U1 Lecture 3

Question 1

Cell Theory

Answer 1

1. Cells are the ‘building blocks’ of animals and plants
2. Cells arise from pre-existing cells
3. Cells are the smallest unit having all the functions of living systems
4. Homeostasis of higher levels of biological organization arises from coordinated activity of cells

Question 2

Basic cell structure

Answer 2

• Plasma membrane = interaction surface between a cell and the world outside of it (aka cell membrane or plasmalemma)
• Nucleus = contains the genetic material of the cell
• Cytoplasm = everything between the membrane and nucleus

Question 3

Parts of the cytoplasm

Answer 3

• Intracellular fluid (the cytosol)

- subcellular structures w/ specific functions (organelles)

Question 4

Two categories of organelles

Answer 4

1. Membranous
   (endoplasmic reticulum, nucleus, mitochondria)
2. Non-membranous (cytoskeleton and ribosomes)

Question 5

Membrane composition

Answer 5

1. Lipid (membrane lipid = phospholipid)
2. Protein
3. Carbohydrate

Question 6

What is the structure of a phospholipid?

Answer 6

It’s an amphipathic molecule meaning it has a polar head and non-polar tail. I is capable of spontaneous ‘self-assembly’

Question 7

Phospholipid Bilayer

Answer 7

The non-polar tails of a phospholipid bond together causing the polar heads to be on the outside layer of the membrane

Question 8

What makes one region of plasma membrane different from another?

Answer 8

Membrane proteins confer different functionality (physiology) upon different membranes in cells

Question 9

Different types of amino acids

Answer 9

• Nonionized amino acid = amino base, carboxyl acid group and side chain
• Ionized amino acid = amino acid with R side chain
• Glycine = amino acid with side H
• Cysteine = amino acid with side S chain
• Tyrosine = amino acid with phenyol OH chain
• Lysine = amino acid with CH2 NH2 side chain

Question 10

Define lipophilic

Answer 10

Tending to combine with or dissolve in lipids or fats

Question 11

Define hydrophilic

Answer 11

Tending to combine or dissolve in water

Question 12

Integral membrane proteins

Answer 12

Proteins that are permanently connected to the cell membrane. Large sections of these proteins are embedded in the hydrophobic (middle) layer of the membrane… they can interact with the polar and non-polar parts of the membranous phospholipid bilayer because they are amphipathic.

Question 13

Peripheral membrane proteins

Answer 13

Proteins that have a weaker and temporary connection to the membrane. They just sit on the surface and are anchored by a few ionic bonds. They don’t bond with the non-polar region in the middle.

Question 14

Primary protein structure

Answer 14

Single sequence of amino acids connected by covalent peptide bonds formed into a chain

Question 15

Secondary protein structures

Answer 15

Two primary structures bonding and folding together to form alpha helices and beta strands

Question 16

Tertiary protein structures

Answer 16

Helices and strands folding together into domains

Question 17

Quaternary protein structures

Answer 17

Functional assemblies of chains (subunits)

Question 18

Why are membranes considered fluid structures?

Answer 18

• Membrane proteins are free to move laterally throughout the cell membrane
• proof: integral membrane proteins diffuse laterally in the plane of the plasma membrane