BIO CHEMISTRY

A newborn develops progressive liver disease.

Biopsy shows accumulation of misfolded alpha-1 antitrypsin inside hepatocytes.

Which organelle is primarily dysfunctional?

A. Golgi

B. Rough ER

C. Lysosome

D. Mitochondria

B. Rough ER

The rough endoplasmic reticulum (Rough ER) is responsible for protein synthesis and folding. In this case, the accumulation of misfolded alpha-1 antitrypsin indicates a dysfunction in the Rough ER.

A child has coarse facial features, developmental delay, and elevated lysosomal enzymes in the blood.

Which defect is most likely?

A. Failure of ATP production

B. Absence of Mannose-6-phosphate tagging

C. Defective glycolysis

D. Defective DNA replication

B. Absence of Mannose-6-phosphate tagging

A patient lacks phosphotransferase enzyme activity.

Which disease develops?

A. Gaucher disease

B. Pompe disease

C. I-cell disease

D. Tay-Sachs disease

C. I-cell disease

What is the biochemical reason lysosomal enzymes are secreted outside the cell in I-cell disease?

A. Defective ribosomes

B. Lack of Mannose-6-phosphate targeting

C. ATP deficiency

D. Lysosomal rupture

B. Lack of Mannose-6-phosphate targeting

A muscle biopsy shows glycogen-filled lysosomes.

Which enzyme is deficient?

A. Hexosaminidase A

B. Acid α-glucosidase

C. β-glucocerebrosidase

D. Catalase

B. Acid α-glucosidase

A child develops progressive neurodegeneration and a cherry-red macula.

Which enzyme is deficient?

A. Acid maltase

B. Hexosaminidase A

C. Catalase

D. Phosphofructokinase

B. Hexosaminidase A

Which disease is caused by accumulation of GM2 ganglioside?

A. Pompe

B. Gaucher

C. Tay-Sachs

D. Niemann-Pick

C. Tay-Sachs

A patient receives enzyme replacement therapy.

The recombinant enzyme contains which molecular tag?

A. Glycoprotein

B. ATP

C. Mannose-6-phosphate

D. Cholesterol

C. Mannose-6-phosphate

Why is Mannose-6-phosphate added?

A. ATP production

B. Protein secretion

C. Lysosomal targeting

D. DNA replication

C. Lysosomal targeting

A patient has elevated very-long-chain fatty acids.

Which organelle is defective?

A. Golgi

B. Peroxisome

C. Lysosome

D. SER

B. Peroxisome

Place these organelles in the correct sequence for secretion of insulin.

A.
Golgi → RER → Ribosome → Plasma membrane

B.
Ribosome → Rough ER → Golgi → Secretory vesicle

C.
Nucleus → Lysosome → Golgi

D.
SER → Golgi → Cytoplasm

B.
Ribosome → Rough ER → Golgi → Secretory vesicle

Protein synthesis begins in

A. Nucleus

B. Ribosome

C. Golgi

D. Lysosome

B. Ribosome

Protein glycosylation begins in

A. SER

B. RER

C. Lysosome

D. Peroxisome

B. RER

Final protein sorting occurs in

A. Golgi apparatus

B. SER

C. Nucleus

D. Cytoplasm

A. Golgi apparatus

Lysosomal hydrolases receive which modification?

A. ATP

B. Mannose-6-phosphate

C. Cholesterol

D. Ubiquitin

B. Mannose-6-phosphate

A child develops recurrent strokes, seizures, muscle weakness, and lactic acidosis.

Which organelle is defective?

A. Lysosome

B. Mitochondria

C. Golgi

D. Rough ER

B. Mitochondria

Diagnosis:
MELAS syndrome

Why does MELAS primarily affect muscles and the nervous system?

A. They lack lysosomes

B. They require large amounts of ATP

C. They lack nuclei

D. They contain no ribosomes

B. They require large amounts of ATP

A mutation affects mitochondrial DNA.

Which inheritance pattern is expected?

A. Autosomal dominant

B. Autosomal recessive

C. Maternal inheritance

D. X-linked

C. Maternal inheritance

Which organelle contains its own DNA?

A. Golgi

B. Mitochondria

C. Lysosome

D. SER

B. Mitochondria

A free radical damages membrane lipids.

The process is called

A. Glycosylation

B. Lipid peroxidation

C. Hydrolysis

D. Glycolysis

B. Lipid peroxidation

Which vitamin deficiency would impair wound healing?

A. Vitamin B1

B. Vitamin B2

C. Vitamin C

D. Vitamin K

C. Vitamin C

Iron deficiency primarily impairs

A. DNA synthesis

B. Oxygen transport

C. Lipid synthesis

D. ATP production

B. Oxygen transport

A bodybuilder takes anabolic steroids.

