MCAT Biology Study Material - Chapter 1: The Cell Flashcards

Robert Hooke

Created the first microscope to visualize cells

Also, Hooke's Law (F=-kx)

Cell Theory

1. All living things are composed of cells

2. Cells are the basic units of structure and function in living things

3. New cells are produced from existing cells

More Recent Addition:

4. Cells carry genetic information in the form of deoxyribonucleic acid (DNA). This genetic material is passed on from parent to daughter cell.

serial endosymbiosis theory

attempts to explain the formation of some of the membrane bound organelles

posits that these organelles formed by engulfing of one prokaryote by another and the establishment of a symbiotic relationship between the two

in addition to mitochondria, chloroplasts in plant cells and organelles of motility (flagella) are believed to have evolved through this process

Cilia

Hairlike projections that extend from the plasma membrane and are used for locomotion

eukaryotic have a 9+2 Structure

Flagella

structures involved in the movement of the cell

eukaryotic have a 9+2 Structure

9+2 structure of cilia and flagella

Eukaryotic cilia and flagella have 9 pairs of microtubules creating an outer ring which surrounds two microtubules in the center

Centrioles

Structures located in the centrosome

organizing centers for microtubules

nine triplets of microtubules surrounding a hollow core

Nucleus

Stores genetic information

Site of transcription

Mitochondria

Involved in ATP production and apoptosis

Lysosomes

break down cellular waste products and endocytosed molecules

also involved in apoptosis

Smooth Endoplasmic Reticulum

lipid synthesis

detoxification

Rough Endoplasmic Reticulum (RER)

synthesizes proteins

Golgi apparatus

Packages, modifies, and distributes cellular products

Peroxisomes

break down fatty acids

synthesize lipids

contribute to the pentose phosphate pathway

produce hydrogen peroxide

A child is diagnosed with an enzyme deficiency that prevents the production of hydrogen peroxide. What would the likely outcome be of such a deficiency?

Peroxisome would not be able to digest long chain fatty acids

undigestible long chain fatty acids would build up in the peroxisome displacing cellular contents and resulting in cell death

What are the predominant proteins of microfilaments?

actin

What are the predominant proteins of microtubules?

tubulin

What are the predominant proteins of intermediate filaments?

keratin

desmin

vimentin

lamins

etc

How do the structures of centrioles differ from that of flagella?

Centrioles: 9 triplets of microtubules with hollow center

Flagella: 9 pairs of microtubules with 2 individual microtubules in the center

Classify as epithelial cells or connective tissue:

Fibroblasts, which produce collagen in a number of organs

Connective tissue

Classify as epithelial cells or connective tissue:

Endothelial cells, which line blood vessels

epithelial cells

Classify as epithelial cells or connective tissue:

alpha-cells, which produce glucagon in the pancreas

epithelial cells

Classify as epithelial cells or connective tissue:

Osteoblasts, which produce osteoid, the material that hardens into bone

Connective tissue

Classify as epithelial cells or connective tissue:

Chondroblasts, which produce cartilage

Connective tissue

Archaea

often extremophiles

harsh environments

alternative energy sources (chemical)

Bacterial shapes

Cocci: spherical

Bacilli: rod-shaped

Spirilli: Spiral-shaped

Facultative anaerobe

can survive with or without oxygen, can use oxygen

Aerotolerant anaerobes

can survive with or without oxygen, but do not use oxygen

Obligate anaerobes

Cannot survive in the presence of oxygen

Obligate aerobes

require oxygen

Prokaryotic flagella

longer projections that propel the prokaryotic cell through its liquid environment

In what ways are Archaea similar to bacteria?

both are single-celled organisms that lack a nucleus or membrane-bound organelles

contain a single circular chromosome

divide by binary fission or budding

In what ways are Archaea similar to eukaryotes?

Start translation with methionine

contain similar RNA polymerases

associate their DNA with histones

What difference between the envelopes of gram-positive and gram-negative bacteria make gram-positive bacteria more susceptible to antibiotics such as penicillin?

Penicillin targets the enzyme which cross-links peptidoglycan

Gram-positive bacteria have a thick layer of peptidoglycan, but no outer membrane

Gram-negative bacteria have a thin layer of peptidoglycan, but do have an outer membrane

Antibiotics like penicillin can more easily reach the peptidoglycan layer of the gram-positive bacteria

How do the structures of eukaryotic and prokaryotic flagella differ?

Eukaryotic: 9+2 microtubules

Prokaryotic: Filament + hook + basal body made of flagellin

Binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

Transformation

integration of foreign genetic material into the host genome

Conjugation

bacterial form of mating

formation of conjugation bridge and transfer of genetic material from the "donor male" to the "recipient female"

requires the sex factor for formation of the conjugation bridge

Transduction

Genetic recombination that requires a vector

Bacteriophage carries genetic info from one bacteria to another by mistake

Bacterial Growth Curve

A semilog plot

Lag phase

Exponential phase

Stationary phase

Death phase

Lag phase

bacteria adapt to new environment, little growth

log/exponential phase

bacteria use available resources to multiply at an exponential rate

stationary phase

bacterial multiplication slows as resources are used up

Death phase

Bacteria die as resources become insufficient to support the colony

Viral life cycle

infection, translation and progeny assembly, progeny release

Lytic cycle

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses

Lysogenic cycle

a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

Prions

infectious proteins

cause disease by triggering misfolding of other proteins

Viroids

small pathogens consisting of a very short circular single-stranded RNA that infect plants

Why are viruses considered obligate intracellular parasites?

