Life Science Grade 10 Term 1

Cells

Cells

Well organized structures where metabolic processes of the body take place

Basic structure of cells

\-surrounded by cell membrane (and cell wall in plant cells)

\-contain cytoplasm and organelles

Cytoplasm

Jelly-like substance that fills the cell; mainly consists of water, mineral salts, gases and inorganic substances such as glucose and proteins

Functions of cytoplasm

\-gives cell it's shape

\-solvent for water-soluble substances

\-transport medium for dissolved substances

\-storage area for water insoluble substance (carbohydrate/lipid/protein molecules)

\-storage and circulation of substances within the cell

Organelles

Structures found within cell that carry out various functions

Examples of organelles

Mitochondria, chloroplasts, vacuoles, nuclei, golgi bodies, endoplasmic reticulum

Cell membrane

\-also known as plasmalemma

\-consist of phospholipid molecules (types of fat molecules)

Fluid mosaic model

\-known as phospholipid bilayer

\-each phospholipid has a head and tail

\-heads attract water (hydrophilic)

\-tails repel water (hydrophobic)

\-protein molecules are embedded into the phospholipid bilayer

Function of proteins in the phospholipid bilayer

\-have various structures and functions

\-shift around in bilayer

contribute to mechanical strength of the membrane

Function of cell membrane

\-semi-permeable (controls the movements of substances in and out of the cell)

* dissolved gasses (O2), sugars, amino acid and nutrients enter the cell (respiration and nutrition)
* waste products leave (excretion)
* hormones and enzymes secreted

\-provides support and flexibility to the cell

\-allows cells to grow and move

Diffusion

movement of molecules from high to low concentration (passive transport)

Osmosis

movement (diffusion) of water from a high concentration to low concentration

Isotonic solution

Equal amount of water in and outside the cell

\-animal cell remains the same

\-plant cell becomes flaccid

Hypotonic solution

High conc. of water outside the cell and low conc. inside the cell

\-water diffuses into plant/animal cell via osmosis

\-animal cell swells and bursts

\-plant cell becomes turgid

Hypertonic solution

Low conc. of water outside the cell and high conc. in the cell

\-water diffuses out of cell via exosmosis

\-animal cell shrinks and shrivels

\-plant cell becomes plasmolysed

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Active transport

large molecules (amino acids, glucose) actively carried through membrane by proteins in membrane

\-use energy

\-goes against concentration gradient

\-from low conc. to high conc.

Nucleus

\-control center of the cell

\-rounded structure

\-centered in animal cells and off centered in plant cells

Structure of nucleus

\-covered by nuclear membrane

\-filled with fluid called nucleoplasm

\-contains long threads of chromosomes folded and packed, forming the chromatic network

\-nucleolus inside

Functions of nucleus

\-contains hereditary info in DNA

\-controls metabolic processes in cell

\-regulate cellular activity

\-nuclear pores allow substances in and out of nucleus

\-ribosome are made in nucleus

Structure of DNA

Two long strands of genetic info made of sugars, phosphates and nitrogen bases

Structure of double helix

Two DNA strands bonded together by weak hydrogen bases, spiraled around eachother

Histones proteins

Give double helix support and together, form a chromosome

Chromosome

Strand of DNA twisted around a backbone of histones proteins

Centromere

joins chromatids in double-threaded chromosomes

Genes

Sections of DNA located on chromosomes; contain the info responsible for unique characteristics in organisms

Centriole

found in cytoplasm; arranged at right angles to eachother

Function of centriole

\-play a role in mitosis

\-control the formation of spindles involved in the anaphase of mitosis

Structure of mitochondrion

Outer membrane

\-smooth

\-control substances that enter and leave

Inner membrane

\-folded

\-finger-like projection (cristae)

\-granules that contain enzymes for respiration

\-fluid called matrix

Function of mitochondrion

\-in charge of respiration

\-oxygen breaks down food in the cell

\-energy (ATP) is released and used to drive functions in the cell

\-products of respiration = CO2 and H2O

Endoplasmic reticulum

\-consists of double membranes that fold and form channels

\-increases surface area of the cell

Rough ER - ribosome attached

Smooth ER - synthesis site if lipids anf other substances

Functions of ER

Makes, stores and transports carbohydrates, lipids and proteins in the cell

Ribosomes

small granules found in cytoplasm (some are attached to rough ER)

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Function of ribosomes

\-make proteins; vital role in growth

\-(in cytoplasm) produce proteins needed by cytoplasm

\-(attached to ER) produce proteins that form part of membranes or are secreted

Golgi bodies

consist of a stack of membranes called cisternae; membranes pinch off to form vesticles that contain lipids and proteins

Function of Golgi bodies

\-distribute molecules from ER to different parts of the cell

\-secrete proteins (hormones or enzymes) needed in the body

\-form lysosomes

Organelles found only in animal cells

Vesicles and vacuoles, and lysosomes

Vesicles and vacuoles

\-smaller than in plant cells

\-vesicles = small vacuoles

\-any structure filled with fluid and surrounded by membrane

\-some only contain water and perform osmoregulation (contractile vacuoles)

Lysosomes

tiny sacs formed from vesicles produced by golgi bodies

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Functions of lysosomes

\-destroy foreign material outside the cell

\-digest and breakdown food particles

\-breakdown dead cells and organelles

Secretion

release of a chemical substance that has a beneficial effect for the cell or the whole body

Organelles only found in plant cells

Cell wall, plant vacuoles and plastids

Structure of cell wall

\-surrounds cell membrane

\-made of cellulose fibers and lignin (which strengthens the wall)

\-permeable to water and minerals

\-openings contain cytoplasm called plasmodesmata which connects adjacent cells

\-cell walls of adjacent cells are joined by lamella

Function of cell wall

gives the cell it's shape and supports and protects the cell

Structure of plant vacuoles

\-large fluid sac that often fill most of the cell

\-surrounded by membrane called tonoplast

\-liquid inside is cell sap

Functions of plant vacuoles

\-stores sugars, minerals, and pigments in water

\-gives cell shape

\-plays a role in digestion and secretion of cellular waste

\-absorbs and releases water in response to changes in and around the cell

Turgor pressure

force exerted by vacuoles on cell wall

Cell wall pressure

force exerted by cell wall on expanding vacuole

Plastids

\-cholorplast, chromoplasts, leucoplasts

\-disc shaped organelles

Chloroplasts

\-present in all plant cells that produce glucose via photosynthesis

\-contain chlorophyll

\-chlorophyll absorbs sunlight, which provides energy for photosynthesis

Structure of chloroplast

\-made up of gelatinous substance called stroma

\-contains enzymes for photosynthesis

\-stroma surrounded by double membrane

\-thylakoids (stacks of membrane-like structures which contain chlorophyll) are suspended in stroma

Photosynthesis formula

Reactants = carbon dioxide and water

Chlorophyll and sunlight

Products = glucose C6H1206 and oxygen

Chromoplasts and leucoplasts

chromoplast - pigment

leucoplast - colorless and stores starch