Biology Chapter: Cell Structure and Function

Questions and Answers

What characteristic distinguishes eukaryotic cells from prokaryotic cells?

Single-celled organisms

Presence of ribosomes

Lack of a defined nucleus

Internal transport system (correct)

What are the primary constituents of membrane lipids?

Phospholipids, glycolipids, and cholesterol (correct)

Phospholipids and proteins

Cholesterol and triglycerides

Carbohydrates and enzymes

Which of the following is a function of the cell membrane?

Performing photosynthesis

Maintaining an appropriate internal environment (correct)

Generating ATP

Storing genetic material

Which type of protein in the plasma membrane primarily functions to transport substances across the membrane?

Carrier proteins Signup and view all the answers

What is the composition ratio of proteins to carbohydrates in cell membranes by dry weight?

60% protein and 40% carbohydrate Signup and view all the answers

Which lipid component of cell membranes has hydrophilic heads and hydrophobic tails?

Phospholipids Signup and view all the answers

What is the role of cholesterol in the cell membrane?

To enhance membrane fluidity Signup and view all the answers

Which structure acts as the 'self-destruct' system within a eukaryotic cell?

Lysosomes Signup and view all the answers

What is essential for the plasma membrane to perform selective interactions with the environment?

Presence of glycoproteins Signup and view all the answers

What type of cell lacks a defined nucleus?

Prokaryotic cells Signup and view all the answers

What role do glycoproteins play in cell recognition?

They determine antigen specificities of the cells. Signup and view all the answers

Which process allows for the selective transport of ions across the cell membrane?

Facilitated diffusion Signup and view all the answers

Which scientist is credited with the discovery of the nucleus?

Robert Brown Signup and view all the answers

What is the main function of the cell membrane receptors?

To mediate communication between cells. Signup and view all the answers

What did Robert Hooke discover when he examined cork under a microscope?

Cells Signup and view all the answers

What explains why macrophages destroy worn-out erythrocytes?

They perform phagocytosis on damaged cells. Signup and view all the answers

What is synthesized by ribosomes and released into the lumen of the ER?

Polypeptide chains Signup and view all the answers

Which of the following was a significant contribution of Matthias Schleiden?

He proposed that all living organisms are made up of cells. Signup and view all the answers

Which hormone receptors are located in the cytoplasm?

Receptors for steroid hormones Signup and view all the answers

What did Rudolph Virchow contribute to cell theory?

He proposed that all cells come from preexisting cells. Signup and view all the answers

What is the primary function of lysosomes?

Degradation of macromolecules Signup and view all the answers

Which of the following statements about mitochondria is true?

They produce ATP and contain their own DNA. Signup and view all the answers

What is the main role of centrioles during cell division?

To help pull chromosome pairs apart Signup and view all the answers

What is the function of vacuoles in plant cells?

Store cell sap and various substances Signup and view all the answers

Where does the Krebs cycle primarily occur?

In the mitochondrial matrix Signup and view all the answers

How do lysosomes contribute to cellular processes?

By degrading unwanted biomolecules Signup and view all the answers

What characterizes the outer membrane of mitochondria?

It is freely permeable to most substances. Signup and view all the answers

Which structure is only found in animal cells?

Centrioles Signup and view all the answers

What is the pH of blood when a total concentration of $H_2CO_3$ is at 1.2 meq/L?

7.4 Signup and view all the answers

How does the pH of blood change when the concentration of bicarbonate increases while CO2 concentration remains constant?

pH increases Signup and view all the answers

What is the correct value of $pK_a$ for the bicarbonate buffer system given that $H_2CO_3$ equilibrium is considered?

6.1 Signup and view all the answers

In respiratory alkalosis, what happens to the ratio of [HCO3-] to [CO2] during hyperventilation?

The ratio increases Signup and view all the answers

How many meq of acid must be added to achieve a pH of 6.8 starting from a normal concentration of bicarbonate?

3.6 meq Signup and view all the answers

What is the total concentration of CO2 in blood expressed in meq/L for an individual with a PCO2 of 20.7 mmHg?

0.3 meq/L Signup and view all the answers

If an individual’s blood pH returns from 7.6 to 7.4, what will the PCO2 be in mmHg?

40 mmHg Signup and view all the answers

What is the relationship between pH and bicarbonate concentration in the blood?

pH increases with increasing bicarbonate Signup and view all the answers

What is the primary function of the nucleolus within the nucleus?

To produce ribosomal RNA Signup and view all the answers

What type of endoplasmic reticulum is involved in the synthesis of proteins for secretion?

