Biology Unit 4:Cell Structure & Function

                                  

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Discovery of Cells

• 1600’s• Robert Hooke

• 1820’s: Rene Dutrochet

• 1830’s: Robert Brown• Matthias Schleiden• Theodore Schwann• Rudulph Virchow

• Discovery of light microscope• Named box-like structures in

cork “cells”• Cells are found in various

parts of organisms• All cells have a nucleus• All plants are composed of

cells• All animals are composed of

cells• All cells come from living cells

Cell Theory

Three parts:• All living things are made of cells• The cell is the basic unit of structure

and function in living things• All cells come from existing cells

Unicellular Organisms

• Cell is the organism• In terms of numbers

> dominate life on Earth

Yeast Volvox aureus Euglena

Chlamydomonas

Multicellular Organisms

• Made up of many cells• Great variety of organisms• All depend on specialized

cells– Cells develop in different ways

to perform different tasks– Ex: Red blood cells transport

oxygen throughout body

Red blood cells

Multicellular Organisms (cont.)Levels of organization

• Cell - Ex: muscle cell

• Tissue - group of similar cells perform a particular function– Ex: muscle tissue

• Organ - group of tissues that work together– Ex: stomach

• Organ system - group of organs that work together to perform specific function– Ex: digestive system

Smooth muscle tissue

Muscle cell

Stomach

Digestive System

Types of Cells• Eukaryotic

– Genetic material contained in nucleus

– Plants, animals, fungi and protists

• Prokaryotic – Genetic material NOT

contained in nucleus (*No nucleus*)

– Bacteria

The Eukaryotic Cell

Cell Structure• Like a factory• Two major parts: cytoplasm &

nucleus• Organelles (“little organs”)

– Act like specialized organs– Some structures developed from early

prokaryotes •Ex: mitochondria & chloroplasts

Cytoplasm

• Gelatin-like material inside the cell membrane, outside the nucleus

• Contains organelles • Site of most cell activity

– Factory floor where products are assembled, finished & shipped

Nucleus• Control center of the

cell > boss or CEO– Responsible for overall

function of factory

• Determines what proteins will be made

• Contains hereditary information > DNA

Nucleolus

• Small, dense region of nucleus

• Assembly of ribosomes begins here

Nuclear Envelope

• Membrane around nucleus only

• Has small pores that allow information and ribosomes to move in and out of nucleus

Ribosomes• Responsible for

assembling proteins– Workers on assembly

line in factory– Responds to orders

from boss > nucleus

• Located throughout cytoplasm

Endoplasmic Reticulum

• Site where lipid components of cell membrane are assembled– Also assembles proteins exported

from cell– Assembly line in factory

• Two types:– Rough ER - appears bumpy due to

ribosomes on surface– Smooth ER - No ribosomes

Endoplasmic Reticulum

Golgi Apparatus

• Prepares proteins and other materials for storage or use outside cell

• Like finishing & packing department in factory– Finishing touches put on

before ready to leave factory

– Sorted & stored or shipped outside of cell

Lysosomes• Small organelles filled

with enzymes• Maintenance crew for

factory• Break down carbs, lipids

& proteins for use by cell• Remove “junk” - waste

and dead material found in cell

Vacuoles

• Saclike structures that store nutrients – water, salts,

proteins & carbs

• Storage rooms of factory

Mitochondria

• Convert nutrients in food into energy for cell use– Local power plant

for factory– Source of energy

Chloroplasts• Capture energy from

sunlight and convert it into chemical energy > photosynthesis – Solar power source for

factory

• Only in plant cells– Chlorophyll > chemical

that causes plant cells to be green

Cytoskeleton

• Network of protein fibers that helps cell maintain its shape– Microtubules and microfilaments– Support structure of factory (beams &

columns that support walls & roof)

• Also used to move cell membrane

Cell Membrane• Phospholipid bilayer• Regulates what enters & leaves the cell

– Like gate into the factory

• Provides protection & support– Gives the cell its shape

Cell Wall• Outside cell

membrane• Provides protection

& support• Present in plants,

algae, fungi and many prokaryotes

* Never in animal cells

Plant Cell

Cell Wall (algae)

Cell Wall (bacteria > prokaryote)

Movement Across Cell Boundaries

Diffusion• Molecules spread into

available space– across membrane– from area of higher

concentration to area of lower concentration

– without use of energy > passive transport

• Equilibrium - when concentration is same throughout a system

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Osmosis• Diffusion of water

through a selectively permeable membrane– Membrane allows only

certain substances to pass through

– Type of diffusion - does not require use of energy > passive transport

How Osmosis Works• Isotonic - “same strength”

– Same concentration on both sides

• Hypertonic - “above strength”– Higher concentration outside cell– Water leaves, cells shrink

• Hypotonic - “below strength”– Lower concentration outside cell– Water comes in, cells swell

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Facilitated Diffusion• Movement of

specific molecules across membranes through transport proteins– Could not cross

without them– Does not require

use of energy > passive transport

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Active Transport• Cells move materials in direction

opposite diffusion– Against concentration difference

(gradient)

• Requires energy• Small molecules or ions (K, Ca, Na)

carried by transport proteins or “pumps” in membrane

Active Transport (cont.)

Larger molecules & clumps of material transported by:

• Endocytosis - movement of materials into cell through vesicles (pockets) of cell membrane– Phagocytosis- “cell eating”– Pinocytosis- “cell drinking”

• Exocytosis - movement of materials out of cell through vesicles

IV. Homeostasis

A. The Cell as an Organism1. Unicellular organism- organism made

up of only one cella. Examples: • Bacteria• Yeast• protists- amoeba, diatoms,

plasmodiumb. Exhibit all 8 features of living things

c. All organisms must maintain homeostasis

• Defined- relatively constant internal; physical and chemical conditions

B. Multicellular Life

1. Cells in multicellular organisms do not live on their own

2. They are interdependent- need to work together

3. Need to communicate- send and receive signals with each other

4. Cell specialization- different types of cells play different roles

a.Some move- throat lining cellsb.Some react- nerve cellsc.Some produce substances- glandular

cells

5. Levels of Organizationcells --> tissues --> organs --> organ systems --

> organisms

a. Tissue – is a group of similar cells that work together to perform a function.

Nerve Cell

Nerve Tissue

Examples of Tissues

b. Organ – is a group of tissues that work together to do a job.

c. Organ system- is a group of organs that work together to do a certain job.

d. Organism – is a living thing that can be made of one or more cells.

Examples of organisms

Amoeba

Crow

Elephant

Bonobo

Human

6. Cellular Communication

a. Cells in large organisms communicate by means of chemical signals

b. The signals can either speed up or slow down an activity of the cells that are receiving them

c. Cellular junctions- hold cells together in tight formations that allow for quick signaling

• Ex: neuromuscular junction

d. Receptor- can be found on or in a cell; a specific protein whose shape fits that of a molecular messenger

• Ex: HormonesThyroid Hormone Receptor

Thyroid gland is controlled chemically by the pituitary- function: metabolism

Careers that study cells and/or tissues

• Histologist- tissues/cells• Pathologist- infected tissues/cells• Oncologist- cancer cells• Embryologist- examines infertility• Geneticist• Veterinarian