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MCAT Biology > Membrane Transport and Tissues > Flashcards

Membrane Transport and Tissues Flashcards

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1
Q

Phospholipid

A

Made up of a glycerol backbone with a phosphate group (phosphatidylcholine) and two fatty acid chains attached (for example, maybe oleic acid and palmitic acid)

Amphipathic: has polar and non polar regions

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2
Q

Micelle

A

A structure formed from phospholipids aggregating in an aqueous solution so that the polar heads are turned outward and nonpolar tails are turned inward

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3
Q



liposome

A

artificial phospholipid bilayer vesicle

formed from suspension of phospholipid molecules

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4
Q

Leaflets

A

Inner and outer layer of phospholipid bilayer membrane

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5
Q

Plasma membrane of Eukaryotic cell

A

Made up of phospholipid bilayer, contains glycolipids and steroids like cholesterol

Regulates substances that enter and leave cell as well as facilitating cell to cell communication

Glycolipids found on outer leafet only

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6
Q

Peripheral Proteins in Membrane

A

Aka extrinsic proteins

Located on surface of membrane and generally polar or hydrophilic, can’t flip sides easily

Can be ionically bonded to polar head of phospholipid or integral protein

Can contain a carbohydrate (would be a glycoprotein), carbohydrate protrude outside of cell

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7
Q

Integral Proteins in Membrane

A

Aka intrinsic proteins

Amphipathic proteins that can cross the membrane from inside of the cell to the outside

Can contain carbohydrate (making it a glycoprotein), carbohydrate protrude towards outer cell

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8
Q

Fluid mosaic model

A

Refers to the fluidity of the plasma membrane due to the ability of the phospholipids and proteins to slide past each other

Forces holding membrane together are intermolecular, parts can slide laterally, but not separate

Mosaic refers to asymmetrical layout of a membrane’s lipids and proteins

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9
Q

Membrane protein functions

A

Can act as:

  • transporters: proteins select which solutes to enter and exit
  • receptors: receive chemical signals from cellular environment
  • attachment sites: anchor to the cytoskeleton
  • identifiers: other cells can recognize
  • adhesive proteins: adhesion from one cell to the next
  • enzymes: control chemical reactions
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10
Q



Brownian Motion

A

The constant, irregular motion of very fine particles (such as fine dust or smoke) suspended in a fluid and observed with a microscope. Brownian motion is taken as evidence for molecules, which collide with the observed particles and cause the jitter motion.

Leads to the tendency of solutions to mixc completely with each other over time

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11
Q

Diffusion:

A

tendency of atoms, molecules, and ions in a liquid or air solution to move from areas of higher concentration to areas of lower concentration, thus becoming more evenly distributed. In general, diffusion is more rapid over shorter distances, larger concentration gradients, and higher temperatures.

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12
Q

Electrochemical Gradient

A

Combination of chemical concentration gradient and electrical gradient

Chemical concentration gradient:
Series of vectors pointing in direction of lower concentration for a solute

Electrical gradient:
Series of vectors pointing in the direction that a positively charged particle will tend to move

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13
Q

Membrane Permeability

A

Increasing polarity and size leads to decreased permeability in membrane

Large steroid hormone diffuses easily

Water diffuses slowly across membrane
Most diffusion of polar or small molecules takes place through incidental holes called leakage channels created by irregular shapes of integral proteins

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14
Q

Passive diffusion

A

Movement across the membrane through leakage channels without the assistance of membrane proteins

No ATP required, down the concentration gradient

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15
Q

Membrane channels

A

Aka carrier proteins

Proteins embedded in the cell membrane that assist molecules in moving across membrane

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16
Q

Facilitated Diffusion

A

Diffusion that occurs down the concentration gradient through membrane channels

No ATP required

Glucose transported this way

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17
Q

Active transport

A

Movement of a compound against its electrochemical gradient

Requires expenditure of energy

Primary active transport: direct use of ATP

Secondary active transport: ATP creates electrochemical gradient which is then used to acquire or expel a second molecules against its gradient

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18
Q

Osmotic Pressure

A

When concentrations of molecules on either side of membrane are not equal, a pulling pressure is generated to equal out the gradient

Water will move towards areas of higher concentration

Colligative property: based on the number of particles present rather than the type

19
Q

Endocytosis

A

Cells acquire substances from extracellular environment by membrane surrounding the contents and allowing the entry of a vesicles to the interior of the cell

