Biomolecules + Animal Cell Structure and Function

What are carbohydrates? What are they composed of?

What are carbohydrates? What are they composed of?

polymers of monosaccharides, composed of C, H, O

What type of linkage holds together glucose molecules?

alpha 1-4 glycosidic bonds

What are the three main places carbohydrates are found in the body?

muscle and liver (as glycogen), and blood glucose

What are the main functions of carbohydrates?

1.) Most serve body as fuel (Glucose used for ATP generation via cellular respiration and Glycogen used via gluconeogenesis to make glucose for energy)

2.) Supply carbons for synthesis of cell components (DNA, RNA)

3.) Form structural components of cells (Glycoproteins, glycolipids)

What are the main characteristics of starch?

• Is a polymer of 100s of glucose monomer (Amylose is the main form)

• Is the storage form of excess glucose in plants

• Found in a single chain

What are the main characteristics of glycogen?

• Polymer of 100s of glucose monomers and has a branched structure, allowing for greater energy extraction

• Main storage form of glucose in animals

In terms of bonds, what is the difference between types of bonds in starch and glycogen?

starch is a single chain with 1-4 alpha glycosidic bonds, glycogen has two chains (branching) held together with 1-6 alpha glycosidic bonds, but individual glucose is held together the same way as starch

What are the main characteristics of cellulose? What is a notable difference in the bonds between cellulose and glycogen/starch?

• Is a polymer of 1000s of glucose monomers

• Is the major structural component of plants, digested by herbivores via microbial fermentation (Important for fiber)

• Contains beta 1-4 glycosidic bonds, CANNOT be hydrolyzed by non-ruminants

What are lipids, what are they composed of?

fats/oils, organic compounds mostly insoluble in water, they yield high energy, composed of C, H, O

What are some of the main roles of lipids?

1.) Energy source

2.) Membrane structure

3.) Animal Insulation

4.) Hormone Synthesis

5.) Vitamin synthesis

What are the four main types of lipds?

triglycerides (TAGs), phospholipids, sterols, glycolipids

What are triaclyglycerols? What molecules form them?

main form of lipid found in body and in the diet, 1 glycerol and three fatty acids

What is the structure of the fatty acid and specify which ends are hydrophilic/hydrophobic?

can be long or short, consist of a long hydrocarbon chain/tail ending with a methyl group (Hydrophobic), and carboxylic acid at one end (Hydrophilic)

What three characteristics of a fatty acid determine whether a compound is solid or liquid?

1.) Chain length (4-24): shorter chains have a lower MP, longer chains have higher MP due to having more hydrophobic components

2.) Degree of Saturation (Or # of double bonds): fatty acids with one double bond is unsaturated, one or more is polyunsaturated, no double bonds = saturated

3.) Shape: double bonds change the shape of the fatty acid, creating kinks which lower the MP

Why does the saturation of fatty acids affect melting point?

unsaturated have kink which increase solubility, saturated are straight and can interact more closely, so have a higher MP

What are nonessential fatty acids? What are essential fatty acids?

fatty acids that can be synthesized by the body, fatty acids that must be obtained from food

What does a phospholipid consist of? Which parts are hydrophobic and hydrophilic?

two fatty acids (hydrophobic lipid tails) and a modified phosphate group attached to a glycerol backbone (hydrophilic)

What characteristic of phospholipid tails allows for fluidity/constant motion?

some tails are saturated, some are unsaturated

How do phospholipids aid in emulsification?

keep oil and water mixed (so they do not separate), e.g. bile

What do phospholipids do in the body/aqueous environments?

spontaneously form a lipid bilayer or cell membrane, tails inside, heads outside

What are the functions of cholesterol?

component of cell membrane, synthesis of sex hormones, vitamin D and bile salts

Describe the structure of sterols?

contain interlinking rings of carbon atoms with side chains C,H, O attached

What are glycolipids?

lipids with attached carbohydrate group

What are some functions of glycolipids?

1.) Protection

2.) Immunity to infection

3.) Transplant compatibility

4.) Cell adhesion

What are proteins and what are they composed of?

macromolecules composed of chains ofnamino acids, contain C, H, O, N

How are amino acids joined together?

via peptide bonds formed between the COOH (carboxyl) and the NH2 (amino group), this backbond is sometimes referred to as, N-C-C-N-C-C-N

What are some functions of proteins?

1.) Enzymes

2.) Hormones

3.) Receptors

What other roles can proteins play?

cell structure (fibres, collagen, keratin, actin), immune system, transport, synthesis of other molecules, source of energy (ketone bodies/gluconeogenesis)

What are nucleotides and their components?

phosphate group, 5-carbon sugar molecule (deoxyribose (DNA) ribose (RNA)), base (purine/pyrimidines)

What are the purines?

adenine + guanine

What are the pyrimidines?

cytosine, thymine, uracil

How do DNA and RNA nucleotides differ?

