Biology Chapter: Cell Structures and Functions

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Questions and Answers

What is the primary function of the nuclear envelope?

Protect the nucleus and regulate substance passage (correct)

Store genetic material

Assist in protein synthesis

Direct metabolic activities

Which of the following processes is directed by the nucleus?

Nutrient transport

Respiration

Cell replication (correct)

Waste elimination

What structural component primarily makes up the plasma membrane?

Proteins

Nucleic acids

Phospholipid bilayer (correct)

Carbohydrate chains

What is the primary function of mitochondria within a cell?

Production of ATP through aerobic respiration Signup and view all the answers

How do phospholipids in the plasma membrane respond to water?

Phosphate ends are hydrophilic, tails are hydrophobic Signup and view all the answers

Which component of the rough endoplasmic reticulum (RER) plays a crucial role in protein synthesis?

Ribosomes Signup and view all the answers

What role do embedded proteins in the plasma membrane play?

They facilitate selective transport and act as receptors Signup and view all the answers

What characteristic of the cytoplasm primarily contributes to the metabolic reactions occurring within it?

Presence of water and various solutes Signup and view all the answers

Which of the following correctly describes the permeability of the plasma membrane?

Partially permeable to certain substances Signup and view all the answers

Which of the following correctly describes the structure of the smooth endoplasmic reticulum (SER)?

Similar to RER but without ribosomes Signup and view all the answers

What is a function of carbohydrate molecules in the plasma membrane?

Acting as immunological recognition sites Signup and view all the answers

Which of the following describes a role of the nucleus?

Controlling metabolic activities through protein instructions Signup and view all the answers

What is a critical feature of the inner membrane of mitochondria that allows for efficient chemical reactions?

Large surface area due to cristae Signup and view all the answers

Which statement is true regarding the rough endoplasmic reticulum (RER)?

It serves as a pathway for material transport within the cell. Signup and view all the answers

Which ions and molecules are commonly found in the cytoplasm of a cell?

Sodium, phosphates, and chlorides Signup and view all the answers

What role does the plasma membrane play in cellular function?

Regulating the movement of substances in and out of the cell Signup and view all the answers

What occurs to the chromosomes during anaphase?

Sister chromatids are pulled apart. Signup and view all the answers

Which of the following statements is true about telophase?

Cytokinesis begins before mitosis concludes. Signup and view all the answers

How many chromosomes do daughter cells have after meiosis?

23 chromosomes Signup and view all the answers

What key process occurs during interphase?

DNA synthesis takes place. Signup and view all the answers

What is the primary role of the spindle fibers during metaphase?

To align chromosomes in the center of the cell Signup and view all the answers

What distinguishes meiosis II from meiosis I?

Meiosis II is similar to mitosis. Signup and view all the answers

Which type of transport uses ATP to move substances across cell membranes?

Active transport Signup and view all the answers

During which stage do homologous chromosomes swap DNA?

Prophase I of meiosis Signup and view all the answers

Which feature is characteristic of cells in interphase?

Cell growth occurs Signup and view all the answers

What happens to the cytoplasm during cytokinesis?

It divides into two distinct cells. Signup and view all the answers

Study Notes

The Nucleus

The nucleus is the largest structure in a cell.
The nuclear envelope has a double membrane, with the outer layer connected to the endoplasmic reticulum.
The envelope contains pores which allow substances to pass through.
The nucleus stores genetic material (DNA).
It directs all metabolic activities of the cell, including growth, metabolism, protein synthesis, and reproduction (cell division).
The nucleus also instructs the synthesis of proteins/ribosomes and RNA.

Plasma (Cell) Membrane

The plasma membrane is partially permeable and composed of a double layer of lipids, mostly phospholipids.
The phospholipid molecules have hydrophilic ("water-loving") phosphate ends that face outwards and hydrophobic ("water-fearing") lipid tail regions that face inwards.
The membrane also contains proteins and carbohydrate molecules embedded within or attached to its surface.

Functions of the Plasma Membrane and Its Proteins

Regulates the transport of substances into and out of the cell.
Acts as receptors (recognition sites) for substances such as hormones.
Allows directed cell or organelle motility.
Provides immunological identity due to the carbohydrate molecules within.
Some proteins act as enzymes.

