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My MCAT > Biology Chapter 1 > Flashcards

Biology Chapter 1 Flashcards

1
Q

Number of cells in body

A

37 trillion cells in body

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2
Q

Cell theory history

A

1674 - anton van Leeuwenhoek was first person view living cell under a microscope Cells can be separated Function of tissue depends on function of cell Diseased cells can arise in normal cells 1850 Rudolph Virchow

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3
Q

Cell theory

A

All living things are composed of cells The cell is the basic functional unit of life Cells arise only from preexisting cells Cells carry genetic information in the form of deoxyribonucleic acid (DNA). This genetic material is passed on from parent to daughter cell

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4
Q

Cell theory and viruses

A

Viruses - small structures that contain genetic material Unable to reproduce on their own: Violates cell theory Some have RNA as genetic material: Violates cell theory Viruses are NOT considered living organisms

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5
Q

Eukaryotic Cells

A
  • Eukaryotic organisms can be uni- or multicellular
  • Contain a true nucleus
  • Major organelles:
    • Golgi apparatus
    • Endoplasmic reticulum
    • Ribosomes
    • Cytoplasm
    • Mitochondrion
    • Lysosome
    • Nuclear membrane
    • Cell membrane
    • Endocytotic vesicle
    • Centrioles
    • Nucleolus
    • Nucleus
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6
Q

Eukaryotic Cell Structure

A
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7
Q

Membrane-bound organelles

A

Cell membrane encloses a semifluid cytosol with organelles

In eukaryotic cells, most are membrane-bound

Allows compartmentalization of functions

Membranes consist of phospholipid bilayer

Surfaces hydrophilic

Interacts with aqueous environments (in and out of cell)

Inner-membrane = hydrophobic

Provides selective barrier

Cytosol: allows diffusion of molecules throughout cell

Nucleus: genetic material encoded in DNA

Organized into chromosomes

Reproduce by mitosis - forms 2 identical duaghter cells

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8
Q

The Nucleus

A

Control center

Contains genetic information for replication

Surrounded by nuclear membrane (envelope)

Nuclear pores allows exchange between cytoplasm and nucleus

Genes: coding regions of DNA

Histones: proteins that linear DNA wraps around

Chromosomes: wound DNA

DNA in nucleus allows DNA transcription to be separate from RNA translation

Nucleolus: subsection

rRNA is synthesized

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9
Q

Mitochondria

A

Power plants of the cell (metabolic function)

Contains 2 layers

Outer membrane:

Barrier

Inner membrane:

Many foldings (cristae)

Contains molecules and enzymes necessary for electron transport

Increases surface area

Intermembrane space: space between inner and outer membrane

Mitochondrial matrix: space inside inner membrane

Pumping protons from matric to intermembrane space establishes the proton-motive force

Protons flow through ATP synthase - generates ATP during oxidative phosphorylation

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10
Q

Mitochondrial Structure

A
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11
Q

Mitochondrial DNA

A

Mitochondria is semi-autonomous

Contain own genes

Replicates independently of nucleus via binary fission

Cytoplasmic or extranuclear inheritance: transmission of genetic material independent from nucleus

Thought to have evolved from anaerobic prokaryote engulfing an aerobic prokaryote and establishing a symbiotic relationship

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12
Q

Mitochondria and Apoptosis

A

Capable of killing the cell

Release enzymes from electron transport chain

Kick-starts apoptosis

Apoptosis = programmed cell death

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13
Q

Lysosomes

A

Membrane-bound structures

Contains hydrolytic enzymes

Capable of breaking down many substrates

Lysosomal membrane sequesters enzymes to prevent damage to the cell

Autolysis: release of enzymes to induce apoptosis

Leads to degradation of cellular components

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14
Q

Endoplasmic Reticulum (ER)

A

ER: series of interconnected membranes

Contiguous with nuclear envelope

Double membrane is folded into numerous invaginations

Creates complex structures and central lumen

Two types of ER

Smooth ER

Lipid synthesis

Detoxification of some drugs/poisons

Transports proteins from RER to Golgi apparatus

Rough ER: studded with ribosomes

Translates proteins destined for secretion in lumen

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15
Q

Golgi Apparatus

A

Consists of stacked membrane-bound sacs

Materials come in vesicles from ER

May be modified with addition of carbohydrates, phosphates, and sulfates

May introduce signal sequences (directs delivery to a certain location)

