Chapter 3 The Cell



Chapter 3 The Cell

I. The Cellular Structure (3-A)

A. Parts of the cell

1. cell membrane/cell wall

2. cytoplasm

3. nucleus

B. Cell theory

1. All living things are composed of cells

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

3. All cells come from pre-existing cells.

C. Cellular functions and Processes

*see table pg 70

D. Levels of cellular organization

1. unicellular – organism consisting of one cell. (Ex: Bacteria)

2. multicellular – organism consisting of many cells. (Ex: plants and animals)

3. colonial – collection of simple cells living together.

4. Multicellular organization – cells(tissues(organs(systems

a. cell- the unit of function and structure of life.

b. Tissue – similar cells that are grouped together to perform similar functions.

c. Organs- tissues grouped together to perform similar functions

d. Systems – groups of organs working together to accomplish life functions.

E. Eucaryotic – has a true nucleus with a membrane around the nucleus. They have organelles.

a. organelles – accomplish the cells functions. Ex: plant and animal cells.

F. Procaryotic – lack a true nucleus. Ex: Bacteria and Blue Green Algae

G. Cell Boundaries –

1. cell membranes – found in and around cells.

a. the plasma membrane- surrounds the cell’s cytoplasm. Separates it from its outside environment.

b. The internal cellular membranes – form many of the structures in the cytoplasm.

2. Cell membranes are composed of the following:

a. phospholipids – have a hydrophobic and hydrophilic region. In water, they form a micelle (a little sphere) or a bilayer.

b. Proteins

3. Cell walls – found only in procaryotic, algae, plants, fungi and many protozoans. Animal cells do not contain a cell wall.

II. Cytoplasm

• all material inside the plasma membrane, excluding the nucleus.

A. Cytoplasmic matrix – watery substance in which granules are suspended.

B. Cytoplasmic organelles – tiny organ-like structures that perform specific functions.

1. ribosome – made up of RNA and proteins; nonmembrane-bound; found in procaryotic and eucaryotic cells. Some are attached to membranes such as ER. Some are in the cytoplasm. Their function is that they provide a site for protein synthesis.

2. Endoplasmic reticulum (ER)

a. smooth ER – folds of cellular membranes without ribosomes on the outside. It is continuous with membranes outside the nucleus. Function- transports materials through the cell. (serves as a channel).

b. Rough ER – outer surface is dotted with ribosomes.

3. Mitochondria – “power house of the cell” – bean shaped, double membrane-bound. – inner membrane having folds called cristae. Function – place where cell respiration takes place; responsible for respiration of sugars to release usable energy. Mitochondria matrix – fluid which is inside the mitochondria. – found in both plant and animal cells. Many are found in muscle cells.

4. Plastids – membrane bound, found in plant and algae but not in animal cells.

a. leucoplasts – colorless storehouses, found in fleshy storage areas of plants. (potatoes, root crops and fruit).

b. Chromoplasts – serves in synthesis processes. – contains red, orange, yellow or other pigments.

1. chloroplast – green sugar manufacturing organelle. Where photosynthesis takes place.

a. stroma –fluid inside chloroplast

b. thylakoids- flattened sacs in chloroplast

c. granum – stacks of thylakoids.

d. Chlorophyll – green pigment found in membranes of grana; catches light energy and uses it to start the synthesis of sugar.

5. Golgi bodies or golgi apparatus – flat curved sacs; polysaccharides, lipids, and proteins are processed, packed in sacs and shipped out into the cell from the golgi. Ex: cellulose in plant cell walls is assembled in the golgi body.

6. Lysosomes – small membrane bound organelles which contain special enzyme, used to break down complex structures. Many found in white blood cells.

