulfing them, and requires energy.
• Exocytosis is when the cell releases large molecules by merging a vesicle with the membrane.
• It requires energy.

Overview of cell structures, including prokaryotic and eukaryotic cells, cell membranes, and cell membrane proteins. The cell membrane is a phospholipid bilayer with hydrophilic heads and hydrophobic tails, selectively regulating substance entry and exit. Various proteins facilitate molecule transport, communication, and immune responses.