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Biology CH 7: Cells

Lecture notes on Cells for a 9th grade biology course

Kelly Quinlan

on 23 October 2015

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Transcript of Biology CH 7: Cells

CH 7: Cells
Ch 7 Essential Questions
- Why is it important to study cells? (7.1)
- How do cell structures enable a cell to carry out basic life processes? (7.2)
- How does a cell transport materials across the cell membrane? (7.3)
- How does a cell maintain homeostasis both within itself and as part of a multicellular organism? (7.4)
Cell Theory:
1. All living things are made of cells
2. Cells are the basic units of structure and function in living things
3. New cells are produced
from existing cells
Robert Hooke used an early microscope to inspect a slice of cork (plant material). He saw thousands of tiny chambers he called "cells"
Anton van Leeuwenhoek examined pond water & cells from his mouth and drew the organisms he saw in his journal. Today these organisms are called Bacteria
Soon after, observations from other scientists made it clear that CELLS were the basic unit of life!
Invention of the Microscope
German botanist Matthias Scheiden concluded that all
PLANTS are made of
German biologist Theodor Schwann concluded that all ANIMALS are made of cells
German physician
Rudolf Virchow concluded that new cells can only be produced from existing live cells.
All these discoveries led to the fundamental concepts of biology that we call .
Cell Theory
Timeline of discoveries leading to current
-Use lenses to magnify the image of an object
Light Microscopes
- allow light to pass through a specimen
- Uses 2 lenses to form an image
What type of technology aided in the discovery of cells?
What are some ways the discovery of new ideas takes place?
What are the 3 components of cell theory?
Lets think about what we just learned...
Cell Stains
- Most living cells are transparent, so chemical stains
are used to make
the cells visible
Electron Microscopes
- Used to observe VERY small things
- Uses beams of electrons, instead of light, that are focused by magnetic fields
2 types...
Transmission Electron Microscope
Scanning Electron Microscope
- Makes it possible to view organelles & large molecules
- Produces flat 2D
- A thin beam of electrons is scanned over the surface of the specimen, so samples do not need to be cut
- produces a 3D image
- Cells that do not
enclose DNA in nuclei
- Bacteria
- Cells that enclose their DNA in nuclei
- Smaller than eukaryotes
- Large, complex, specialized cells
- Contain organelles and internal membranes
- Ex. Plants, animals, fungi, protists
At first glance, a factory is a busy looking place. The sheer diversity of all the activities can be confusing. But, if you take your time and watch carefully, what might at first seem like chaos begins to make sense.
The same is true for a living cell. All its functions take place like a well run factory.
Cell Organization
The cell is divided into 2 major parts:
- nucleus
- cytoplasm
- Control center of the cell
- Contains DNA and the coded instructions for making proteins and other molecules
The Nucleus is surrounded by a Nuclear Envelope with tiny nuclear pores that allow material to move in and out of the nucleus
Chromosomes contain genetic material that are spread throughout the nucleus
- Fluid portion of the cell
- have DNA and cytoplasm, but do not contain a nucleus
- Structures within a cell that act as specialized organs
Organelles the Store, Clean Up, and Support
- structures that store materials
- Animal cells have many small vacuoles, while plant cells have one large vacuole.
- Small structures that store
and move materials between
- Filled with enzymes that break down waste and remove it from the cell
- "Clean up crew"
- Network of proteins that give cells their shape
2 main protein filaments
- Form extensive networks that supports the cell
- Maintain cell shape
- pull chromosomes apart during cell division
- Located near the nucleus and organize cell division.
- Only found in eukaryotic . cells
Organelles that Build Proteins
Cells need to build proteins to carry out many essential functions of living things
Endoplasmic Reticulum (ER)
Golgi Apparatus
- Use RNA (coding instructions copied from DNA) to make Proteins
- only in Eukaryotic cells
Rough ER
Smooth ER
- Contain ribosomes on the surface
- New proteins leave the ribosomes and are inserted into the Rough ER, where they are modified
- No ribosomes
- helps with protein synthesis
- Sorts, and packages proteins and other materials from ER for storage in the cell or release outside the cell
Organelles that Capture and Release Energy
- found in Plant cells
- Capture energy from sunlight and convert it into food that contains chemical energy in a process called Photosynthesis
- In all eukaryotic cells
- Convert energy from glucose into a form of energy the cell can use
Cell Boundaries
Cell Wall
- Strong supporting structure that surrounds and protects the cell
- found in plants, algae, fungi, and some prokaryotes
Cell Membrane
- Surrounds and protects animal cells
- Regulates what enters and exits the cell (selectively permeable)
- contains proteins that can move molecules across the membrane
When thinking about how cells move materials in and out, it can be helpful to think of a cell as a nation. The boundaries of a nation are its borders, and nearly every country controls the goods that move across those borders.
Cells have their own borders, which
separate the cell from its surroundings
and also determine what comes in and
what goes out.
How can a cell separate itself from its
environment and still allow material to
enter and leave?
Cell Transport
There are 2 categories of transport:
Passive Transport
Active Transport
- Movement of materials across a membrane without using energy
- Transport of materials across a membrane that . requires energy
Passive Transport
Facilitated Diffusion
- When substances move from an area of greater concentration to an area of lower concentration
- Molecules that cannot directly diffuse across the membrane pass through special protein channels
- The diffusion of water through a selectively permeable membrane.
- Involves the movement of water molecules from an area of higher concentration to an area of lower concentration
Many cells contain water channel proteins, known as aquaporins, that allow water to pass right through them. Without aquaporins, water would diffuse in and out of cells very slowly.
This extremely important biological process is called osmosis.
For example:
When the concentration is the same on both sides of the membrane, the two solutions will be isotonic, which means “same strength.”
The more concentrated sugar solution is hypertonic, or “above strength,” compared to the dilute sugar solution, which is hypotonic, or “below strength.”
The net movement of water out of or into a cell exerts a force known as osmotic pressure.
Vacuole swells
Cell swells
Cell shrinks
Vacuole shrinks
Plant cells can hold their shape under high osmotic pressure because of their strong cell walls, while animals cells can swell and shrink with the changes in pressure
Active Transport
- Requires energy
- moves from an area of lower concentration to greater concentration (against the gradient)
Transport by Pumps
- The transport of small molecules across a cell membrane is carried out by transport protein pumps that are found in the membrane itself.

- Many cells use protein pumps to
move calcium, potassium, & sodium
ions across cell membranes against the
concentration gradient.
Large Molecule Transport
- The process of taking material into the cell by forming a pocket around the particle .
2 types of Endocytosis
- ingestion of solid material by the cell.
- ingestion of liquids by a cell
"cell eating"
"cell drinking"
-A vessicle surrounds the material, then fuses with the cell membrane. The contents are forces out of the cell
A relatively constant internal environment
The paramicium contains a vacuole that expands and contracts depending on whether the environment is hypotonic or hypotonic
Homeostasis in Unicellular (single celled) Organisms
- grow, respond to the environment
Lets think...
What would happen if a nurse accidentally injected you with water instead the 15% glucose solution she was suppose to?
*Assume that inside the cell is 15% glucose
Red Blood Cell
(containing 15% glucose)
Glucose molecules
Water (0% glucose)
What type of solution is this cell in? Hypotonic, hypertonic, isotonic?
Would water flow into the cell or out of the cell?
7.2 Organelles
Plant cell
Animal cell
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