Products are sorted and repackaged in vesicles

Vesicles are transferred to correct location

Exocytosis: secretory vesicles merge with cell membrane to release contents

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16
Q

Peroxisomes

A

Contain hydrogen peroxide

Breaks down long chain fatty acids via 𝛃-oxidation

Participate in synthesis of phospholipids

Contain some enzymes involved in pentose phosphate pathway

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17
Q

The Cytoskeleton

A

Provides structure to the cell

Helps maintain shape

Provides conduit for transport of materials around cell

Three components:

Microfilaments

Microtubules

Intermediate filaments

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18
Q

Microfilaments

A

Provides structure to the cell

Helps maintain shape

Provides conduit for transport of materials around cell

Three components:

Microfilaments

Microtubules

Intermediate filaments

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19
Q

Microtubules

A

Hollow polymers of tubulin proteins

Radiate throughout cell

Provides primary pathways that motor proteins like kinesin and dynein carry vesicles

Form cilia and flagella (motile structures)

Cilia: projections from cell that are involved in movements of materials along the surface of the cell (respiratory tract)

Flagella: involved in the movement of the cell itself (sperm cells)

9+2 structure: 9 pairs of microtubules form outer ring, 2 microtubules in the center

Only seen in eukaryotic organelles of motility

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20
Q

Centrioles

A

Found in the centrosome

Organizing centers for microtubules

Structures as 9 triplets of microtubules with hollow center

During mitosis, they migrate to opposite poles of the cell and organize mitotic spindle

Kinetochores: microtubules emanating from centrioles that attach to chromosomes to pull sister chromatids apart

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21
Q

Intermediate Filaments

A

Diverse group of filamentous proteins

Keratin

Desmin

Vimentin

Lamins

Many involved in cell-cell adhesion or integrity of cytoskeleton

Able to withstand tremendous tension

Makes structure more rigid

Help to anchor other organelles (nucleus

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22
Q

Tissue Formation

A

Characteristic of eukaryotic cells: different cells in a tissue perform different functions

Heart cells: different cells conduct, contract, and provide support

Four tissue types

Epithelial

Connective

Muscle

Nervous

23
Q

Epithelial Tissue

A

Covers body and lines cavity

Provides protection against pathogens

Have many functions; some involved in absorption, secretion, and sensation

Joined tightly together to be cohesive unit

Basement membrane: connective tissue tightly joined to epithelial cells

Parenchyma: functional part of organ

Many epithelials make-up parenchyma

Nephrons in kidney

Hepatocytes in liver

Acid-producing cells in stomach

Often polarized (one side faces lumen/outside world, other side interacts with blood vessels and other cells

Small intestine: one side involved with absorption, other with release of nutrients

Classified by number of layers and shape

Simple epithelia: one layer of cells

Stratified epithelia: multiple layers

Pseudostratified epithelia: appear to have multiple layers (height differences in cells, but is one layer

Cuboidal: cube-shape

Columnar: long and thin

Squamous: flat and scale-like

24
Q

Connective Tissue

A

Supports the body

Provides framework for epithelial cells to carry out their functions

Stroma: support structure

Bone

Cartilage

Tendons

Ligaments

Adipose tissue

Blood

Many produce and secrete materials (collagen and elastin)

Forms extracellular matrix

25
Q

Prokaryotes

A

Prokaryotes are simplest organisms

Includes all bacteria

No membrane-bound organelles

Nucleoid region: single circular molecule of DNA

Incredibly diverse

Many cause infections

26
Q

Prokaryotic Domains

A

Three domains organisms are classified in

Archaea

Bacteria

Eukarya

Archaea and bacteria contain prokaryotes

27
Q

Archaea

A

Single-celled organisms

Visually similar to bacteria

Contain genes and many metabolic pathways that are similar to eukaryotes

Some are extremophiles (live in environments of high heat, salinity, no light, etc.