Vesicle can fuse with Golgi apparatus or targeted for destruction by lysosome

20
Q

Phagocytosis

A

Cell membrane protrudes outward to engulf and envelop particulate matter

Triggered by binding of matter to protein receptors on cell

E.g., macrophages

21
Q

Pinocytosos

A

Extracellular fluid is engulfed by small invaginations of cell membrane

Performed by most cells in random non-selective fashion

22
Q

Receptor-mediated endocytosis

A

Specific uptake of macromolecules by ligand binding to receptor protein on cell membrane and then moved to a Claritin coated pit which forms a coated vesicle

Uptake of hormones or nutrients

23
Q

Exocytosis

A

Reverse of endocytosis, where substances leave the cell in a vesicle that fuses with the cell membrane

24
Q

Stages of cell cycle of typical somatic cell

A

First Growth phase (G1)
Synthesis (S)
Second Growth Phase (G2)
Mitosis or Meiosis (M)

Interphase: G1, S, G2

25
Q

G1 of Cell Cycle

A

Cell grows in size, producing new organelles and proteins

RNA and protein synthesis

ER creates phospholipids and new portions of the cell membrane as secretory vesicles

Cell growth assessed at G1 checkpoint

26
Q

G1 Cell Checkpoint

A

Assessed size of cell

If cell size is large enough (ratio of cytoplasm to DNA exceeds threshold), then cell moves to S phase, otherwise moves to G0 phase

27
Q

G0 Cell Cycle Phase

A

Non-growing state distinct from interphase

Causes variations in cell cycle length between cells

Some cells remain in G0 permanently (neurons)

28
Q

S Cell Cycle Phase

A

Cell focused on DNA replication, exact duplicate of each chromosome is created

Organelle and protein production slows

29
Q

G2 Cell Cycle Phase

A

Cellular organelles duplicate
RNA and protein synthesis
10-20% of cell life cycle

G2 checkpoint at end of the G2 checks for mitosis promoting factor

30
Q

G2 Cell Checkpoint

A

If mitosis promoting factor (MPF) is high enough, mitosis is triggered

31
Q

M Cell Checkpoint

A

End of Mitosis, checks if chromosomes are aligned correctly score dividing

32
Q

Two types of Cancer Mutations

A

Tumor repressor: deactivation of checkpoint protein

Oncogene: activation of a gene that causes proliferation of cell

33
Q

Fibroblast

A

Cells that can secrete fibrous proteins such as elastin and collagen which forms a molecular network that holds cells in place

Network known as extracellular matrix

34
Q

Extracellular Matrix

A

Molecular network that holds cells in place

Varies greatly from cell type to cell type
Can be liquid or solid

May provide structural support, determine cell shape and motility, and affect cell growth

35
Q

Three classes of molecules that comprise animal cell matrices

A
  1. Glycosaminoglycans and proteoglycans Provides pliability to matrix, over 90% of matrix by mass
    1. Structural proteins Provide matrix with strength (collagen)
    1. Adhesive proteins Help individual tissues stick together
36
Q

Basal lamina

A

Thin sheet of matrix material that separates epithelial cells from support tissue

Acts as a sieve-like barrier, selectively allowing passage of some molecules, but not others

37
Q

Glycocalyx

A

Separates cell membrane from ECM, some animal cells contain this layer

Involved in cell-to-cell recognition, adhesion, cell surface protection, and permeability

Same material as ECM

38
Q

Tight junctions

A

Form watertight seal from cell to cell that blocks water, ions, and other molecules from moving around and past cells

Barrier to protein movement between apical and basolateral surfaces of cell (apical side of cell faces lumen of cavity)

39
Q

Desmosomes

A

Join two cells at a single point, strongly attached directly to cytoskeleton of cell

Do not prevent fluid from circulating around cell, but found in tissues that experience a lot of stress due to sliding (skin or intestinal epithelium)

40
Q

Gap junctions

A

Small tunnels that connect cells, facilitate movement of small molecules and ions between cells

41
Q

Cell communication with non adjacent cells

A

Cell sends out chemical message or hormone which can picked up receptor of other cell

If hormone small and lipophilic (steroid), can cross membrane and bind to receptor in cell (cytosol or nucleus) to change transcription

If hormone large and lipophobic (protein), binds to receptor on surface of cell which can change membrane permeability, or deactivate/activate other membrane proteins, or activates an intracellular second messenger

42
Q

Intracellular second messenger

A

Activated as the second part of a signal cascade with a hormone binding to outside the cell possibly as first signal

cAMP, cGMP, or calmodulin

43
Q

Four types of tissue

A

Epithelial: separates free body surfaces from surroundings
Muscle
Connective: characterized by an extensive ECM (blood, lymph, bone, cartilage, connective tissue)
Nervous

44
Q

Organs

A

Various types of tissues work together to form

MCAT Biology (14 decks)

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