Cell form and function Rosalie Crawford - Veronica Revel
biologyCourmayeur FondazioneCLIL Liceo Linguistico
The cell theory
• Every organism is made of cells and every cell comes from another cell. • A cell is the basic unit of form and function. • Every organism is made of one or more cells, and each cell carries on functions so that the organism can live. • The form and structure of a cell provide protection and support, forming a protective barrier between the cell and its environment, transporting materials, building and repairing, storing and releasing energy and waste materials and reproducing. 1- The main source for this presentation is Cecie Starr, Biology: Progetto Bioenglish, LifeSciences, Garzanti Scuola, 2009.
Specialized cell â€˘ Smallest unit that can live and reproduce on its own or as part of a muticelled organism. â€˘ A cell has DNA, an outermost membrane and other components.
Tissue â€˘ Organized array of cells and substances that are interacting in some task. â€˘ Bone tissue consists of secretions from cells such as this one.
Organ â€˘ Structural unit of two or more tissues that interact in one or more tasks. â€˘ This parrotfish eye is a sensory organ used in vision.
Organ system â€˘ Organs that interact in one or more tasks. â€˘ The skin of this parrotfish is an organ system with tissue layers, organs such as glands and other parts.
The cell wall • The cell wall is made of cellulose, which is a non-living material. • It is made up of a chain of sugar molecules. • This stiff, rigid wall is found only in plant cells, not in animal cells. • This wall allows certain gases and water to enter ths cell.
The cell membrane • Inside a plant cell, it’s inside the cell wall. • In an animal cell, it forms an outer covering for the cell. • It maintains the correct chemical environment within the cell. • The functions of the membrane are to help control movement of materials in and out of the cell and to change its shape under pressure.
The nucleus • The nucleus controls the cell activities (growth, development and reproduction). • It could be said it is the brain of the cell that regulates and controls the various cell activities. • The nucleus is surrounded by a membrane as well. • This nuclear membrane lets materials pass into and out of the nucleus. • Pores (small openings) act as entryways.
Chromosomes • Chromosomes are rod-shaped and delicate. • They are located in the nucleus and direct all the activities of the cell, including reproduction and growth. • Chromosones are large and complex molecules that are compounds referred to as nucleic acids, which store information that help the cell make its necessary proteins. • Some proteins are made up of different enzymes and hormones. These substances regulate many cell activities. • The two nucleic acids found in cells are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) • The DNA stays in the nucleus and the RNA carries its information (mostly protein building) outside the nucleus through the pores. • It is important to know that chromosomes and nucleolus are located in the nucleus. • The nucleolus is responsible for the production of ribosomes.
The endoplasmic reticulum • These are passageways that make up the transportation system of the cell. They are important cell organelles that carry proteins and are located in the cytoplasm, the material inside a cell between the cell’s nucleus and the cell membrane. • On the inner surface of the endoplasmic reticulum the ribosomes are attached. Produced in the nucleolus, they leave the nucleolus via the nucleus. • Ribosomes are made up of the nucleic acid RNA and they are an important protein producing place. • The RNA directs the production of proteins. • NB the production of RNA is controlled by the DNA in the chomosomes, and the DNA is the main control centre of the cell.
Mitochondria • Mitochondria supply energy to the cell. • They are larger than the ribosomes, are rod-shaped, and are said to be the “powerhouses” of the cell. • This is where energy is released from food in the process known as respiration. • Plant cells and some animal cells have vacuoles, which are water-filled, round and sac-like structures that float in the cytoplasm and act as storage tanks that hold food and other materials. • In healthy plants they are large and help support the cell.
Lysosomes â€˘ Lysosomes are structures involved with the digestive processes of the cell. â€˘ They contain enzymes that break down food molecules into smaller ones. When the lysosomes have done their work, food molecules are then transported to the mitochondria where they are used to make energy for the cell.
Chloroplasts â€˘ Chloroplasts are structures that contain the green pigment chlorophyll which absorbs the light energy that plants need to make food. This process is called photosynthesis. â€˘ Chloroplasts and chlorophyll only exist in plant cells.
