Lecture 2a:Cells

Lecture 2a:Cells

Plasma Membrane

Forms the boundary of the cell

It is the ‘gatekeeper’ for the cell

Here is a simple bilayer

Plasma Membrane

There are proteins imbedded in the membrane - these are the keymasters

Membrane ProteinsThere are several different functions that the membrane proteins perform for the cell - write in the definitions!

Channel

Transport

Recognition

Membrane Proteins

There are several different functions that the membrane proteins perform for the cell - write in the definitions!

Receptor

Signal molecule

Enzymatic

Junction

Eukaryotic Cells

Have a membrane-bound nucleus

Organelles

The ‘organs’ of the cell- the organelles concentrate the molecules needed for various functions in one place

NucleusNucleus: where the DNA is, the CEO of the cell

Chromatin: ‘uncoiled’ DNA- long strands of DNA, what condenses into chromosomes during cell division

Some RNA and protein are in chromatin too

Nucleus and RibosomesMessenger RNA (mRNA) takes the genetic information from the DNA to the ribosomes

mRNA is made in the nucleus

Ribosomal RNA (rRNA) forms part of the ribosomes

rRNA is made in the nucleolus

Nucleus

The nucleus has a double membrane- the nuclear envelope, with pores that allow various RNA/ proteins in and out.

Anatomy of the Nucleus

Ribosomes

The site of protein synthesis - receives mRNA from nucleus

Has two subunits: large and small

Some free-floating, some attached to endoplasmic reticulum

Proteins made on ER move inside it; where finalization takes place

Endomembrane System

The membranous parts of the cell that help to organize it

Includes: nuclear envelope, ER, Golgi appratus, vesicles

Vesicle: membranous sac

Endoplasmic ReticulumThe factory of the cell

Rough ER: Makes proteins, studded with ribosomes

Smooth ER: makes lipids, specific to cell type

ex: smooth ER in testes makes testosterone

Both make transport vesicles

Golgi Apparatus

It is the transport station of the cell

Receives transport vesicles from ER

Modifies proteins or lipids

Sorts and organizes products for shipment, either to cytoplasm or out of the cell

Lysosomes

The body’s recycling plant

Specialized vesicles that digest waste or unused molecules or cell parts

Contain enzymes

Vacuoles

Super-size vesicles with specialized functions

Water in plant cells

Color, toxins in plant cells

Fat cells store lipids in vaculoles

Energy Organelles

Chloroplasts: plants

Mitochondria: plants and animals

Things common to both:

Bound by double membrane, then another membrane inside

Have their own DNA and ribosomes; theory is that they are derived from bacteria that invaded eukaryotic cells

Chloroplasts

Chloroplasts: Where plants do their magic! - Turn sunlight into glucose

This is photosynthesis

Chloroplasts

Parts to know:

Stroma: Inner space - Where enzymes that make glucose are

Thylakoids: disklike sacs, which when stacked together are called

Granum - this is where pigments capture sunlight

MitochondriaVery small- but very important!

Make ATP, the energy molecule, via

Cellular Respiration

Can move from place to place as needed

adenosine triphosphate: ATP

Mitochondria

Parts to know:

Matrix: inner area, contains enzymes to break down carbohydrates

Cristae: highly folded inner membrane

Where ATP is actually made

Structure and MotionCytoskeleton: provides structure

Microtubules: small hollow cylinders

Provide structure and pathways

Intermediate filaments

Support between nucleus and membrane

Actin Filaments

Form a web inside membrane

Structure and Motion

Motor Proteins

Three proteins used: myosin, kinesin, dynein

Myosin moves entire cell in some way

Others attach with organelles to move them around the cell

Structure and Motion

Cilia and Flagella

Used to move the entire cell around

Single-celled organisms

The Outer Layer

Cell Wall

All plant cells have this - where the cellulose is

Gives the plant its strength, both through structure and by joining to other cells

The Outer Layer

Extracellular Matrix

In animal cells, Provides stucture to animal

Where you find collagen and elastin

Can be very strong or rather weak, depending on the tissue

The Outer LayerJunctions

Adhesion: Creates sturdy but flexible sheet of cells - like in the bladder

Tight: plasma membranes attach to each other - cells that are barriers

Gap: allows cells to communicate, it is the joining of two identical membrane channels - what allows heart cells to contract as one unit