Cell Structure

Chapter 7

7-1: Introduction to Cells

The Discovery of Cells

In 1665, Robert Hooke, an English scientist, used a simple microscope (which magnified objects 30 times their normal size) to observe “little boxes” in thin slices of cork.

He called the boxes “cells” because they reminded him of the small rooms in which monks lived.

The Discovery of Cells

In 1675, Anton van Leeuwenhoek, a Dutch scientist, used a stronger microscope (that could magnify objects 300-fold)

He named pond water creatures “animalcules” or “tiny animals”.

First to observe living cells

Cell Theory

1. All living things are made up of one or more cells.

2. Cells are the basic units of structure and function in organisms.

3. All cells arise from existing cells.

Looking at Cells

Cell size is limited by a cell’s surface area-to-volume ratio

Larger cells often have shapes that increase the surface area available for exchange

Similarities and Differences in Prokaryotic and Eukaryotic CellsProkaryotic Eukaryotic

Average Cell Size

1-10 µm 10-100 µm

Cell Wall YES SOMETIMES

Cell Membrane YES YES

Nucleus NO YES

Cytoplasm YES YES

DNA YES, in cytoplasm

YES, in nucleus

Continuation on next slide

Similarities and Differences in Prokaryotic and Eukaryotic CellsProkaryotic Eukaryotic

Ribosomes YES YES

Membrane Enclosed Organelles

NO YES

Mode of Locomotion

One or more flagella

One or two flagella or cilia

Found in -- Bacteria only Fungi, protists, plants, animals

7-2: Inside the Eukaryotic Cell

The Framework of the Cell

Cytoskeleton – helps the cell move, keep its shape, and organize its parts Microfilaments and microtubules are two types of

cytoskeletons

Directing Cellular Activity

Nucleus – membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction The nucleus (nuclei – plural) houses

deoxyribonucleic acid (DNA) Genetic material in

cells Has information to

make proteins

Directing Cellular Activity

Nuclear membrane – a double membrane that surrounds the nucleus

Pores – openings in

the outer nuclear

membrane that

allow substances

to enter and leave the

nucleus

Directing Cellular Activity

Nucleolus (nucleoli) – small, dark-stained, round structures that makes ribosomes

Chromatin – DNA is in thread-like form; the cell is not dividing

Chromosome – condensed chromatin; forms a “X” structure duringcellular division

Directing Cellular Activity

Ribosomes – Organelles that help in the synthesis of proteins “Free” ribosomes make proteins that remain

inside the cell “Bound” ribosomes make proteins that are

exported from the cell

Directing Cellular Activity

Cytoplasm – the gel-like substance found between the cell membrane and the nucleus

Directing Cellular Activity

Centriole – one of a pair of organelles that are found in animal cells that function in the formation of spindle fibers during cell division

Protein Processing

Vesicle – (means “small vessel”) Sac-like membrane that helps store and transport products produced by cells

Protein Processing

The endoplasmic reticulum and the Golgi apparatus are organelles that prepare proteins for extracellular export

Endoplasmic reticulum (ER) – a network of membranes throughout the cytoplasm of the cell

Protein Processing

Two types of ER Rough ER – proteins are made in ribosomes and

then packaged into vesicles Smooth ER – synthesize lipids in the cell and

helps in the detoxification of harmful substances in the cell

Protein Processing

Golgi complex – responsible for sorting and correctly shipping the proteins produced in the ER Resembles a post office in cells

Storage and Maintenance

Lysosome – a vesicle that contains specific enzymes that breaks down large molecules

They also help recycle materials in the cell by digesting old, damaged, or unused organelles

Lysosomes are in animal cells

Storage and Maintenance

Mitochondrion (mitochondria = plural) – an organelle that uses energy from organic compounds to make ATP

Mitochondria and chloroplasts have their own DNA

Storage and Maintenance

Vacuole – an organelle that stores water, ions, nutrients, and wastes; it can also store toxins and pigments Animal cells have small vacuoles When water fills the central vacuole (only in plant

cells), it makes the cell rigid, allowing the plant to stand upright.

Storage and Maintenance

Some protists have contractile vacuoles, which pump excess water out of the cell

Storage and Maintenance

Chloroplast – an organelle that uses light energy to make sugar from carbon dioxide and water

Plant Cell vs. Animal Cell

Cell wall – provides additional support for certain cells; they have cellulose which aids in its structure

Plant Cell vs. Animal Cell

Organelles that are exclusively found in plant cells Cell wall Central vacuole Chloroplast

Organelles that are exclusively found in animal cells Lysosome Centriole

Picture of animal cell vs. plant cell

Cellular Movement

Flagella – long finger-like projections that push cells forward by snakelike wriggling

Cellular Movement

Cilia – short hair-like projections of certain cells that beat in a regular fashion to create currents that sweep materials along

7-3: From Cell to Organism

Levels of Organization

Cell – the smallest unit of life Tissue – group of cells that work together and

have a common function Organ – group of tissues that work together… Organ system – group of organs… Organism – group of organ systems…

Cellular Differentiation

Cellular differentiation – The normal process by which a less specialized cell develops or matures to possess a more distinct form and function