7. Vacuoles and Vesicles – membrane bound sac which contains food, water, waste products and other materials.

a. Phagocytic vacuole

1. phagocytosis – engulfing of food by a cell. Cytoplasm flows around the food. Plasma membranes meet, they fuse, leaving the substance in a food vacuole.

b. Food vacuole – site of cellular digestion. Lysosomes fuse with food vacuoles releasing digestive enzymes.

c. Waste vacuoles

d. Secretion vesicle

e. Pinocytic vesicle – pinocytosis – cellular drinking.

f. Central vacuole – found in most plant and algae cells. Large vacuole filled with water. Puts pressure on the cytoplasm which puts pressure on the cell wall.

g. Contractile vacuole – found in single cell organisms. When water enters cell because of the environment, the contractile vacuole collects the water, fuses with the membrane and releases the water.

C. Cytoskeleton – internal structure of cytoplasm. Composed of microfilaments and microtubules.

D. Centrioles, flagella and cilia

1. centrioles – occur in pairs, aid in cell division.

2. Flagella – long tubular extension of plasma membrane. Used for locomotion of the cell.

3. Cilia – similar to flagella but shorter and usually cover the entire cell or portion of the cell.

E. Nucleus – “Control center of the cell” – contains DNA – code for all function of the cell.

1. structure of the nucleus

a. nuclear envelope – double membrane around it.

b. Nuclear pores – allows nuclear material to flow into the cytoplasm.

c. Chromatin material – composed of DNA and proteins. (in nucleus).

d. Nucleolus – large amounts of RNA; involved in decoding of DNA to RNA.

- Where ribosomes are made.

III. The Living State of Cells

• Homeostasis – “steady state” – dynamic equilibrium of the cell.

A. Optimal point and Range of Tolerance

1. all cells function best at their optimal point but can function reasonably well in their range of tolerance.

2. The farther away from the optimal point the poorer the cell will function.

B. Solutions around cells

1. the concentration of the materials in the solution around the cell influence the cell. Ex: alcohol can break down the fat in the cell membrane and cause the cell to die.

2. Some valuable substances like water, ions and food dissolved in the cells environment can cause problems for cells.

a. isotonic solution – the ratio of solutes to water is the same inside and outside the cell membrane.

b. Hypotonic solution – the outside of the cell has a higher concentration of water molecules and a lower concentration of solutes than the inside.

• water will rapidly diffuse into the cell causing it to expand and burst .

• cytolysis- cell bursting from internal pressure

c. hypertonic solution – outside of the cell has a lower concentration of water molecules and a higher concentration of solutes than the inside.

• water will diffuse out of the cell

• the cell will shrink

• plasmolysis- a collapse of the cell’s cytoplasm.

IV. Transport across membranes

A. Passive Transport

1. diffusion – process by which molecules tend to scatter themselves throughout the available space.

a. molecules move down their concentration gradient.

b. Plasma membrane is a barrier to diffusion. Molecules move passively through if:

1. small enough to pass through pores

2. can dissolve in the fatty portion of the membrane. This is considered simple diffusion.

c. osmosis – diffusion of water across a selectively permeable membrane.

d. Facilitative diffusion – larger molecules can not fit through pores, use a carrier protein.

2. Filtration – process by which water and solutes are forced through a membrane.

a. pressure gradient – solute containing fluid is actually pushed from a higher pressure to a lower pressure. Not as selective Ex: In kidneys.

B. Active Transport Process – when energy is used to move substances across the membrane.

1. solute pumping – (active transport) – similar to facilitated diffusion. – both require carrier proteins.

a. facil. diff. - ( uses kinetic energy

b. sol. pump ( uses ATP to energize protein carriers.

- solute pumps – most move against concentration gradient. Ex: Na+ are moved out of the cell by solute pumps.

- Sodium-potassium pumps – carries sodium out and potassium in. ** Needed for transmission of nerve impulses.

2. Bulk Transport – substances that could not get in or out any other way are by bulk transport.

a. Exocytosis – moves substances out of a cell.

b. Endocytosis – cell takes up or engulfs extracellular substances

1. phagocytosis – engulfing of large particles or dead cells.

2. Pinocytosis – cell drinking.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download