Cells

Bell Ringer: Observations

• Record your observations about the picture to the right.

• What do you think you are you looking at?

• Describe the structure with as much detail as possible?

• Is there organization to what you see?

• Is it a single unit or many units?

Robert HookeThe picture you observed is a micrograph of Robert Hooke’s first etchings of his observation of cork using a microscope.

• “Hooke, struck by the orderly little squares that reminded him of monks' rooms in a monastery, called the little boxes "cells," and the term stuck.”

Scientists of Cell Theory

• Robert Hooke-First to observe cells. (1665)

• Anton van Leeuwenhoek- first to observe living cells.(1674)

• Matthias Schleiden- first to state plants are made of cells. (1838)

• Theodore Schwann-animal tissues are made of cells. (1839)

Cell Theory

Cell theory is the foundation of cell biology.

Modern cell theory states the following 3 principles:

1. All organisms are composed of one or more cells, and the life processes of metabolism and heredity occur within these cells.

2. Cells are the small units of living things, the basic units of organization of all organisms.

3. Cells arise only by division of pre-existing cells.

Cell size limits

Cells need to be small for the purposes of diffusion of materials into and out of the cell across the cell membrane.

• The cell membrane surface area-to-volume ratio limits how large a cell can be in order be able to perform metabolic functions.

• As a cell gets larger the volume of the cell increases at a faster rate then the surface area. • If the cells radius increase 10 times the volume will increase by 100 times

Cell Shape

A cells shape reflects the different functions of cells.

Each cell shape has evolved to allow the cell to effectively perform its job.

• A nerve cells has long extensions that reach out in various directions for sending and receiving nerve impulses.

• A Skin cell is a flat , platelike cells that protect the surface of the body.

Two Basic Type of Cells

• Prokaryotes- Organisms that do not have a membrane bound nucleus or membrane bound organelles.• The do have DNA that is often concentrated in the region of the cell called the

nucleoid.

• Bacteria are prokaryotes

• Eukaryotes-Organisms made up of one or more cells, they have a nucleus and membrane-bound organelles.• You are a Eukaryote

Prokaryote vs Eukaryote

Cell Organelles

• An organelle (tiny organ)- is a well-defined, intracellular body that performs specific functions for the cell.

Cytoplasm

• The cytoplasm is the region of the cell inside of the cell membrane. • It includes: fluid, the cytoskeleton and all organelles except the nucleus.

• The cytosol includes all of the fluid, small particles, ribosomes but NOT the organelles.

Microscope

• How to use a microscope.• Plug it in and turn on the light.• Lower the stage so it is furthest from the objective lens.• Adjust the objective lens to the lowest magnification• Place the prepared slide on the center stage.• While looking into the ocular lens, slowly move the stage towards you using the

course adjustment knob until the sample comes into view.• Use the fine adjustment knob to focus your image better. You can also adjust the

diaphragm to let in an optimal amount of light.• Move to a higher power if necessary. DO NOT LET THE OBJECTIVE LENS TOUCH THE

SLIDE when switching to a higher power. You may need to lower the stage.

• Labeling practice link

Cell Structures Overview

• Cell membrane

• Cell wall

• Nucleus

• Endoplasmic Reticulum (smooth & rough)

• Golgi Bodies

• Lysosome

• Ribosomes

• Cytoskeleton

• Mitochondria

• Chloroplasts

• Unicellular Movement

Cell Membrane

• Plasma Membrane (aka cell membrane) – covers the cell surface and acts as barrier between the inside and outside of the cell. All materials (nutrients and waste) enter and exit through the cell membrane.

• Fluid mosaic model-the phospholipid bilayer behaves more like a liquid than a solid

• Video Clip .

Cell Wall (Plants)

• Cell Wall- A rigid layer that lies outside of the cell membrane. • The cell wall is made of cellulose.

• Pores in the cell wall allow water, ions and other molecules to enter and exit the cell.

Nucleus

• The nucleus controls most functions in eukaryotic cells.• Stores the genetic information. –Deoxyribonucleic acid (DNA)

Inside of the nucleus:

• Chromatin-thread like DNA that is not condensed

• Chromosome- Condensed DNA that is organized around a protein called a histone.

• Nucleolus-a dense DNA region of the nucleus where the rRNA is made. (ribosomal rna)

Endoplasmic Reticulum- ER

• ER- a system of membranous tubes and sacs called cisternae (sis-tuhr-nee).

• It acts as an intracellular highway that transports molecules from one part of the cell to another.

• There are two types, Smooth ER and Rough ER

Rough ER

• Has ribosomes attached.

• Responsible for producing phospholipids and proteins.• These molecules are exported from the cell or inserted into the cell

membrane.

Smooth ER

• Does not have ribosomes. Looks smooth.

• Responsible for building lipids like cholesterol

• Releases calcium in the heart to stimulate contraction (cardiac cells)

• Produces estrogen and testosterone (ovary and testes cells)

• Detoxifies drugs (liver cells)• Long term abuse can cause your body to produce more smooth ER leading to drug

tolerance.

• The smooth and rough ER are interconnected

Golgi Apparatus (AKA Golgi complex or Golgi body)

• A system of FLATTENED, membranous sacs.

• The golgi apparatus receives packages (vesicles) from the ER. They modify the new proteins and lipids They direct them to various places in the cell.

Vesicle

• A vesicle is a small, spherical sac that is surrounded by a membrane.

• They often merge with the cell membrane and release contents out of the cell.

Types of Vesicles

• Lysosome-digestive enzymes• Peroxisome-detoxify and neutralize

• Glyoxysomes-breaks down fats

• Endosomes-engulfed material being brought into the cell.

Ribosome

• Small spherical organelles that are responsible for building proteinmolecules.

• The do not have a membrane!

• Some ribosomes are free in the cytosol others are attached to the ROUGH ER.

Cytoskeleton

• A network of thin-tubes and filaments that crisscrosses the cytosol.

Mitochondria

• Creates ATP(cell energy) using organic molecules (glucose).• ATP- Adenosine Triphosphate is the universal energy molecule within the cell.

• Mitochondria have their own DNA and can reproduce by dividing. Scientist think the mitochondria originated from prokaryotic cells.

Chloroplast

• Found in plants and algae

• Use light energy to make carbohydrates from carbon dioxide and water.• Contain their own DNA and are thought to descend from ancient prokaryotes.

Central Vacuole-plants

• Large fluid-filled organelle that stores not only water but also enzymes, waste and other materials.

• Since plants cannot move to their source of food this structure allows them to survive longer periods without water.

Cellular Organization

Unicellular-One celled organism

Multicellular-many celled organism

Over time cells began to form groups that functioned together to create multicellular organism.

Type of Unicellular Movement

• Cilia-tiny little hair like structures.

• Flagella- Whip-like tail.

• Psuedopodia (“false foot”)- extension of the cytoplasm.