Viruses do not contain organelles such as ribosomes for production of proteins and reproduction, so they must hijack the machinery of a host cell

Coronavirus, which causes the common cold, is described as an enveloped, single-stranded positive-sense RNA virus. What does this description indicate about the virus?

The virus is weaker due to the envelope rather than a protein capsid

The RNA does not have to enter the nucleus to be used by the host cell machinery

Briefly describe the pathway of retroviral nucleic acids from infection of a host cell to release of viral progeny

ssRNA to dsDNA to mRNA to Proteins and replicated viral ssRNA

What are the differences between the lytic and lysogenic cycles?

Lytic: Bacteriophage replicates in extremely high numbers causing the host to rupture

Lysogenic: Bacteriophage genome is incorporated into the host genome and replicates with the host cell, can be used to synthesize new virions upon the appropriate signal

How do prions cause disease?

Prions cause disease by triggering a change in the conformation of a protein from an alpha helix to a beta pleated sheet

This change reduces solubility of the protein and makes it highly resistant to degradation.

Hyperbaric oxygen may be used as a treatment for certain types of bacterial infections. In this therapy, the patient is placed in a chamber in which the partial pressure of oxygen is significantly increased, increasing the partial pressure of oxygen in the patient's tissues. This treatment is most likely used for infections with:

A. obligate aerobic bacteria

B. facultative anaerobic bacteria

C. aerotolerant anaerobic bacteria

D. obligate anaerobic bacteria

D. obligate anaerobic bacteria

Which of the following does NOT describe connective tissue cells?

A. They account for most cells in muscles, bones, and tendons

B. They secrete substances to form the extracellular matrix

C. In organs, they tend to form the stroma

D. In organs, they provide support for epithelial cells

A. They account for most cells in muscles, bones, and tendons

Which of the following types of nucleic acid could form the genome of a virus?

I. Single-Stranded RNA

II. Double-stranded DNA

III. Single-stranded RNA

A. I only

B. II only

C. I and II only

D. I, II, and III

D. I, II, and III

Which of the following activities occurs in the Golgi apparatus?

A. Synthesis of proteins

B. Modification and distribution of proteins

C. Breakdown of lipids and carbohydrates

D. Production of ATP

B. Modification and distribution of proteins

Mitochondrial DNA is:

I. circular

II. self-replicating

III. single-stranded

A. I only

B. II only

C. I and II only

D. I, II, and III

C. I and II only

Which of the following is NOT a function of the smooth endoplasmic reticulum?

A. Lipid synthesis

B. Poison detoxification

C. Protein synthesis

D. Transport of proteins

C. Protein synthesis

What is the main function of the nucleolus?

A. Ribosomal RNA Synthesis

B. DNA Replication

C. Cell Division

D. Transport of Proteins

A. Ribosomal RNA Synthesis

Which of the following organelles is surrounded by a single membrane?

A. Lysosomes

B. Mitochondria

C. Nuclei

D. Ribosomes

A. Lysosomes

Which of the following is NOT a difference that would allow one to distinguish a prokaryotic and a eukaryotic cell?

A. Ribosomal subunit weight

B. Presence of a nucleus

C. Presence of a membrane on the outside surface of the cell

D. Presence of membrane-bound organelles

C. Presence of a membrane on the outside surface of the cell

Which of the following does NOT contain tubulin?

A. Cilia

B. Flagella

C. Microfilaments

D. Centrioles

C. Microfilaments

Herpes simplex virus (HSV) enters the human body and remains dormant in the nervous system until it produces an outbreak after exposure to heat, radiation, or other stimuli. Which of the following statements correctly describes HSV?

A. While it remains dormant in the nervous system, the virus is in its lytic cycle.

B. During an outbreak, the virus is in the lysogenic cycle.

C. Herpes simplex virus adds its genetic information to the genetic information of the cell.

D. The herpes simplex virus contains a tail sheath and tail fibers.

C. Herpes simplex virus adds its genetic information to the genetic information of the cell

A and B have the terms flip-flopped. D describes bacteriophage features, not present in human viruses

Resistance to antibiotics is a well-recognized medical problem. Which mechanism(s) can account for a bacterium's ability to increase its genetic variability and thus adapt itself to resist different antibiotics?

I. Binary fission

II. Conjugation

III. Transduction

A. I and II only

B. I and III only

C. II and III only

D. I, II, and III

C. II and III only

A bacterial cell is noted to be resistant to penicillin. The bacterium is transferred to a colony that lacks the fertility factor, and the rest of the colony does not become resistant to penicillin. However, the penicillin-resistant cell has also started to exhibit other phenotypic characteristics, including secretion of a novel protein. Which of the following methods of bacterial recombination is NOT likely to account for this change?

A. Conjugation

B. Transformation

C. Transduction

D. Infection with a bacteriophage

A. Conjugation

In Alzheimer's disease, a protein called the amyloid precursor protein (APP) is cleaved to form a protein called beta-amyloid. This protein has a beta-pleated sheet structure and precipitates to form plaques in the brain. This mechanism of disease is most similar to which of the following pathogens?

A. Bacteria

B. Viruses

C. Prions

D. Viroids

C. Prions

After infection of a cell, a viral particle must transport itself to the nucleus in order to produce viral proteins. What is the likely genomic content of the virus?

A. Double-stranded DNA

B. Double-stranded RNA

C. Positive-sense RNA

D. Negative-sense RNA

A. Double-stranded DNA

A virus that requires nuclear transport likely requires use of the nuclear RNA polymerase to create mRNA. Thus only DNA viruses need to be transported to the nucleus to produce viral proteins