Rough endoplasmic reticulum Signup and view all the answers

Which structure acts as the 'protein factory' of the cell?

Ribosomes Signup and view all the answers

What is the main role of the Golgi complex in relation to the proteins synthesized by ribosomes?

To modify, package, and transport proteins out of the cell Signup and view all the answers

What describes the internal structure of the endoplasmic reticulum?

Cisternae Signup and view all the answers

What distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?

Presence of ribosomes Signup and view all the answers

How is genetic information organized within the nucleus?

In chromatin as DNA and proteins Signup and view all the answers

What component is essential for metabolic pathways like fatty acid synthesis found in the smooth endoplasmic reticulum?

Enzymes Signup and view all the answers

Study Notes

The Cell's Nucleus and Cytoplasm

The nucleus acts as the cell's control center, regulating a limited amount of cytoplasm.
Typical cell sizes range from 5-50 micrometers in diameter.

Prokaryotic Cells

Lack a nucleus and have nuclear material not enclosed by a membrane.
Generally smaller than eukaryotic cells and are primarily single-celled organisms.
Include bacteria and cyanobacteria, which contain genetic material in regions known as nucleoids.

Eukaryotic Cells

Feature a defined nucleus and an extensive internal structure, including organelles.
Organelles include transport systems, power plants (like mitochondria), and packaging centers (like the Golgi apparatus).

Plasma Membrane

Maintains internal environment and facilitates chemical reactions necessary for life.
Comprised of a thin membrane (plasmalemma) which is essential for selective interactions.
Structurally complex, containing lipoproteins, carbohydrates, and various membrane systems.

Membrane Composition

Cell membranes are around 10 nm thick with 60% protein and 40% carbohydrate by dry weight.
Membrane lipids are polar, having a hydrophilic head and hydrophobic tails, primarily phospholipids, glycolipids, and cholesterol.

Protein Classes in Membranes

Membrane proteins include structural proteins, enzymes, and carrier proteins.
Carrier proteins transport substances across the membrane against concentration gradients.

Functions of Cell Membrane

Acts as an active component, not just a protective barrier.
Regulates material traffic and facilitates processes like transport, signal transduction, and cell recognition.
Cell membrane glycoproteins serve as identity markers, aiding in cell recognition.

Cell Signaling and Hormone Reception

Contains receptors for hormones that trigger metabolic changes within the cell.
Steroid hormone receptors are positioned in the cytoplasm, while others reside in the plasma membrane.

Secretion Mechanism

Polypeptides are synthesized in ribosomes, transported to the Golgi apparatus, stored in vesicles, and released to the cell exterior.

Historical Milestones in Cell Biology

The first compound microscope was invented in 1590 by Hans and Zacharias Janssen.
Robert Hook coined the term "cells" in 1665 after observing cork.
Anton Van Leeuwenhoek observed living cells in 1673.
Cell theory was developed by Schleiden, Schwann, and Virchow, stating all living organisms are composed of cells.

Modern Cell Theory

All living organisms consist of cells; cells are the fundamental unit of life, originating from pre-existing cells.

Nucleus Structure

The largest organelle, enclosed by a double membrane with nuclear pores, containing chromatin for DNA and RNA processes.
Houses the nucleolus, responsible for ribosomal RNA production.

Endoplasmic Reticulum (ER)

Composed of smooth and rough types; smooth ER is involved in lipid synthesis and rough ER contains ribosomes for protein synthesis.

Ribosomes

Non-membranous structures where protein synthesis occurs; can be free-floating or attached to the ER.

Golgi Complex

Modifies, packages, and transports proteins and materials out of the cell; works in conjunction with ribosomes and ER.

Lysosomes

Contain hydrolytic enzymes for degrading macromolecules; involved in cellular digestion and recycling.

Mitochondria

Known as the powerhouses of eukaryotic cells; involved in ATP production and contain their own DNA.

Centrioles

Present only in animal cells; help in cell division by forming the mitotic spindle.

Vacuoles

Fluid-filled sacs for storage; large central vacuoles in plant cells store various substances, while minimal or none are present in animal cells.

Cytoplasm

The intracellular space surrounding organelles, with the soluble portion referred to as cytosol.

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Description

Explore the fascinating world of cell biology with a focus on the cell's nucleus and its crucial role in cellular activity. This quiz covers the differences between prokaryotic and eukaryotic cells, including their sizes and structures. Test your knowledge on cell organization and gain a deeper understanding of these fundamental units of life.