Biology: Cells and Cell Theory

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Questions and Answers

Who was the first to name cells, and what was he observing?

Anton van Leeuwenhoek; living bacteria

Robert Hooke; thin sections of dried cork (correct)

Louis Pasteur; microbial growth in broth

Robert Brown; the nucleus of plant cells

Which statement describes a characteristic of prokaryotic cells?

They lack internal compartmentalization. (correct)

They have a nucleus.

They have multiple chromosomes.

They are typically larger than eukaryotic cells.

What type of chromosomes do eukaryotic cells have?

Single-stranded chromosomes

Diploid chromosomes (correct)

Haploid chromosomes

Circular chromosomes

How do cholesterol molecules influence cell membranes?

They moderate fluidity and rigidity of membranes. Signup and view all the answers

What is a significant difference in the transcription location between prokaryotic and eukaryotic cells?

Prokaryotes transcribe in the nucleoid; eukaryotes transcribe in the nucleus. Signup and view all the answers

Which feature is true regarding phospholipids in cell membranes?

They have a hydrophobic tail and a hydrophilic head. Signup and view all the answers

Which domain do prokaryotic cells belong to?

Both Archaea and Bacteria Signup and view all the answers

What is a key characteristic of eukaryotic cells compared to prokaryotic cells?

They have specialized organelles such as mitochondria. Signup and view all the answers

What is the primary function of cholesterol in animal cell membranes?

To serve as a buffer for membrane fluidity. Signup and view all the answers

What type of lipids spontaneously form a liposome in water?

Phospholipids with large polar heads and two hydrophobic tails. Signup and view all the answers

Which of the following statements about integral membrane proteins is true?

They can cross the entire membrane. Signup and view all the answers

How do saturated and unsaturated fatty acid tails affect membrane fluidity?

Unsaturated tails increase fluidity by introducing kinks that prevent tight packing. Signup and view all the answers

What is the role of peripheral membrane proteins?

They temporarily associate with either side of the membrane. Signup and view all the answers

What factor does NOT influence membrane fluidity?

Protein concentration in the membrane. Signup and view all the answers

What type of structure is formed when phospholipids with small bulky heads and a single hydrophobic tail aggregate?

Micelle. Signup and view all the answers

Which statement regarding membrane self-healing is true?

Membranes spontaneously reform due to the nature of phospholipid interactions. Signup and view all the answers

Study Notes

Robert Hooke and Cells

Hooke constructed a microscope to study dried cork slices.
He determined that the cork was made up of small, box-like compartments, and called them “cells”.

Cell Theory

All organisms are composed of cells.
The cell is the fundamental unit of life.
Cells come from pre-existing cells.

Prokaryotes vs. Eukaryotes

Cells are classed as prokaryotes or eukaryotes.
Prokaryotes are characterized by the lack of a nucleus and internal compartmentalization.
Eukaryotes have a nucleus and internal, membrane-bound organelles.
Prokaryotes are found in Domains Bacteria and Archaea.
Eukaryotes are in Domain Eukarya.

Prokaryotes vs. Eukaryotes

Prokaryotes have a nucleoid region instead of a nucleus.
Prokaryotes are haploid, while eukaryotes are diploid.
In prokaryotes, transcription occurs in the cytoplasm.
In eukaryotes, transcription occurs in the nucleus.
Both prokaryotes and eukaryotes translate in the cytoplasm.
Prokaryotic cells are smaller than eukaryotic cells (average 1-2 micrometers vs. 10-20 micrometers).
Prokaryotic cells have a higher surface area to volume ratio.
Prokaryotes lack internal organelles, and eukaryotes contain organelles like mitochondria and chloroplasts.
Prokaryotes have hopanoids in their cell membranes to regulate fluidity and rigidity.
Eukaryotes have sterols, like cholesterol, in their membranes to regulate fluidity and rigidity.

Cholesterol

Cholesterol is a component of many animal cell membranes.
Cholesterol has polar and nonpolar regions, enabling it to associate with cell membranes.
Cholesterol can influence membrane fluidity.

Cell Membrane

Most cell membranes are mainly composed of phospholipids.
Phospholipids are amphipathic, with hydrophobic tails and hydrophilic heads.

Lipid Structures

Micelles form from phospholipids with large, bulky heads and a single hydrophobic tail.
Bilayers and liposomes form from phospholipids with smaller heads and two hydrophobic tails.
Phospholipids spontaneously form liposomes (lipid vesicles) in water, where the polar heads and nonpolar tails associate with each other in a bilayer.

Membrane Fluidity

Membranes are self-healing, reforming spontaneously.
Membranes are fluid mosaics, composed of lipids and proteins.
Lipids can move laterally within the membrane.
The fluidity of the membrane is influenced by several factors, including the nature of the phospholipid tails.

Saturated vs. Unsaturated

Saturated fatty acid tails are straight and pack tightly, decreasing membrane fluidity.
Unsaturated fatty acid tails have kinks, reducing packing density and increasing membrane fluidity.
Van der Waals forces between fatty acid tails help stabilize membranes, while their weakness allows for lipid movement within the membrane.

Cholesterol and Fluidity

Cholesterol acts as a buffer, regulating membrane fluidity.
At low temperatures, cholesterol can increase fluidity by preventing tight packing.
At high temperatures, cholesterol can decrease fluidity by hindering movement.

Proteins in the Membrane

The membrane contains several types of proteins, including:
- Transporters, which move ions and molecules.
- Receptors, which receive signals from the environment.
- Enzymes, which catalyze chemical reactions within the cell.
- Anchors, which attach to other proteins, such as actin, or the cytoskeleton, helping maintain cell structure and shape.

Integral vs. Peripheral Proteins

Integral membrane proteins are permanently embedded in the membrane and can span its entire width.
Peripheral membrane proteins are temporarily associated with either side of the membrane.

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Description

Explore the fundamental concepts of cells with this quiz, focusing on key figures like Robert Hooke and the development of cell theory. Delve into the differences between prokaryotic and eukaryotic cells, understanding their unique characteristics and functions.