Intro to Cells + Membrane Transport

who wanted to try out his new microscope and what did he want to examine

Robert hooke wanted to examine cork in 1665

what did Robert hooke find

he noticed tiny square spaces, reminded him of dormitories or “cells”

what did Hooke learn

cells = basic unit of life

cell theory

• all living things are made up of one or more cells; uni or multi cellular

• all cells arise from other, preexisting cells; cell division

cells at its simplest

• genetic material

• lipid membrane

• cytoplasm

prokaryotic cells

• relatively simple + small, lack nucleus, + organelles (bacteria)

eukaryotic cells

• more complex, larger, contains nucleus, + organelles (plants + animals)

prokaryotes and eukaryote share

• dna

• cytoplasm

• cell membrane

• ribosomes

animal cells don’t have

cellulose

plant cells don’t have

• chloroplast

• cell wall

• vacuole

plant + animal cells have

• nucleus

• plasma membrane

• ribosome

• mitochondria

• rough ER

• smooth ER

• cytoplasm

• cytoskeleton

• golgi

• lysosome

Cytoplasm is made up of what and what does it support

mostly water + supports internal cell components, organelles, genetic material, proteins, molecules and ions

how does it differ from fluid around cell

concentration of ions is different inside vs. outside (important for cell functions); higher concentration inside

• uses proteins in the cell membrane to keep the correct concentration of ions

what composes a cell membrane

a bilayer of phospholipids creating a barrier

what does the cell membrane control

What is allowed to enter + leave the cell ensures they acquire the molecules they need and block/ expel the ones they don’t

cell membrane is home to

Different types of proteins: each cell in the human body has different sets of proteins in its membrane, which dictate the function of the cell

the fluid mosaic model

cell membrane has fluid-like quality + contains many proteins interspersed among phospholipids

for cells to function properly they must

constantly move materials in + out across membrane: ions, nutrients, waste, etc

membranes are

Selectively permeable: only a subset of molecules can pass through directly, while others need help from proteins

molecules that can pass through a selectively permeable membrane

• small hydrophobic molecules

• small, uncharged polar molecules

both freely diffuse

molecules that can not pass through a selectively permeable membrane

• large uncharged polar molecules

• ions

impermeable

active transport

transport of substances from areas of lower concentration to areas of higher concentration (requires energy)

passive transport + types

transport of substances from areas of higher concentration to areas of lower concentration (no energy)

• simple diffusion: small, non polar molecules moving through membrane: gasses or lipids

• facilitated diffusion: uses channel proteins to facilitate diffusion of large or charged molecules

concentration gradient

difference in concentration of a substance across membrane

osmosis

diffusion of water

can water pass through membrane

• Water can also diffuse across the membrane, despite being polar

• Water can move in/out of a cell depending on the concentration of solutes/ substances dissolved in water

water always moves from areas of what concentration to what concentration

low to high; we can describe the direction in which water diffuses into cells based on solute concentration inside + outside of cells

Isotonic solution

• Solute concentration is balanced, water movement is balanced

hypotonic solution

Solute concentration is lower in extracellular fluid; water diffuses into the cell

• Unlike in plants, animal cells may explode because no cell wall

hypertonic solution

Solute concentration is higher in extracellular fluid; water moves out of cells

• Water will always move towards a region having a greater concentration of solutes

over hydration

Leads to hemolysis, life-threatening; consuming large amounts of water in short periods of time

active transport requires what type of energy

atp; to move from low to high concentration and uses pumps

primary active transport

uses ATP + pump protein to move molecules from low to high concentration across membrane

secondary active transport

• Must go through primary active transport first

• uses the concentration gradient built by the pump to facilitate the transport of another molecule from low to high concentration across the membrane

• The transport protein moves one molecule against its concentration gradient, powered by simultaneous flow of another molecule down its concentration gradient

active transport also describes movement of substances within

vesicles: small bubbles of phospholipids used to carry large amounts of a certain type of molecule

active transport: exocytosis

releasing substances within vesicles from the cell to the outside

active transport: endocytosis

refers to taking in substances from the inside by enclosing them in vesicles

active transport: phagocytosis

Special kind of endocytosis for taking in large things

• macrophages, a type of immune cell, use phagocytosis to engulf bacteria and destroy them