1. Characteristics of Life & Cells
Topic 1
Characteristics of Life
& Cells

2. Characteristics of Life
Cells are the basic unit of life. All living things are made of one or more cells.
Metabolism is the sum of all chemical reactions in an organism. Since all living things use energy they undergo metabolism.

3. 3. Homeostasis is the maintenance of a relatively stable internal environment.
Reproduction is the passing on of genetic information.
Biotic = living
Abiotic = nonliving

4. Similarities Among Living Things
Obtaining nutrients from the environment
Transportation of materials throughout the organism
Breaking nutrients into smaller units to release chemical energy
Synthesis – building large units out of small ones
Growth – increasing the # or size of cells
Excretion – removal of waste products
Responding to internal and external stimuli
Reproduction of the species

5. Organic Chemistry
The 4 main elements that all living organisms are made of include: Carbon, Hydrogen, Oxygen and Nitrogen
Organic – describes molecules that contain both carbon and hydrogen
Inorganic – Does not contain both Carbon and Hydrogen

6. Major Organic Compounds in the Body
Carbohydrates (ex. starches, glucose…)
Lipids (ex. fats, cell membrane…..)
Proteins (muscle, enzymes…..)
Nucleic Acids (the building blocks of genes)

7. Major Inorganic Substance in the Body
Water
Oxygen
Carbon Dioxide
Salts (many minerals are classified as salts)

8. Levels of Organization in Living Organisms
Larger - Organism
- Organ System
- Organ
- Tissue
- Cell
Smaller -Organelle

9. Cell Theory
Cells are the basic unit of living things. All living things are made up of cells.
Given #1, all life functions that are carried out by a living organism are carried out by a cell.
Cells arise from other cells – not non-living matter.

10. Exceptions to Cell Theory
Viruses are not made up of cells, yet they can act like living things and do contain genetic information.
The first cell could not have come from another cell.

11. Question
What are 4 differences between a plant and animal cell?

12. Differences Between Plant and Animal Cells
Plants have a cell wall, animals do not.
Plants have chloroplasts, animals do not.
Plants have large vacuoles and animals have small vacuoles.
Animals have many more mitochondria than plants.
Animal cells are more oval shaped and plant cells are more box shaped.

13. Organelles
Cytoplasm – the jellylike substance inside of a cell that: surrounds organelles, transports materials in and out of the cell and is the site of many chem. reactions.
Nucleus – stores genetic info and controls metabolism
Vacuoles – storage sacs for food, water and waste. (vacuoles in plants tend to be much larger than those in animals)
Ribosomes – important to the protein making process

14. Organelles
The Cell Membrane: is selectively permeable, controls what moves in and out of the cell and plays a major role in maintaining homeostasis in the cell
It is make of a double layered structure called a lipid bi-layer, proteins and carbohydrates.
Mitochondria – contain enzymes used to extract energy from nutrients

15. Organelles
Chloroplasts – only in plants and some single celled organisms, they contain a green pigment called chlorophyll which capture light energy and converts it to chemical compound used for food
Cell Wall – provides the cell with structure and protection. Only in Plants!

16. Types of Transport in the Cell
Passive Transport: Requires no Energy (ex. sled downhill)
Diffusion- direct movement determined by concentration gradient (Areas of high concentration diffuse to areas of low concentration. (Salt on roads destroying plants ex.)
Facilitated Diffusion- Transport proteins in the lipid membrane move molecules along the concentration gradient faster than normal diffusion (the express lane).
Ex. Glucose
Osmosis- Diffusion of water

17. Types of Transport Cont.
Active Transport = Movement against the concentration gradient, energy is required in the form of ATP (ex. pulling a sled up hill) (desert plants use A.T.P. a lot to pull water up from their roots)

18. Types of Active Transport
Endocytosis- moving materials into the cell
Exocytosis- moving materials out of the cell.
Pinocytosis- cell drinking
Phagocytosis- cell eating

19. Digestion in a Cell
Most proteins and carbohydrates are too large to enter the cell and must be broken down first.
Protein digestion results in smaller molecules of amino acids
Carbohydrate (starch) digestion results in smaller molecules of simple sugars

20. Signal Recognition
Receptor Molecule – certain protein molecules in the cell membrane that can receive chem. messages (ex. nerve cell communication ex. Neurotransmitters=N.T.)
Hormone – chemical produces in the endocrine glands and responsible for communication b/t cells
If nerve cell or hormone communication is interrupted than homeostasis may be affected.