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Lesson 4.1: What Is a Cell?
Goals:
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Date
Period
Identify what a cell is
List the types of molecules found in a cell
Explain how cells were discovered
Define the cell theory
Introduction
 A cell is the smallest unit of life
 Carbohydrates, lipids, proteins, and nucleic acids organize themselves into
different structures that make up the cell
Major Functions of Cells
 Functions of cells
o Break down food we eat
o Produce energy from the food we eat
o Use the oxygen we take in
o Reproduce to make more cells
o Store DNA, the instructions for life
 Macromolecules in cells
o Carbohydrates are used for energy in the form of ATP,
communicating with other cells, storing energy and supporting
structures in the cell
 ATP – adenosine triphosphate – a molecule in all living cells
that acts as fuel
o Lipids are used for storing energy, membrane construction (making
cell membranes), making hormones
 Hormones – chemical signals the body used to control body
function
o Proteins are used for helping keep the structure of a cell steady,
communicating with other proteins, controlling what goes in and
out of the cell, and acting as enzymes
o Nucleic acids are used for storing genetic information (DNA) and
helping to make proteins (RNA)
Microscopes and Cells
 Microscope – an instrument used to magnify things
o 2 Types
 Light microscopes – use natural light to magnify things
 Electron microscopes – use a beam of electrons to magnify
objects
 After the microscope was invented, scientists could see cells and make
observations
o Robert Hooke – look at cork cells and called what he saw “cells”
o Anton von Leeuwenhoek – the first person to see living cells under
the microscope
o Matthias Schleiden – showed all plants are made of cells
o Theodor Schwann – showed all animals are made of cells
o Rudolf Virchow – discovered that cells can only come from other
cells
The Cell Theory
 The discoveries made by scientists helped to form the cell theory
 There are 3 parts to the cell theory:
o All living things are made of cells. All cells have some structures
in common, such as DNA.
o Cells are the basic units of structure and function in living things.
o Cells only come from already present cells.
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Date
Lesson 4.2: Cellular Structure and Function
Period
Goals:
 Relate a cell’s structure to its function
 Define homeostasis
 Predict the direction of diffusion
 Identify the three different kinds of osmotic environments
Intro
 Cell structure
o Determines the cell’s function
o Determines what activities the cell can perform
 Molecules in a cell do different activities
o Cells produce certain molecules when they need to do different
activities
o If a cell can’t produce certain molecules then it will not be able to
perform the activities
 Cells use basic functions to stay alive
o Cells want to maintain a balance with their surrounding
environment
o Homeostasis – the ability of organisms to maintain their internal
conditions
o Cells may move materials into or out of the cell to keep a balance
 Transport – to move molecules from one side of a membrane
to the other
o Molecules are constantly in motion
 When molecules group together they are concentrated
 Concentration – a measurement of the amount of
dissolved substance in a fixed amount of solvent
 HIGH concentration – means having MANY molecules in
an area
 LOW concentration – means having FEW molecules in an
area
 Molecules will naturally move to an area where they have
more space – from an area where there is a HIGH
concentration to an area where there is a LOW
concentration
 Diffusion – the movement of molecules from an area of high
concentration to an area of low concentration
 Example – sugar dissolving in a beaker
 Cells use diffusion to control the concentrations of their
molecules
 A cell’s membrane is the main barrier that separates a
cell from its environment
 Selectively permeable – a membrane that allows some
molecules to pass but blocks other molecules from
coming through
 Sometimes the concentration of molecules is different
on either side of the cell’s membrane
 Concentration gradient – forms when different
concentrations of a molecule are on either side of the
membrane
Osmosis: A Special Type of Diffusion
 Water is the main solvent for most chemicals in an organism’s body
 Cells can change the concentration of molecules by changing the
concentration of water molecules by performing osmosis
o Osmosis – the movement of water through a cell membrane
 There are three different environments that explain the movement of
water molecules
o Hypotonic - has a solute concentration that is lower than the
inside of the cell
 Hypo = “lower”
Tonic = “solute molecules”
 Water will move into the cell causing it to get bigger and
possibly burst
o Hypertonic - has a solute concentration that is higher than the
inside of the cell
 Hyper = “higher”
 Water will move out of the cell causing it to get smaller and
shrink
o Isotonic - has a solute concentration that is equal on both sides of
the cell
 Iso = “same”
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 The cell is at equilibrium
 Equilibrium – a state where concentrations are equal in
all parts of an area
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Lesson 4.3: What Kind of Cell Is It?
Date
Period
Goals:
 Identify the two major categories of cells
 Compare the major structural differences between cells
 Describe the kinds of organisms that cells make
Intro
 Cells can be grouped by their structure or function
Prokaryotic Cells
 Prokaryote – a cell with only one outside membrane and no nucleus or other
internal structures
o Simplest organisms
o Commonly called bacteria
o Have only one membrane
o Everything (DNA, molecules) free floats inside the cell
o Does NOT have a nucleus
 There are both good and bad bacteria
o Good bacteria:
 Help us live
 Help us break down food and use chemicals
 Help make different kinds of food (bread, cheese, and
yogurt)
 Bacteria come in three different shapes
o Rods
o Spirals
o Spheres
 Prokaryotes can be found in all types of environments
 Grow and reproduce quickly
o To reproduce they simply make a copy of
their DNA and then divide by a process
called binary fission
o Binary fission – reproduction in which a
bacterial cell divides into two cells that
look the same as the original cell
Eukaryotic Cells
 Eukaryote – a cell with several internal structures, including the nucleus,
that are surrounded by membranes
o Complex cells
o Have more structures compared to
prokaryotes
o Have a nucleus
 Nucleus controls growth and
reproduction
 Nucleus is the information and control center of the cell
 Nucleus holds the cell’s DNA
 Nucleus is usually the largest organelle in a eukaryote
o Eukaryotes include fungi (mushrooms and molds), plants, animals,
and protists
 Additional membranes surround structures inside cells called organelles
o Organelles – a tiny membrane-bound structure inside a cell
o Each organelle has a different function or job
 Some produce food or fuel for the cell
 Some help the cells to talk or communicate with each other
 The nucleus controls the activities of all of the organelles
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1. organelles
2. binary fission
3. nucleus
4. A
5. B
6. D
Name
Lesson 4.4: After the Cell
Date
Period
Goals:
 Name the four levels of organization in complex organisms
 Identify examples of each level of organization
Multicellular organisms are made up of many cells
 Cells that make up larger organisms have different functions based on
their structures
 Different kinds of cells are found in different parts of an organism
 Cells are put together in an organized way
The organized way of grouping cells is as follows:
 Cells are grouped into tissues
o Tissue – a group of cells that are similar and work together
o Examples
 Skin is made up of epithelial cells which work together
as skin tissue to protect parts of your body
 Nerve cells work together to form nervous tissue that
relays messages to and from the brain
 Muscle cells make up muscle tissue that help to move
your body
 Tissues are grouped into organs
o Organ – a group of different tissues that work together to
perform specific functions
o Example
 Heart – made up of muscle tissue that contracts and
pump blood
 Organs are grouped into organ systems
o Organ system – a group of organs that work together to
perform specific connected tasks
o Example
 Circulatory system – a collection of organs, including
the heart, which moves blood and gases throughout the
body
 Organ systems make up the organism
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1. organ system
2. cells
3. organ
4. A, protect parts of the body
5. B, tissue
6. B, nerve