Chapter 3 & 4 cell membrane, cytoplasm, and nucelus

Function of cell membrane

control what enters and leaves the cell

Characteristics and types of transport occurring in cell membrane

• Selective-permeable 

•  Transport may occur by: 

  • Simple or facilitated diffusion  

  • Osmosis 

  • Active transport 

  • Endo or exocytosis

Define diffusion

a passive transport mechanism – NO ENERGY Required 

define and characteristics of simple diffusion

movement of particles from high to low concentration without a protein

• Small nonpolar molecules, or lipid soluble molecules

  • Oxygen, carbon dioxide, steroid hormones, fatty acids

• Directly through the phospholipid bilayer, does NOT involve membrane proteins 

• Rate depends only on the concentration gradient

  • Super high and low concentrations cause diffusion to go faster

What are the types of passive diffusion?

• simple diffusion

• facilitated diffusion

• osmosis

define and characteristics of facilitated diffusion

Movement of particles from high to low concentration using a protein

• Polar. charged , or larger molecules 

  • Glucose, amino acids, ions like Na⁺, K⁺, Cl-

• Cannot diffuse pass phospholipid bilayer, need help from: 

  • Channel proteins- Ex. Aquaporins - fast 

  • Carrier proteins - Glucose transporter 1 slow 

  • Most channels are specific to a specific ion or small number of specific ions 

• Rate can reach a maximum because transport proteins can only work so fast or become fully occupied

  • Can get too congested (rush hour)

Define and characteristics of osmosis

the passive movement of water molecules across a selectively permeable cell membrane

• Water does not move freely across lipid bilayer must diffuse through water channels formed by transmembrane proteins called aquaporins

• Dilute concentrated areas (water goes to where there is less water)

define osmotic pressure

move water from region of low solute concentration (high water concentration) to a region of high solute concentration (low water concentration).

define isotonic

• Solute concentration equal inside and outside the cell

• No net movement of water

• Cell retains normal shape (equilibrium)

define Hypotonic

• Lower solute concentration outside than inside the cell

• Water enters the cell

• Cell swells

define Hypertonic

• Higher solute concentration outside than inside the cell

• Water leaves the cell

• Cell shrinks

define and characterize Active transport

 movement of molecules and ions across cell membranes that occurs against concentration (against the gradient) 

• This movement (carrier protein) against the gradient consumes energy (ATP) produced by the cell! 

• Ex. Sodium/Potassium pump 

• Important for the maintenance of homeostasis

What are the types of active transport?

• Endocytosis

• Exocytosis

define and characterize Endocytosis

• Exterior cell membrane moves to surround extracellular materials in a membrane pocket

  • Takes in cells to use as vesicles 

define and characterize Exocytosis

• Vesicles formed inside the cell fuse with the plasma membrane and release their contents to the outside 

  • Release waste 

  •  Ex. 

    • Secretion of proteins like hormones- secretion 

    • Release of neurotransmitters at synapses - communication 

    • Disposal of waste products from lysosomes – waste disposal

what are the three types of endocytosis

• Phagocytosis (“cell eating”)

• Pinocytosis (“cell drinking”)

• Receptor-mediated endocytosis

Define Phagocytosis (“cell eating”)

the cell engulfs large particles or microorganisms 

Define Pinocytosis (“cell drinking”)

the cell takes in extracellular fluid and dissolved substances 

Define Receptor-mediated endocytosis

highly specific; receptors bind to target molecules (like LDL cholesterol) before vesicle formation 

define cytoplasm

the factor floor. Everything inside the cell membrane but outside the nucleus 

what are the three main components of cytoplasm

• Cytosol - a jelly-like fluid matrix, mostly water (70-80%), with dissolved ions, carbohydrates and proteins

• Organelles - little organs that suspended in the cytosol, each with specialized function 

• Cytoskeleton - provides structural support 

define mitochondria

(powerhouse of the cell) - generates most of the cell’s energy in the form of ATP (adenosine triophosphate)

What is the structure of the mitochondria

• Outer membrane 

• Inner membrane

• Intermembrane space

• Matrix - contain enzymes and its own DNA, RNA, and ribosome 

what are the 3 types of energy production and how much ATP is produced

• Glycolysis - 2 ATP

• Krebs Cycle - 2 ATP

• Electron Transport chain (ETC) and oxidative Phosphorylation ~ 26-28 ATP

where are each of the 3 types of energy production located?

