1. Cells
Unit 4

2. Levels of Organization
1. Organelle - structure that has a specific function in the cell 2. Cell – basic unit of life 3. Tissue - group of cells working together to perform a common function 4. Organ - tissues working together 5. Organ System - group of organs working together 6. Organism - entire living being

3. Development of the Cell Theory
Early 1600s – Invention of the light microscope
This allowed people to see life at a microscopic level!
1665: Hooke: looked at cork (a plant) under a microscope and called the boxes he saw “cells”
1683: Leeuwenhoek: made a better light microscope that could magnify up to 200X. He was the first to observe small single-celled organisms.
1838: Schleiden: plants are made of cells
1839: Schwann: animals are made of cells
1858: Virchow: cells come from
pre-existing cells

4. Better Technology = Better Understandings
Development of better technology like electron and scanning microscopes show more detail so we can observe parts of the cells and cellular processes.

5. The Cell Theory Living things are composed of one or more cells.
Cells are the basic units of structure and function of living things.
New cells arise from pre-existing cells.

6. Main Jobs of Cells
Cells perform chemical reactions so that organism can:
Acquire energy
Reproduce
Maintain homeostasis (stable internal environment)
Produce proteins for growth and repair

7. Prokaryotic v. Eukaryotic Cells
The simplest life forms are prokaryotes. These are single-celled organisms that were the earliest life on Earth.
Prokaryotic cells exist in two major forms: bacteria and archaea.
Prokaryotes are Earth’s most abundant inhabitants.
Eukaryotes arose from prokaryotes and developed into larger, more complex organisms, like protists, fungi, plants, and animals.
Eukaryotes have many cell structures (organelles) that perform a specific function.

8. Organelles Nucleus Contains DNA, site where RNA is made
Nucleolus – dark region where ribosomes are assembled.
Mitochondria
Site of cell respiration (breaks down energy sources - “powerhouse”)

9. Organelles Ribosome Site of protein synthesis (production)
Endoplasmic Reticulum
(Rough or
Smooth)
Transports materials through the cell. Rough ER has ribosomes.
Golgi Apparatus
Site where cell products are packaged for export

10. Organelles Lysosome Contains digestive enzymes Vacuole
Storage of food, water, or wastes. Plants have 1 central vacuole, animals have many small vacuoles.
Chloroplasts
(plant only)
Site of photosynthesis (uses sun’s energy to make glucose)
Centrioles
(animal only)
Organize spindle fibers during cell division.

11. Organelles
Cytoplasm
Fluid inside the cell that contains organelles and is the site of many reactions
Cell (Plasma) membrane
Controls what enters and leaves the cell. Made of phospholipid bilayer.
Cell wall
(plants only)
Provides support (for plant cells)
Cytoskeleton
Helps maintain cell shape (made of microfilaments and microtubules)

12. Organelles Structures for cell movement: Cilia
Many short hair-like projections that draw materials in towards cell
Flagella
Long whip-like tail that moves cell through surroundings
Pseudopodia
*Not really
an organelle!
Temporary extension of cytoplasm that allows cell to drag itself in one direction

13. Unicellular vs. Multicellular Organisms
Some organisms exist as a single cell (unicellular), while others are composed of many cells (multicellular).
All organisms need to perform the same functions to survive.
A single-celled organism has to conduct all processes in one cell.
However, a multicellular organism has groups of cells that specialize to perform specific functions (ex. - skin cells, muscle cells, brain cells…).

14. Two Types of Cells Prokaryote Eukaryote Simple, smaller
NO nucleus or membrane-bound organelles
Ex) bacteria
More complex, larger
Has nucleus and membrane-bound organelles
Ex) plants, animals, fungi

15. Plant vs. Animal Cells Animal Cells Plant Cells No cell wall Cell wall
Both eukaryotic cells!
Animal Cells
No cell wall
Many small vacuoles
Contain centrioles for cell division
Rounded irregular shape
Plant Cells
Cell wall
Have chloroplasts
One central vacuole
Fixed, rectangular shape

16. Plant vs. Animal Cells Foldable
Fold so that plant and animal cell halves meet in the middle
Label organelles
On the inside, list name and function of –
Shared organelles in the middle
Plant only organelles on the left
Animal only organelles on the right

17. Unit 4
The Light Microscope

18. Light Microscopes
Light passes through lenses to produce an enlarged image of a specimen.

19. Magnification v. Resolution
Magnification: ability to make an object appear larger (“zoom” in)
Resolution: how clear the image is
To calculate the total magnification:
Eyepiece: magnifies specimen 10x by itself
Objectives : 4x, 10x, 20x, 40x, 100x
Total Magnification: Eyepiece x Objective
Ex) total magnification of 40x objective is 10x40 = 400x

