Biology Chapter: What are Cells?

Study Notes

What are Cells?

Cells are the smallest living units of an organism
All cells share three common features: a cell membrane, cytoplasm, and DNA

Cell Membrane

Separates the cell's interior from the external environment

Cytoplasm

Gelatinous fluid within the cell

DNA

The cell's genetic material

Types of Cells

Eukaryotic Cells

More complex than prokaryotic cells
Contain organelles, including the nucleus and other specialized structures
Found in plants and animals

Prokaryotic Cells

Lack a nucleus or membrane-bound organelles
Genetic material is not enclosed within a nucleus
Always single-celled organisms (unicellular), like bacteria

What are Organelles?

“Small organs”
Specialized parts of the cell with specific functions

Nucleus

Control center of the cell
Contains DNA
Dictates cellular processes and function

Chromatin

DNA in its interlinked and dispersed form within the nuclear membrane
Condenses into chromosomes when the cell is about to divide

Nucleolus

Structure within the nucleus responsible for ribosome production

Ribosomes

Synthesize proteins
Move freely within the cytoplasm or attach to the endoplasmic reticulum (ER)

Endoplasmic Reticulum (ER)

Network of membranes that transport materials like proteins (synthesized by ribosomes)
Two types:
- Rough (granular) ER - ribosomes attached
- Smooth (agranular) ER - no ribosomes

Golgi Apparatus

Also called Golgi body
Receives proteins and other materials from the ER
Modifies proteins
Packages them into usable forms for the cell
Adds lipids or carbohydrates to proteins

Vacuoles

Sac-like structures for storing various materials
In plant cells, the central vacuole stores water

Lysosomes

Waste disposal centers
Contain enzymes to break down used or damaged parts of the cell

Mitochondria

Powerhouses of both plant and animal cells
Produce ATP molecules through cellular respiration, which provides energy for cellular processes
Cells with higher energy requirements have more mitochondria

Cytoskeleton

Supports and maintains the shape of the cell
Contains:
- Microfilaments: thin protein filaments
- Microtubules: hollow tubes

Chloroplasts

Found in plant cells
Site of photosynthesis
Green due to the pigment chlorophyll

Cell Wall

Present in plant cells outside the cell membrane
Provides shape, support, and protection

Cilia

Tiny hair-like projections
Found in cells lining the respiratory tract
Wave-like movements help capture inhaled particles and expel them through coughing

Flagella

Tail-like structures
Found in some bacteria
Allow the cell to move or propel itself forward
The only human cell with a flagellum is the sperm

Summary

Eukaryotic cells (plant and animal cells) have a nucleus and membrane-bound organelles
Prokaryotic cells (unicellular organisms) lack these features
All cells have a cell membrane, cytoplasm, and genetic material
Only plant cells have chloroplasts, but both plant and animal cells have mitochondria

Description

Explore the fundamental unit of life in this biology quiz on cells. Learn about the differences between prokaryotic and eukaryotic cells, their structures, and functions. Test your understanding of organelles and the significance of the nucleus and DNA.

Biology Chapter: What are Cells?

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Questions and Answers

What is the primary function of the nucleus in a cell?

Which type of cells lack a nucleus?

What are ribosomes primarily responsible for?

What is the role of mitochondria in a cell?

Which structure within the nucleus is responsible for ribosome production?

What distinguishes rough ER from smooth ER?

What is the function of lysosomes in a cell?

Which structure is responsible for the wave-like movements in cells lining the respiratory tract?

What components do all cells have in common?

Which organelle modifies and packages proteins for the cell?