Cell Bio Unit 2 (1/23/2025)

Cell structure consists of:

• cell membrane

• cytoplasm

• cytoplasmic organelles

• nucleus

Explain the structure and function of the cell membrane

• frail, semipermeable, flexible structure that encases and surrounds the cell

• made of lipids and proteins

• functions as a barrier to protect contents from the outside environment and controls passage of water and materials into and out of the cell

• plays primary role in cell’s transport system

Explain the structure and function of the cytoplasm

• the protoplasm that exists outside the cell’s nucleus

  • is everything but the nucleus

  • makes up the majority of the cell

• primarily water, but contains proteins, carbs, lipids, salts, and minerals

• all cellular metabolic functions occur in the cytoplasm

What are the 4 major functions of the cytoplasm?

1. accepts unrefined material and assembles them into new substances (i.e. proteins)

2. breaks down organic materials to produce energy

3. packaging substances for distribution to other areas of the cell or to various sites in the body through the circulation

4. eliminating waste products

What are cytoplasmic organelles?

• tiny “organs”, tubules, vesicles, granules, and fibrils

• perform various functions of the cell

How do DNA and mRNA affect the cytoplasmic organelles?

DNA determines the function of each organelle

mRNA carries the instructions into the cytoplasm

What are the 6 major organelles?

• endoplasmic reticulum

• golgi complex

• mitochondria

• lysosomes

• ribosomes

• centrosomes

Explain the endoplasmic reticulum (ER)

• highway system of the cell

  • food transfer

  • passageway for mRNA

• network of tubules that spread in all directions throughout the cytoplasm

• enables cell to communicate with extracellular environment

• 2 types:

  • rough surfaced

  • smooth surfaced

Explain the golgi complex/apparatus

• hauls “freight” into and out of the cell

• located near the nucleus and extends to the cell membrane

• unites large carbohydrate molecules and combines them with proteins to form glycoproteins

• (if a cell manufactures enzymes or hormones, the golgi complex concentrates, packages, and transports them through the cell membrane into the blood stream)

Explain the mitochondria

• “power generating station” of the cell

• large, bean-like structures

  • number varies greatly between cells

  • greatest number is found in cells exhibiting the greatest activity

• produce energy for cellular activity by breaking down nutrients through oxidation

• some enzymes contained in the mitochondria are essential in the production of ATP

What does ATP stand for?

adenosine triphosphate

Explain mitochondrial ATP

• the prime energy containing molecule in the cell

• essential for sustaining life

• plays a major role in active transport within the cell

Explain lysosomes

• “garbage bags with poison pills”

• small, pea-like sacs containing digestive enzymes

• digestive organs of the cells

  • help control intracellular contaminants

  • dispose of bacteria and food

  • etc.

• failure results in accumulation of “stuff” that may be toxic

Why are lysosomes termed “suicide bags”?

the enzymes they contain can break down and digest the cell itself when lysosome’s membrane breaks

What can happen to lysosomes with exposure to radiation?

can rupture (this causes the cell to die)

Explain ribosomes

• “manufacturing facilities of the cell”

• small spherical organelles that attach to endoplasmic reticulum

• consists of 2/3 RNA and 1/3 protein

• job is to manufacture the various proteins that the cell requires

• the site of protein synthesis

Explain centrosomes

• “weavers of the spindle”

• located in the center of the cell near the nucleus

• contain centrioles

What are centrioles?

pairs of small, hollow, cylindrical structures that are believed to play a part in the formation of the mitotic spindle during cell division

Explain the nucleus

• “information processing and administrative center”

• separated from other parts of the cell by a double walled membrane with pores, called the nuclear envelope

• contains the DNA

• contains rounded body called the nucleolus

What is the nucleolus?

the RNA copy center

What is cell division?

the multiplication process whereby one cell divides to form 2 or more cells

(AKA cell proliferation)

What are the 2 types of cell division?

mitosis (for all somatic cells)

meiosis (for all primary germ cells)

What are female germ cells called?

ovum, oocytes, ootid, or ova

What are male germ cells called?

spermatid or spermatozoa

What are the 2 reasons for somatic cell division?

• repair of damage

• growth of new tissue

What is mitosis?

the formation of 2 daughter cells identical to the parent (approximately equal distribution of all cellular material between the 2 daughter cells)

46 chromosomes each

What are the 4 distinct phases of the cell life cycle?

• M - mitosis

• G₁ - gap in cell growth (pre mRNA synthesis)

• S - DNA synthesis phase

• G₂ - post DNA synthesis

interphase is made up of the G₁, S, and G₂ phases

Which phase of the cell life cycle is most radiosensitive?

Which phase of the cell life cycle is most radioresistant?

most radiosensitive: mitosis

most radioresistant: synthesis

What is interphase?

the period of cell growth between divisions (the bulk of the cell’s lifetime)

What are the 4 phases of mitosis?

• prophase

• metaphase

• anaphase

• telophase

Explain prophase as 1 of the 4 stages of mitosis

nucleus swells, DNA begins to take form

Explain metaphase as 1 of the 4 stages of mitosis

chromosomes appear and line up in the middle of the nucleus

Explain anaphase as 1 of the 4 stages of mitosis

chromosomes split

Explain telophase as 1 of the 4 stages of mitosis

split chromosomes disappear into its own DNA mass, nuclear membrane closes off

What is cell time?

• “generation time”

• the average time from one mitosis to another

• most human cells have a generation time of 10-20 hours

• some specialized cells have a cell time of several hundred hours

• some cells, such as nerve cells, do not reproduce

What is meiosis?

special type of division that reduces the number of chromosomes in each daughter cell to ½ the number of chromosomes in the parent cell

What are the 2 separate steps in meiosis?

1. replication - cell proceeds through the same phase of mitosis like somatic cells

2. reduction - the 2 daughter cells from the first step undergo another division but WITHOUT THE S PHASE (there is no duplication of chromosomes)

What is the end result of meiosis?

4 cells with 23 chromosomes each (when combined with another germ cell, the result will be a cell with 46 chromosomes)