Cell Structure and Function

Essential Question: How are cell structures adapted to their functions?

7.1 Life is cellularRobert Hooke discovered cells by using an early compound microscope to examine a cork screw. There appeared to be thousands of tiny empty chambers, which he named “cells” b/c they looked like the tiny rooms that monks lived in which were called cells?

What is cell theory?

All living things are made of cellsCells are the basic units of structure and function in living thingsNew cells are produced from pre-existing cells

How do microscopes work?

Most microscopes use lenses to magnify the image of an object by focusing light or electrons

We usually use a compound microscope. 2 different lenses (ocular- what you look through, and objective, an adjustable magnification) are used to view an object.

Magnification is found by multiplying the objective lens power by the ocular lens power. Ex: 40x 10x= 400x

Light microscopes can magnify objects to about 1000x

Most cells are nearly transparent, but we use stains or dyes to visualize cells and their structures.

Fluorescent microscopy- fluorescent dyes are attached to specific molecules that can be used to identify the location movement of molecules around a cell.

Electron microscopes

Use beams of electrons that are focused by magnetic fields to view objects that are too small to be seen with a light microscope.

Types of electron microscopes:Transmission: Can view cell structures and proteins. Samples are cut thin, so images appear 2-dimensionalScanning: Scan the surface of cells. Images appear 3-D

How are prokaryotic and eukaryotic cells different?

All cells contain a cell membrane- a thin, flexible barrier on the outside of the cell.

Cells are categorized by the presence or absence of a nucleus:

Eukaryotic cells- contain a nucleus to enclose their DNAProkaryotic cells- DNA is NOT enclosed within a nucleus

7.2 Cell StructureWhat is the role of the cell nucleus?

Both prokaryotic and eukaryotic cells contain cytoplasm- a gel-like substance that holds the cell together.

Organelles- the specialized structures that help the cell perform vital functions

The nucleus contains the cell’s genetic information, and with it, the coded instructions for making proteins and other important molecules

Organelle video

Nucleus

Surrounded by a “nuclear envelope.” Nuclear pores allow material to move in and out of the nucleus. –like a manager

Nucleus is control center of the cell.DNAchromosomeschromatinnuleolusnucleus

What are the functions of vacuoles, lysosomes, and the cytoskeleton?

Vacuole- a sac-like membrane that stores water, salts, proteins, and carbohydrates. Also can store away harmful substances.-like a storage closet

Lysosomes- break down lipids, carbs, and proteins into small molecules the cell can use. Recycle and clean up materials that have lost their use.-like a janitor

2 principal protein filaments that make up the cytoskeleton:

Microfilaments: Thread-like structures composed of the protein actin. Responsible for cytoplasmic movement

Microtubules: Larger (hollow) and much more rigid than microfilaments. Maintain cell shape and responsible for cell division.

Centrioles- made of microtubules, organize cell division*Only found in animal cells

Cytoskeleton- Maintains cell shape and is involved in movement and transfer of substances.

Organelles that build proteins

Proteins are assembled on ribosomes. Ribosome-a small particle of RNA and protein

Endoplasmic reticulum (ER)- an internal membrane system where lipids and proteins are assembled and exported from the cell.

Rough ER-site of protein synthesisSmooth ER- site of lipid synthesis

Proteins made on the rough ER include those that will be released, or secreted, from the cell as well as many menbrane proteins and proteins destined for lysosomes and other specialized locations.

Golgi apparatus

-Appears as a stack of flattened membranes.

The Golgi apparatus modifies, sorts, and packages proteins and other materials from the ER for storage in the cell, or release from the cell

Energy in the cell

Chloroplast- capture energy from the sun and convert it into food that contains chemical energy via photosynthesis*Only present in plant cells

Mitochondria- converts chemical energy stored in food into compounds easier for the cell to use-like the powerhouse*Present in both plant and animal cells

What is the function of the cell membrane?

Cell wall- Protect cell and support its structure. Porous, allowing for exchange of materials.- Like walls *Found in plant cells and some prokaryotic cells

Cell membrane (lipid bilayer)- regulates what enters and leaves the cell. Also functions in support and protection.

Lipid structure- Hydrophobic (water-hating) head, hydrophilic (water-loving) tails. The heads cluster together, and the tails do the same. This creates the lipid bilayer.

Fluid mosaic model- describes the mobile embedding of proteins throughout the lipid bilayer. The proteins and other molecules float among the lipids

Selective permeability- membrane allows certain materials to pass, and others not to

7.3 Cell TransportWhat is passive transport?

Passive transport- the movement of materials w/out using cellular energyDiffusion- a type of passive transport in which particles move from an area of high low concentration.

Facilitated diffusion- substance passes through a membrane with the aid of an intermediary or a facilitator

Osmosis- the diffusion of water through a selectively permeable membrane.

Water channels proteins that allow for movement through membrane= aquaporins.

Isotonic- [solution] = [solutes] Water in and out of cell are = (normal)Hypotonic- [solution] < [solutes] More water inside of cell (bursting)Hypertonic- [solution] > [solutes] More water outside of cell (shriveled)

Osmotic pressure- pressure that must be applied to prevent osmotic movement across a selectively permeable membrane.

What is active transport?

The movement of materials against a concentration difference. It requires energy.

Endocytosis vs. Exocytosis

Endocytosis is the process of taking materials into the cell via enfoldings of pocketings in the membrane.

Exocytosis is when the membrane of the vacuole fuses w/ the cell membrane to force contents out of the cell.

7.4 Homeostasis and CellsHow do individual cells maintain homeostasis?

To maintain homeostasis, unicellular organisms grow, respond to the environment, transform energy, and reproduce.

How do the cells of multicellular organisms work together to maintain homeostasis?

They become specialized for particular tasks and communicate w/ one another to maintain homeostasis.

Levels of Organization

Cell tissue organ organ system organismTissue- a group of similar cells that work together to perform a particular function

Organ- Groups of tissues that work together to perform a particular function

Organ system- a group of organs that work together to perform a particular function

Cellular communication

Cells communicate via chemical signals.

To respond to a chemical signal a cell must have a receptor to which the signaling molecule can bind.

Chemical signals can cause important changes in cellular activity.