Biochemistry MC 2: Cell and Buffers

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Questions and Answers

What did Robert Hooke observe in 1665 under the microscope?

Blood corpuscles

Mitochondria

Bacteria

Cells in cork (correct)

Which of the following statements is NOT part of the cell theory formulated by Schleiden and Schwann?

Cells have well-defined organelles. (correct)

Cells arise from pre-existing cells.

All organisms are composed of cells.

Cells are the basic unit of life.

Which component is found in all eukaryotic cells?

Cytoplasm

Cell membrane

Nuclear membrane (correct)

Naked DNA

What term describes organisms that do not possess a well-defined nucleus?

Prokaryotes Signup and view all the answers

In which part of the cell is the nucleus located?

Protoplasm Signup and view all the answers

What is the primary difference between archaebacteria and eubacteria?

Their evolutionary origin Signup and view all the answers

Which of the following organelles is NOT typically found in prokaryotic cells?

Mitochondria Signup and view all the answers

What term is used to describe the life-giving substance that includes the cytoplasm and nucleus in a cell?

Protoplasm Signup and view all the answers

What characteristic is true about Archaebacteria?

They mostly inhabit extreme environments. Signup and view all the answers

Which of the following is a well-studied eubacterium?

Escherichia coli Signup and view all the answers

What is the main function of the cell membrane?

To allow selective passage of substances. Signup and view all the answers

What is a distinguishing feature of the cell wall?

It is thicker than the cell membrane. Signup and view all the answers

What does the Endoplasmic Reticulum (ER) provide to the cytoplasmic matrix?

Mechanical support. Signup and view all the answers

Which organelle is responsible for packaging materials within the cell?

Golgi Complex/Apparatus Signup and view all the answers

What best describes the Ribosomes?

Factories in the cell for protein synthesis. Signup and view all the answers

Which feature of the Golgi Complex is responsible for its shape?

Flat disc-shaped structures called cisternae. Signup and view all the answers

What is the primary function of flagella?

Facilitating up and down movement of the cell Signup and view all the answers

What do plastids in plant cells primarily contribute to?

Photosynthesis and storage Signup and view all the answers

What role do vacuoles primarily serve in plant cells?

Storage of molecules Signup and view all the answers

Which of the following best describes peroxisomes?

They are involved in the synthesis of amino acids. Signup and view all the answers

How do vesicles assist in cellular function?

By storing and transporting materials Signup and view all the answers

What type of molecules do vacuoles store?

Cell waste and water Signup and view all the answers

Which type of organelle is characterized by being a membrane-bound compartment filled with fluid?

Vacuole Signup and view all the answers

What distinguishes cilia from flagella?

Cilia are shorter and rotate while flagella are longer and whip-like. Signup and view all the answers

What occurs to the carboxylate ion when the pH becomes acidic?

It takes up excess hydrogen ions to revert to carboxylic acid. Signup and view all the answers

How does hemoglobin assist in buffering during exercise?

By simultaneously binding protons and releasing molecular oxygen. Signup and view all the answers

What happens to amino groups in proteins when blood pH is alkaline?

They convert to the NH2 form by releasing protons. Signup and view all the answers

What is the role of the globin portion of hemoglobin in buffering?

It is responsible for binding protons. Signup and view all the answers

How does alkaline condition affect dihydrogen phosphate ions in the cell?

They accept excess hydroxide ions present in the cell. Signup and view all the answers

Which property of a buffer system ensures it does not pass through cell membranes?

Membrane permeability Signup and view all the answers

Why should citrate and phosphate buffers be avoided in calcium dependent reactions?

They chelate calcium Signup and view all the answers

What is the ideal physiological ionic strength range for buffer systems?

100 mM - 200 mM Signup and view all the answers

What type of absorbance should a buffer system have to avoid interference in spectrophotometric assays?

Absorbance at 230 to 700 nm Signup and view all the answers

What is a key feature of the bicarbonate buffer system related to blood pH?

It converts bicarbonate into carbon dioxide Signup and view all the answers

What characteristic should buffers possess regarding their chemical interactions in biological systems?

Be biochemically inert Signup and view all the answers

What is a primary component of the phosphate buffer system in cells?

