chapter 2; cells

• The digestive system is responsible for breaking down food into nutrients that can be absorbed by the body.
• The respiratory system brings oxygen to cells through breathing, while the circulatory system transports blood throughout the body.
• The nervous system controls all bodily functions and sends messages between different parts of the body.
• The endocrine system produces hormones that regulate various processes such as growth, metabolism, and reproduction.
• Proteins in the cell membrane

  • Allowing molecules to be transported across the membrane
• Endocytosis types

  • Pinocytosis (taking liquids)
  • Phagocytosis (taking solids by vesicles)
• Simple diffusion

  The spreading out of particles evenly from high to low concentration, occurring in liquids and gases due to constant molecular movement
• Facilitated diffusion


  Molecules attaching to a binding site on a specific carrier protein and passing through the membrane without energy input
• Exocytosis


  The contents of a vesicle inside the cell are passed to the outside by the vesicle migrating to the cell membrane and pushing out its contents into the extracellular fluid
• Carrier-mediated transport


  Characteristics: Carrier proteins are specific and saturable, carrier activity is regulated by substances like hormones
• Endocytosis


  Taking liquids or solids into the cell by the cell membrane folding around a droplet or solid particle until completely enclosed
• Channel proteins


  • Forming protein channels and carrier proteins, allowing carrier-mediated transport
• Osmosis


  The diffusion of water across a differentially permeable membrane to balance the concentration of solutes, with high concentration leading to high osmotic pressure
• Shallow concentration gradient


  Slow diffusion
• The higher the concentration gradient


  The greater the rate of diffusion
• Cell membranes act as a physical barrier, regulate the passage of materials, control movement of materials into/out of the cell, and are sensitive to changes in the extracellular fluid
• Diffusion


  Moving from high area of concentration to low, occurs in liquids and in gases as their molecules are constantly changing and moving
• Phospholipid bilayer

  Composed of phospholipid molecules arranged in two layers (lipid bilayers), with hydrophilic heads and hydrophobic tails
• Ribosomes are responsible for protein synthesis by linking amino acids together
• Cell membranes

  Differentially permeable; allow certain ions/molecules to pass through but restrict the movement of others
• Substances that enter or leave the cell must pass through the cell membrane
• The nucleus contains DNA, controls the structure and function of the cell
• Cytoplasm holds the components of the cell, protects them from damage, and breaks down materials taken into the cell or worn-out organelles
• Endoplasmic reticulum extends from the nuclear membrane throughout the cytoplasm
• Active transport

  The movement of molecules or ions across a cell membrane from a region of lower concentration to higher (goes against the concentration gradient), requires cellular energy
• The fluid mosaic model of the cell membrane is fluid because the molecules are constantly changing position and mosaic because it is composed of many different kinds of molecules
• Cell membranes are important for the function, integrity, and stability of the membrane
• Diffusion

  The spreading out of particles so that they are evenly distributed, e.g. sugar cube being dropped in the water
• Steep concentration gradient

  Fast diffusion
• Diffusion

  Substances move along the concentration gradient from high concentration to low, does not require energy
• Lysosomes contain digestive enzymes able to break down proteins, lipids, nucleic acids, and carbohydrates
• Mitochondria use aerobic respiration to generate ATP and are the site of cellular respiration
• Materials may pass through cell membranes in different ways: simple diffusion, passive transport/active transport, facilitated transport, vesicular transport
• Cell membranes help support the cell by being attached to the microfilaments of the cell's cytoskeleton
• Vesicles are membrane-bound sacs that transport materials into, out of, or within the cell
• Cytoplasm

  • Holds the components of the cell and protects them from damage
  • Breaks down materials taken into the cell or worn-out organelles to keep the cell clean
• Cell membrane


  Separates the cell's contents from the external environment, regulates the transport of materials entering and exiting
• Cytoplasm

  Gelatinous liquid that fills the inside of the cell, suspending organelles within apart from the nucleus
• Organelles


  Small structures that perform specific jobs in the cell
• Endoplasmic Reticulum


  Pairs of parallel membranes extending through the cytoplasm providing a surface for chemical reactions