Animal cell diagram
Plant cell diagram
Language focus • • • • • • • • • •
Although – sebbene As a result of – di conseguenza Because of – a causa di Despite – nonostante Even though – anche se First of all – innanzitutto For instance – per esempio However – sebbene In addition – inoltre In order to – in modo da
• • • • • • • • • • •
In spite of – invece di Instead – invece Once – una volta On the other hand – d’altra parte Moreover – inoltre So that – cossichè Thanks to – grazie a Therefore – pertanto Unless –a meno che Until – fino a che Whereas/ while - mentre
Glossary • The cell membrane keeps all the components of the cell close together and controls chemicals in and out of the cell. • The cell wall gives strength and support to the cell. • A chromosome is a structure in the nucleus composed of DNA and proteins. • Endoplasmic reticulum is found in cytoplasm and is a system of tubules or vesicles. • Mitochondria is where respiration takes place.
Glossary continued • The nucleolus is part of the cell nucleus producing ribosomes. • The nucleus controls all chemical reactions and it carries all the information of the cell. • An organ is tissue working together. • An organism is the smallest unit that can live and reproduce of its own. • A ribosome is a particle in the cell which assembles proteins . • Tissue is a group of specialized cells.
CELL SPECIALIZATION • So far, we have spoken about “typical” cells. • Different cells are specialized to function at a variety of jobs. • An example of a specialized cell is the sperm cell, whose job is to swim to the egg and fertilize it.
The sperm cell • It has a tail to enable it to swim; • It has many mitochondria to provide energy for this swimming; • The acrosome contains digestive enzymes that make an opening in the egg cell membrane to allow entry; • The nucleus contains chromosomes which carry the genetic material that will be transmitted to the offspring.
CELL ORGANIZATION â€˘ There is a division of labour within a multicellular organism, which is an expression meaning that the work of keeping the organism alive is divided among the different parts of the body. The arrangement of specialized parts within an organism is often referred to as levels of organization.
ORGAN SYSTEMS AND FUNCTIONS • THE INTEGUMENTARY SYSTEM: protects body from injury, dehydration and some pathogens; controls its temperature; excretes certain wastes; receives some external stimuli. • THE NERVOUS SYSTEM: detects external and internal stimuli; controls and coordinates the responses to stimuli; integrates all organ system activities. • THE MUSCULAR SYSTEM: moves body and its internal parts; maintains posture; generates heat by increases in metabolic activity.
ORGAN SYSTEMS AND FUNCTIONS • THE SKELETAR SYSTEM: supports and protects body parts; provides muscle attachment sites; produces red blood cells; stores calcium, phosphorus. • THE CIRCULATORY SYSTEM: rapidly transports many materials to and from interstitial fluid and cells; helps stabilize internal PH and temperature. • THE ENDOCRINE SYSTEM: hormonally controls body functioning; with nervous system integrates short- and longterm activities. • THE LYMPHATIC SYSTEM: collects and returns some tissue fluid to the bloodstream; defends the body against infection and tissue damage.
ORGAN SYSTEMS AND FUNCTIONS • THE RESPIRATORY SYSTEM: rapidly delivers oxygen to the tissue fluid thus bathes all living cells; removes carbon dioxide wastes of cells; helps regulate pH. • THE DIGESTIVE SYSTEM: ingests food and water, chemically breaks down food and absorbs small mollecules into internal environment; eliminates food residues. • THE URINARY SYSTEM: maintains the volume and compostion of internal environment; excretes excess fluid and bloodborne wastes. • THE REPRODUCTIVE SYSTEM: female: produces eggs; after fertilization, ensures a protected, nutritive environment for the development of new individuals; male: produces and transfers sperm to the female; hormones of both systems also influence other organ systems.
Without great minds, these discoveries would never have happened â€˘ The existence of organelles was not known until the 17th century, when the microscope was invented by a Dutchman, Anton von Leeuwenhoek (1632-1723).
The first man to see cellsâ€Ś. â€˘ An English scientist, Robert Hooke (1635 -1703), using a very simple microscope, saw dead plant cells on a thin piece of cork.