Which organelle becomes highly active?

A. Rough ER

B. Smooth ER

C. Lysosome

D. Peroxisome

B. Smooth ER

Macrophages digest bacteria primarily through

A. Exocytosis

B. Phagocytosis

C. Diffusion

D. Osmosis

B. Phagocytosis

An old mitochondrion is recycled by the cell.

Which process is responsible?

A. Endocytosis

B. Exocytosis

C. Autophagy

D. Pinocytosis

C. Autophagy

Which organelle is known as the "command center" of the cell?

A. Golgi apparatus
B. Nucleus
C. Lysosome
D. Ribosome

B. Nucleus

The plasma membrane is primarily composed of

A. Protein monolayer
B. Lipid bilayer with embedded proteins
C. Cellulose
D. Triglycerides

B. Lipid bilayer with embedded proteins

Which membrane component maintains membrane fluidity?

A. Glycoproteins
B. Cholesterol
C. Actin
D. ATP

B. Cholesterol

Which organelle performs glycolysis?

A. Cytosol
B. Mitochondria
C. Golgi
D. Lysosome

A. Cytosol

Which metabolic pathway occurs exclusively inside mitochondria?

A. Glycolysis
B. Pentose phosphate pathway
C. Electron transport chain
D. Glycogen synthesis

C. Electron transport chain

The nucleolus is responsible for

A. DNA replication

B. ATP production

C. Ribosomal RNA synthesis

D. Lipid synthesis

C. Ribosomal RNA synthesis

Bound ribosomes synthesize proteins destined for

A. Cytoplasm

B. Nucleus

C. Secretion

D. Mitochondria

C. Secretion

Free ribosomes synthesize proteins destined for

A. Lysosomes

B. Cell membrane

C. Cytoplasm

D. Extracellular space

C. Cytoplasm

Which organelle detoxifies drugs?

A. Golgi

B. Rough ER

C. Smooth ER

D. Lysosome

C. Smooth ER

Cytochrome P450 enzymes are primarily located in

A. Mitochondria

B. Smooth ER

C. Lysosomes

D. Nucleus

B. Smooth ER

Why are phospholipids called amphipathic molecules?

A. They contain ATP

B. They have hydrophilic heads and hydrophobic tails

C. They produce energy

D. They are enzymes

B. They have hydrophilic heads and hydrophobic tails

Why would cholesterol be important during cold temperatures?

A. Prevents excessive membrane rigidity

B. Produces ATP

C. Synthesizes proteins

D. Increases DNA replication

A. Prevents excessive membrane rigidity

A mutation causes proteins to misfold in the Rough ER.

What happens first?

A. Secreted immediately

B. Stored in lysosomes

C. Retained inside ER

D. Stored in Golgi

C. Retained inside ER

Why does the Rough ER contain ribosomes?

A. To synthesize proteins

B. Produce ATP

C. Digest bacteria

D. Detoxify drugs

A. To synthesize proteins

Which organelle performs quality control of newly synthesized proteins?

A. Golgi

B. Rough ER

C. Mitochondria

D. Peroxisome

B. Rough ER

Which organelle is responsible for DNA replication?

A. Golgi apparatus
B. Rough ER
C. Nucleus
D. Ribosome

C. Nucleus

Which intracellular compartment contains approximately 50–60% of the cell volume?

A. Nucleus
B. Cytosol
C. Golgi
D. Lysosome

The Hexose Monophosphate (HMP) shunt occurs primarily in the

A. Cytosol

B. Nucleus

C. Golgi

D. Mitochondria

A. Cytosol

Which organelle performs O-linked glycosylation?

A. Rough ER

B. Golgi apparatus

C. SER

D. Nucleus

B. Golgi apparatus

Which organelle contains acid hydrolases?

A. Golgi

B. Lysosome

C. Peroxisome

D. Mitochondria

B. Lysosome

The optimal pH inside lysosomes is approximately

A. 2

B. 5

C. 7.4

D. 9

B. 5

Which enzyme maintains lysosomal acidity?

A. ATP synthase

B. Na-K ATPase

C. Vesicular H⁺ ATPase

D. Catalase

C. Vesicular H⁺ ATPase

Peroxisomes contain abundant

A. DNA polymerase

B. Catalase

C. RNA polymerase

D. Acid phosphatase

B. Catalase

Peroxisomes primarily metabolize

A. Short-chain fatty acids

B. Very long-chain fatty acids

C. Glycogen

D. Glucose

B. Very long-chain fatty acids

Why is the plasma membrane considered selectively permeable?

