Cell Components Quiz

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Questions and Answers

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

Storage of genetic material

Synthesis of lipid molecules

Regulation of cellular temperature

Site of RNA transcription and ribosome assembly (correct)

Which component of the cytoskeleton provides structural support and a framework for organelles?

Microtubules (correct)

Microfilaments

Ribosomes

Intermediate filaments

What characteristic of the inner mitochondrial membrane is important for its function?

Contains ribosomes

Relatively porous

Selectively permeable (correct)

Absorbs nutrients

How does glycolysis contribute to cellular metabolism?

It breaks down glucose to release energy Signup and view all the answers

What distinguishes the outer mitochondrial membrane from the inner mitochondrial membrane?

It is less selective and porous Signup and view all the answers

Which organelle is described as the largest within a cell and surrounded by a nuclear envelope?

Nucleus Signup and view all the answers

What role do glucose transporters play in cellular metabolism?

They help regulate glucose uptake Signup and view all the answers

Where does the process of ribosome assembly begin and complete?

Begins in the nucleus and completes in the cytoplasm Signup and view all the answers

Which nucleotide is unique to RNA and not found in DNA?

Uracil Signup and view all the answers

What role does the lin-4 microRNA play in relation to lin-14?

Negative regulator of lin-14 Signup and view all the answers

Which of the following statements about protein synthesis is true?

Ribosomes link amino acids to form proteins. Signup and view all the answers

What is the primary function of ATP in cellular processes?

Major storage form of energy Signup and view all the answers

What significant discovery did Ambros make about the lin-4 gene?

It encodes a tiny RNA that does not code for protein. Signup and view all the answers

What consequence can result from hyperuricemia in the body?

Formation of kidney stones Signup and view all the answers

Which of the following is a key role of microRNA in multicellular organisms?

Regulates gene expression Signup and view all the answers

What important function does ATP synthase perform in cells?

Catalyzes ATP formation Signup and view all the answers

What is the net gain of ATP molecules during glycolysis for each molecule of glucose?

Two ATP molecules Signup and view all the answers

At what concentration of ADP is the enzyme activity increased during the preparatory stage of glycolysis?

High ADP concentration Signup and view all the answers

Which products are generated from one molecule of glucose during glycolysis?

Two pyruvate, two NADH, and two ATP Signup and view all the answers

What happens to NAD+ during glycolysis?

It is converted back to NADH Signup and view all the answers

Where does glycolysis primarily occur within a cell?

Cytosol Signup and view all the answers

What effect does oxygen availability have on glycolysis in certain cells?

Glycolysis is essential for cells with low oxygen access Signup and view all the answers

What is the primary outcome of the conversion of pyruvate to lactate under anaerobic conditions?

Recycling of NAD+ Signup and view all the answers

Which of the following statements is true about the energy-releasing phase of glycolysis?

It involves the conversion of glyceraldehyde-3-phosphate to pyruvate Signup and view all the answers

What is the primary function of GLUT1?

Allowing glucose to cross the blood-brain barrier. Signup and view all the answers

What happens to pyruvate during aerobic glycolysis?

It is oxidized to acetyl-CoA. Signup and view all the answers

Which glucose transporter has a low affinity but high capacity?

GLUT2 Signup and view all the answers

In which tissues is GLUT3 primarily expressed?

Brain and neurons. Signup and view all the answers

What syndrome is associated with GLUT1 deficiency?

Seizure syndrome. Signup and view all the answers

How does GLUT4 respond to insulin?

It increases cellular uptake of blood glucose. Signup and view all the answers

What role does GLUT2 play in glucose metabolism?

It transports glucose from enterocytes to portal blood. Signup and view all the answers

Which GLUT transporter is primarily responsible for regulating insulin secretion?

GLUT2 Signup and view all the answers

Which cells do not depend on insulin for glucose uptake?

Erythrocytes Signup and view all the answers

What is the primary function of GLUT5?

To facilitate the uptake of dietary fructose Signup and view all the answers

How is the glycemic index (GI) calculated?

By dividing the area under the curve for the test food by that of the reference food and multiplying by 100 Signup and view all the answers

Which of the following foods has a glycemic index higher than glucose?

White bread Signup and view all the answers

What happens to GLUT4 in response to insulin?

It is translocated to the plasma membrane Signup and view all the answers

Which statement about the glycemic index is true?

GI of the reference food is assigned a score of 100. Signup and view all the answers

Which cells express GLUT4?

Skeletal muscle cells Signup and view all the answers

When measuring the glycemic index, how long after eating is blood glucose typically monitored?

