Cell Structure and Function

• Prokaryotic cells are smaller and simpler, lacking a nucleus.
• Eukaryotic cells are more complex and larger, and contain a nucleus.
• All cells share the following components: plasma membrane, cytoplasm, DNA, and ribosomes.
• The cell membrane comprises a phospholipid bilayer and regulates the entry and exit of substances.
• The cell membrane regulates what enters and exits the cell by way of a selectively permeable barrier.

Cell Membrane Proteins

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

Cell Walls

• Primary cell walls constitute the initial layer in plant cells.
• Primary Cell walls facilitate growth and flexibility with a cellulose composition.
• Secondary cell walls are inside the primary wall, offering additional rigidity with components like lignin.
• Middle lamella, a pectin layer, glues adjacent plant cells together.
• Gram-positive bacteria possess a thick peptidoglycan layer, influencing their Gram staining properties.
• Gram-negative bacteria have a thinner peptidoglycan layer and an additional outer membrane of increased complexity.

Organelles and Functions

• Organelles are specialized structures within a cell, each performing a specific function.
• The Nucleus stores DNA and coordinates cellular activities like growth and reproduction and is considered the "brain" of the cell.
• Mitochondria produce cellular energy through cellular respiration.
• Ribosomes are responsible for protein synthesis.
• The Endoplasmic Reticulum (ER) is a membrane network involved in protein and lipid synthesis; rough ER contains ribosomes, while smooth ER does not
• The 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 products, being particularly prominent in plant cells.
• The Cell Membrane separates the cell from its environment, thus controlling what enters and exits
• The Cytoplasm is the jelly-like substance within the cell where many cellular processes occur.
• Centrioles organize microtubules during mitosis for cell division.
• Mitochondria and chloroplasts both contain ribosomes.

Cell Junctions

• Tight junctions form a continuous seal between cells, preventing leakage, crucial in tissues like the intestines or bladder.
• Adherens junctions provide strong cell-to-cell adhesion, important for tissues experiencing mechanical stress like skin and muscle.
• Desmosomes are specialized adherens junctions with strong spot-like connections, especially important in high-tensile strength tissues like the epidermis.
• Gap junctions create small channels for direct exchange of ions and molecules between cells, crucial for coordinated activity in tissues like cardiac muscle.

Cytoskeleton

• Microfilaments (actin filaments) aid in cell movement, shape, and division, important for processes like muscle contraction.
• Intermediate filaments provide strength and stability, helping the cell resist stress and maintain its shape.
• Microtubules act like tracks for moving things around the cell and are important during cell division to separate chromosomes.

Energy

• Potential energy is stored energy due to an object's position or condition.
• Kinetic energy is energy an object has because of its motion.
• Potential energy is stored energy, while kinetic energy is energy in motion.
• Electrons transfer energy as they move.
• When electrons move in a circuit, such as a battery or wire, they transfer energy to generate electricity.
• Oxidation is the process of losing electrons.
• Reduction is the process of gaining electrons.
• ATP is the main energy source for cells, storing energy in the bond between its second and third phosphate groups.
• ATP is converted to ADP when a cell needs energy by breaking off the third phosphate group.
• ATP functions as a charged battery, releasing energy upon losing a phosphate.
• The sun is the primary energy source.
• Photosynthesis produces glucose and oxygen, while respiration uses glucose and oxygen to release energy.
• Carbon dioxide from respiration is used in photosynthesis, forming a cycle.

Photosynthesis and Respiration

• Photosynthesis: carbon dioxide, water, and light energy
• Respiration: glucose and oxygen

Enzymes

• Enzymes are proteins made of amino acids
• The active site is part of the enzyme where the substrate binds.
• It can be likened to a “lock”, and the substrate the “key”.
• Enzymes are proteins with an active site that speed up reactions by lowering the energy needed.
• Active site is where the enzyme works.
• Competitive inhibition blocks the active site.
• Non-competitive inhibition changes the enzyme shape.

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 their concentration gradient, requiring energy (ATP).
• Endocytosis is when the cell engulfs large molecules, requiring energy.
• Exocytosis is when the cell releases large molecules by merging a vesicle with the membrane, requiring energy.

Explore cell structure, including prokaryotic/eukaryotic differences and shared components. Learn about the plasma membrane, its phospholipid bilayer, and selective permeability. Discover cell membrane proteins (integral, peripheral, channel, carrier, receptor, glycoproteins) and their roles in transport, communication, and cell recognition.