Science 10 Dec. 3 1. Finish textbook questions from ...

Chapter 2 notes.notebook December 04, 2014

Science 10 Dec. 3

1. Finish textbook questions from chapter 1

2. Parts of the cell lesson

3. Parts of the cell assignment


Chapter Two

Structure and Cell Function


2.1 The Cell as an Efficient System

Thought Questions:Why would a cell be considered an open system?

Why would a cell be considered the basic unit of life?

A cell is important because it carries out all life processes including:

1) Intake of nutrients2) Movement3) Growth 4) Response to stimuli5) Exchange of gases6) Waste removal7) Reproduction


The Most Important Part of the Cell

One of the most important parts of the cell is considered to be the cell membrane. Other common names of this is the phospholipid bilayer or the plasma membrane. It is the outer encasement of the cell.

What is the cell membrane made up of?

1) Phospholipids these are lipids (fats) that are made up of a hydrophillic (water loving) and hydrophobic (water hating) sides. Since we have a bilayer this means we have two layers of these phospholipid molecules. If one looks like the following diagram, hypothesize what a phospholipid bilayer would look like. Keep in mind 70% of your body, including the cells are made up of water.


2) Proteins there are many different types of proteins that make up the cell membrane, but each fall into two categories:

a) Peripheral proteins refer to proteins that do not span the entire phospholipid bilayer.i) Receptor proteins grab or bind on to

extracellular substances, such as hormones, that trigger changes in cell

activitiesii) Recognition proteins are molecular

finger prints identifying the cell as “self” so that they won’t be attacked by the

organism’s defense system.b) Integral proteins refer to proteins that span the

entire phospholipid bilayer.i) Transport proteins allow the passage of

watersoluble materials in and out of the cell.

Now, let's add the proteins to our phosopholipid bilayer diagram.


3) Cholesterol allows for membrane fluidity. The cell is very fluid which is why it is sometimes referred to as a fluid mosaic model because it can change shape and size.

4) Carbohydrates are attached to either the proteins (glycoproteins) or the phospholipids (glycolipids) to act as the markers for the immune system.

Now, let's add carbohydrates and cholesterol to our plasma membrane model.



Functions of the Cell Membrane

1) Defense the cell membrane plays a role in the immune system by having marker molecules on the cell membrane to recognize foreign and self.

2) Transport the cell membrane is selectively semipermeable meaning that it allows specific things in and out of the membrane.

a) Small things diffuse, passively (does not require energy), through the membrane itself.

b) Big things need to move, actively (requires energy), through the protein channels in the membrane.


Nucleus

The nucleus acts as the "control center" of the cell. DNA (deoxyribonucleic acid) controls all the actions inside the cell which are acting as instructions. The DNA mainly exists in a region of the nucleus called the nucleolus.

The DNA exists in clumps of matter called chromatin when the cell is not replicating and when the cell does start to replicate, the chromatin thickens into strands called chromosomes.

DNA chromatin chromosomes


Cytoplasm

The cytoplasm is the area of “life material” that exists within the cell membrane but outside of the nucleus. It is an environment that allows the cell to carry out the life functions. I like to refer to the cytoplasm as the broth that holds to the soup together.

Cytoplasmic streaming allows for the movement of organelles and molecules within cells.


Vacuoles

A vacuole is any membrane bound organelle with little or no internal structure. It can change in size; thereby, increasing the surface area of the cell – increases rate of material movement in cell. In some cases, it can act as a storage sac.

In plants, water is taken into the vacuole to create turgor pressure which is the pressure exerted against a cell wall by the water that has entered the cell via osmosis.

Vacuoles in plants are very large, animal cells have few and they are usually very small.


Ribosomes

Ribosomes use instructions from the nucleus (DNA)to synthesize proteins. Proteins are made up of amino acids and when assembled, they code for specific things that our body needs to do. The ribosomes can be found throughout the cell but usually are attached to the endoplasmic reticulum (sometimes referred to as the rough ER.)

They are extremely small in size – 25 nm; however, they make up the greatest portion of the cytoplasm.


Golgi Body

The Golgi body collects, manufactures and packages proteins and fats before shipping them to parts of the cell, or outside the cell. It can also be referred to as the Golgi complex or the Golgi apparatus.


Endoplasmic Reticulum

The endoplasmic reticulum is a transport system. Protein molecules move from the rough ER into the smooth ER, which then sends them enclosed within the vesicles usually to the Golgi complex.

1) The rough ER specializes in protein synthesis. It contains ribosomes on the surface of its structure.

2) The smooth ER specializes in lipid synthesis. It does not contain ribosomes on the surface of its structure.


Lysosomes

Lysosomes are single membraneenclosed sacs of digestive enzymes that the cell uses to digest large molecules and cell parts found in the cytoplasm. They can sometimes be referred to as “suicide sacs” because they can kill the cell itself by bursting open and the juices will destroy the cell itself.

Science 10 Dec. 3 1. Finish textbook questions from ...

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