Chapter 6 A Tour of the Cell

Types of Cells

Prokaryotic (bacteria) - lack a nucleus and other membrane bounded structures (simple)

Eukaryotic (plant and animal) - have a nucleus and other membrane bounded structures (more complex)

Prokaryotic Eukaryotic

Nucleus

Prokaryotic

Eukaryotic

Why Are Cells So Small?

Cell volume to surface area ratios favor small size.

Nucleus to cytoplasm consideration (control).

Metabolic requirements.

Basic Eukaryotic Cell Organization

Membrane Nucleus Cytoplasm Organelles

Animal Cell

Plant Cell

Plasma Membrane

Separates the cell from the environment.

Regulates the movement of materials in/out of a cell.

Cytoplasm

Cell substance between the cell membrane and the nucleus.

The “fluid” part of a cell. Contains all organelles

Organelle

Term means "small organ” Structure in a cell with a

specialized function.

Nucleus

Contains genetic material (DNA) Directs all cell functions

Nucleus Structure

Nuclear membrane Nuclear pores Nucleolus Chromatin

Nuclear Membrane

Double membrane making up the boundary of the nucleus

Nuclear Pores

Regular “holes” through both nuclear membranes.

Allows materials in/out of nucleus.

Nucleolus

Storage area for ribosomes.

Chromatin

Chrom: colored - tin: threads DNA and Protein in a “loose”

format. Will form the cell’s chromosomes.

Ribosomes

Structure: 2 subunits made of protein and ribosomal RNA (rRNA)

No membrane.

Function: protein synthesis.

Ribosome Locations

Free in the cytoplasm - make proteins for use in cytosol.

Membrane bound (attached to a membrane) - make proteins that are exported from the cell.

Endomembrane System Related membranes throughout the cell Nuclear envelope endoplasmic reticulum golgi apparatus lysosomes vacuoles plasma membrane

Endomembrane System

Endoplasmic Reticulum

Often referred to as the ER. Often continuous with

(connects to) the nuclear membrane.

Structure of ER

Folded sheets or tubes of membranes.

Types of ER

Smooth ER: no ribosomes. Used for lipid synthesis,

carbohydrate storage, detoxification of poisons.

Rough ER: covered with ribosomes Makes secretory proteins.

Golgi Apparatus

Structure: parallel array of flattened cisternae. (looks like a stack of Pita bread)

Found close to the ER

Structure Has 2 Faces

Cis face - side toward the nucleus. Receiving side.

Trans faceface - side away from - side away from the nucleus. Shipping side.the nucleus. Shipping side.

Function of Golgi Bodies

Processing - modification of ER products

Distribution - packaging of ER products for transport. ER products packaged into vesicles

and shipped out

Lysosome

Single membrane. Made from the Trans face of

the Golgi apparatus.

Lysosome Function

Breakdown and degradation of cellular materials.

Group Questions

Which of the following structures would be found in a prokaryotic cell? A. Endoplasmic reticulum B. Ribosome C. Golgi apparatus D. Nuclear envelope E. Flagellum

Group Questions

Why are most animal cells, regardless of species, relatively small and about the same size? A. small cells avoid excessive osmosis and subsequent

lysis B. small cells have a small surface to volume ratio C. small cells have a large surface to volume ratio D. small cells require less energy E. small cells fit together more tightly

Group Questions

To manufacture the components of the plasma membrane, activity from all of the following are required EXCEPT: A. lysosomes B. rough ER C. mRNA D. Golgi apparatus E. vesicles

Group Questions

In the inherited disorder Pompe’s disease, glycogen breakdown in the cytosol occurs normally and blood glucose levels are normal, yet glycogen accumulates in lysosomes. This suggests a malfunction with: A. catabolic enzymes in the mitochondria B. anabolic enzymes in the lysosomes C. catabolic enzymes in the lysosomes D. membrane transport during exocytosis E. membrane transport during endocytosis

Group Questions

All of the following are membrane bound bodies in eukaryotic cells EXCEPT: A. lysosome B. mitochondrion C. endoplasmic reticulum D. nucleolus E. Golgi body

Vacuoles

Structure - single membrane, usually larger than the Golgi vesicles.

Function - depends on the organism. Pump out water Store food or water

Plant Vacuole

Large single vacuole when mature making up to 90% of the cell's volume.

Tonoplast - the name for the vacuole membrane.

Peroxisomes

Similar to lysosomes, but they contain enzymes to break down hydrogen peroxide

Enzymes in a crystal

Mitochondria Structure

2 membranes ATP generated at inner membrane

Matrix: inner space. Intermembrane space: area

between the membranes.

Mitochondria Functions

Cell Respiration - the release of energy from food.

Major location of ATP generation.

“Powerhouse” of the cell.

Mitochondria

Have ribosomes. Have their own DNA. Can reproduce themselves. May have been independent

cells at one time.

Chloroplast Function

Photosynthesis - the use of light energy to make food.

Chloroplasts

Contain ribosomes. Contain DNA. Can reproduce themselves. Often contain starch. May have been independent

cells at one time.

Cytoskeleton

Network of rods and filaments in the cytoplasm

Cytoskeleton Functions

Cell structure and shape. Cell movement. Cell division - helps build cell

walls and move the chromosomes apart.

Cilia and Flagella

Cilia - short, but numerous. Flagella - long, but few. Function - to move cells or to

sweep materials past a cell.

Centrioles

Usually one pair per cell, located close to the nucleus.

Found in animal cells. Help in cell division.

Cytoskeleton

Very dynamic; changing in composition and shape frequently.

Cell is not just a "bag" of cytoplasm within a cell membrane.

Cell Wall

Nonliving “jacket” that surrounds some cells.

Found in: Plants Prokaryotes Fungi Some Protists

Cell Walls

Function as the cell's exoskeleton for support and protection.

Extracellular Matrix - ECM

“Fuzzy coat” on animal cells. Helps glue cells together. Made of glycoproteins and

collagen.

Evidence suggests ECM is involved with cell behavior and cell communication.

Intercellular Junctions Join neighboring cells Plant cells

Plasmodesmata

Animal cells Tight junctions Desmosomes Gap junctions

Plasmodesmata

Channels between cells through adjacent cell walls.

Intercellular Juctions

Animals: Tight junctions Desmosomes Gap junctions

Tight Junctions

Very tight fusion of the membranes of adjacent cells.

Seals off areas between the cells.

Prevents movement of materials around cells.

Desmosomes Bundles of filaments which

anchor junctions between cells.

Does not close off the area between adjacent cells.

Gap Junctions

Open channels between cells, similar to plasmodesmata.

Allows “communication” between cells.

Summary

Answer: Why is Life cellular and what are the factors that affect cell size?

Be able to identify cellular parts, their structure, and their functions.