Able to use alternate sources of energy

Some are chemosynthetic (can generate energy from inorganic compounds like sulfur and nitrogen-based compounds)

28
Q

Archaea’s Similarities to Eukaryotes

A

Hypothesized that they share a common origin

Both start translation with methionine

Both contain similar RNA polymerases

Both associated their DNA with histones

Archaea contain single circular chromosomes, divide by binary fission or budding, and are similar in structure to bacteria

Archaea are resistant to many antibiotics

29
Q

Bacteria

A

Contain cell membrane and cytoplasm

Some have flagella or fimbriae

Eukaryotes and bacteria sometimes have analogous structures

Makes it hard to make antibiotics target only bacteria

Sometimes structures have enough biochemical differences to allow targeting (flagella vs cilia; ribosomes)

Appx 5 x 1030 bacteria on earth

Outnumber plants and animals combined

30
Q

Bacteria and Humans

A

More bacteria in human body than human cells (10:1)

Mutualistic symbiotes: both humans and bacteria benefit from the relationship

Some microbiota produce vit K and biotin (vit B7) and prevent growth of pathogenic bacteria

Pathogenic bacteria (parasites) cause disease to host

Can live intra- or extracellularly

Chlamydia trachomatis - lives inside reproductive tract cells

Clostridium tetani - lives outside of cells and produces toxins that enter the bloodstream

31
Q

Classification of Bacteria by Shape

A

Provides a common language to talk about and identify bacteria

3 common shapes:

Cocci: spherical

Bacilli: rod-shaped

Spirilli: spiral-shaped

32
Q

Aerobes and anaerobes

A

Obligate aerobes: bacteria that require oxygen for metabolism

Anaerobes: bacteria that do not require oxygen for metabolism

Obligate anaerobes: can’t survive in oxygen-containing environment

Oxygen produces reactive oxygen-containing radicals that leads to death

Facultative anaerobes: can switch to using oxygen when present or perform anaerobic metabolism if not

Aerotolerant anaerobes: unable to use oxygen but not harmed by the presence

33
Q

Prokaryotic Cell structure

A

Differences between eukaryotes:

Lack nucleus and membrane-bound organelles

Single-celled organism (each cell performs all necessary functions for life)

May live in colonies and signal to each other about environment

34
Q

Cell Wall

A

Forms outer barrier of cell

Protects from environment

Provides structure

Controls movement of solutes in and out

Maintains concentration gradients

Cell membrane (plasma membrane) is beneath cell wall

Contains phospholipids

Envelope = Cell wall + Cell membrane

2 Types of cell walls:

Gram positive

Gram negative

35
Q

Gram Stain

A

Determines if cells are Gram-positive or Gram-negative

Process:

Crystal violet

Alcohol

Water

Counterstain (safranin)

Water

If purple: gram positive

If red: gram negative

36
Q

Gram Positive Cells

A

Contain thick layer of peptidoglycan

Polymeric compound made of amino acids and sugars

May aid pathogenic bacteria from being harmed from host’s immune system

Contains lipoteichoic acid

Function unknown

May activate human immune system

37
Q

Gram Negative Cells

A

Cell walls are very thin

Contain smaller amounts of peptidoglycan

Cell wall touches cell membrane

Have outer membranes

Contains phospholipids and lipopolysaccharides

Lipopolysaccharides triggers an immune response stronger than when triggered by lipoteichoic acid

38
Q

Flagella

A

Long, whip-like structures used for propulsion

May have many

Chemotaxis: ability to detect chemical stimulus and move away or towards

Composition:

Filament: helical structure composed of flagellin

Basal body: anchors flagellum to cytoplasmic membrane; motor (can rotate up to 300 Hz)

Hook: connects filament and basal body (causes rotation to exert torque on filament - can spin and propel bacterium forward)

Similar in gram positive and negative (slight differences)

39
Q

Flagella Structure

A
40
Q

Other organelles

A

Have nucleoid region where DNA is concentrated

No nuclear envelope or histones

Singular circular chromosome

Plasmids: DNA acquired from external sources

Small circular structures

Not necessary for survival - not part of genome, but may be advantageous

Cell membrane: used for electron transport chain

Generates ATP

Primitive cytoskeleton

Ribosomes: contain 30S and 50S subunits

Eukaryotic contain 40S and 60D

41
Q

Genetics and Growth of Prokaryotes

A

Prokaryotes reproduce asexually through binary fission

Prokaryotes can acquire genetic material from outside the cell and use it

42
Q

Binary Fission

A

Simple form of asexual reproduction

Steps:

Circular chromosome attaches to cell wall and replicates

Cell continues to grow in size

Plasma membrane and cell wall grow inward along midline

Two identical daughter cells are produced

Can proceed more rapidly than mitosis

43
Q

Genetic Recombination

A

Nucleoid contains genome - necessary information

Plasmids are extragenomic material that are beneficial to the bacterium, but not necessary

May contain virulence factors: traits that increase how pathogenic the bacterium is to the host