A. All substances diffuse freely.

B. Only proteins cross.

C. Membrane proteins regulate movement of selected molecules.

D. Water cannot cross.

C. Membrane proteins regulate movement of selected molecules.

Why would destruction of membrane cholesterol make cells more fragile?

A. Cholesterol increases DNA synthesis.

B. Cholesterol stabilizes membrane fluidity.

C. Cholesterol produces ATP.

D. Cholesterol activates ribosomes.

B. Cholesterol stabilizes membrane fluidity.

Why are lysosomal enzymes inactive when accidentally released into the cytoplasm?

A. Lack of ATP

B. Neutral cytoplasmic pH

C. Lack of calcium

D. Absence of glucose

B. Neutral cytoplasmic pH

Why is compartmentalization important inside cells?

A. Organelles work independently.

B. Different biochemical reactions require different environments.

C. Organelles produce ATP equally.

D. DNA replication occurs everywhere.

B. Different biochemical reactions require different environments.

Why does the Golgi apparatus have a cis and trans face?

A. To increase ATP production

B. To establish directional protein processing

C. To store DNA

D. To degrade proteins

B. To establish directional protein processing

A patient with chronic alcoholism develops severe oxidative stress.

Which cellular component is damaged first?

A. DNA

B. Plasma membrane lipids

C. Ribosomes

D. Centrioles

B. Plasma membrane lipids

Which biochemical process explains membrane damage after reperfusion injury?

A. Glycolysis

B. Lipid peroxidation

C. Glycogenesis

D. DNA methylation

B. Lipid peroxidation

A liver biopsy shows abundant Smooth ER.

Which patient most likely has this finding?

A. Heavy alcohol drinker

B. Marathon runner

C. Patient with bacterial pneumonia

D. Patient with anemia

A. Heavy alcohol drinker

Which organ enlarges after chronic phenobarbital therapy?

A. Lysosomes

B. Smooth ER

C. Golgi

D. Ribosomes

B. Smooth ER

A bodybuilder taking anabolic steroids develops increased SER activity because steroid hormones are synthesized in the

A. Golgi

B. SER

C. RER

D. Lysosome

B. SER

Electron microscopy shows numerous flattened sacs covered with ribosomes.

Identify the organelle.

A. Golgi

B. SER

C. Rough ER

D. Peroxisome

C. Rough ER

A cell specializing in protein secretion would have abundant

A. Smooth ER

B. Rough ER

C. Lysosomes

D. Peroxisomes

B. Rough ER

A hepatocyte rich in detoxification enzymes will have extensive

A. SER

B. Golgi

C. Lysosome

D. Nucleolus

A. SER

A circular organelle with numerous internal folds is shown.

The folds are called

A. Cisternae

B. Cristae

C. Lamellae

D. Microvilli

B. Cristae

A micrograph shows stacked flattened sacs with budding vesicles.

Identify the organelle.

A. Golgi

B. Rough ER

C. SER

D. Mitochondria

A. Golgi

An EM image demonstrates many small dense vesicles filled with hydrolytic enzymes.

Identify the organelle.

A. Lysosome

B. Peroxisome

C. Golgi

D. Endosome

A. Lysosome

A newborn has hepatomegaly and severe emphysema later in life.

Misfolded proteins accumulate inside hepatocytes.

Which protein is defective?

A. Collagen

B. Alpha-1 antitrypsin

C. Albumin

D. Hemoglobin

B. Alpha-1 antitrypsin

A child presents with hypotonia, cardiomegaly, and glycogen-filled lysosomes.

Most likely diagnosis?

A. McArdle disease

B. Pompe disease

C. Tay-Sachs

D. Von Gierke disease

B. Pompe disease

Which enzyme replacement therapy would benefit this patient?

A. Acid α-glucosidase

B. Hexosaminidase

C. Catalase

D. ATP synthase

A. Acid α-glucosidase

During prolonged exercise ATP demand increases dramatically.

Which organelle primarily meets this demand?

A. Nucleus

B. Golgi

C. Mitochondria

D. SER

C. Mitochondria

Cardiac muscle contains many mitochondria because it

A. Stores glycogen

B. Performs continuous aerobic metabolism

C. Synthesizes antibodies

D. Produces hormones

B. Performs continuous aerobic metabolism

Which tissue has the greatest mitochondrial density?

A. Skeletal muscle

B. Cardiac muscle

C. Adipose tissue

D. Epidermis

B. Cardiac muscle

Which cell would contain the most Rough ER?

A. Plasma cell

B. Adipocyte

C. Neuron

D. RBC

A. Plasma cell

Which cell contains abundant SER?

