Transcript Cell Structure and Function

Essential Question: How are cell structures adapted to
their functions?
7.1 Life is cellular
Robert 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 cells
Cells are the basic units of structure and function in
living things
New 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-dimensional
Scanning: 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 DNA
Prokaryotic cells- DNA is NOT enclosed within a
nucleus
7.2 Cell Structure
What 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
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.
DNAchromosomeschromatin
nuleolus
nucleus
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
Cytoskeleton- Maintains cell shape
and is involved in movement and
transfer of substances.
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
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 synthesis
Smooth 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 Transport
What is passive
transport?
Passive transportthe movement of
materials w/out using
cellular energy
Diffusion- 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]
(normal)
Hypotonic- [solution] < [solutes]
(bursting)
Hypertonic- [solution] > [solutes]
(shriveled)
Water in and out of cell are =
More water inside of cell
More water outside of cell
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 Cells
How 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 organism
Tissue- 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.