Hydrogen phosphate and dihydrogen phosphate Signup and view all the answers

What feature of buffers contributes to their practical use in laboratory settings?

Ease of preparation and low cost Signup and view all the answers

Study Notes

Cell Landmarks

Anton Van Leeuwenhoek invented the microscope; Robert Hooke observed cork cells in 1665, coining the term "cell" from Latin meaning "small room."
Leeuwenhoek identified bacteria, sperm, and red blood cells in 1672.
In 1831, Robert Brown discovered the nucleus in all cells.

Cell Theory

Formulated in 1838 by M.J. Schleiden and Theodore Schwann.
Asserts that all organisms are made of cells, cells are the structural and functional units of life, and new cells arise from existing ones.

Definition of a Cell

A cell is a unit of protoplasm, enclosed by a plasma membrane, containing a nucleus.
Protoplasm comprises cytoplasm and the nucleus; cytoplasm contains organelles like ribosomes, mitochondria, Golgi bodies, plastids, lysosomes, and endoplasmic reticulum.
Plant cells have large vacuoles; bacteria lack defined organelles and a well-formed nucleus.

Types of Cells

Two main categories: prokaryotic and eukaryotic.
Prokaryotes lack a well-formed nucleus (e.g., bacteria); eukaryotes have a defined nucleus.

Prokaryotic Cells

Simple, single-celled organisms; have basic organelles.
Divided into two groups:
- Archaebacteria: thrive in extreme environments.
- Eubacteria: true bacteria, commonly found in diverse habitats (e.g., Escherichia coli).

Organelles Overview

Structures that enable cell function, growth, and reproduction.

Cell Membrane

Semi-permeable outer layer of the cell made of proteins, carbohydrates, and a phospholipid bilayer (Fluid Mosaic Model).
Facilitates selective passage and transport of molecules.

Cell Wall

Found in plants and fungi; thicker than the cell membrane, consisting of three layers.
Provides shape, facilitates cell interaction, and protects from harmful substances.

Endoplasmic Reticulum (ER)

A system of tubular structures; two types: rough (with ribosomes) and smooth.
Directly connected to the nucleus, provides mechanical support.

Golgi Complex/Apparatus

Composed of flat, disc-shaped structures (cisternae) near the nucleus.
Responsible for packaging materials, modifying proteins, and forming glycolipids and glycoproteins.

Ribosomes

Composed of ribonucleic acid and proteins; essential for protein synthesis.
Flagella provide movement; cilia assist with cell movement.

Plastids

Double-membrane organelles in plants, containing pigments (chloroplasts, chromoplasts, leukoplasts).
Involved in photosynthesis and synthesis of organic compounds.

Peroxisomes

Membrane-bound organelles that oxidize biomolecules, producing hydrogen peroxide.
Contain catalase to convert hydrogen peroxide into water and oxygen.

Vacuoles

Membrane-bound, fluid-filled spaces that store water, enzymes, and waste products.
Take up 80-90% of plant cells, involved in detoxifying and waste export.

Vesicles

Spherical compartments formed from the Golgi apparatus, ER, or cell membrane.
Function in storage, transport, and isolation of materials, including waste and nutrients.

Characteristics of Water

Major chemical component of Earth's surface; essential for biological systems.
High solubility and membrane permeability important for buffer efficacy.
Excessive ions can disrupt biological processes; ideal buffer should minimize ion buildup.

Buffer Preparation Considerations

Should remain inert, stable, and should not absorb light in spectrophotometric ranges.
Should allow selective ion concentration without forming complexes, easy to prepare, and inexpensive.

Buffer Systems in Biological Systems

Bicarbonate Buffer: Maintains blood pH; converts excess acids into carbon dioxide and bicarbonate ions for excretion.
Phosphate Buffer: Operates in cell fluids; manages pH by reacting with excess hydrogen or hydroxide ions.
Protein Buffer: Utilizes amino acids' carboxylic acid and amino groups to balance pH changes.
Hemoglobin Buffer: Regulates tissue pH by binding protons or oxygen, crucial during physical exertion.

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Description

This quiz focuses on the key concepts related to cells, water, and buffers in biochemistry. It explores historical discoveries in the study of cells, including observations made by pioneers like Anton Van Leeuwenhoek and Robert Hooke. Test your knowledge on the significance of cells and their components.