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Questions and Answers

What is the primary function of the genetic material stored in DNA?

To provide structural support to the plasma membrane

To regulate the entry and exit of substances in the cell

To serve as a source of energy for cellular functions

To direct metabolic activities including growth and reproduction (correct)

Which best describes the arrangement of phospholipids in the plasma membrane?

Triple layer of lipids with tails facing both inwards and outwards

Single layer of lipids with hydrophilic heads facing inwards

Double layer with hydrophilic heads facing outwards and hydrophobic tails facing inwards (correct)

Double layer with hydrophobic tails facing outwards

What is the significance of proteins embedded within the plasma membrane?

They provide mechanical strength to the cell

They insulate the cell from its environment

They store energy for cellular activities

They facilitate the transfer of substances across the membrane (correct)

Which statement about the plasma membrane is true regarding its permeability?

It is selectively permeable, allowing only small molecules to pass through Signup and view all the answers

How do carbohydrate side chains contribute to the function of the plasma membrane?

They assist in identifying cells for immune responses Signup and view all the answers

What role do lysosomes play in the degradation of cellular components?

They contain enzymes that degrade proteins and membranes. Signup and view all the answers

How are lysosomal enzymes kept from harming the cell?

They remain inactive in an alkaline environment. Signup and view all the answers

Which process describes the degradation of a cell's own components through lysosomal action?

Autophagy Signup and view all the answers

What is the main purpose of lysosomes releasing enzymes through exocytosis?

To break down other cells extracellularly. Signup and view all the answers

What is meant by autolysis in the context of lysosomal function?

The self-destruction of a cell initiated by its own enzymes. Signup and view all the answers

What is the primary function of lysosomes in a cell?

Digestion of macromolecules and cellular debris Signup and view all the answers

Which of the following describes the structure of the centrosome?

A structure comprising a pair of centrioles oriented at right angles Signup and view all the answers

What role do microfilaments play in cellular processes?

They facilitate cellular movement and division Signup and view all the answers

During which cell process does the centrosome play a critical role?

Cell division Signup and view all the answers

What is the relationship between myosin and microfilaments?

Myosin interacts with actin to facilitate muscle contraction Signup and view all the answers

Which component of the lysosome is responsible for breaking down cellular waste?

Digestion enzymes Signup and view all the answers

What is the diameter range of microfilaments?

3-6 nm Signup and view all the answers

What cellular function is NOT associated with microtubules?

Mechanism of muscle contraction Signup and view all the answers

What happens to a cell that is damaged beyond repair, in relation to lysosomes?

The cell undergoes apoptosis Signup and view all the answers

Which protein is primarily associated with the contraction of muscle tissue?

Actin Signup and view all the answers

Study Notes

Nucleus

Stores genetic material (DNA)
Directs all metabolic activities of the cell, including growth, metabolism, protein synthesis, and reproduction (cell division)
Involved in cell division
Instructs the synthesis of proteins/ribosomes & RNA
Fundamental to cell survival

Plasma Membrane

Controls the passage of substances in and out of the cell, regulating the intracellular environment
Partially permeable
Composed of two layers of lipids (mostly phospholipids)
Phospholipids are hydrophilic ("water-loving") at their phosphate ends – facing outwards, and hydrophobic ("water-fearing") along their lipid tail regions – orientated inwards
Embedded with proteins and carbohydrate molecules, which influence the transfer of substances that pass through the membrane
Proteins passing all the way through the membrane allow for passage of electrolytes

Lysosomes

A secretory vesicle formed by the Golgi apparatus
Contain enzymes responsible for degrading proteins and membranes in the cell
Aids degradation of materials ingested by the cell (due to hydrolytic (digestive) enzymes)
Enzymes are kept apart from the cell to prevent them from destroying the cell's contents
Kept inactive by an alkaline environment within the lysosome
Abundant in cells with phagocytic activity, e.g. leukocytes

Lysosomes continued: Functions

Autophagy: A process involving the degradation of a cell's own components through the lysosomal machinery
Self Destruction: They release enzymes outside the cell (exocytosis) in order to break down other cells
Autolysis: The destruction of a cell through the action of its own enzymes

Centrosome

Directs the organization of microtubules within the cell
Comprises a pair of centrioles (small clusters of microtubules)
Plays an important part during cell division

Centrosome Function: Cell Division

2 centrioles, cylindrical structures, orientated at right angles to each other
Act as organizers of the nuclear spindle during cell division

Microfilaments

Composed predominantly of a contractile protein called actin, which is the most abundant cellular protein
Fine, thread-like protein fibers, 3-6nm in diameter.
Can carry out cellular movements, including gliding, contraction, and cytokinesis (the division of cytoplasm following division of a nucleus)
Association with the protein myosin is responsible for muscle contraction

Microtubules

Cylindrical tubes, 20-25nm in diameter, providing mechanical support and structure to the cell
Involved in intracellular transport, e.g. the movement of chromosomes during cell division
Important in the formation of flagella and cilia, which help move fluids and cells

Chromosomes

Diploid = Complete set of chromosomes
Gametes = Haploid (single set of chromosomes)

Meiosis

A form of cell division which produces gametes
Results in two genetically different daughter cells
The homologous pairs swap some DNA
Each daughter cell has 23 chromosomes only - haploid

Meiosis I

The stages are similar to mitosis
Homologous chromosomes pair up
Homologous pairs divide and 2 daughter cells are produced

Meiosis II

Genetic material in daughter cells is halved by a second division
One chromosome from the original pair form a gamete
4 daughter haploid cells are produced

Cellular Transport

The passage across cell plasma membranes is semi-permeable.

Transport of Substances Across Cell Membranes

Passive transport: Diffusion and osmosis (no energy required)
Active transport: Uses ATP (energy) to move substances against their concentration gradient.
Bulk transport: Pinocytosis & Phagocytosis

Types of Cell Transport

Diffusion: The process by which a substance moves from a region of high concentration to a region of low concentration
Osmosis: The passage of water down its concentration gradient towards equilibrium across a semi-permeable membrane
Active transport: Movement of a substance against its concentration gradient; requires ATP
Phagocytosis: Cell engulfs large particles (e.g., bacteria)
Pinocytosis: Cell engulfs fluids and dissolved substances

Lysosome Function: Apoptosis

If a cell is damaged beyond repair, lysosomes help it to self-destruct by apoptosis (programmed cell death)
Destroy invading viruses and bacteria
Break down excess or worn-out cell parts

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Description

Test your knowledge on essential cell components including the nucleus, plasma membrane, and lysosomes. This quiz covers their structures, functions, and importance to cell survival and metabolism. Prepare to explore how these organelles contribute to the overall functioning of cells.