Cells Structure and Function. Fig. 3.2 Life on Earth All living things are made of one or more cells There are two major types of cells Prokaryotic cells.

Cells

Structure and Function

Fig. 3.2

Life on Earth

All living things are made of one or more cells There are two major types of cells

Prokaryotic cells Eukaryotic cells

Fig. 3.5

Prokaryotic and Eukaryotic Cells

Prokaryotic cells have: DNA Cell wall and plasma membrane Cytoplasm and ribosomes

Prokaryotic cells DO NOT have: A nucleus Compartmentalized specialized structures

(organelles)

DNA

Cell wall

cell membrane

Prokaryotic and Eukaryotic Cells

Bacteria are prokaryotic cells and are generally much smaller than eukaryotic cells

Prokaryotic and Eukaryotic Cells Eukaryotic cells include cells of

Plants Protozoa and Algae Fungi Animals

Eukaryotic cells have A plasma membrane Ribosomes DNA enclosed in a nucleus Compartmentalized specialized structures (organelles)

Cell Structure

All cells are enclosed by a structure called a plasma membrane

The function of the plasma membrane is to control what enters and leaves the cell

Cell Structure

All membranes in a cell have similar structural components: phospholipids and proteins

The phospholipids arrange themselves to form phospholipid bilayers with water both on the inside and the outside of the bilayer

Cell Structure

Since the phospholipids have two hydrophobic tails at one end and a hydrophilic head at the other end, they tend to gather in a specific arrangement

Two layers with the hydrophilic heads pointing out and the hydrophobic tails on the inside.

A Fluid Mosaic ofLipids and Proteins

A Fluid Mosaic ofLipids and Proteins Because lipids and proteins can move about

laterally within the membrane, the membrane is a fluid mosaic of lipids and proteins

A Fluid Mosaic ofLipids and Proteins

Cell membranes are semipermeable Allow some things through but not others Water freely crosses the membranes

This can be a problem If too much water enters the cell, it may swell or burst If too much water leaves the cell, it may shrink

All organisms have ways of regulating how much water is in their cells. In most animals (except some simple marine

invertebrates) the water content of tissues is regulated by the kidneys, so this isn’t normally a problem.

A Fluid Mosaic ofLipids and Proteins

Cell membranes are semipermeable Allow some things through but not others

Gases such as oxygen and carbon dioxide pass freely But substances such as glucose and proteins require

the help of the proteins in the cell membrane in order to enter the cell.

A Fluid Mosaic ofLipids and Proteins

Some cells (like plant cells and fungal cells) have a cell wall outside of the plasma membrane that give the cell structure and protect against water damage

The cell wall is purely structural and has no control over what enters or leaves the cell

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Fig. 3.7

Fig. 3.8

Fig. 3.10

Fig. 3.11

Fig. 3.12

Fig. 3.14

Fig. 3.16

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Fig. 3.18

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Mitochondria are organelles that carry out the process of aerobic respiration, which converts food energy to ATP, the type of energy a cell can use.

Fig. 3.19

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Fig. 3.20

The nucleus is a membrane bound structure that encloses the DNA

Cytosol and Cytoplasm

The cytoplasm is made up of the watery mixture inside the cell (called the cytosol) and the organelles

The cytoplasm is contained by the plasma membrane.

Organelles are membrane bound structures that carry out specific jobs for the cells.

Cellular functions are more efficient when the work is compartmentalized in organelles.

Chloroplasts are organelles found in plant cells. Chloroplasts can convert sunlight energy into chemical energy stored in the chemical bonds of glucose.

Lysosomes are small membrane sacs that contain digestive enzymes which break down food and other materials for the cell.

Ribosomes are small structures that act like workbenches. Proteins are assembled at the ribosomes. Some ribosomes are free in the cytoplasm and some are bound to a structure called the endoplasmic reticulum.

Some subcellular structures help cells divide and maintain their shape. Centrioles are involved in moving genetic material around when a cell divides

Plant Cell Wall