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Questions and Answers
What is the primary function of the nucleolus?
Which cellular organelle is known as the powerhouse of the cell?
What distinguishes rough endoplasmic reticulum (ER) from smooth ER?
What role do lysosomes play in the cell?
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The Golgi body is primarily responsible for which function?
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Which of the following describes the structure of the cell membrane?
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What is the primary composition of the phospholipid found in the cell membrane?
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What do the cristae in mitochondria signify?
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What is the primary function of the cell membrane?
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Which of the following accurately describes catabolic pathways?
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Which of the following are main reactants in cellular respiration?
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In which part of the cell does photosynthesis primarily take place?
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What main products are generated from cellular respiration?
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Which of these statements about anabolism is correct?
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Which pathways are part of cellular respiration in eukaryotes?
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What is the role of metabolic pathways within cells?
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What is the fundamental unit of a living organism?
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Which scientist is known as the ‘Father of Cytology’?
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According to cell theory, which statement is true?
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What primarily limits the size of a cell?
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Who discovered the nucleus of the cell?
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What does the shape of a cell generally reflect?
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Which of the following is NOT a characteristic of cells?
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What did Rudolf Virchow contribute to cell theory?
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Study Notes
Introduction
- All living organisms are made up of cells.
- Cells are the basic unit of life.
- Organisms are either unicellular or multi-cellular.
- Unicellular organisms are composed of one cell, such as bacteria.
- Multicellular organisms are made up of more than one cell, such as humans.
Cell History
- Cytology is the study of cells.
- Robert Hooke is considered the "Father of Cytology".
- Hooke observed cork using a microscope.
- Hooke named the structures he observed "cells".
- Robert Brown discovered the nucleus in 1833.
- Matthias Schleiden, a German botanist, determined all plants are composed of cells.
- Theodor Schwann, in 1838, discovered animals were made of cells.
- Rudolf Virchow, a German physician, stated that all cells come from other cells in 1855.
- Virchow's statement disproved the "Theory of Spontaneous Generation".
Cell Theory
- The Cell Theory combines the work of Schleiden, Schwann, and Virchow.
- The Cell Theory states:
- All living things are made up of one or more cells.
- Cells are the basic unit of life.
- All cells arise from pre-existing cells.
Cell Diversity
- Cells within the same organism vary greatly in:
- Size
- Shape
- Internal organization
Cell Size
- Cells are generally small for two reasons:
- The ratio between their Outer Surface Area and Volume. Smaller cells have more surface area for a given volume.
- The nucleus can only control a certain amount of cytoplasm.
Cell Shape
- The shape of a cell is dependent on its function.
- Different cell shapes indicate different functions.
Internal Organization
- All cells have an outer membrane.
- The cell membrane is semi-permeable.
- The inside of the cell contains organelles.
- The cytoplasm is the gel-like substance that surrounds the organelles.
Cellular Organelles
- Organelles are specialized structures within a cell.
- Each organelle performs a specific function.
Nucleus
- The nucleus is a spherical body surrounded by the nuclear membrane.
- The nucleus contains many organelles, including the nucleolus.
- The nucleus is the site of nucleic acid synthesis.
Nucleolus
- The nucleolus is often visible as a dark spot in the nucleus.
- The nucleolus is the site of ribosome formation and RNA and protein synthesis.
Mitochondria
- Mitochondria are spherical to rod-shaped.
- Mitochondria have a double membrane.
- The inner membrane forms folds called cristae.
- Mitochondria are the powerhouses of the cell.
- Mitochondria are responsible for oxidative reactions and electron transport.
- Mitochondria convert energy from food into usable energy for the cell.
Lysosomes
- Lysosomes are small and round organelles surrounded by a membrane.
- Lysosomes contain digestive enzymes that break down materials in the cell.
- Lysosomes break down large food particles and old cell parts.
- Lysosomes are considered the cell's cleanup crew.
Endoplasmic Reticulum
- The endoplasmic reticulum (ER) is attached to the outside of the nucleus.
- The ER is a network of membranes.
- The ER can be smooth or rough.
- Smooth ER does not have ribosomes attached. It is the site of lipid synthesis.
- Rough ER has ribosomes attached. It aids ribosomes in synthesizing proteins.
Golgi Body
- The Golgi body is a flattened, layered, sac-like organelle.
- The Golgi body resembles a stack of pancakes.
- The Golgi body is located near the nucleus.
- The Golgi body produces membranes that surround lysosomes.
- The Golgi body packages proteins and carbohydrates into vesicles for export from the cell.
Cell Membrane
- The cell membrane is also known as the plasma membrane.
- Electron microscopy has led to the development of the lipid bilayer model, also known as the fluid-mosaic model.
- The cell membrane is primarily composed of phospholipids.
- Phospholipids have a hydrophilic head and two hydrophobic tails.
- The nonpolar tails form a hydrophobic region between the hydrophilic heads.
Cytoplasm
- The cytoplasm is the jellylike substance between the plasma membrane and the nuclear envelope.
- Organelles are located in the cytoplasm.
Cell Metabolic Process
- Cell metabolism is the collection of chemical reactions occurring within living cells.
- Metabolic processes sustain life and maintain cellular functions.
- Metabolic processes include the conversion of nutrients into energy, the synthesis of biomolecules, and the regulation of metabolic pathways.
- Cell metabolism is essential for understanding how cells obtain energy, generate cellular components, and adapt to environmental changes.
Anabolic and Catabolic Pathways
- Cellular metabolic pathways can be categorized into two: anabolic and catabolic.
- Anabolic pathways require energy to build larger molecules from smaller ones. An example of an anabolic pathway is photosynthesis.
- Catabolic pathways release energy by breaking down larger molecules into smaller ones. Examples of catabolic pathways are cellular respiration and glycolysis.
Cellular Respiration
- Cellular respiration is a metabolic pathway that breaks down glucose to produce ATP (adenosine triphosphate).
- The main reactants in cellular respiration are glucose and oxygen.
- The main products of cellular respiration are carbon dioxide, water, and ATP.
- The chemical equation for cellular respiration is: C6H12O6 + O2 -→ CO2 + H2O + ATP
Cellular Respiration Pathways in Eukaryotes
- Cellular respiration occurs in eukaryotic cells.
- The different pathways of cellular respiration in eukaryotes are:
- Glycolysis
- Pyruvate oxidation
- Citric acid cycle (Krebs cycle)
- Oxidative phosphorylation
Photosynthesis
- Photosynthesis is a metabolic process that occurs in plant cells, some algae, and certain bacteria called cyanobacteria.
- Photosynthesis takes place in chloroplasts.
- Photosynthesis produces sugar and oxygen.
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