Komorka – budowa i funkcje – matura biologia 2026 – lekcja – Kurs maturalny z biologii Biomedica

Introduction to Cell Structure and Function

Overview of the Session

• The session begins with a greeting and a request for confirmation on audio and visual clarity. Participants are encouraged to ask questions via chat.

• The focus will be on cell structure, function, and comparisons between different types of cells, including prokaryotic cells.

Types of Cells

• Cells are categorized into two main types: somatic (body) cells and generative (sex) cells. Somatic cells build the organism's body, while generative cells participate in sexual reproduction.

• In humans, generative cells include motile sperm and non-motile egg cells; somatic cells can only partake in asexual reproduction or not at all.

Why Are Cells Small?

Surface Area to Volume Ratio

• A critical concept discussed is the relationship between cell size and efficiency in substance exchange; larger volumes lead to an unfavorable surface area-to-volume ratio that hampers effective transport processes.

• Smaller cells maintain a favorable ratio that allows efficient exchange of substances with their environment and internal transport mechanisms. This principle is often tested in examinations.

Implications for Organism Size

• As cell size increases, the surface area-to-volume ratio decreases, complicating efficient transport both into the cell from its surroundings and within its interior structures. Thus, larger organisms consist of many small cells rather than fewer large ones.

Cell Compartments: Prokaryotic vs Eukaryotic

Differences Between Cell Types

• Prokaryotic cells lack internal compartments; they have one compartment defined by a plasma membrane without organelles like nuclei or chloroplasts. In contrast, eukaryotic cells contain multiple compartments such as nuclei and various organelles that allow for specialized functions under different environmental conditions.

• The presence or absence of a nucleus distinguishes eukaryotic (nucleated) from prokaryotic (non-nucleated) cells; some specialized eukaryotic cells may lose their nuclei during differentiation but still retain other cellular functions. Examples include erythrocytes (red blood cells).

Understanding Cell Structures: Key Concepts

Types of Cells

• The discussion begins with the definition of nucleated and non-nucleated cells, highlighting that mature erythrocytes (red blood cells) are an example of non-nucleated cells.

Cell Membrane Functions

• The cell membrane serves as a boundary, facilitating the exchange of substances with the environment while maintaining cellular integrity.

Cytoplasm vs. Cytosol

• Cytoplasm is defined as the entire content within a cell excluding the nucleus, while cytosol refers specifically to the gel-like fluid filling spaces between organelles.

• Visual aids illustrate cytosol in a light purple color, emphasizing its role in supporting cellular structures.

Golgi Apparatus Role

• The Golgi apparatus consists of flattened cisternae and is crucial for modifying, sorting, packaging, and transporting proteins and lipids within vesicles.

• Distinction made between rough and smooth endoplasmic reticulum; rough ER synthesizes proteins while smooth ER synthesizes lipids. The Golgi modifies these macromolecules for transport.

Lysosomes and Their Functions

• Lysosomes contain digestive enzymes essential for breaking down food particles ingested by animal cells through processes like phagocytosis and pinocytosis.

• These enzymes facilitate intracellular digestion by hydrolyzing larger molecules into smaller ones that can be reused by the cell.

Vacuoles: Structure and Function

• Discussion on vacuoles highlights their dual terminology—vacuoles in plant cells versus vesicles in animal cells—and their roles in storage and maintaining turgor pressure.

• Central vacuoles are primarily found in plant cells for storing nutrients, whereas food vacuoles are more common in animal cells.

• Vacuoles store various substances including water, minerals, organic compounds like anthocyanins (color pigments), which vary based on pH levels affecting plant coloration.

• Additional contents of vacuoles include alkaloids and glycosides that contribute to plants' bitter taste deterring herbivores; they also play roles in cellular digestion processes.

Cellular Structures and Functions

Vacuoles in Plant and Animal Cells

• The vacuole in plant cells contains water, mineral salts, pigments, alkaloids, tannins, glycosides, and may include hydrolytic enzymes that aid in the digestion of damaged cellular structures.

• In animal cells, food vacuoles are present; additionally, contractile vacuoles exist in protists which will be discussed later.

Peroxisomes: Structure and Function

• Peroxisomes are single-membrane-bound organelles containing catalase, an enzyme that decomposes toxic hydrogen peroxide into water and oxygen.

• Hydrogen peroxide negatively impacts cellular structures by causing damage and mutations to DNA; thus, its breakdown is crucial for cell health.