• Glycolysis (outside mitochondria, in the cytoplasm) - 2 ATP

• Krebs Cycle (citiric Acid Cycle, in the mitocondrial matrix) - 2 ATP

• Electron Transport chain (ETC) and oxidative Phosphorylation (on the inner mitochondrial membrane) ~ 26-28 ATP

What is the Endoplasmic Reticulum

continuous membranous network with the nuclear envelope

• Directly connected to the outer membrane of the nucleus 

What is Cisternae

form of tubules, sheets, and occasional enlarged sac or vesicles in the ER

what are the two main types of ER

• Rough ER – small bumps (ribosomes) on the surface 

• Smooth ER – smooth surface with no ribosomes 

Rough ER characteristics

• Has bumps on their surface 

• Associated with ribosomes (produces proteins)

• Rough appearance along the membrane 

• Shaped like flattened sheets 

• These specific ribosomes specialize in synthesis of proteins

Smooth ER characteristics

• No ribosomes 

• Smooth appearance 

• Tubular network 

• Involved in lipid synthesis such as steroids and phospholipids 

• Most of the specialized ERs are derived from smooth ER 

• Ex. sarcoplasmic reticulum in muscle cells, specialized in calcium storage

What is Golgi Apparatus?

Packaging center

Characterize and function of Gogi Apparatus

• Made up of stacks of flattened, membrane-enclosed sacs called cisternae

• Sorting and packaging

  • Sorts modified proteins and lipids into vesicles 

  • Send the vesicles out to their destination

• Make vesicles filled with digestive enzymes that later matures into lysosomes for waste break down

  • Low in pH

What are the 3 zones in the Gogi apparatus and function of each

• Cis face - receives what’s being made in the th ER

• Medial cisternae - starts putting the product in a box (vesicle) 

• Trans face - shipping doc, gets stuff ready to be moved out 

What are Lysomes

made by golgi. Small, membrane-bound organelles that contain a variety of hydrolytic enzymes(proteases, lipases, glycosidases) – low pH

Key functions of Lysomes

• Intracellular digestion – digest molecules from inside the cell 

  • Digest macromolecules like glucose to then be used as individual building blocks and made into other things 

• Endocytosis digestion - digest molecules from outside the cell 

  • Kills pathogens and breaks them down 

• Autophagy –digest worn-out or damaged organelles 

  • Kills inefficient organelles 

• Apoptosis – trigger cell death

  • Cell can suicide because no longer fit for survival (in extreme cases)

What are Peroxisomes?

Also a small, single membrane-bound organelle like the lysosome

key functions of peroxisomes

• Packed with oxidase to oxidize and break down fatty acids 

• Packed with catalase – an antioxidant that scavenges free radicals – detoxifying the cell 

  • Triggers cell death and mutations (too much free radical is bad)

  • Scavenges the free radicals and maintains the health in the cell 

• Produce some important lipids like plasmalogen and bile acids

Function of cyto Skeletons

provides structural support and enables the cell to move, divide, transport materials, and sense its environment

3 major components of the cyto skeleton

• Microtubules – larger hollow tubes radiate out of nucleus(~ 25 nm in diameter) 

  • Thickest 

  • Tubulin

  • Functions like highways or bridges 

    • Tracks for intracellular transport

• Microfilaments – thin filament just beneath the cell membrane (~7 nm in diameter) 

  • Supports the cell membrane 

  • Thinnest

  • actin

  •  Drive endocytosis and exocytosis

• Intermediate filaments – network of rope-like fibers with high tensile strength. Stretched throughout the cytoplasm (~10 nm in diameter

  • Provide main structural support (mechanical strength)

  • Keratin

  • Anchor organelles in place

Function of nucleus

• Cell’s control center

•  It houses the genetic material and coordinates essential processes such as gene expression, DNA replication, and RNA processing

Structures and function in the nucleus

• Nuclear Envelope –double membrane 

  • Outer membrane -continuous with the rough ER, often studded with ribosome 

  • Inner membrane - interacts with the nucleoplasm and chromatin 

  • Nuclear pore complex- large pores permit exchange between nucleoplasm and cytoplasm

  • Nucleoplasm- gel-like interior with ions, enzymes and soluble proteins 

  • Chromatin - DNA packaged with histone proteins 

    • Packed in a chromosome 

    • Rolled up DNA (histones)

  • Nucleolus - Non membranous structure ribosome subunits are assembled 

    • Makes ribosomes

Function of Transcription

the process of copying DNA into RNA by RNA polymerases (in nucleus)

function of RNA polymerase

binds to sections of DNA and uncoils the two strands

Function of mRNA

 is transported out of the nucleus into the cytoplasm

function of translation

the process where the mRNA message is read by ribosome to build a protein (in cytoplasm

• Decodes and matches up the code on the mRNA