Cells and Cell Structures Lecture

A comprehensive set of question-and-answer flashcards covering cell theory, history, cell size and types, as well as structures and functions of major and minor organelles.

What is the basic structural and functional unit of living organisms?

The cell.

State the three classical postulates of cell theory.

1) The cell is the basic unit of life. 2) All living organisms are composed of one or more cells. 3) All cells arise from pre-existing cells.

Which scientist coined the term “cells” after observing cork in 1665?

Robert Hooke.

Who observed living ‘animalcules’ with a refined microscope in the late 1600s?

Anton van Leeuwenhoek.

Which botanist concluded in 1838 that plants are composed of cells?

Matthias Jakob Schleiden.

Which zoologist stated in 1839 that animals are made of cells?

Theodor Schwann.

Who introduced the idea "Omnis cellula e cellula" meaning cells come from pre-existing cells?

Rudolf Virchow (1858).

What contribution did Robert Brown make to cell biology in 1831?

He discovered the nucleus.

Name the unit commonly used to measure cell size.

Micrometer (µm).

Give the approximate size of the smallest human cell and its example.

About 5 µm; the sperm cell.

Which human cell is the largest by diameter, and what is its size?

The ovum at roughly 120 µm.

Which human cell is the longest, reaching up to about 1 m?

Certain nerve (neuronal) cells/axons.

Define ‘ultrastructure’.

The detailed structure of a cell as seen with an electron microscope.

What is cellular homeostasis?

A state of balance among all body systems that allows the cell to survive and function correctly.

Describe the main composition of the cell membrane.

A semi-permeable phospholipid bilayer embedded with proteins and carbohydrates.

Why does glucose need transport proteins to cross the membrane?

Because glucose is a polar solute and cannot diffuse freely through the hydrophobic lipid bilayer.

What is cytosol?

The semifluid component of cytoplasm in which organelles are suspended.

List three major activities that occur in the cytoplasm.

Glycolysis, protein synthesis, and fat (lipid) synthesis.

State three functions of the plant cell wall.

Provides shape and rigidity, prevents desiccation, and protects against pathogens.

What is the largest membrane-bound organelle that contains chromosomes?

The nucleus.

What are genes?

Stretches of DNA on chromosomes that carry hereditary information.

Give two functions of the nucleolus.

Synthesizes ribosomal RNA and assembles ribosome subunits.

What is the role of nuclear pores?

They allow large molecules such as RNA and ribosomal proteins to move between nucleus and cytoplasm.

Describe the endoplasmic reticulum (general function).

An interconnected membranous system that transports materials within the cell.

Differentiate rough ER from smooth ER.

Rough ER has ribosomes and synthesizes proteins; smooth ER lacks ribosomes and synthesizes lipids/steroid hormones and detoxifies drugs.

Which enzyme, produced in pancreas and salivary glands, digests carbohydrates?

Amylase.

State the primary function of the Golgi apparatus.

Modification, packaging, and distribution of proteins and lipids from the ER.

What are the ‘cis’ and ‘trans’ faces of the Golgi body?

The cis face is the forming/receiving side; the trans face is the maturing/shipping side.

What is the main function of lysosomes?

Digestive breakdown of worn-out organelles or macromolecules; can trigger apoptosis.

Give two key functions of vacuoles in plant cells.

Store water and solutes, and provide turgidity/rigidity to the cell.

How do plant and animal vacuoles differ?

Plant cells typically have one large central vacuole; animal cells have many small temporary vacuoles.

Why are mitochondria called the ‘powerhouse’ of the cell?

They generate most ATP required for cellular biochemical reactions.

From which parent are mitochondria usually inherited?

Exclusively from the mother.

Why do muscle cells contain many mitochondria?

Because muscle contraction requires large amounts of energy.

Name the green plastid responsible for photosynthesis.

Chloroplast.

What pigment inside chloroplasts captures light energy?

Chlorophyll.

What are chromoplasts?

Plastids that synthesize and store colored pigments found in leaves, fruits, and flowers.

What is the primary function of ribosomes?

Protein synthesis.

Define cytoskeleton.

A network of protein fibers that maintains cell shape, facilitates movement, and organizes organelles.

What is the key role of peroxisomes?

Carry out oxidative reactions, detoxify reactive oxygen species, and support metabolism.

Explain plasmodesmata.

Cytoplasmic channels that traverse plant cell walls, enabling direct communication between adjacent cells.

State two distinctions between plant and animal cells.

Plant cells have a cell wall and a large central vacuole; animal cells lack a cell wall and have multiple small vacuoles.

What are the two primary cell types distinguished by nucleus presence?

Eukaryotic cells (with nucleus) and prokaryotic cells (without nucleus).

Name three structures common to all cells.

Cell membrane, cytoplasm, and genetic material (DNA/RNA).

What discovery did Louis Pasteur’s fermentation studies support regarding cells?

Bacteria reproduce by dividing from pre-existing bacterial cells.

Who stated that sperm and egg are composed of cells in 1840?

Albrecht von Kölliker (Roelliker).

Which early Dutch maker invented a primitive microscope around 1590?

Zacharias Janssen (with his father Hans).

What term describes programmed self-destruction of cells often mediated by lysosomes?

Apoptosis.

Why can some protists like Amoeba change shape while most cells cannot?

Because their flexible cytoskeleton and lack of rigid cell walls allow dynamic shape alteration for movement and feeding.

What cellular structure links the ER to nuclear envelope?

The endoplasmic reticulum membrane is continuous with the nuclear envelope.

Which cellular pigment storage organelles give carrots their orange color?

Chromoplasts containing carotenoid pigments.