2 hours Signup and view all the answers

Study Notes

Cell Components

Cytoplasmic Matrix: Provides structural support and a framework for cell organelles.
Cytoskeleton:
- Composed of Microtubules, Intermediate Filaments, and Microfilaments.
- Facilitates intercellular communication.
Mitochondrion:
- Contains two membranes:
  - Outer membrane: Porous
  - Inner membrane: Selectively permeable, and site of the electron transport chain.
Nucleus:
- Largest organelle.
- Surrounded by the nuclear envelope.
- Contains DNA, forming the cell genome (entire set of genetic information).
Nucleolus:
- Site of RNA transcription and ribosome assembly/synthesis, starting in the nucleus and completing in the cytoplasm.
Nucleic Acids:
- DNA and RNA.
- Composed of adenine, guanine, and cytosine, with uracil only found in RNA and thymine only found in DNA.
- DNA is double stranded with complementary base pairing.
- RNA is single stranded, capable of folding to create complex secondary structures.

Protein Synthesis

Ribosomes link amino acids together to form proteins.

Biological Energy

ATP: Major energy storage form in cells.
ATP synthase:
- Protein that catalyzes ATP formation using ADP and inorganic phosphate.
- Generates two molecules of ATP and two molecules of NADH.

Glucose Metabolism

Complete glucose oxidation:
- Formula: Glucose + 6O2 = 6 CO2 + H2O
- Releases -2840 kJ/mol of free energy.
Glycolysis:
- Takes place in the cytosol.
- Formula: Glucose + 2NAD+ = 2Pyruvate + 2NADH + 2H+
- Releases -146 kJ/mol of free energy (5.2% of total energy from glucose oxidation).
- Essential for tissues like the brain and cells with limited oxygen access.
- Generates lactate and ATP under anaerobic conditions.

Stages of Glycolysis

Stage 1 (Reactions 1-5):
- Preparatory phase involving phosphorylation of glucose, conversion to fructose, re-phosphorylation, and cleavage into two glyceraldehyde-3-phosphate molecules.
- Requires an investment of 2 ATP molecules.
Stage 2 (Reactions 6-10):
- Conversion of two glyceraldehyde-3-phosphate molecules to pyruvate, generating four ATP molecules and two NADH molecules.
- Results in a net gain of two ATP molecules per glucose molecule.

Membrane Transporters of Glucose

GLUT1:
- Most ubiquitously expressed transporter.
- Responsible for glucose transport across the blood-brain barrier and supply to the developing central nervous system.
- Essential for erythrocytes, brain endothelial cells, and fetal tissue.
- Deficiency leads to GLUT1 deficiency syndrome, characterized by seizures due to insufficient brain glucose.
GLUT2:
- Low-affinity, high-capacity transporter.
- Predominant expression in pancreatic β-cells, liver, small intestine, and kidneys.
- Transports monosaccharides from enterocytes into the portal blood.
- Involved in insulin release from β-cells in response to blood glucose levels.
GLUT3:
- High-affinity transporter.
- Primarily expressed in glucose-dependent tissues, such as the brain and neurons as well as spermatozoa, placenta, and preimplantation embryos.
- Potential dysregulation could lead to glucose deficits in the brain and associated with dyslexia.
GLUT4:
- Primary transporter for insulin-regulated glucose uptake in muscle and adipose tissue.
- Absence in other tissues renders them independent of insulin for glucose uptake.
- Insulin promotes translocation of GLUT4 from intracellular storage to the plasma membrane.
GLUT5:
- Highly specific for fructose.
- Expressed in the small intestine, kidneys, brain, muscles, and adipose tissue.
- Primarily responsible for fructose transport across enterocyte brush border membranes.

Glycemic Index

Measures the rate at which a particular food raises blood glucose levels.
Calculated by comparing the area under the blood glucose curve after consuming the food with the area under the curve for a reference food (either glucose or white bread).
Foods with a high glycemic index cause rapid and significant spikes in blood glucose, while foods with a low glycemic index cause slower and more gradual rises.
Factors influencing Glycemic Index:
- Type of carbohydrate: Simple sugars have a higher GI than complex carbohydrates.
- Processing of food: Processed foods have a higher GI than unprocessed or minimally processed foods.
- Cooking methods: Boiling or steaming vegetables lowers GI compared with frying.
- Fat content: Adding fat can lower the GI.
- Fiber content: Foods high in fiber have a lower GI.
- Amount of food: Consuming a larger amount of food will increase the GI.
- Individual factors: Factors like age, fitness levels, and genetics can affect GI.

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Description

Test your knowledge on the essential components of a cell! This quiz covers various organelles such as the cytoplasmic matrix, mitochondria, nucleus, and nucleic acids. Understand the structures and functions that make up cellular biology.