CHAPTER 7Cell Structure

Standard 2: Life Science Students know and understand the

characteristics and structure of living things, the processes of life, and how living things interact with each other and their environment.

Benchmark 3.9: Cellular organelles have specific functions.

Assessment Objective 3.9a: Describe the function of cellular organelles.

Vocabulary

Centriole Chloroplast Chromatin Chromosome Cilia Cytoplasm Endoplasmic reticulum Eukaryote Flagella Golgi body Lysosome Metabolism

Videos approximately 35:00 minutes

Microfilament Microtubule Mitochondria Nucleoli Nucleus Organ Prokaryote Ribosome Symbiosis Organ System Tissue Vacuole Colonial organism

Discovery of Cells

Cell Theory

All living things are made up of one or more cells.

Cells are the basic units of structure and function in organisms.

All cells arise from existing cells. Eukaryote/Prokaryote

What am I?

What is A Cell? (3:40)

Structure of Cells

Cells are: Three-dimensional Shaped like spheres,

cubes, or bricks. One-celled

(unicellular) organisms may be either prokaryotes or eukaryotes.

Bacteria are prokaryotes.

Primitive cells (0:46)

Protists

Other members of the Family Protista, are unicellular and multicellular but lack specialized cells.

An example is euglena of the Phylum Euglenophyta. They can make their own food by photosynthesis and also ingest food from their surroundings.

Euglena

Multicellular Organisms

Many-celled organisms that evolved from unicellular organisms.

Almost all carry out basic functions.

Ex: Not all tree cells perform photosynthesis, only those with chlorophyll.

Specialized cells like blood cells are dependent upon one another.

Parts of an animal cell (4:55)

Tissues

A group of cells that have the same structure and function is called a tissue.

Examples of cells that make up tissues include: Skin cells (0:37)

Muscle cells (0:49)

Bone cells (0:13)

Nerve cells (1:12)

Blood cells (1:16)Cell Review (1:57)

Organs Cells work together to

form tissues. Tissues work together to

form organs. An organ is a structure

composed of many different tissues that work together to perform a particular function.

Your heart is an example of an organ.

A group of organs working together form a system.

Systems working together form an organism

Organs (1:01)

Cytoplasm

Cytoplasm, found in the cell, is composed of 70% water, 30% proteins, fats , carbohydrates, nucleic acids, and ions.

The exact composition varies from cell to cell because of chemical changes.

The sum of all the chemical changes is called metabolism.

Cytoplasm has three main functions: energy, storage, and manufacturing.Cytoplasm (1:30)

Functions and Interactions of Cell Parts

Almost all living cells contain organelles that are surrounded by a membrane.

There are two types of cells:

Eukaryote: Cells that contain a nucleus. Example: Almost all cells

in the living world. Prokaryote: Cells without

a membrane or nucleus. Example: bacteria Comparing

prokarytoic and eukaryotic cells (0:30)

Eukaryotic (Plant and Animal) Cell Organelles

Nucleus Nucleolus Endoplasmic Reticulum (ER) Centriole Centrosome Golgi Apparatus Cytoskeleton Cytosol Mitochondrion Secretory Vesicle Lysosome Peroxisome Vacuole Ribosome

 

Click on picture for interactive cell modelsIncludes animal, plant, bacteria and prokaryote cells courtesy: cellsalive.com

The Nucleus (2:11)

Nucleus: The Cell’s Control Center

The nucleus is the control center of the cell.

It has a double membrane with a dense mass of material called chromatin.

The chromatin is made up of individual chromosomes.

Chromosomes are made of proteins and DNA.

By coding for RNA, DNA controls the activities within the cell.

Nucleus: Draw me!

DNA and RNA

DNA stays in the nucleus but RNA can move from out of the nucleus into the cytoplasm.

Some RNA acts like a messenger for DNA. It delivers instructions for making proteins at the ribosomes.

Before a cell reproduces, it’s chromosomes are copied so that the new cell has the same genes.

Large molecules that pass in and out of the nucleus do so through pores in the membrane.

Smaller particles can go through the membrane itself or through membrane proteins.

Nucleoli are chromosome parts that are copies of the DNA that codes for the RNA present in ribosomes.

Cytoplasmic Cell Structures (2:13)

Other Eukaryotic Cell Structures

Some plastids can be found in plants and algae. Some store lipids and starches and some have pigments (color).

The most common one is the chloroplast which contains chlorophyll and other pigments needed for photosynthesis.

Plant cell vs. animal cell (6:05)

Lysosomes (0:39)

Lysosomes are vesicles formed by the Golgi body.

Lysosmes fuse with vesicles containing food and release enzymes to break the food down.

They also digest worn out cell parts.

The rest of the cell is protected from the enzymes by the lysosome’s membrane.

Vacuoles (1:14)

Sometimes cells produce substances that they don’t need right away.

Vacuoles are fluid-filled, membrane-bound structures that store these substances for later use.

Many freshwater protists have contractile vacuoles used to remove excess water.

Cytoskeleton

Proteins in a cell manufacture long, thin structures that give shape and support to the cell.

Microfilaments are made of actin and myosin (proteins) that assist in cell movement as well as structure.

Microtubules provide structures that can help certain organelles like mitochondria move through the cytoplasm.

Actin and Microtubules (0:39)

Microtubules:Centrioles, Cilia and Flagella

In cells of animals, some fungi and algae, two pairs of centrioles play a role in cell division.

Cilia and flagella are flexible projections that extend outward from the cell, while still surrounded by the cell membrane. They are used to move the cell around its environment.

They are also found in your lungs where the cells don’t move, but the cilia move mucus up and out of your lungs.

Centrioles, Cilia and Flagella (0:40)

Evolution of Eukaryotes Prokaryotes were the first

cells. So where did eukaryotes come from?

Symbiotic Theory states that sometime during evolution, prokaryotic cells became symbiotic partners of other cells which led to eukaryotes.

Evidence for this is that mitochondria and chloroplasts ( which are not in the nucleus) contain their own DNA, RNA and ribosomes.

It’s thought that these organelles are what remains of once free-living prokaryotes.

Mitochondria: An Example ofEvolutionary Symbiosis (02:34)

VIDEO QUIZ

Images Euglena: mac122.icu.ac.jp Microscope: en.academic.ru 1st Cell: library.thinkquest.org