Cell Notes

Cell – the basic unit of life; 50,000 would fit into a typed letter “o”

Historical steps that led up to the Cell Theory:

1. In the 1600s, Dutch businessman Anton Van Leeuvenhock described tiny living organisms in a drop of water using a single magnifying lens

2. In 1665, Robert Hooke used a crude compound microscope (series of lenses) to examine thin slices of cork. Hooke called the tiny boxes found in the cork, “cells”.

3. In the 1830s, Schleiden concluded that all plants are composed of cells. Schwann concluded that all animals were composed of cells.

Cell Notes Continued

4. Virchow, in 1855, studied cell reproduction and stated that where a cell exists, there must have been one before it

Cell Theory

1. All living things are composed of cells.

2. Cells are the basic units of structure and function in living things

3. New cells are produced from existing cells.

Basic Cell Structures

Cells come in many shapes and sizes.

1. Cell membrane:

-thin

-flexible

-support

-protect

2. Cell wall:

-not found in animal cells

-support

-protect

Basic Cell Structures continued

3. Nucleus (plural – nuclei) “brain of the cell”

- contains genetic material

- controls cell’s activities

4. Cytoplasm

- surrounds the nucleus, inside the cell

membrane

- contains important structures nucleus

cytoplasm

cell membrane

cell wall

Prokaryotes and Eukaryotes

1. Prokaryotes

-have a cell membrane and cytoplasm

-do not contain nuclei

-bacteria

2. Eukaryotes

- do contain nuclei

- have a cell membrane and cytoplasm

- have specialized structures (organelles)

-plants, animals, and fungi

Cell Structures

Cell Wall

- found in plants, algae, fungi, and nearly all prokaryotes

-animal cells do not have

-lie outside the cell membrane

- allow water, oxygen, carbon dioxide, and other substances to pass through

- provide support and protection

- made from carbohydrates and proteins

- plant cell walls are made of cellulose (principal component of both wood and paper)

Cell Structures

Cell Wall

- found in plants, algae, fungi, and nearly all prokaryotes

-animal cells do not have

-lie outside the cell membrane

- allow water, oxygen, carbon dioxide, and other substances to pass through

- provide support and protection

- made from carbohydrates and proteins

- plant cell walls are made of cellulose (principal component of both wood and paper)

Cell Structures continuedNucleus

-controls most cell processes-contains the hereditary information of DNA-found in almost all eukaryotic cells-contains chromatin (chromosomes)-contain nucleolus which assemble ribosomes-surrounded by a double-membrane layer called the Nuclear Envelope which allows material to move into and out of the nucleus (RNA)

Cytoskeleton-a network of protein filaments that helps the cell to

maintain its shape-aids in cell movement

Cell Structures continuedImportant Structures of Cytoskeleton

1. Microtubules- hollow protein tubes - help maintain shape -aid movement of organelles

(cilia and flagella) - help in cell division

(centrioles in animal cells) 2. Microfilaments

-function in movement and support

Organelles in the Cytoplasm

Ribosomes

-place where proteins are assembled

Endoplasmic Reticulum (ER)

- where components of the cell membrane are assembled and some proteins are modified

Organelles in the Cytoplasm continued

Types of Endoplasmic Reticulum (ER)

1. Rough Endoplasmic Reticulum

-ribosomes appear on the surface, hence the name “rough”

-newly made proteins move directly from the ribosomes into the rough ER, where they may be chemically changed

Other cellular proteins are made by “free” ribosomes which are not

attached to any membrane.

2. Smooth Endoplasmic Reticulum

-does not have ribosomes

Organelles in the Cytoplasm continued

Golgi Apparatus

- proteins produced by the rough ER are received into the Golgi

-enzymes in the Golgi attach carbohydrates and lipids to the proteins

-from the Golgi, proteins are sent to their final destinations

Lysosomes

-filled with enzymes

-break down lipids, carbohydrates, and proteins from food

-break down “old” organelles

-remove waste

Organelles in the Cytoplasm continued

Vacuoles

-place to store materials such as water, salts, proteins, and carbohydrates

- saclike structures

- plant cells have a single large, central vacuole

-animal cells have many, smaller, vacuoles

Chloroplast

-found in plants

-not in animal and fungal cells

-use energy from sunlight to make energy-rich food molecules (photosynthesis)

- contain green pigment chlorophyll

Organelles in the Cytoplasm continued

Mitochondria

- organelles that release energy from stored food molecules

- the energy is used to power growth, development, and movement

-found in nearly all eukaryotic cells

Comparing Cells

Plant Animal

Cell walls no cell wall

Large vacuoles small vacuoles

Chloroplasts no chloroplasts

Cell membrane – regulates what enters and leaves the cell (food, water, waste) and also provides protection and support

What makes up the cell membrane?

1. Lipids

-a double-layered (bilayer) sheet of lipids

-gives a cell membrane a tough, flexible structure

2. Proteins

-some form channels and pumps

Passive Transport

Passive transport does not require the cell to use energy.

Diffusion – movement of molecules from an area of high concentration to an area of lower concentration (Fig. 7-16)

Osmosis – the diffusion of water through a selectively permeable membrane (Figure 7-17)

Selectively permeable – some substances can pass through the membrane and others cannot (or semi permeable)

the cell membrane is permeable to water but impermeable to sugar/like other substances, water tends to diffuse from a region where it is highly concentrated to one where it is less concentrated

Passive Transport

Isotonic solution – a solution in which the concentration of dissolved substances is the same as the concentration inside the cell

• In an isotonic solution, water molecules move into and out of the cell at random

Hypotonic solution – a solution in which the concentration of dissolved substances is lower than the concentration inside the cell

• In a hypotonic solution, water moves through the membrane into the cell. HYPO filled water balloon

Passive Transport

Hypertonic solution – a solution in which the concentration of dissolved substances is higher than the concentration inside the cell

• If a cell is placed in a hypertonic solution, osmosis will cause water to leave the cell Hype exit

Facilitated diffusion – when molecules that cannot cross the cell membrane’s lipid bilayer do so by moving throughprotein channels instead; movement is from high to low concentration

• Molecules that can cross the lipid bilayer include:

-water

-alcohol

-small lipids

Passive Transport• Molecules that cannot pass through the lipid bilayer include:

-ions

-sugars

-salts

Active Transport

Active transport – when the material moves from an area of lower concentration to an area of greater concentration; requires the input of energy

example: most animal cells have membrane proteins that pump sodium ions (Na+) out of the cell and pump potassium ions (K) in

Types of Active Transport:

1. pumps

2. endocytosis

3. exocytosis

Types of Active Transport continued

endocytosis – taking material into the cell by means of infoldings,

or pockets, of the cell membrane

exocytosis – the removal of large amounts of material from a cell

Cellular Organization

Cell muscle cell

Tissue – group of cells that muscle tissue

Function together

Organs – group of 2 or more stomach (organ)

tissues that function together

Organ system – a group of organs digestive System

that work togther -mouth -gall bladder

-esophagus –pancreas

-small intestine –large intestine