Endoplasmic Reticulum (ER)

Smooth Endoplasmic Reticulum

• The smooth ER lacks ribosomes on its surface and is primarily involved in lipid synthesis; it is well-developed in glandular tissues producing fatty substances.

• Examples include adrenal cortex cells that produce steroid hormones like cortisol as well as ovaries and testes which produce estrogen and testosterone.

Rough Endoplasmic Reticulum

• The rough ER has ribosomes on its surface; these ribosomes are essential for protein synthesis. They consist of proteins and rRNA (ribosomal RNA).

Ribosomes: Types and Locations

• Ribosomal RNA (rRNA), a component of ribosomes, plays a critical role in protein synthesis during translation.

• Prokaryotic cells have smaller 70S ribosomes while eukaryotic cells contain both 70S (in mitochondria and plastids) and larger 80S ribosomes found in cytoplasm or associated with rough ER.

Key Comparisons of Ribosome Types

• It’s important to note the differences between prokaryotic (70S) and eukaryotic (70S & 80S) ribosomes for exam purposes.

• When comparing them directly: prokaryotic ribosomes are smaller at 70S while eukaryotic ones can be either 70S or larger at 80S depending on their location within the cell.

Ribosomes and Their Role in Protein Synthesis

Differences in Ribosomes

• Ribosomes vary in size and location, but the discussion avoids generalizations about which are larger or smaller.

• The rough endoplasmic reticulum (RER) is involved in protein synthesis and initial modifications of proteins.

Protein Synthesis Process

• Protein synthesis often begins on ribosomes attached to the RER, where polypeptide chains enter for preliminary modifications.

• Proteins are packaged into vesicles for transport either outside the cell or to specific locations within it.

Mitochondria: Structure and Function

Mitochondrial Structure

• Mitochondria are organelles surrounded by two membranes: an outer membrane and a highly folded inner membrane forming cristae.

Key Functions of Mitochondria

• Students should articulate that mitochondria release energy rather than produce it; they contain mitochondrial DNA (mtDNA) and 70S ribosomes.

• Correct terminology emphasizes that ATP is synthesized within mitochondria, while energy is released during this process.

Misconceptions About Energy Production

• It’s incorrect to state that energy is produced in mitochondria; instead, it's more accurate to say that energy is released there.

Autonomy of Mitochondria

Semi-Autonomous Nature

• Mitochondria can synthesize some proteins independently due to their mtDNA, but not all proteins are encoded by it; some come from nuclear DNA.

Endosymbiotic Theory

• The endosymbiotic theory explains how mitochondria likely originated through symbiosis with ancestral prokaryotic cells.

Cell Nucleus Overview

Structure of the Nucleus

• The nucleus is encased in a nuclear envelope containing nuclear pores, housing chromatin (DNA wrapped around proteins).

Functions of the Nucleus

• The primary role of the nucleus includes storing genetic information and protecting it from damage.

Cytoskeleton Components

Types of Cytoskeletal Elements

• Three main types include microtubules, microfilaments, and intermediate filaments; microtubules form spindle fibers during cell division.

Cell Structure and Function

Role of Microtubules

• Microtubules are essential for building spindle fibers during cell division (mitosis) and also form cilia.

• They facilitate intracellular transport by creating pathways within the cell and help position various cellular structures, contributing to spatial organization.

Function of Microfilaments

• Composed of actin, microfilaments are responsible for cytoplasmic movement, enabling cells to extend cytoplasmic projections for processes like phagocytosis.

• They strengthen microvilli, significantly increasing the surface area for absorption and secretion.

Intermediate Filaments

• Intermediate filaments enhance mechanical strength in cells, providing resistance against tearing and stretching in various tissues.

• They create a robust network that protects cells from mechanical injuries.

Plant Cell Structures

• The discussion shifts to plant cells, highlighting the cell wall as a key structural component.

• Key components of plant cell walls include cellulose; fungal cell walls contain chitin, while bacterial walls consist of peptidoglycan.

Functions of the Cell Wall

• The cell wall protects against environmental stressors and prevents pathogen entry into the cell.

• It also prevents bursting due to osmotic pressure by maintaining structural integrity through primary (more flexible) and secondary (more rigid with less water content) layers.

