Cell Structure and Function Cells and their Functions Organelle Functions

Levels of Organization Cells can be grouped together into tissues, a group of cells that are similar and work together. –Epithelial cells  epidermis Neurons  nerve Tissues can be grouped together into organs, a group of different tissues that work together to perform a specific function. –Epidermis, dermis, subcutaneous tissue  skin

Levels of Organization Organs can be grouped together into organ systems, a group of organs that work together to perform specific connected tasks. –Stomach, Intestines, Liver, etc.  Digestive system Cells  Tissues  Organs  Organ systems

Major functions of cells Break down food into nutrients –Polymers into monomers Transport materials –O 2 to cells; CO 2 away from cells Produce chemicals –Hormones – a chemical signal used to control body functions Work together to build tissues organs organ systems organism

Cell Theory All living things are made of cells. All cells have some structures in common, such as DNA. Cells are the basic units of structure and function in living things. Cells only come from already present cells (pre-existing).

Cell Types Prokaryotes – a cell with only one outside membrane and no nucleus or other internal structures Simple cells Grow quickly –Binary fission, cell divides into identical daughter cells Ex. - bacteria Eukaryotes – a cell with several internal structures, including the nucleus, that are surrounded by membranes Complex cells Ex. – plant cells, animal cells, fungi cells

Cell Structure and Function Maintain homeostasis, the ability of organisms to maintain their internal conditions Diffusion – the movement of molecules from an area of high concentration to an area of low concentration Osmosis – the movement of water through a cell membrane Selectively permeable membrane – a membrane that allows some molecules to pass but blocks other molecules from coming through (semi- permeable)

Selectively permeable membranes

Concentration Gradient A difference in the concentration of a substance across a distance is the concentration gradient. Hypotonic – a solution whose solute concentration is lower than the solute concentration of another solution Hypertonic – a solution whose solute concentration is higher than the solute concentration of another solution Isotonic – a solution whose solute concentration is equal to the solute concentration of another solution

Concentration Gradients

Eukaryotic Cells Contain a membrane-bound nucleus –Controls the activities of the cell Contain membrane-bound organelles –Transports materials –Produces chemicals and substances Complex in structure –Can reproduce in several different ways; asexual and sexual reproduction

Cell Membrane Composed of a lipid bilayer. Hydrophilic outside, hydrophobic inside Proteins help transport large molecules across the membrane Glycoproteins help cells “communicate” with each other

Cell Membrane

Cell Membrane Function Regulates which materials enter and leave the cell Protects the cell from outside environment Passive transport – the movement of molecules across a membrane when the movement requires no energy –Ex. Diffusion and osmosis Facilitated diffusion – passive transport that involves membrane proteins

Cell Membrane Function Active Transport – the movement of molecules across a membrane when the movement requires energy Endocytosis – a process in which a cell membrane surrounds and encloses a substance to bring the substance into the cell Exocytosis – a process in which a substance is released from a cell through a pouch that transports the substance to the cell surface.

Nucleus Controls information in the cell Surrounded by the nuclear envelope; bilayer contains pores to let substances enter and leave Contains the DNA, which is folded with proteins making up the chromosomes Nucleolus – a ball of fibers in the nucleus that makes ribosomes

Nucleus

Ribosomes Make proteins from directions found in DNA Made from a combination of RNA and other proteins Found throughout the cell Found on the rough endoplasmic reticulum

Mitochondria Converts energy from bonds in glucose into ATP through respiration, process in which cells break down food to release energy

Chloroplast Harvests energy from the sun through photosynthesis Found in plants, some bacteria and protists

Endoplasmic Reticulum (ER) Makes different molecules Rough ER packages and sends off proteins Smooth ER makes lipids and carbohydrates

Golgi Apparatus Responsible for synthesizing, modifying, and packaging proteins for export

Vacuoles and Lysosomes Vacuoles - transports and stores molecules Lysosomes – contain special enzymes to break down large molecules Found throughout the cell

Cytoskeleton A group of fibers running throughout the inside of a cell that supports the cell and helps the cell move Microfilament – a long fiber used to move the cell –Made of a ball-shaped protein called actin Intermediate filament – a rod-like fiber used to strengthen the cells shape and hold organelles in place Microtubule – a fiber used by organelles to move around. –Made of a ball-shaped protein called tubulin

Cytoskeleton

Plant Cells Plant cells contain chloroplast used in photosynthesis Cell wall – rigid layer of cellulose outside the cell membrane Plasmodesmata – openings in the cell wall used for communication and transport of molecules Central vacuole – a large sac in the center of the plant cell used for water storage.

Plant Cells