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GED Study Notes

GED Science

Life Science

Lesson 1: Cell Structures and Functions
Lesson 2: Cell Processes and Energy
Lesson 3: Human Body Systems
Lesson 4: Health Issues
Lesson 5: Reproduction and Heredity
Lesson 6: Modern Genetics
Lesson 7: Evolution and Natural Selection
Lesson 8: Organization of Ecosystems

Earth and Space Science

Lesson 1: Structure of Earth
Lesson 2: Earth’s Resources
Lesson 3: Weather and Climate
Lesson 4: Earth in the Solar System
Lesson 5: The Expanding Universe

Physical Science

Lesson 1: Atoms and Molecules
Lesson 2: Properties and States of Matter
Lesson 3: Chemical Reactions
Lesson 4: The Nature of Energy
Lesson 5: Motion and Forces
Lesson 6: Electricity and Magnetism

Lesson 1: Cell Structures and Functions

  • The basic unit of all living things is the cell, which carries out the life functions, including movement, growth, and reproduction.

  • All cells have a cell membrane, cytoplasm, and genetic material.

  • Unlike an animal cell, a plant cell contains a cell wall—a structure that gives the cell rigidity and shape.​

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All living things are made of cells, the basic unit of life. Some organisms, like bacteria and protozoa, are unicellular—they consist of a single cell. Others, like plants and animals, are multicellular, consisting of many different types of specialized cells. For example, humans have skin cells, blood cells, and nerve cells, to name just a few. All cells carry out the basic life functions: movement, growth, cell maintenance, reproduction, and the manufacture of specialized substances.


Although cells differ widely in size and appearance, they all have basic structures in common. All cells have a cell membrane, a structure that keeps the cell’s contents separate from its external environment. The cell membrane is selectively permeable, which means that it allows certain sub stances, such as water, nutrients, and wastes, to pass between the cell’s interior and the surrounding environment. Inside the cell membrane is the cytoplasm, a watery, jellylike substance that can include other cell structures.


Finally, all cells have genetic material, which contains coded instructions for carrying out the cell’s activities. In bacteria, the genetic material consists of a single molecule suspended in the cytoplasm. Bacteria are called prokaryotes. In all other cells, the genetic material is contained within a nucleus. Such cells are called eukaryotic cells. All plant and animal cells are eukaryotic. A typical plant cell is shown below. Note that a plant cell has a cell wall, which gives the cell shape and rigidity, and an animal cell does not.

Animal cell structure

  • They contain a nucleus with a distinct membrane

  • Cells do not have cellulose cell walls

  • Their cells do not contain chloroplasts (so they are unable to carry out photosynthesis)

  • They contain carbohydrates stored as glycogen

Plant cell structure

  • They contain a nucleus with a distinct membrane

  • Cells have cell walls made out of cellulose

  • They contain chloroplasts (so they can carry out photosynthesis)

  • Carbohydrates are stored as starch or sucrose

Difference Between Plant cell and Animal cell

The cell is the fundamental unit of life. All the life activities are carried out by cells. The organisms can be classified based on the number of cells present in them. Unicellular organisms are single-celled, while multicellular organisms have a large number of cells.

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  • Unicellular organisms are believed to be one of the earliest forms of life on earth. Eventually, more complex multicellular organisms evolved from these unicellular life forms over the aeons.

  • Multicellular organisms have specialized cells with complicated cell organelles, which unicellular organisms typically lack.

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In an ecosystem, plants have the role of producers, while animals have taken the role of consumers. Hence, their daily activities and functions vary, and so does their cell structure. Cell structure and organelles vary in plants and animals, and are primarily classified based on their function. The difference in their cell composition is the reason behind the difference between plant and animal cells.

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Each cell organelle has a particular function to perform. Some of the cell organelles are present in both plant cells and animal cells, while others are unique to just one of them. Most of the earth’s higher organisms are eukaryotes, including all plants and animals. Hence, these cells share some similarities typically associated with eukaryotes. For example, all eukaryotic cells consist of a nucleus, plasma membrane, cytoplasm,  peroxisomes, mitochondria, ribosomes and other cell organelles.

Animal & Plant_edited.jpg

Palisade cells

  • Found underneath the upper epidermis of a plant leaf.

  • Makes food for the plant by photosynthesizing, using carbon dioxide, water, and light.
     

Adaptations

  • Found closer to the surface of the leaf, so absorbs more sunlight to photosynthesize.

  • Has many chloroplasts to absorb energy from the sun.

  • Very thin and long.

  • Many palisade cells can be packed together in 1 leaf to ensure maximum light energy absorption.

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Animal cell
 

Nucleus

  • Is the control Centre of the cell.

  • Contains genetic material - DNA (Deoxyribonucleic Acid)

  • DNA is made from groups of atoms linked together, forming a long chain.

  • DNA gives Instructions to the rest of the cell, on how to function and build cell parts.

  • When the cell divides to create more cells - the DNA also divides, and new cells have the same DNA as the original.
     

Cytoplasm

  • Is a watery jelly-like substance.

  • Takes up most of the space in the cell.

  • Can move around inside the cell.

  • Contains stored food in the form of grains.

  • Chemical reactions that keep the cell alive takes place here.
     

Cell membrane

  • Covers the outside of the cell.

  • Is semi-permeable (controls and allows movements of specific substances in and out of the cell.)

  • Stops harmful chemicals and substances from entering.

  • Allows food, oxygen and carbon dioxide to pass through.

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Specialized Cells

  • Specialized cells in animals

  • Specialized cells are those which have developed certain characteristics in order to perform particular functions. These differences are controlled by genes in the nucleus

  • Cells specialize by undergoing differentiation: this is a process by which cells develop the structure and characteristics needed to be able to carry out their functions

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