gen bio - lecture 5: cell structure

cell

• basic unit of structure and function

• essential for life, can perform processes and specialize

prokaryotic cells (size, dna, organelles, division, cell border)

• size: tiny, 1-10micrometers

• dna: unbound + stored in NUCLEOID

• organelles:

  • no organelles

  • ribosomes in cytosol (not membrane bound)

• division: binary fission

• cell border: cell membrane + cell wall

eukaryotic cells (size, dna, organelles, division, cell border)

• size: large, 10-100micrometers

• dna: inside NUCLEUS

• organelles:

  • membrane bound organelles

  • ribosomes in cytosol

• divide: mitosis

• cell border: cell membrane (plants have cell walls)

7 common features of all cells

1. small size (surface area limits)

2. distinct internal environment

3. bound by plasma membrane

4. have genetic information

5. reproduce by division

6. carry out metabolism (break down molecules for energy)

7. maintain homeostasis (stable set point)

2 limits to cell size

1. plasma membrane

• all material must pass through to enter cell AND surface area limits the rate at which material can enter

2. advantageous to maximize surface-area-to-volume ratio (think of a balloon; don’t want volume to get too big while surface area stays the same)

nucleus (include: nuclear envelope, nuclear lamina, nuclear pores, chromosomes, chromatin, nucleolus)

• nuclear envelope: membrane that surrounds nucleus

  • has 2 sub membranes w/lipid bilayers

  • nuclear lamina: lines inside of envelope (maintains shape, made up by proteins

  • nuclear pore: regulates transport

• chromosomes: DNA is organized as linear chromosomes

  • chromatin = DNA + proteins (squiggly)

• nucleolus: makes ribosomes, RNA, and proteins

  • no membrane!

define endosymbiosis and how mitochondria + chloroplasts exhibit the concept

an evolutionary idea where organelles mutually benefit from each other by consuming each other

• mitochondria + chloroplasts have…

  • double membranes

  • similar size, enzymes, ribosomes to bacteria/prokaryotes

  • DNA sequences similar to bacteria

  • divide by binary fission

mitochondria (5 characteristics)

• has inner + outer membranes

• has own DNA

• has own ribosomes

• undergoes binary fission

• aerobic respiration (use O2 to create energy)

chloroplasts (main characteristic)

only found in photosynthetic lineages (plants and algae)

ribosomes (structure, function, free vs bound)

ALL CELLS HAVE RIBOSOMES :)

• structure:

  • non membrane bound = NOT an organelle

  • ribosomal RNA + proteins

• function:

  • synthesize primary polypeptides

• free ribosomes: found in ALL cells + mitochondria + chloroplasts

• bound ribosomes: attach to ROUGH ENDOPLASMIC RETICULUM

endomembrane system (define, structure, function, and LIST 6 PARTS)

• define: group of organelles responsible for creating proteins and lipids

  • phospholipid bilayer separates internal space (lumen) and external space

• structure is either…

  • continuous (one long structure)

  • connected via vesicles (transfer membrane segments)

• functions:

  • regulates protein folding/movement

  • metabolic functions

• parts:

1. plasma membrane

2. nuclear envelope

3. endoplasmic reticulum

4. golgi apparatus

5. lysosomes

6. vacuoles

plasma membrane

• NOT a cell wall

• in all cells

• encloses cell contents

• selectively permeable

  • regulates what and how much passes through

nuclear envelope

• encloses DNA

• contains instructions for mRNA

  • leaves through nuclear pores

  • picked up by ribosomes to form primary polypeptides

endoplasmic reticulum (include difference in function between rough and smooth er)

• continuous with nuclear envelope

• smooth er: no ribosomes

  • synthesizes lipids

  • metabolizes polysaccharides, breaks down glycogen

  • detoxifies drugs and poison

  • stores calcium ions

**most present in liver

• rough er: surface has ribosomes

  • proteins folded + modified

  • secretes glycoproteins

  • distributes transport vesicles

  • cell membrane factory

golgi apparatus (structure + function)

GO(LGI) TO POST OFFICE

• structure:

  • stacks of membraneous sacs/cisternae

  • not continuous with ER

    • cis face: receiving side

    • trans face: shipping/ TRANSport side

• functions:

  • modifies ER products

  • sorts and packages

  • manufactures some macromolecules

  • ships products using transport vesicles

lysosomes

• sacs of hydrolytic enzymes; “cell stomach”

• primary lysosome:

  • buds off golgi (no food yet)

  • food enters in vacuole and it fuses with lysosome to form

• secondary lysosome:

  • breaks down complex molecules

vacuoles (structure + function)

• maintenance compartments

• structure:

  • membrane bound containers from er + golgi

• functions: (vary by cell)

  • food vacuoles = store food

  • contractile vacuoles = pump water out

  • central vacuoles = hold water (in plant cells)