Cytoplasm

The cytoplasm is a gel-like, semi-transparent fluid that fills most cells and is where metabolic reactions occur.
It mainly consists of water with many solutes, including glucose, proteins, and ions.
It contains vital cellular chemicals such as sodium, phosphates, chlorides, amino acids, ATP, and storage material like oil droplets.

Mitochondrion (Mitochondria)

The mitochondria are known as the "powerhouse of the cell".
It has outer and inner membranes.
The inner membrane folds into cristae, maximizing surface area for chemical reactions to occur.
Mitochondria are involved in cellular aerobic (O2) respiration, the process that makes chemical energy available in the cell.
Energy in the form of ATP (Adenosine triphosphate) is formed from the catabolism of carbohydrates, fats, and proteins in the cell.
The number of mitochondria varies depending on the cell and its function, with the highest number found in cells that are physically and metabolically active, such as skeletal muscles.

Rough Endoplasmic Reticulum (RER)

The RER is a series of interconnected membranous canals that enclose flattened sacs called cisternae.
It is an extension of the outer nuclear membrane.
It has a large surface area for chemical reactions.
It is covered with ribosomes, which make proteins.

Function of Rough Endoplasmic Reticulum

Produces proteins, especially enzymes.
Provides a pathway for the transport of materials through the cell.
Collects and stores synthesized material.
Provides a structural skeleton to maintain cellular shape.

Smooth Endoplasmic Reticulum (SER)

The SER has similar features to the RER, but is found in large amounts in cells that secrete steroids, such as telophase.

Interphase

During interphase, the cell grows and DNA synthesis occurs.
Chromosomes replicate into two pairs of chromatids.
Two pairs of centrioles appear.

Early Prophase

Each chromosome has two chromatids joined at a centromere.
The mitotic spindle, composed of microtubules and proteins, forms in the cytoplasm.
The two pairs of centrioles move away from each other toward opposite ends of the cell.

Late Prophase

The nuclear envelope breaks up.
Microtubules that make up the spindle fibers reach from each cell pole to the cell's equator.
Chromosomes/chromatids begin to migrate toward the cell center.

Metaphase

The nuclear membrane disappears completely.
Two pairs of centrioles align at opposite poles of the cell.
Chromosomes/chromatids align at the metaphase plate at right angles to the spindle poles.

Anaphase

The paired chromatids in each distinct chromosome begin to move apart.
Once the paired sister chromatids separate from one another, each is considered a "full" chromosome, referred to as daughter chromosomes.
The daughter chromosomes move to the poles at opposite ends of the cell.

Telophase

Nuclei begin to form at opposite poles.
The chromatin fibers of chromosomes uncoil.
Cytokinesis, the division of the original cell's cytoplasm, begins before the end of mitosis and completes shortly after telophase.
At the end of cytokinesis, there are two distinct daughter cells.

Meiosis

Meiosis is the type of cell division that occurs in the formation of reproductive cells known as gametes: ova (eggs) and spermatozoa (sperm).
The ova grow to maturity in the ovaries of the female and the spermatozoa in the testes of the male.
After division, each daughter cell has only 23 chromosomes.
When the ovum is fertilized, the resultant zygote has the full complement of 46 chromosomes, half from the father and half from the mother.

Stages of Meiosis - Meiosis I

The chromosomes of the diploid cells replicate.
Homologous (similar) chromosomes pair up.
The stages are similar to mitosis.
Homologous pairs swap some DNA.
Two daughter cells are produced, each with only 23 chromosomes (haploid).

Stages of Meiosis - Meiosis II

Meiosis II is similar to mitosis, and four daughter haploid cells are produced as a result.

Cellular Transport

Transport of substances across cell membranes can be achieved through passive or active transport.
Passive transport includes diffusion and osmosis and does not require energy.
Active transport utilizes ATP (energy) to move substances across the cell membrane.
Bulk transport includes pinocytosis (cell drinking) and phagocytosis (cell eating) and involves engulfing larger quantities of substances.

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Description

This quiz covers essential aspects of cell structures, including the nucleus and plasma membrane. Explore topics such as the nuclear envelope, genetic material, and the composition of the plasma membrane. Test your understanding of how these structures contribute to cell functionality.