Cell Structure Life Science Chapter 4

Cell Membranes Each Cell is surrounded by a Cell Membrane The membrane is a thin covering that makes the outer boundary of the cell. Keeps the insides in and the surroundings out. Membranes sense and respond to the changes in the surrounding environment.

Membrane Structure There seems to be ONE basic design found in ALL cells. Membranes are composed of molecules of lipids and proteins. Many variations to this one primary design Model of the Cell membrane – Fluid Mosaic Model Lipids form a flexible fluid Proteins embeded in a two-layered film Makes different patterns (mosaics)

Membrane Properties By learning some properties of membranes, we learn much about how the cell operates. Selectively Permeable- certain molecules go through them, and others do not. Not all materials permeable to the same molecule.

Membrane Properties cont… Active Transport- movement by use of the cell’s own energy. Passive Transport- movement of substances through a membrane without the use of a cell’s own energy. Diffusion Osmosis

Passive Transport Diffusion- The movement of molecules from a place with a lot of them (high concentration) to a place where there are few of them (low concentration) Diffusion can be accelerated by things such as heat, movement, and pressure Sugar passes from our blood to our cells by diffusion.

Passive Transport Cont.. Osmosis- diffusion of water through a selectively permeable membrane. A type of diffusion Moving from an area of LOW concentration to HIGH concentration Primary means by which a plant obtains water

Osmosis Cont… Some organisms have to control the amount of water that osmosis brings into their cells. Cell could swell and burst if it did not regulate this.

Typical Parts of a Cell Cells are like tiny factories In different cells, the basic structures come in different shapes, sizes, and quantities. All cells have THREE basic parts Cellular boundaries Cytoplasm Genetic Material

Cellular Boundries All factories have walls that protect the machinery. Cell membrane is like that factory wall Some factories have further protection (fences, boundaries, gates) Some cells also have additional boundaries Cell Walls- substances found in this boundary are made by the cell and assembled just outside of the membrane. The cell wall supports and protects the cell

Cytoplasm Cytoplasm- a thick fluid that contains many small organelles Organelles- parts of a cell that perform many of the functions needed to keep the cell alive.

Types of organelles Mitochondria- The Powerhouse of the cell Usually long oval structures made of two membranes Outer membrane smooth, inner has ridges Stores and uses energy

Types of organelles Endoplasmic Reticulum (ER) – passageways (canals) formed by a folded membrane passing throughout the cytoplasm. Connects the nucleus to the cell membrane Cell’s Delivery System

Types of organelles Ribosomes – Tiny organelles that direct the assembling of proteins. Scattered throughout the cytoplasm Receive coded instructions from the nucleus to form proteins.

Types of organelles Golgi Apparatus- Collect Chemicals from the cytoplasm. Sometimes they process these chemicals and make them complex. Connected with the ER

Types of organelles Vacuoles- organelles that look like bubbles and serve as containers inside the cytoplasm of some cells. Made of a membrane and may contain food, water, waste, fats, or chemicals.

Types of organelles Lysosomes- tiny enzyme filled capsules Use their enzymes as a “demolition crew” Dissolve structures that are no longer needed, or invading bacteria or viruses. Can also be used for digestion.

Types of organelles Chloroplasts – made of an outer membrane and stacks of inner membranes that contain the green pigment chlorophyll. Many plant cells and some other cells have chloroplasts

Types of organelles Cilia and Flagella- Propels the cell, or moves material by the cell. Cilia- tiny hair-like structures on the outside of the cell that are extentions of the membrane. Short and many Flagella- Hair like structures that are smaller and the cell has fewer. Usually one or two.

Genetic Material. Nucleus- compact roundish structure that functions as the control center for the cell. Main office Surrounded by a nuclear membrane which has larger pores that allow substances to pass back and forth between the nucleus and the cytoplasm.

Nucleus Cont… Inside the nucleus are chromosomes. Chromosomes – composed of DNA and other molecules. Chromosomes control the “plans” for all of the “machines” of the “factory”

Cell Comparison Some cells may completely lack organelles and some may be packed with one particular type. Bacteria cells lack a nuclear membrane among other organelles. Prokaryotes- lack a nuclear membrane Eukaryotes- cells that have a nuclear membrane.

What to Cells tell us about our God? When you view a piece of art, you not only appreciate the piece, but the creator of the piece. Cells show marvelous complexity, design, and efficiency. This should point to the Creator of life! And some people still believe this all happened from a big bang and evolution?!?!?

Anton van Leeuwenhoek Microscopist of the late 1600’s and 1700’s Viewed many tiny things with lenses he made himself. Other scientists had difficulty believing that the organisms Leeuwenhoek saw actually existed.