20. Parts of the Microscope
A. Eyepiece
B. Objective (lens)
C. Stage
D. Course Adjustment
E. Fine Adjustment
F. Arm or Neck
G. Light source
H. Base

21. Review – Label each organelle

22. The Cell Membrane and Cell Transport
Unit 4
The Cell Membrane and Cell Transport

23. Functions of the Cell Membrane
All cells are surrounded by a cell membrane – also called the plasma membrane or phospholipid bilayer
Function:
Maintains homeostasis – stable internal conditions
Controls movement of materials in and out of the cell - selectively permeable means that the membrane only allows some materials through, not all
Communication between cells
Recognition of cells

24. Structure of the Cell Membrane
The fluid mosaic model says that the cell membrane is made of different components that move around.
Double layer of phospholipids: lipids that have charged phosphate heads – main component of membrane
Cholesterol: stabilizes the membrane
Transport proteins: allow specific molecules through
Carbohydrates: important for cell recognition 1 2 4 3

25. Phospholipid Structure
Polar Heads: hydrophilic (like water)- always face outside or inside of cell
Fatty Acid Tails: hydrophobic (doesn’t like water)- always face inside of membrane
Fluidity Animation
Inside and outside environment of cells are mostly water. Hydrophobic tails are repelled by this water and orient themselves in a double layer.

26. Cell Transport Movement of materials in and out of cell.
Concentration gradient – the difference in concentration inside the cell vs. outside.
Materials can move down concentration gradient (from high to low) on their own (passive transport).
Cells must use energy to move materials from areas of low concentration to high (active transport).

27. Passive Transport
Does NOT require energy to move molecules from areas of HIGH concentration  LOW
Diffusion
Facilitated Diffusion
Osmosis

28. Types of Passive Transport
Diffusion: substances move from an area of higher to lower concentration.
Facilitated diffusion: larger substances are moved from high to low with the assistance of a transport protein (still no energy used!)
Osmosis: movement of water through a semi-permeable membrane
Small, neutral molecules can move straight through membrane phospholipids – oxygen, carbon dioxide
Large or charged molecules must go through protein channels – glucose, amino acids

29. Dynamic Equilibrium
Through passive transport, molecules will reach equilibrium where the concentration inside is the same as outside the cell
Dynamic Equilibrium: molecules continue to move back and forth equally but there is no net change in concentration.

30. Active Transport
Active transport: movement of solid or liquid particles in and out of a cell that requires input of energy (ATP).
Move large particles and remove wastes.
Move materials against concentration gradient (low  high concentration).

31. Types of Active Transport
Protein pump: membrane protein uses energy to move materials (from low to high)
Endocytosis: membrane pinches in to take particles into the cell
Pinocytosis: liquids in
Phagocytosis: solids in
Exocytosis: particles surrounded by membrane are moved out of cell

32. Cell Transport Summary
Osmosis (Water)

33. Solutions
Most membranes are permeable to water, but not permeable to many solutes.
Solvent – Dissolving agent (ex. Water)
Solute – Substance that is dissolved (ex. Kool aid mix)
If the concentration of solutes is different on the inside and outside of a cell, water will move across the membrane to equalize the concentrations.

34. How Osmosis Works
Click for animation

35. Hypertonic Solutions: contain a high concentration of solute
Hypertonic Solutions: contain a high concentration of solute. When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrink.
Hypotonic Solutions: contain a low concentration of solute. When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell.
Isotonic Solutions: contain the same concentration of solute as the cell. When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds body cells is isotonic.

36. Turgor Pressure
Water pushing out on the plant cell wall – helps give plants their shape.
This is why plants wilt if they don’t get enough water 36

37. B C A What type of solution are these cells in? Hypertonic Isotonic
Hypotonic 37

38. Surface Area to Volume Ratio
As cells increase in size, surface area to volume ratios decrease. This makes cells unable to obtain nutrients or remove wastes (bigger cells = less efficient).
To increase surface to volume ratio, cells divide to stay small or change shape in order to increase surface area or reduce volume (smaller cells = more efficient).
*Small cell = LARGE surface area to vol. ratio
*Large cell = SMALL surface area to volume ratio

39. Three Types of Solutions
90% H2O
10% solute
90% H2O
10% solute
90% H2O
10% solute
90% H2O
10% solute
95% H2O
5% solute
85% H2O
15% solute
Hypotonic
Hypertonic
Isotonic
(no net movement
of water)

40. Passive Transport Review Animation