Cell Structure and Function

Cell Structure and Function

The discovery and the basic theory of cells. Cell size and number. The two major kinds of cells. Plant cells and animal cells. Cell me mbrane (plasma membrane). Cytoplasm. Nucleus. Ribosomes.

Endoplasmic reticulum (rough ER and smooth ER). Golgi complex (body). Lysosomes. Peroxisomes. Mitochondria. Chloroplasts. Cytoskeleton. Vacuoles.

The Discovery and Basic Theoryof Cells

Robert Hooke

About 1663, Hooke directed an instrument maker to improve his own microscope.

Robert Hooke Discovered and Named Cells

Hooke began to focus his new instrument on everyday objects.

When Hooke peered at a thin slice of cork, he saw what he called “pores” or “cells”.

Anton Van Leeuwenhoek

Leeuwenhoek’s small, simple, hand-held microscope

Leeuwenhoek had far greater success at seeing living cells such as Euglena.

He discovered bacteria and called them “animalcules”.

Matthias Schleiden

In 1838, Schleiden drew an important conclusion based on years studying plant tissues.

All plants, he said, are made up of cells.

Theodor Schwann

In 1839, Schwann drew an important conclusion based on years studying animal tissues.

All animals, he said, are made up of cells.

Schleiden and Schwann

1n 1839, both together published the even broader conclusion that:

All living things are composed of cells.

Rudolph Virchow

20 years later, Virchow stated that living cells arise only from preexisting cells.

The Modern Cell Theory

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

2. Cells are the basic living units within organism, and the chemical reactions of life take place within cells.

3. All cells arise from preexisting cells.

Cell Size

Not all cells have the same size. We use the micrometer to measure the

sizes of cells. There are 1,000 millimeters in 1 meter. There are 1,000,000 micrometers in 1

meter.

Surface-to-Volume Ratio

The life of a cell depends on exchanges of materials with the environment.

Movement of of all these materials takes place through the cell’s surface.

The larger a cell’s volume, the greater the amount of material to be exchanged.

Since this exchange depends on the cell’s surface area, the surface-to-volume ratio imposes limits on cell size.

Surface-to-Volume Ratio

Surface: 6x4= 24 cm2 Surface: 8x6= 48 cm2 Volume: 2x2x2= 8 cm3 Volume: 8x1= 8 cm3

Surface-to-volume: 24/8= 3 Surface-to-volume: 48/8= 6

Small size increases surface-to-volume ratio

Question 1

Four of the five answers listed below are portions of a well-known theory. Select the exception:

A. cells are the structural and functional components of living things.

B. cells arise from preexisting cells. C. all organisms are made up of cells. D. all cells have a nucleus.

Question 2

Select the correct statement: A. as a cell increases in size, its surface-to-

volume ratio increases. B. as a cell decreases in size, its surface-to-

volume ratio increases. C. as a cell increases in size, its surface-to-

volume ratio stays the same.

Question 3

The fingerlike extensions of the outer membrane of the cells lining the intestine serve to:

A. increase the cells’ cytoplasm. B. decrease the cells’ cytoplasm. C. increase the cells’ surface-to-volume ratio. D. decrease the cells’ surface-to-volume ratio.

Answers

Question 1: D Question 2: B Question 3: C