Chapter 7: Cell Structure & Function Section 2: Cell Structure

Structure & Support Cell Membrane: the cell’s outer boundary, acts as a barrier between the outside environment. outer, protective layer of the cell controls how easily things can pass in and out of the cell The cell membrane is “selectively permeable” which means that it only lets certain things in and out of the cell Sometimes called the plasma membrane Made of Phospholipids which form a lipid bilayer Hydrophilic Heads: “Water Loving” face outside and inside the cell Hydrophobic Tails: “Water Fearing” inside of the bilayer

Cell Membrane

Cell Wall: found mainly in plant cells, support and protect the cell made up of cellulose, which is a carbohydrate Found in prokaryotes (bacteria), protists, fungi, and plants Most cell walls are porous enough to allow water, oxygen, and carbon dioxide to pass through them and get into the cell

Cytoplasm: Fluid or jelly-like substance inside the cell and almost all structures in the cell that are suspended in it similar to broth in a pot of soup

Cellular Activity Nucleus: Found only in eukaryotic cell, and contains DNA If found in a cell it immediately indicated a eukaryote control center of the cell; directs cellular activity; stored heredity information “brain of the cell” Nucleolus: ribosome parts are made here; interior part of nucleus Nuclear Envelope: double membrane surrounding nucleus

Molecule that stores genetic information used to make proteins DNA: Molecule that stores genetic information used to make proteins in the Nucleus double helix shape Made of: Phosphate Group 5 carbon sugar; deoxyribose Nitrogenous bases: adenine, thymine, guanine, and cytosine

Ribosomes: place where proteins and enzymes (speed up bodies chemical reactions) are made/synthesized by following the instructions that come from DNA Made of proteins and RNA There are 2 types of ribosomes: Free Ribosomes: can be found floating in the cytoplasm Bound Ribosomes: can also be found attached to the membrane an organelle Example: the rough endoplasmic reticulum has ribosomes bound to it’s membrane and help make proteins

Protein Packaging Endoplasmic Reticulum (ER): a system of internal membranes that aids in the production, processing, and transport of proteins and lipids (fats) through the cell Rough ER: ribosomes are attached to endoplasmic reticulum, proteins are made here; produce vesicles filled with proteins Smooth ER: no ribosomes on endoplasmic reticulum, makes lipids; produce vesicles filled with lipids

Golgi Apparatus: process, package, and secrete substances to the outside of the cell Modifies, sorts, and packages proteins for distribution throughout the cell and for export considered the “UPS” of the cell

Storage & Maintenance Lysosome: small, spherical structures that contain enzymes breakdown and digest molecules like carbohydrates, proteins, fats, and DNA & RNA Digest damaged organelles & foreign substances “Garbage Man” of the cell

Storage & Maintenance Vesicle Membrane bound sac that buds off of other organelles Joins/fuses with other organelles Store, transport, and digest cellular particles & waste Examples: Vesicles bud off of the ER and store proteins and lipids to be used within the cell or transported to other organelles Vesicles can join/fuse with the lysosome to deliver particles that need to be digested

Vacuole: membrane bound sac used for storage of water, waste, & nutrients larger and more common in plant cells; Central Vacuole example: cacti have a large vacuoles for storing water.

Energy Production Mitochondria: place where cellular respiration occurs where most of a cell’s ATP is made – made in the inner membrane Adenosine Triphosphate (ATP): compound used by cells to store and release energy called the “powerhouse” of the cell Cells that require/need a lot of energy have more mitochondria than cells that do not require/need as much energy found in plant and animal cells has its own DNA

Chloroplast: found in plant cells only, site/place where photosynthesis occurs converts energy from the sunlight into chemical energy (sugars) using carbon dioxide & water contains its own DNA and ribosomes Reason plants are green

Movement Structures Cytoskeleton: a web of protein fibers Supports the cell like bones support your body Helps the cell move, keep its shape, & organize its parts

Movement Structures 3 types of cytoskeleton fibers: Microfilaments: long, thin fibers that are made of protein actin Some attach to the cell membrane Contract to pull the membrane in some places & expand to push it out in others

Movement Structures Intermediate Fibers: Moderately thick & mainly anchor organelles & enzymes to certain parts of the cell

Movement Structures Microtubules: Thick, hallow fibers that are made of protein tubulin Information molecules move through these tubes to various parts of the cell

Cytoskeleton

In these cells, microfilaments appear light purple, microtubules yellow, and nuclei greenish blue. ↓ ↑ The three fibers of the cytoskeleton: microtubules in blue, intermediate filaments in red, and microfilaments in green–play countless roles in the cell.

Movement Structures Centrioles – help pull the chromosomes (DNA) apart when the cell divides and reproduces (contain microtubules)

Movement Structures Flagella: long, Whip-like extension that help the cell move (contain microtubules) usually only one flagella on a cell example: sperm cell Cilia: short hair-like extensions that help the cell move (contain microtubules) there are hundreds of cilia on each cell

Diversity in Cells Diversity in Prokaryotes: Vary in shape Way they obtain energy Makeup of the cell walls Ability to move Flagella; to move quickly Pili: short, thick outgrowths that allow them to attach to surfaces and other cells

Diversity in Eukaryotes Plants: Chloroplasts Large central vacuole Cell wall that surrounds the cell membrane Vary structure by function Some organelles are more prominent in specialized cells Varying internal makeup can allow cells to be specialized for specific functions Example: muscle cells have lots of mitochondria bc muscles require a lot of energy

Prokaryote vs Eukaryote

Animal Cell

Plant Cell

Plant cell vs Animal cell

Levels of Organization Cells: the smallest unit that can carry on all of the processes of life A group of cells that are organized and working together make up tissues.

Tissues: a distinct group of cells that have similar structures and functions Ex: muscle tissue is group of many cells that have bundles of cytoskeletal structures. A group of tissues working together make up organs.

Organ: different types of tissues arranged so that specialized functions can be carried on. Ex: Lungs being able to pump oxygen in and out to the rest of your body. A group of organs working together make up organ systems

Organ Systems: various organs that carry out a major body functions. Ex: Respiratory System major function is the uptake of oxygen into our bodies.

Cells → Tissues → Organs → Organ Systems

Body Types Sometimes, entire body of an organism is made up of a single cell Cell must carry out all of the activities Growing Using energy Responding to the environment Reproducing More than half of the biomass on earth is composed of unicellular organisms Single cells cannot grow larger than a certain size

Multicellular organisms are composed of many individual, permanently associated cells that coordinate their activities Distinct types of cells have specialized function Individual cells cannot survive alone and are dependent on the other cells of the organism

Cell Groups Some unicellular thrive independently, but others live in groups Colonial organisms: Cells that live as a connected group but DO NOT depend on each other for survival Example: cell walls of some bacteria adhere to one another after dividing, but can survive independently

Multicellularity Only in Eukaryotes Cells in a multicellular body perform highly specific functions Some cells protect organisms from disease & predators Some cells help with movement, feeding, & reproduction Most multicellular organisms begin as a single cell Example: a chicken starts as an egg; new cells form from cell division; cells grow & undergo differentiation(process of developing specialized forms & functions); specialized cells arrange into tissues, organs, & organ systems to make the entire chicken