Episomes: subset of plasmids that can integrate into genome of bacteria

Increases diversity - permits evolution over time

Process includes:

Transformation

Conjugation

Transduction

44
Q

Genetic Recombination - Transformation

A

Integration of foreign genetic material into host genome

Foreign material often from other bacteria that have been lysed and spill their contents

Many gram-negative rods are able to carry out transformation

45
Q

Genetic Recombination - Conjugation

A

Bacterial form of sexual reproduction

Two cells form conjugation bridge that allows transfer of genetic material

Transfer is unidirectional

From donor male (+) → recipient female (-)

Bridge made from sex pili found on donor male

Must contain sex factor plasmids

F (fertility) factor: commonly studied sex factor

Bacteria with F factor are F+, those without are F-

F+ replicates F factor and donates copy

Allows rapid acquisition of antibiotic resistance or virulent factors

Sex factor is a plasmid - but through transformation it can become incorporated in the genome

Entire genome will copy during conjugation to donate, but bridge often breaks before full genome is transferred

These cells are referred to as high frequency of recombination (Hfr)

46
Q

Genetic Recombination - Transduction

A

Requires a vector - a virus that carries genetic material from one bacterium to another

Viruses (obligate intracellular pathogens)

Bacteriophages: viruses that infect bacteria

Can trap segments of host DNA, when it infects a new bacterium, it can release this DNA into new host

This DNA can then integrate into new hosts genome - gives new/additional genes

47
Q

Bacterial Growth

A

Binary fission implies that all bacteria are exactly the same in a local colony (no mutations or recombination) and all bacteria will divide at same speed

Bacteria grow in series of phases

Lag phase: adapt to new local condition - no growth

Exponential phase: growth increases exponentially

Stationary phase: resources reduced due to growth - no growth

Death phase: exceed ability of environment to support growth, death occurs due to lack of resources

48
Q

Transposons

A

Genetic elements capable of inserting and removing themselves from the genome

Seen in eukaryotes as well

If inserted into a coding region of a gene, gene may be disrupted

49
Q

Viruses and Subviral particles

A

Viruses are not living - they are acellular

Can be as small as 20 nm or as large as 300 nm

Lack organelles and a nucleus

50
Q

Viral Structure

A

Composed of: genetic material, protein coat (capsid), sometimes a lipid envelope

Genetic information can be circular, linear, single- or double-stranded, and composed of RNA or DNA

Capsid: composed of phospholipids and virus-specific proteins

Envelop: sensitive to heat, detergents, and desiccation

Easier to kill

Non-enveloped viruses: more resistant to sterilization and likely to persist on surfaces for an extended time

51
Q

Obligate Intracellular parasites

A

Viruses cannot reproduce independently

Express and replicate within a host - lack ribosomes to carry out protein synthesis

Virions: viral progeny that can be released and infect other cells

Bacteriophages: viruses that specifically target bacteria

Do not enter, just inject genetic material

Contain tail sheath (acts as a syringe to inject material) and tail fibers (help bacteriophage to recognize and connect to correct cell)

52
Q

Bacteriophage structure

A
53
Q

Viral Genome

A

Variety of shapes and sizes

Some have a few genes, others hundreds

Some DNA, other RNA and single- or double-stranded in either case

Single-stranded RNA can be positive or negative sense

Positive sense: genome can directly translate into functional proteins by ribosomes of host (like mRNA

Negative sense: genome needs synthesis of complementary strand to then translate

Must carry RNA replicase to replicate a complementary strand

Retroviruses: enveloped, single-stranded RNA viruses

Retroviridae family

Contains 2 identical RNA molecules

Contains reverse transcriptase - synthesizes DNA from sRNA

DNA then integrates into host genome ere is it replicated and transcribed

Causes cell to indefinitely be infected - to kill the virus, you must kill the host cell

HIV is a retrovirus - why it is so hard to treat

54
Q

Viral Life Cycle - Infection

A

Viruses can only infect cells that they are able to bind with

Without correct receptor, the virus is “blind” to the cell

Once virus is bound, it is brought close to cell to allow additional interactions

Enveloped viruses fuse with plasma membrane of cell to allow entry

Host cell may confuse virus with a nutrient and bring it into the cytoplasm via endocytosis

Bacteriophages use tail fibers to anchor to cell and inject genome (tail sheath)

Some tail fibers are enzymatic - creates pores in cell membrane

Different portion of virion will be inserted into host cell depending on the type of virus

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