Plastids: Types and Functions

Chloroplast Structure

• Chloroplasts are vital for photosynthesis, featuring an outer membrane, inner membrane, stroma containing ribosomes similar to prokaryotes, and thylakoids involved in light reactions.

Pigments in Plastids

• Chloroplast pigments include chlorophyll (green), which is crucial for capturing light energy during photosynthesis. Other pigments like carotenoids contribute to color variations in fruits and flowers.

Importance of Coloration

• Brightly colored flowers attract pollinators while vividly colored fruits aid seed dispersal by attracting animals that consume them.

Endosymbiotic Theory

Origin of Organelles

• The endosymbiotic theory posits that mitochondria and plastids originated from free-living bacteria engulfed by ancestral eukaryotic cells.

Evidence Supporting Endosymbiosis

• Mitochondria and plastids possess their own DNA resembling prokaryotic DNA; they also have ribosomes akin to those found in bacteria. This supports their evolutionary origin from independent organisms.

Overview of Fungal and Bacterial Cell Structures and Reproduction

Fungal Reproduction

• Discussion on the types of DNA in fungi, specifically mitochondrial and plastid DNA, highlighting their double membrane structure.

• Emphasis on the importance of understanding sexual and asexual reproduction in fungi, referencing developmental cycles found in textbooks.

• Key methods of asexual reproduction include spore dispersal, fragmentation, gametogamy, gametangiogamy, somatogamy, and budding.

• Mention of intercellular connections in plant cells (plasmodesmata) versus animal cells (tight junctions, desmosomes), noting significant differences between cell types.

• Summary table comparing animal cells with fungal cells; highlights that animal cells lack cell walls while both fungal and plant cells contain chloroplasts.

Bacterial Cell Structure

• Introduction to bacterial cells: they lack a nucleus and have a cell wall primarily made of peptidoglycan.

• Explanation that genetic information is stored as a genophore within the nucleoid region; distinction between genophore (DNA) and nucleoid (location).

• Description of plasmids as small circular DNA molecules that can carry antibiotic resistance genes; mention of bacterial movement via flagella or fimbriae for attachment.

• Recap on key characteristics: absence of a nucleus, presence of peptidoglycan cell wall without internal membranes.

Classroom Activities

• Transition to classroom tasks involving microscopy to identify organelles in onion scale cells; students are prompted to name structures marked X and Y.

• True/false exercise regarding vacuoles in plant and fungal cells containing hydrolytic enzymes; clarification provided about vacuole functions.

• Identification task where students recognize large spaces filled with cellular sap as vacuoles; discussion on how these structures are often depicted schematically as empty spaces.

• Explanation about hydrolytic enzymes' role in digesting non-functional cellular structures for recycling materials within the cell.

Understanding Surface Area to Volume Ratio in Cells

Importance of Cell Size

• The discussion begins with the significance of cell size, emphasizing that smaller cells have a higher surface area to volume ratio, which is crucial for efficient substance exchange.

• A table is referenced that illustrates the relationship between surface area and volume, comparing small cubes to larger ones made up of smaller cubes, highlighting efficiency in transport.

Efficiency of Substance Exchange

• It is noted that larger cells (e.g., a cube with a side length of 10) exhibit a lower surface area to volume ratio (0.6), making them inefficient for substance exchange due to limited interaction with their environment.

• The conversation stresses that organisms must maintain a high surface area to volume ratio for effective transport and exchange of substances within cells.

Multicellular vs. Unicellular Organisms

• A question arises regarding why multicellular organisms do not consist of large cells; it’s explained that large cells would struggle with efficient substance exchange and internal transport.

• The importance of maintaining an optimal surface area to volume ratio is reiterated, as low ratios hinder cellular functions.

Specialized Structures in Cells

• Enterocytes in the small intestine are discussed; they possess microvilli which significantly increase their absorptive surface area, enhancing nutrient uptake during digestion.

• Microvilli are highlighted as critical adaptations allowing enterocytes to efficiently absorb nutrients like amino acids and sugars from digested food.

Cell Wall Composition and Storage Substances

• A question about the composition of cell walls leads to identifying fungal cells characterized by cell walls without chloroplasts, distinguishing them from plant cells.

• Chitin is identified as the primary component of fungal cell walls, while glycogen and fats are mentioned as key storage substances within these cells.

Membrane Structure Discussion

• The session transitions into discussing cell membrane structures, prompting students to identify whether depicted membranes belong to animal or plant cells based on specific characteristics observed in diagrams.

