unit a – cells and systems. chapter 1 - cells cells – key ideas living things share many...

Unit A – Cells and

Systems

Chapter 1 - Cells

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Cells – Key Ideas

• Living things share many characteristics

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

• Animal and plant cells are similar in some ways and different in others

• Technology helps us learn about the structure and function of cells

• Substances move in and out of cells

1.1 – Characteristics of

Living Things

How do you know if something is alive?

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Organism – any individual living thing

Before something can be classified as an organism, it must show all of the characteristics of living things

(see Table 1 p5)

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Characteristics of Living Things• Living things are composed of cells

• Living things reproduce, grow, and repair themselves.

• Living things require energy

• Living things respond to their environment

• Living things have a life span

• Living things produce waste

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Why isn’t a Solar Calculator Alive?

What characteristic’s of life does it have?

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Is a Star Fish Living?

What characteristics does a star fish have?

Require energy?

Respond to environment?

Reproduce? Grow? And repair?

Have a lifespan?

Produce waste?

Is it made of cells?

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Cell Theory

• Cells are the basic unit of all living things

• The Cell Theory:

• All living things are composed of one or more cells

• All new cells arise only from cells that already exist (new cells come from old cells)

1.2 – Using a Microscope

Be careful…please

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The Parts of a Microscope

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Microscope – Field of View• The Field of View – is the circle of light you see when

you look through the eyepiece of a microscope

• Ratio = magnification of high-power lens/magnification of low-power lens

• Diameter of field (high power) = diameter of field (low power)/ratio

1.3 – Plant and Animal

Cells

What’s the Difference?

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Plant and Animal Cells

• The cells of all plants and the cells of all animals have many structures in common

• Using a microscope it is easy to tell between plant and animal cell but it is hard to tell which plant cell came from which plant and which plant cell came from which animal

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Animal Cell Structures

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The Nucleus

• The NUCLEUS is the control centre. It directs all of the cell’s activities.

• In plant and animal cells, the nucleus is surrounded by a membrane.

• Cells with a nuclear membrane are known as EUKARYOTIC CELLS

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The Nucleus

• In some one-celled organisms, such as bacteria, the nucleus is not surrounded by a membrane. These cells are known as PROKARYOTIC cells

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The Nucleus

Eukaryotic Prokaryotic

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Chromosomes

inside the nucleus

Contain DNA or genetic information, which holds “construction plans” for all the pieces of the cell.

This genetic information is duplicated and passed on to other identical cells.

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Cell Membrane

holds the contents of the cell in place

Controls the movement of materials (nutrients and waste) into and out of the cell.

consists of a double layer of fat molecules.

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Cytoplasm

watery fluid that contains everything inside the cell membrane and outside the nucleus.

Allows materials to be transported quickly

Stores wastes until they can be disposed of

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Vacuole

Used to store water and nutrients

Also used to store waste and move excess water out of the cell

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Animal Cell - Movement

Some animal cells may have special structures that help them move in their environment

Flagellum

Cilia

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The Flagellum

Flagellum- a whip-like tail that helps a cell to move

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Cilia

Cilia- tiny hairs that work to move a cell or the fluid around a cell

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Plant Cell Structures

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Vacuole

Just like animal cells except usually much larger

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Cell Wall

Provides protection and support to the plant cell

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Chloroplasts

Are the food factories of the cell

Contain many molecules of a green pigment called chlorophyll

Chlorophyll is necessary for photosynthesis

1.4-Technological Advances of

the Microscope

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The Single – Lens Microscope

Anton van Leeuwenhoek’s (1660’s) single lens microscope magnified things 10 x’s

(made objects 10 times bigger than their normal size)

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The Compound Light Microscope

Single lens were not enough for scientists who wanted to see things in greater detail

Eventually a second lens was added to magnify the image ( 10x’s X 10 x’s = 100 x’s)

Light microscope is limited to about 2000 x’s (image becomes too blurry)

Greater magnification is needed to see the details of a human cell

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Compound Light Microscope

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The Transmission Electron Microscope

Are capable of 2 000 000 x’s magnification

Use electrons instead of light

Limitations

Must use extremely thin specimens

Only dead cells can be observed

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The Transmission Electron Microscope

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The Scanning Electron Microscope

It uses electrons that are deflected of a specimen to create a digital three-dimensional image

Because it uses only reflected electrons the thickness of the specimen does not matter

Limitations

Only the outside of the specimen can be seen

Cannot magnify as high as the transmission electron microscope

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The Scanning Electron Microscope

1.6 – Parts of a Cell Seen with

an Electron Microscope

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Organelles

organelle -a tiny structure within the cytoplasm of a cell; specialized to carry out a function

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Mitochondria: Energy Production

mitochondria (sing. mitochondrion) - circular or rod-shaped organelles that provide the cells with energy through a process called cellular respiration.

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Cellular Respiration

cellular respiration - a process in which mitochondria release energy by combining sugar molecules with oxygen to form carbon dioxide and water

Sugar + O2 CO2 + ENERGY

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Ribosomes: Protein Manufacturing

ribosome - a very small organelle that uses information from the nucleus and molecules from the cytoplasm to produce proteins

Proteins are needed for

Cell growth

Repair

Reproduction

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Endoplasmic Reticulum: Material Transport

endoplasmic reticulum (ER) - a cell structure that consists of a series of folded membranes that act as canals to carry materials through the cytoplasm

Rough – with ribosomes (proteins)

Smooth – without ribosomes (lipids (fats))

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The Golgi Apparatus: Protein Storage

Golgi apparatus - an organelle that stores proteins and puts them into packages, called vesicles

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Lysosomes: Recycling

lysosome - an organelle formed by the Golgi apparatus to control and clean the cytoplasm; contains special proteins used to break down large molecules into smaller molecules; also destroys damaged or worn-out cells

Also destroy harmful substances and bacteria that enter the cell.

1.7 – Cells in Their

Environment

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Cell Membranes

Cells allow some materials to enter and leave but not others

Permeable = permitting passage

Impermeable = not permitting passage

The cell membrane is said to be selectively permeable

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Selectively Permeable

A membrane that allows certain substances to enter or leave

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Diffusion

DIFFUSION- the movement of molecules from an area of high concentration to an area of low concentration

Molecules are constantly in motion, when they collide, they bounce off each other which causes the molecules to spread out

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Diffusion and Cells

Diffusion is one of the ways that substances move into and out of cells

Substances that the cell needs (oxygen) are in higher concentration outside the cell and then diffuse across the membrane into the lower concentration inside the cell

Substances the cell doesn’t need (waste – carbon dioxide) tend to get more concentrated inside the cell, so they will diffuse across the cell membrane to the lower concentration

1.8 - Osmosis

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Osmosis

Osmosis - is the diffusion of water across a selectively permeable membrane

The direction of water movement depends on the concentration of water inside the cell compared with the concentration outside the cell

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A Model of Osmosis (see p.25 fig.

2)

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Cells in Solutions of Different Concentrations

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Turgor Pressure (see p.27)

Turgor Pressure - the pressure created inside a plant cell when water molecules enter the cell by osmosis; the water fills the vacuole and cytoplasm, causing them to swell up and push against the cell wall

1.11 – Career Profile:

Modellers