Ribose has OH group at C2, deoxyribose has H at C2

Thymine is only found in ____.

U is only found in ____.

DNA, RNA

How are nucleotides joined together?

via phosphodiester bonds, forming the sugar phosphate backbone

How is the DNA helix joined together?

H-bonding due to complementary base pairing between purines and pyrimidines (adenine and thymine - 2 bonds) (guanine and cytosine - 3 bonds)

How are DNA strands oriented?

antiparallel, one runs 5’ to 3’, other runs 3’ to 5’

Describe how DNA is packaged:

1.) DNA wraps around histone octamers, forming nucleosomes

2.) Nucleosomes compact into chromatin fiber

3.) Chromatin packaged into chromosomes

What is the nucleus comprised of?

1.) Nuclear membrane with nuclear pores

2.) Nucleolus - responsible for synthesis of ribosomal RNAs

3.) DNA material (chromosomes)

4.) Nucleoplasm

What is the function of the nucleus?

contains DNA, site of DNA replication and transcription

What sort of things do the nuclear pores allow to be transported?

mRNA, transcription factors and ribosomal RNA

What is the function of ribosomes? What is their structure and how can they be found in the cell?

site of protein synthesis, are complexes of proteins and ribosomal RNAs (rRNAs) with 2 subunits (one large and small), bound to ER, free in cytoplasm

What is the function of the endoplasmic reticulum? What is it’s structure like?

main function of rough ER is protein synthesis, smooth ER no ribosomes, is a continuous membrane system of flattened tubes

Describe the relationship between the ribosomes and the rough ER.

ER ribosomes synthesize proteins, as chain grows it enters the ER lumen, these proteins are packaged into membrane bound vesicles from ER membrane

What is the process of ER to Golgi transport?

1.) Proteins synthesized on rough ER exit in transport vesicles

2.) Vesicles fuse with CIS-GOLGI complex

3.) Proteins migrate through cisternae to TRANS-GOLGI

4.) Proteins again packaged into secretory vesicles

5.) Transport to cell membrane and fuse (exocytosis) or transported to other areas of the cell

What is the function of the golgi?

post-translational modifications of proteins to make them functionally active

What are some post translational modifications?

• Formation of disulfide bonds

• Addition and processing of carbohydrates

• Specific proteolytic cleavages

• Assembly into multimeric proteins

• Proper folding

What is the function of the mitochondria? What is it’s structure like?

energy production, harness ATP from oxidation of food molecules (oxidative phosphorylation, electron transport chain, krebs cycle)

contains an outer membrane and inner membrane, large surface area for ATP production

What are the functions of lysosomes? What is their structure?

degradation of molecules and waste

contains lipid bilayer membrane with degradative enzymes (acid hydrolases) that are active at acidic pH

What are the functions of the cytoskeleton and what are the three types of structures?

holds cell organelles in place, providing shape and structure

1.) Microfilaments: polymers of actin, providing flexibility, modified during cell movement (migration, endo/exocytosis)

2.) Microtubules: polymers of tubulin, provide cell shape, important for mitosis/meiosis, chromosomes attach to microtubules via centromere

3.) Intermediate filaments: structural function

List the cytoskeleton structures from large to small.

microtubule, intermediate filament, actin filament

How can lipid composition of the plasma membrane reflect function?

plasma membrane - 50% protein, 50% lipids

mitochondrial membrane - higher protein content, needed for synthesis of ATP with membrane proteins

What are the three main classes of membrane lipids in animal cells?

phospholipids (majority), cholesterol (15%), glycolipids (5%)

What are some ways the cell membrane might undergo remodelling?

mitosis, endocytosis, exocytosis

What three factors control the fluidity of cell membranes?

1.) Length of fatty acid chains, longer HC chains result in stronger interactions, less fluid

2.) Degree of saturation: more double bonds = weaker interactions and is more fluid

3.) Cholesterol content: rigid molecule, more cholesterol means more rigid, less fluid

What types of movements contribute to fluidity of the membranes?

1.) Lateral diffusion: phospholipids can move side to side BUT only on the same side (Flip-Flop is very rare due to thermodynamics, need specialized enzymes)

2.) Rotation: phospholipids can rotate in ones spot

3.) Bobbing: each phospholipid can bob up and down in the same position

4.) Flexion: hydrocarbon tails can move/flop around

What are characteristics of integral proteins?

extend through entire bilayer, cannot move

What are characteristics of peripheral proteins?

bound indirectly to face of phospholipid, inside or outside, weaker bond so can move around

What is passive diffusion?

transport of molecules into cell without the need for energy

What is facilitated diffusion?

requires transport proteins

What is active transport?

requires energy in the form of ATP and transport protein