Cholesterol and Cell Structure

Role of Cholesterol in Animal Cells

• Cholesterol is essential for animal cells, contributing to the fluidity and stability of cell membranes.

• Glycolipids are also present, forming part of the glycocalyx, which is crucial for cell recognition and signaling.

Differences Between Plant and Animal Cells

• Key distinguishing features include the presence of plastids in plant cells, while animal cells lack them.

• Plant cells have a cell wall made primarily of cellulose, whereas animal cells do not possess a cell wall.

Understanding Cell Division Structures

Unique Structures in Plant Cell Division

• The structure that appears only during plant cell division due to the presence of a cell wall is called the fragmoplast.

Functions of Water in Human Physiology

• Water serves multiple roles in human physiology; one function discussed is its role as a solvent.

• Osmoregulation involves maintaining water and mineral balance within the body through various processes.

Metabolic Processes Involving Water

Importance of Water Regulation

• Water plays a critical role in regulating body temperature through sweating, highlighting its importance in thermoregulation.

Cellular Mechanisms for Enzyme Production

• The pancreas produces digestive enzymes via ribosomes and endoplasmic reticulum (ER), where proteins undergo initial modifications before being sent to Golgi apparatus for final processing.

• Secretory vesicles transport these enzymes to their destination within the glandular lumen.

Diversity Among Living Organisms

Common Features Across Different Cell Types

• Both prokaryotic (bacterial) and eukaryotic (plant/animal) cells share common structures such as ribosomes, emphasizing fundamental cellular functions across life forms.

Cell Structure and Function in Eukaryotic Cells

Overview of Plant Cell Characteristics

• The cell wall of a land plant cell is layered, primarily composed of mannan, which raises questions about its accuracy.

• Cytoplasm appears uniform; however, older cells contain vacuoles. Glycogen is mentioned as a storage material, but it is not typical for plant cells.

• The presence of a single nucleus containing genetic material indicates that the cell type must be identified correctly; glycogen and mannan are not suitable descriptors for plant cells.

• Correct identification leads to recognizing that the cell wall consists mainly of cellulose, with large vacuoles and numerous chloroplasts present in the cytoplasm.

• Starch serves as the primary storage material in this context, confirming that option C accurately describes the plant cell.

Distinguishing Eukaryotic Cell Types

• Among eukaryotic cells, distinctions are made between plant, animal, and fungal cells based on structural characteristics depicted in diagrams.

• Identifying types A and B requires understanding their unique features; one has a cell wall while the other does not.

• The presence of chloroplasts in one type confirms it as a plant cell (B), while the absence indicates that type A is fungal.

Key Structural Elements

• Students are encouraged to describe elements marked on diagrams by associating them with specific functions or characteristics relevant to each structure.

• Emphasis is placed on internal structures rather than external shapes when identifying cell types; shape should not dictate classification.

Understanding Cellular Components

• Chloroplast presence differentiates plant from fungal cells. This distinction highlights critical cellular components necessary for photosynthesis.

• Element 1 refers to the cell wall while Element 2 pertains to the plasma membrane; both have distinct compositions affecting their functions.

Protein Synthesis Locations

• Mitochondria are identified as sites for protein synthesis alongside rough endoplasmic reticulum (RER).

• Chloroplast involvement in ATP synthesis is noted; however, they do not exist within fungal cells impacting their metabolic processes.

Summary of Protein Biosynthesis

• In eukaryotic cells like plants (cell B), biosynthesis occurs across mitochondria and chloroplast ribosomes.

• Conversely, fungi lack chloroplast structures leading to differences in protein synthesis capabilities compared to plants.

Mitochondria and ATP Synthesis

Role of Mitochondria in Energy Production

• Mitochondria are involved in the synthesis of ATP, which is crucial for cellular energy, but they do not directly produce energy.

• The process of ATP synthesis occurs within the cell, highlighting the importance of mitochondria in metabolic functions.

Chloroplasts and ATP Creation

• Chloroplasts also participate in ATP production, indicating that both mitochondria and chloroplasts play significant roles in energy metabolism within cells.

Cellular Transport Mechanisms

Upcoming Topics on Membrane Structure

• Future discussions will focus on plasma membrane structure and transport mechanisms, including osmosis.

Importance of Independent Study

• Emphasis is placed on the necessity for students to engage in independent study and practice with exam-related tasks to reinforce learning.