Cells: The Basic Units of Life: Tutorial

All living things have a particular shape. They all have a boundary or an outline that defines their shape (Skin is the body's fence or boundary), while...

nonliving things, such as fire and air, do not have a defined boundary.

What contains the genetic information (DNA) for the cell, which enables the cell to carry out all of its other functions?

nucleus

What is the command center of the cell and the largest organelle

nucleus

smooth endoplasmic reticulum

produces lipids (fats and cholesterol) for the cells. (does not contain ribosomes)

What are single-celled organisms, which look and behave like animals?

protists

Organisms grow and develop throughout their lifespan. Growth is not limited to height and width. Even when we reach adulthood and stop growing taller, our cells continue to...

repair and replace themselves for the rest of our lives.

What does cellulose provide?

structure and strength to the cell.

nucleus (of a cell)

the largest organelle in the cell, which contains genetic information and controls cell function

cell wall

the outer layer of cells in plants, fungi, and certain prokaryotes

Viruses share many of the characteristics of life, including carrying genetic information, but...

they do not fully meet all the characteristics of life.

What lets let substances move in and out of the cell in plasma membranes?

transport proteins

electron microscope (EM)

uses a beam of electrons instead of light to magnify objects.

Compound microscope

uses two lenses to magnify the object. It uses visible light to generate a magnified image of the specimen.

cytoplasm

a mixture of water and salt that suspends the organelles within the cell

Cytoskeleton

a support network of protein fibers that form a framework for the cell.

Eukaryote

a unicellular or multicellular organism that has cells with a defined nucleus

prokaryote

a unicellular organism that lacks a nucleus

Microtubules

act as a scaffold, giving shape to the cell.

cytoplasm is present in...

all prokaryote and eukaryotic cells.

chloroplast

an organelle that allows for photosynthesis in plants and some protists

mitochondria

an organelle that generates energy for a cell

rough endoplasmic reticulum

an organelle that synthesizes protein for the cell (contains ribosomes)

Endoplasmic reticulum

appears in the cytoplasm as a network of tubules

Centrioles

are a pair of cylindrical tubular organelles. They play an important role in cell division. They are found in animal cells, many single-celled protists, and a few lower-level plants.

Cilia and flagella

are hairlike structures that extend from the surface of the cell. Both of these organelles are responsible for movement. They are found in some eukaryotic and prokaryotic cells.

lysosome

are the "digestion" organelles of the cell. They break down big molecules into smaller molecules that the cell can use or excrete. They are found in animal cells and rarely in plants.

All living things need energy to...

carry out basic life functions, such as breathing, movement, and reproduction.

when it's cold outside, you shiver, causing

causing your muscles to contract, and this contraction of muscles helps warm up your body and maintain a stable internal temperature.

What contains chlorophyll, a pigment that gives plants their green color?

chloroplasts

eukaryotic cells are quite...

complex, as they have many different organelles that support the function of the cell.

Living things reproduce to

create new organisms.

What is is present in all eukaryotic cells?

cytoskeleton & nucleus

Vacuoles are present in all...

eukaryotic cells. However, they tend to be significantly larger in plant cells than in animal cells.

All organisms have basic structures or processes that...

help them carry out the basic functions of life.

Where are cell walls are found?

in plant cells and in some prokaryotic cells, such as some bacteria.

Homeostasis means

internal balance.

Golgi apparatus

is like the post office, packaging and sorting substances for delivery.

What is unicellular?

made up of one cell, such as amoebas and bacteria

vesicle

means "small carrier." They are the mail trucks, which send substances to their destination (either to a different part of the cell or outside the cell).

cell theory started to form only after scientists invented the...

microscope because the great majority of cells are microscopic

What are viruses?

microscopic organisms that are made up of organic chemicals.

Prokaryotic cells lack...

most organelles.

What do carbohydrate chains attached to the protein in a cell do?

Help define the cell's structures and read chemical signals from the environment.

vacuole

a storage area for a cell. They store nutrients for the cell. They can even store waste products to protect the cell from contamination.

Cell theory states three important points about cells:

1 - All living things are made of cells. 2 - Cells are the basic units of structure and organization in all forms of life. All tissues, organs, and systems are made up of cells. 3 - Cells form from previously existing cells.

A cell is about what % water?

70

Plasma Membrane

Also called, cell membrane, it is a flexible boundary that exists outside the cell.

The Formation of Cell Theory

Between 1830 and 1855, three German scientists conducted research that helped develop cell theory. In 1838, the botanist Mathias Schleiden concluded that the cell was the basic building block of all plants. In 1839, Theodor Schwann stated that animals were also made of cells. In 1855, Rudolf Virchow concluded that all cells develop from existing cells.

What is the structure of Plasma Membrane?

Bilayer, consisting of two layers of phospholipids. Each phospholipid structure consists of three parts: a phosphate group, two fatty acid chains, and a glycerol backbone.

The Discovery of Single-Celled Organisms

Biologist Anton van Leeuwenhoek built his own simple microscope. He observed pond water under his microscope and was the first to observe live cells under a microscope. In 1683, the Royal Society published his work describing his discovery of single-celled organisms in pond water and milk.

What are the differences between Cilia and flagella?

Cilia are usually shorter and more numerous than flagella.

Biologists commonly use two types of microscopes:

Compound microscope & Electron microscope

Biologists divide cells into two groups based on their structure:

Eukaryote & Prokaryote

Microfilaments

Fine, threadlike proteins found in the cell's cytoskeleton

Viruses share many characteristics of life: They have genetic information. They reproduce. They have internal organization. They can adapt to their environment.

However, viruses lack some important characteristics of life: They lack cells. They can reproduce only inside the cell of another organism. Their genetic information is in the form of DNA or RNA but not both. (Living things have both DNA and RNA.) Once assembled in a host cell, they do not change their size or composition. They do not possess any structures or internal organization to perform biological processes. They do not use energy or release waste.

The First Microscope

In 1590, Dutch lens grinders Hans and Zacharias Janssen invented the first compound microscope. It consisted of a tube with lenses at both ends.

The Discovery of Cells

In 1665, Robert Hooke used a compound microscope to examine a thin piece of cork. He noticed a honeycomb-like structure that consisted of compartments with empty spaces. Hooke coined the term cells to represent these individual compartments.

What does Cholesterol have to do with the structure of Plasma Membrane?

It helps prevent the phospholipid tails from sticking together, which make up the 2 bilayers of the structure.

What is multicellular?

Made of many cells such as plants and animals

What rod-shaped organelles, converts food into energy for the cell?

Mitochondria

How does the plasma membrane protects the organelles within the cell from outside elements that could damage it?

The membrane is selectively permeable. It prevents harmful substances from entering the cell. However, it does allow food, water, and other useful substances to pass into the cell. It also helps waste leave the cell. Another major function of the plasma membrane is to maintain homeostasis.

What is known as the fluid mosaic model?

The plasma membrane structure because it is fluid. It is like a sea in which other substances, such as cholesterol and proteins, appear to float.

How do vacuoles play a vital role in plant structure?

When water is abundant, the vacuoles of plant cells grow, allowing the plant to stand tall and look healthy. When water is scarce, the vacuoles shrink and the plant wilts.

What is the smallest functional unit of life?

a cell

ribosome

a cell structure responsible for the production of protein in a cell