A. Plasma cell

B. Adrenal cortex cell

C. Fibroblast

D. Chondrocyte

B. Adrenal cortex cell

A mutation affecting mitochondrial DNA is transmitted through

A. Father only

B. Mother only

C. Both parents equally

D. Y chromosome

B. Mother only

During embryonic development, failure of protein folding would most directly affect

A. Rough ER

B. Golgi

C. Lysosome

D. Nucleus

A. Rough ER

A patient has elevated serum lysosomal enzymes but deficient intracellular lysosomal enzymes.

Which diagnosis best explains these findings?

A. Gaucher disease

B. Pompe disease

C. I-cell disease

D. Tay-Sachs

C. I-cell disease

A biopsy demonstrates numerous autophagosomes.

Which cellular process is occurring?

A. DNA replication

B. Cellular recycling

C. Protein secretion

D. Lipid synthesis

B. Cellular recycling

A phosphotransferase deficiency prevents Mannose-6-phosphate formation.

What happens next?

A. Lysosomal enzymes accumulate inside Golgi.

B. Lysosomal enzymes are secreted extracellularly.

C. Lysosomes become more acidic.

D. ATP production increases.

B. Lysosomal enzymes are secreted extracellularly.

Which sequence correctly describes the path of a secreted protein?

A.
Ribosome → Golgi → Rough ER

B.
Rough ER → Ribosome → Golgi

C.
Ribosome → Rough ER → Golgi → Secretory vesicle → Plasma membrane

D.
Golgi → Lysosome → Plasma membrane

C.
Ribosome → Rough ER → Golgi → Secretory vesicle → Plasma membrane

A researcher genetically deletes the signal peptide of insulin. What is the most likely consequence?

A. Insulin will be secreted normally.

B. Insulin will remain in the cytosol because it cannot enter the rough ER.

C. Insulin will be transported directly to the Golgi.

D. Insulin synthesis will stop completely.

B. Insulin will remain in the cytosol because it cannot enter the rough ER.

A mutation causes loss of vesicular H⁺-ATPase function in lysosomes. Which cellular process would be most impaired?

A. DNA replication

B. Protein translation

C. Intracellular digestion due to failure to maintain an acidic lysosomal pH

D. Cholesterol synthesis

C. Intracellular digestion due to failure to maintain an acidic lysosomal pH

A hepatocyte is exposed to high concentrations of carbon tetrachloride (CCl₄), generating excessive free radicals. Which sequence best explains the resulting cell injury?

A. Increased ATP production → membrane stabilization → cell survival

B. Lipid peroxidation → membrane disruption → loss of homeostasis → necrosis/apoptosis

C. DNA replication → mitochondrial proliferation → recovery

D. Golgi hypertrophy → increased secretion → repair

B. Lipid peroxidation → membrane disruption → loss of homeostasis → necrosis/apoptosis

A patient has a hereditary disorder preventing degradation of very long-chain fatty acids (VLCFAs). Which additional abnormality would most likely occur?

A. Increased glycogen storage

B. Defective plasmalogen synthesis affecting myelin

C. Failure of N-linked glycosylation

D. Reduced rRNA synthesis

B. Defective plasmalogen synthesis affecting myelin

A scientist experimentally blocks COPII-coated vesicle formation from the rough ER. Which process would be directly affected first?

A. DNA replication

B. Transport of newly synthesized proteins to the Golgi apparatus

C. Mitochondrial ATP synthesis

D. Lysosomal degradation

B. Transport of newly synthesized proteins to the Golgi apparatus

What serves as cofactors in metabolic processes in the entire body?

Nutrients

What is the difference between Thiamine, Riboflavin, and Folate?

Thiamine (B1) for energy production, digestion and nerve function

Riboflavin (B2) for energy creation, body growth and fundamental cell function

Folate (B9) reduces birth defects and drives ongoing cell renewal

What are the chemical cofactors in the metabolic processes throughout the body?

Micronutrients

What is MELAS syndrome?

Caused by mutations in the mtDNA that impairs the mitochondria’s ability to produce energy.

Typically maternally inherited

Stands for Mitochondrial Encephalomyopathy, LActic Aciddosis, and Stroke like episodes

Basic overview of the processes of ATP production

"GPKEA" (pronounced "gee-pee-kay")

• G = Glycolysis

• P = Pyruvate → Acetyl-CoA

• K = Krebs (TCA) cycle

• E = Electron Transport Chain

• A = ATP Synthase

Remember: ATP is made a little in glycolysis, a little in the Krebs cycle, but mostly by ATP synthase after the electron transport chain creates the proton gradient. This overall concept is one of the highest-yield topics in first-year medical biochemistry.