Cell Energy, Mitochondria, and Cytoskeleton Quiz

Plasma Membrane

• The plasma membrane is a selectively permeable barrier controlling the passage of substances in and out of the cell
• It is a double layer of phospholipids with embedded proteins, providing a physical barrier separating the inside and outside of the cell
• Phospholipids have a hydrophobic region and hydrophilic polar heads, arranged in a double layer with their tails facing each other
• Plasma membrane proteins mediate the movement of hydrophilic substances and are often amphipathic, having both hydrophilic and hydrophobic regions
• Integral proteins are embedded (partially or fully) into the membrane

Transmembrane Proteins

• Transmembrane proteins are integral membrane proteins that fully span the entire membrane, contacting both extracellular and cytoplasmic areas
• They carry out various functions, such as:
  • Channels and transporters, which can be general or selective, gated or not
  • Carrying out chemical reactions, either alone or as part of a team of enzymes
  • Acting as receptors for external signaling molecules

Cellular Organelles

• Major organelles include:
  • Nucleus
  • Endoplasmic Reticulum (smooth and rough)
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Ribosomes
• The endomembrane system includes the plasma membrane, along with the above organelles, working together to package, label, and ship molecules

Golgi Apparatus

• The Golgi apparatus is a series of flattened sacs or cisternae that contain enzymes of different functions
• Proteins move from the cis to trans side of the Golgi, maturing at the exit cisternae, and then travel to their destination
• Modifications occur within each sac, including the formation of glycoproteins, glycolipids, and lipoproteins

Lysosomes

• Lysosomes contain powerful digestive enzymes and are formed from the Golgi membrane
• They have a membrane that pumps H+ ions to maintain an acidic pH, protecting the rest of the cell from digestion
• Lysosomes are responsible for the digestion of:
  • Substances that enter the cell
  • Cell components, such as organelles (autophagy)
  • Entire cells (autolysis)

Mitochondria

• Mitochondria are responsible for generating ATP through cellular respiration
• They are made up of an outer mitochondrial membrane, an inner mitochondrial membrane with folds called cristae, and a fluid-filled interior cavity called the mitochondrial matrix
• Mitochondria have a separate small genome encoding mitochondrial-specific products
• The number of mitochondria present in a cell is directly related to the amount of energy required by the cell

Cytoskeleton

• The cytoskeleton is a structural support system of the cell, providing shape, size, and integrity
• It is composed of three types of fibers:
  • Microfilaments (diameter: ~7 nm, composed of actin molecules)
  • Intermediate filaments (diameter: 8-12 nm, composed of diverse materials)
  • Microtubules (diameter: 25 nm, composed of tubulin dimers)
• The cytoskeleton acts as scaffolding across the cell and is involved in intracellular transportation and cell movement

Nucleus

• The nucleus is the largest distinct structure inside the cell, enclosed by a double lipid bilayer called the nuclear envelope
• It is continuous with the rough Endoplasmic Reticulum and has nuclear pores that regulate the movement of substances in and out
• The nucleus contains DNA, which is wrapped around histones to form nucleosomes, and is responsible for:
  • Housing and protecting DNA
  • Making RNA and assembling ribosomes
  • Regulating the movement of substances in and out of the nucleus

Cell Theory

• All living organisms are composed of one or more cells
• The cell is the basic unit of structure and organization
• All cells arise only from pre-existing cells
• Universal similarities between cells include:
  • DNA as the heritable material
  • RNA as a messenger
  • Proteins as the workers
  • ATP as an energy source

Prokaryote vs. Eukaryote Cells

• Prokaryote cells lack a membrane-bound nucleus and are typically smaller than eukaryote cells
• Eukaryote cells have membrane-bound organelles and are generally larger than prokaryote cells
• Both types of cells have plasma membranes, cytosol, DNA, RNA, proteins, and ribosomes

Test your knowledge on the relationship between cell energy, mitochondrial functions, and cytoskeleton components. Learn about the ATP production in relation to cell energy needs, the key role of mitochondria in carrying a separate genome, and the structural support provided by the cytoskeleton in cells.